ARCTIC SYSTEM SCIENCE
This is one of four coordinated projects that will make use of the camp facilities established on the ice sheet in the interior of Greenland as part of the GISP2 ice core drilling effort, in order to investigate how atmospheric trace elements are deposited on the ice and what kind of changes they undergo as they are being incorporated into the ice. An understanding of such processes is necessary in order to properly interpret the proxy climate data that can be recovered from ice cores. While significant progress has been made recently in extracting and analyzing ice cores, progress in understanding the air-to-snow transfer process for reactive chemical species has lagged behind. The goal of this project is to determine the atmosphere-to-snow transfer function for chemical species whose deposition is reversible (i.e., ones that can move from the snow back into the atmosphere to be removed or redeposited elsewhere). The two species to be investigated are hydrogen peroxide and formaldehyde. Based on measurements of their concentration in the free atmosphere and in the air within the snow, as well as in snow and ice, a transfer model will be developed. Concurrent laboratory studies will be done to determine and constrain model parameters such as chemical equilibrium coefficients and mass transfer coefficients. The model will be generalized to other reactive species, such as nitric acid and organic acids.
This award supports a theoretical and modeling effort to determine the effects of the Greenland Ice Sheet on the rotation and gravity field of Earth. To accomplish the goals, the secular and interannual changes in the geopotential, the position in the Earth's rotation axis and certain other parameters, such as center-of-mass motion and length of day, will be calculated from mass balance changes in ice. The largest gravitational effects of ice-thickness change shown in simple models are up to many times higher than the observed effects. This suggests that the viscous response of the mantle to long-term changes in ice loading may be canceling some of the elastic response. Current changes in gravity and crustal motion depend critically on the time-lagged response of the Earth's mantle to previous loading histories, lasting as long as tens of thousands of years. Spatial and temporal changes in mass balance from late Pleistocene deglaciation and the subsequent interglacial period will be combined with current mass balance estimates to assemble time histories for ice thickness throughout the ice sheet. From these histories, the elastic results for gravity, rotation and deformation can be corrected by the use of glacial rebound models, such as the visco-elastic spherical Earth model. The viscous correction to the elastic loading for several cases of late Pleistocene deglaciation and more recent thickness change will be calculated for various upper- and lower-mantle viscosity profiles. A 20 km x 20 km grid will provide means of projecting the viscous rebound rates for the point mass model into the non-pointlike structure of the Greenland Ice Sheet. In addition to gravity, the components of crustal deformation and tilt are important in geodetic measurements from space. This project also will assess the impact that future observational improvements will have on understanding the mass balance of Greenland. The observational improvements are anticipated from global positioning system (GPS) studies and studies involving satellites that use laser ranging. The use of existing gridded meteorological, accumulation, ablation and ice-thickness data, along with ice-flow models to predict future ice thickness changes in Greenland, are expected to greatly reduce the difficulty in calculating gravity coefficients and crustal motion for both the elastic and viscous cases. The effects of the possible changes in the position of the upper boundary of appreciable summer snow melt that roughly follows the periphery of the ice sheet called the Benson Line can be used to predict vertical motion near the ice sheet boundary and the results may be checked against sea-level records, where they exist. Greenland strain and velocity data may be used to estimate retention time of new accumulation and the rates of discharge at the perimeter of the ice sheet. The sensitivity of ice model contributions to the total mass loss (or gain) to the oceans and to changes in other ice systems will be investigated.
This award is for support to complete the oxygen isotope GISP2 ice core at 1.0-m and 0.2-m resolution. The relative importance of central Greenland temperature change versus ocean source temperature change will be investigated (in cooperation with James White, University of Colorado, Boulder) by calculating the deuterium excess of these samples. In addition, the phase relationships between oxygen isotope patterns and changes in accumulation rate, ice chemistry, dust content and atmospheric trace gases will be determined. The climatic and environmental significance of the ice core record will be assessed, and the spatial and temporal variability of the isotope record will determined.
This award is for support for a three-year project to obtain temperature logs in the GISP2 and Greenland Ice Core Project (GRIP) boreholes at Summit, Greenland, using the U.S. Geological Survey's (USGS) high-precision temperature logging system. Temperatures also will be logged in several dry holes near GISP2 and (GRIP), since the upper 100 m in the main holes have been thermally disturbed by the drill domes and drilling activities. The data are needed to derive surface paleotemperatures directly from the present-day temperature transients remaining at depth at these sites, and to better calibrate the isotope paleothermometer over the past 25,000 years. Simultaneous inversion of high-precision data from both deep holes will allow isolation of the paleoclimate signal from ice dynamics effects. The temperature data may also allow detection of rapid shearing in the silty basal ice, thus providing a test independent of the borehole deformation.
This award supports a program to measure Beryllium-10, Aluminum-26 and Chlorine-36 in samples from the GISP2 ice core. A continuous profile of cosmogenic nuclide concentrations from the surface to the bottom of the core will be measured and the resulting time series of nuclide concentrations will be applied to deducing the history of solar activity, deducing the history of variations in the geomagnetic field and dating of ice cores. The time series also will be used to study climatic history through the effects of atmospheric circulation and of atmospheric chemistry on nuclide deposition. The successful coring of the sub-ice bedrock has also provided the opportunity of studying the exposure age of the sub-ice surface.
This award is for support to provide a high-resolution paleoenvironmental record of major anions and cations in the GISP2 ice core. The parameters to be measured include chloride, nitrate, sulfate, sodium, calcium, magnesium, potassium and ammonium. The high quality, continuous, high-resolution multivariate chemical series will be combined with mathematical and statistical techniques in order to examine the history and understand the causes of climate change. This work will allow the characterization of the fundamental connections among the glaciochemical signals and the other parameters measured in the GISP2 core, and will permit a comparison with other ice core records, instrumental records and other proxy records. This study also will allow for the interpretation of changes in the sources and production rates of the chemical species recorded in the GISP2 ice, and will permit an investigation into the causes of climate change on a variety of time scales.
This award is for support for three years of funding for the Science Management Office (SMO) for GISP2. The major tasks are: to act as an organizational tool for GISP2 PIs; to continue data handling and development of a "final" data set; to coordinate ice core collection activities in Denver at the National Ice Core Laboratory; to guide and organize statistical tools; to maintain current ties with the European Greenland Ice Core Project (GRIP); to include additional viewpoints and disciplines; to handle specific issues (e.g., dating and intercalibration); to coordinate workshops and meetings; to organize final products including a compendium volume and papers; and continued communications with PIs, other scientists, the NSF, (GRIP) and the public.
This award is for support to continue research on the concentration of methane, the isotopic composition and concentration of oxygen, nitrogen, argon and total gas content of samples from the GISP2 ice core. The methane concentration of air is a proxy for the extent of wetlands and the warm, wet climates they signify. Methane is also a radiatively active gas which affects climate. The isotopic composition of oxygen in air reflects relative rates of primary production in the terrestrial and marine environments, and humidity in productive continental areas. Methane and the isotopic composition of oxygen are also constant (or nearly so) throughout the atmosphere at any one time. They therefore serve as time stratigraphic markers for correlating Greenland and Antarctic ice cores. Nitrogen and argon isotopes indicate the extent of gravitational fractionation during the trapping process and allow for correction of the measured concentrations and isotopic compositions of these gases. Total gas content reflects paleoelevation of ice sheets among other poorly understood influences. This work will provide information on climate and biogeochemistry during the last approximately 250,000 years of Earth history.
This award is for support to investigate, in detail, the timing between changes in temperature (indicated by the isotopes of oxygen and hydrogen in the ice, as well as the accumulation rate) and atmospheric carbon dioxide (from measurements of occluded air) in the high-resolution GISP2 ice core from central Greenland. The carbon dioxide measurements will be performed over periods of rapid climate change, such as the last glacial-to-interglacial transition, and during the glacial interstadials, the Eemian and the previous glacial. The determination of leads or lags between temperature and atmospheric carbon dioxide will help to understand the interplay of carbon dioxide and climate. The carbon isotope composition of atmospheric carbon dioxide will also be analyzed for these periods in order to gain more information about the mechanisms and processes responsible for carbon dioxide and climate variations.
This award is for support to continue measurements of deuterium on samples from the GISP2 ice core. The values of deuterium measured on the GISP2 ice core samples will be used to reconstruct and interpret the temperature history recorded in the core. Deuterium excess values will also be calculated in order to determine the climate conditions at the oceanic moisture source. This work will be coordinated with the group from the University of Washington that is measuring oxygen isotope ratios on the ice core. Work to date suggests that records of pressure (North Atlantic Oscillation) and temperature (Jakobshave-Oslo seesaw) oscillations are recorded in the deuterium and deuterium excess values. Values of deuterium excess during the last glacial period show sharp changes at the times of some, but not all, of the massive fluxes of icebergs into the North Atlantic (Heinrich Events). Major questions to be addressed include the nature of rapid climate changes seen in many of the climate proxies measured in the core, the existence of modes of climate as reflected by preferred states of the climate proxies and the importance for the climate record of differential thinning and thickening of layers, as well as possible folding and faulting of the near basal ice.
This award is for support for a three-year project to complete physical properties work (analysis of visual stratigraphy, density variations and c-axis fabric measurements) on the GISP2 ice core. The objectives of this project are to: (1) complete the dating of the core, providing as highly accurate a depth/age scale as is possible using all available parameters; (2) determine the accumulation history at Summit, Greenland, to the maximum possible depth; (3) use ice crystal c-axis fabrics and related structural parameters to assess the extent and nature of the distortion which has been observed in the bottom 200300 m of ice; (4) continue monitoring relaxation characteristics of the ice through repeated measurements of ice sample density and ultrasonic velocities; and (5) carry out detailed examination of the basal debris layer to determine its compositional and structural characteristics and to delineate the origin and mechanics of incorporation of the debris-rich ice.
This award is for support for a three-year project to complete measurements of stratigraphy on the GISP2 ice core with laser-light scattering, using both a solid technique and a technique that involves analysis of meltwater. At present, the resolution of the meltwater measurements only allows annual layers larger than 3 cm to be distinguished, so ice below 1900 m cannot be properly analyzed by scattering from meltwater. The resolution of these measurements will be improved so that annual layers as small as 1 cm will be able to be measured by this technique. Measurements using the solid technique have, so far, only been applied to bubble-free ice. It will be demonstrated that this technique can be extended to bubbly ice, and this method will be used to analyze all remaining sections of the ice core. The laser-light scattering measurements will be calibrated so that they give the variation in number of particles larger than 0.5 microns along the core, rather than just the relative scattered light intensity. Finally, selected sections of the core will be measured at regular time intervals to determine how the scattered signal changes with time as bubbles reemerge.
This award is for support for an investigation of the distribution of methanesulfonate (MSA) in the GISP2 ice core in order to assess the relationship between biogenic sulfur emissions, atmospheric aerosols and climate change over the North Atlantic. This project is primarily directed at completing the GISP2 MSA record from Summit, Greenland, which will cover an entire glacial/interglacial cycle. The GISP2 record already has demonstrated dramatic differences between glacial/interglacial trends in Greenland as compared to Antarctica. This work will provide new information about the factors controlling the variability in the atmospheric sulfur signal and its relationship to other changes in atmospheric chemistry. Samples from two other Greenland ice cores (Camp Century and Dye-3) will also be studied to examine climate-related variability of MSA during the Holocene.
This project is the continuation of an investigation of the transport of chemical trace elements and species from source regions through the atmosphere to the Greenland Ice Sheet. Its goal is to provide information for the interpretation of the trace element distribution in the long ice core that has been obtained through the GISP2 drilling effort. The ice core will provide a detailed record spanning 200,000 years. The project has three specific objectives: (1) the identification of source regions and atmospheric pathways for the chemical constituents reaching the drill site, including the possible changes in air mass characteristics during transit; (2) the quantification of relationships between chemical species in the atmosphere and those in the ice sheet; and (3) the interpretation of the deep ice core data using this information. Prior field work has resulted in the collection of samples of air, aerosol, precipitation and deposited snow, which will be analyzed for various anions and cations, trace elements, carbon compounds and trace gases. This project will emphasize the deposition mechanisms. The first objective will be achieved by measuring concentrations of chemical species in air and snow, and then combining this information with meteorological data of other investigators. Concentrations of major anions and cations will be determined by ion chromatography in our laboratories, while concentrations of trace elements and other species will be obtained by collaboration with other groups. The second objective involves measurement of wet, dry and fog deposition, as well as changes that occur in the snow pack after deposition of chemical species. The third objective will be achieved by developing models to explain the processes influencing air and snow chemistry at the site in collaboration with GISP2 researchers who are actively working with the core data. The results will be a better interpretation of the ice core data, and the reduction of uncertainties involved in using the core data to determine past atmospheric conditions.
Researchers at the University of New Hampshire will investigate the relationship between climate and volcanism by extracting ash layers from ice cores recovered by the GISP2. Large volumes of volcanic material in the atmosphere may affect the global heat budget for years. The relationship of volcanism and climate change, however, has not been convincingly demonstrated due to the lack of a data set that contains records of both volcanism and climate. GISP2 ice cores provide such a record. The ash layers will be analyzed geochemically so that the "fingerprint" of individual ash layers may be used to determine the volcanic center where the eruption occurred. Once the source of the ash is determined and the timing is established by the location of the ash within the well-dated ice core, then the relative magnitude of the eruption will be known. By comparing the timing of the volcanic eruptions to the climate record in the ice core, the potential impact of large eruptions on climate change may be examined.
This award is for support for a two-year program to study the origin of nitrate in the atmosphere and surface snow at Summit, Greenland. Preliminary results from unfunded pilot studies suggest that nitric acid (HNO3) is not the only, and may not be even the major, nitrogen species contributing to nitrate (NO3-) in summertime snow at Summit. Peroxy acetyl nitrate and one or more alkyl nitrate species seem to be the most likely candidates, and they also may be contributing to the elevated concentrations of organic acids observed just above the snow surface at Summit. Gradient measurements of soluble acidic gases will be made with two mist chamber samplers at different heights in the 1995 and 1996 seasons at Summit. These measurements will be complemented with intensive experiments comparing mist chamber samples to nylon filter samples and the use of nylon filters on the mist chamber inlet, to quantify soluble nitrogen species besides nitric acid. The primary goal of this study will be to enable improved interpretation of the nitrate records in polar ice, but additional insights into reactive nitrogen chemistry over snow covered surfaces are also anticipated.
The research is a collaborative project among researchers at six universities. The researchers will extend their previous study of the record of atmospheric chemistry concentrations recorded in the glacial ice at Summit, Greenland, from a summer only to a full year study by adding a winter sampling program. The ice core record from the GISP2 has been analyzed for traces of atmospheric chemistry, but the results cannot be assessed fully until a complete annual record of present chemistry is available because the largest signal in the ice core results from snow that accumulates during the winter months. A winter sampling program has been logistically impossible until this year.
The PI proposes to study the record of the cosmogenic and atmospheric 14C in air samples that have been trapped in the ice core recovered from the summit of the Greenland Ice Sheet by the GISP2. The abundance of 14C in the GISP2 ice core will be used to determine the atmospheric chemistry at the site for the past 30,000 years and to determine the chronology of climatic changes. Changes in the 14C tracer are an important piece of the evidence of a changing atmosphere during the transition from full glacial conditions to the present interglacial period.
Investigators will continue a project of extracting dust samples from the GISP2 ice core. The origin of the dust will be determined by comparing the geochemistry of the dust from the ice core to that of samples taken from potential continental sources worldwide. Changes in the source area for the dust in the ice cores will reveal how continental weathering and atmospheric transport have changed in response to changing climate during the past 100,000 years. Changes in atmospheric transport patterns will provide data for testing climate models that predict changes in atmospheric conditions during climate events during both glacial and interglacial climate extremes.
The Arctic Ocean Section is under the auspices of the Arctic Systems Science (ARCSS) Global Change Research Program and research is jointly sponsored by the Division of Ocean Sciences, the Office of Polar Programs and Office of Naval Research (ONR). Data collected should be relevant to improving our understanding of how the Arctic is an indicator of changing global climate conditions, and how it affects the physical, chemical and biological features of the more temperate oceans and regions. This specific research project encompasses part of the hydrography program. Precision temperature, conductivity, oxygen and nutrient profiles will be collected at intervals along the cruise track. Resulting data will be analyzed to increase understanding of the structure and circulation of the Arctic Ocean. Research will focus on three areas: (1) the structure of the halocine, wherein density differences between masses of seawater may drive the circulation and mixing of deep Arctic Ocean water with water from other parts of the world's oceans; (2) seawater properties and gradients near major sea floor features; and (3) the horizontal and vertical structure of the water column below 1500 m.
This work is a component of the collaborative biology program. Research will be undertaken to determine the rates of oxygen consumption and carbon oxidation in sediments along the cruise track. Sedimentary oxidation rates are said to relate to the flux of usable organic matter from overlying surface waters. Hence, it is an indicator of primary production and possible transport of carbon and nutrients from the marginal regions. A series of box and piston cores will be taken and sub-samples provided to a number of PIs. Measurements will be made of key biogeochemical solutes [oxygen, nutrients, alkalinity, pH, soluble iron and manganese, sulfate, chloride, calcium, magnesium, sulfide (if present)] and solid constituents such as porosity, surface area, organic carbon and nitrogen and carbonate. Sites to be sampled include continental shelves, slopes, abyssal plains and mid-basin ridges. The data will be used to evaluate sediment-bottom water fluxes and to estimate rates of oxygen consumption, denitrification and carbon oxidation. Information will provide a greater understanding of the carbon budget and nitrogen budget in the Arctic and global ocean.
This project is part of the program that focuses on the interrelationship of sea-ice physical and electromagnetic properties. A two-stage approach will be undertaken: Small-scale detailed studies of the different ice types and large-scale surveys to determine their relative areal coverage will be performed. Measurements of spectral albedo, bidirectional reflectance and wavelength integrated albedo at visible and near-infrared wavelengths will be made. Ice cores will be taken and studied for physical state and structure, including vertical profiles of temperature, salinity, brine and air volume, crystallography and inclusion size distribution. These small-scale measurements will be done in conjunction with helicopter surveys of active and passive microwave observations of the same ice to determine the range of physical properties, and also to determine the impact of changes in the physical properties on electromagnetic signatures. Helicopter transects, using an airborne spectroradiometer, as well as conventional photographic and video cameras will be used to determine a quantitative estimate of large-scale albedo, ice concentration, melt pond fraction and floe size distribution. These large-scale measurements will be linked with small-scale data to provide an understanding of the spatial and temporal variability of ice albedo and the coupling of shortwave irradiance to ice ablation. Such measurements are critical to our understanding of how the Arctic Ocean stores and reflects heat and its influence on climate variability.
This specific research effort involves the study of rare-earth element (REE) and Nd isotope systematics in order to gain insights on the interplay of ocean chemistry, biology and physics. (REE) and Nd isotope measurements will be obtained from sediment and water samples collected during the cruise and will be used to determine the origin of different water masses comprising the Arctic Ocean. Information also will be derived on the origin and maintenance of the seawater stratification, mixing processes, circulation and biogeochemical processes. In addition, these data will allow the Arctic Ocean to be placed in context with other existing (REE) and Nd isotope data from the sub-Arctic oceans and to be integrated into existing global, interoceanic circulation models. Analysis of ice-borne and seabed sediments for Pb, (REE), and Nd-Pb-Sr isotopes will allow integration of Late Cenozoic Arctic Ocean sediment geochemistry to the current understanding of sediment sources and dispersal in the Arctic Ocean.
This work is a component of the collaborative paleoceanographic program. Work will involve research on ostracodes contained in sediment samples to be collected, as well as from existing surface sediments collected by the Geological Survey of Canada from several other Arctic Ocean sites, including the northern Canadian Arctic Archipelago. Ostracodes are small calcareous bivalved crustaceans, and some benthic marine ostracodes are attuned, within narrow limits, to several environmental variables, the most important of which are temperature, salinity, dissolved O2, nutrients and substrate. Their distribution on the sea floor therefore reflects bottom water conditions, making ostracodes ideal monitors of water mass changes and circulation anomalies through geological time. Previous investigations have suggested that ostracodes are useful for paleoceanographic reconstructions of water mass history. This work will provide a better understanding of the relationship between modern ostracodes, water masses and Arctic bathymetry; of the relationship between intermediate-depth and deep-water ostracodes and Atlantic and Pacific faunas; and of faunal history and inferred ocean history during the Holocene, the Last Glaciation, and possibly, the whole of the Brunhes Epoch.
Investigators at the Woods Hole Oceanographic Institution will undertake research to increase the complexity of computer model simulations of the formation of dense high-salinity water that leaves the Arctic continental shelf and flows to the deep Arctic Ocean. The flows are capable of carrying nutrients and sediments from the continental shelf to the deeper ocean, and may play a major role in the transfer of heat between the atmosphere and deep ocean. Fluctuations in the formation of the cross-shelf flow could affect the transfer of heat from warm deep water in the Arctic Ocean that is produced in the Atlantic Ocean. Heat from that warm deep flow controls the formation of sea ice in the climatically sensitive Arctic Ocean. The improved computer models will, for the first time, take into account the effects of coastal currents, topographic complexities and water mass stratification of the continental slopes so that the models may begin to approach real world conditions. The improved models are necessary to understand how the Arctic oceanatmosphereice system operates to affect, and be affected by, global climates.
Research supported by this grant is under the auspices of the Arctic Systems Science (ARCSS) Global Change Research Program and is jointly sponsored by the Division of Ocean Sciences and the Office of Polar Programs. Work to be performed represents preliminary steps towards a major five-year research project named (SHEBA), which is envisioned to study the heat budget of the Arctic Ocean and its impact on global change. The primary goals of SHEBA are to: (1) develop, test and implement models of Arctic oceanatmosphereice processes that demonstrably improve simulations of the present day arctic climate, including its variability, using General Circulation Models (GCMs), and (2) improve the interpretation of satellite remote sensing data in the Arctic for analysis of the arctic climate system and provide reliable data for model input, model validation and climate monitoring. Researchers at the University of CaliforniaSan Diego, will build an instrument that will measure the vertical and horizontal flux of heat and momentum under the sea ice at the location of the proposed ice camp in 1997. The proposed sonar system will provide accurate measurements of mixing processes that will improve the ability of models to predict the component of the heat budget of the Arctic that is produced within the ocean.
This work will develop, construct and prepare for deployment two new instruments that will be built specifically for autonomous operation at the main (SHEBA) ice camp. The first is a wind profiler to provide wind and temperature profiles continuously to 2.5 km altitude. The second is a lidar for cloud and aerosol monitoring, which will measure optical depth and provide ice/water determinations. The instruments will be designed to optimize performance under Arctic conditions. This instrumentation will be useful in addressing an identified critical issue of (SHEBA), the sea Arctic cloud-radiation feedback mechanism.
Researchers at the University of Colorado will use data taken from aircraft in previous experiments similar to (SHEBA) to analyze the status cloud data so that the (SHEBA) field experiment may be planned more efficiently. The aircraft-derived data will be used to validate the results from remote sensing data taken from satellites so that those results may be extended beyond the specific region of the proposed field experiment.
This work is a collaborative effort between the University of NevadaDesert Research Institute and the University of AlaskaGeophysical Institute. Several key atmospheric measurements during the (SHEBA) field program will be made from tethered balloons that will carry scientific instruments up to 1 km above the ice surface. Some of these instruments must be adapted and tested for Arctic conditions. One group of measurements focuses on cloud microphysics and another group involves radiative heat flux measurements. The microphysics instruments will provide characterizations of cloud particles at different altitudes as the balloon moves vertically through cloud layers. The radiative instrument package will consist of self-leveling up and down short-wave flux radiometers, cloud liquid water instruments, and meteorological packages for pressure, temperature, humidity and wind. The collaborative effort will provide common operational and data logging components. Partial support is also being provided by the Department of Energy.
This award to the University of Washington establishes a Science Project Office for the (SHEBA) Program. The Office will coordinate planning activities and data collection, and will also serve as the primary point of contact for the project. The data generated by all of the Phase I PIs will be transmitted to the Office and made available to other investigators so that the planning effort for the field program will be efficiently conducted with the most recent data set available.
By interagency agreement the U.S. Navy/NOAA Joint Ice Center will provide the management structure and coordination necessary to establish and maintain a network of drifting meteorological buoys in the Arctic. The buoys will be emplaced at a sufficient spatial resolution and longevity to define surface synoptic scale atmospheric pressure, air temperature and sea-ice fields. The data will be made available in real time for operational weather forecasting and will be used by researchers for studying global change in the climatically sensitive Arctic.
The northward flow through the Bering Strait transports nitrate-rich Pacific waters into the Arctic basin. This influx supports the richest productivity found in the Arctic. It has been hypothesized that export of part of this productivity could supply significant amounts of organic matter to the central Arctic. Part of the productivity is consumed within the Chukchi Sea, via sedimentary carbon oxidation, and the rates in the U.S. region of the Chukchi are moderately high. However, new measurements of sedimentary sulfate reduction rates indicate that past estimates were severalfold low. Furthermore, conversion of inorganic nitrogen to N2 by denitrification in these sediments appears to be rapid. Thus, the sediments in the U.S. Chukchi Sea may oxidize more of the productivity and remove more of the nitrogen than previously thought. Furthermore, a large pool of organic rich sediments underlies much of the Russian Chukchi Sea, suggesting that even larger areas of sedimentary consumption, perhaps with even greater rates of oxidation and denitrification, may occur in the Russian areas. The organic rich areas of the U.S. and Russian Chukchi Sea will be sampled throughout the ice-free regions in midsummer of 1996. At each site, sediment-water fluxes of O2, N2, N2O, inorganic nutrients, TCO2 and alkalinity will be measured in replicate flux experiments. Vertical profiles of sulfate reduction rates will be determined by current 35SO4 tracer techniques. Porosity, organic matter content and pore water distributions of key solutes will also be determined. These data would expand our knowledge of sedimentary carbon oxidation and denitrification rates and their role in the productivity cycle in the Chukchi Sea. The improved estimates of these sedimentary processes will better estimate the potential for this region to export significant quantities of organic matter to the rest of the Arctic basin.
The PI proposes to conduct a research project on a cruise aboard the German research vessel Polarstern as a part of the international initiative ACSYS planned by the World Meteorological Organization. He will make tritium, helium, and oxygen isotope measurements in the eastern Arctic Ocean to determine the extent of Atlantic water that has recently been found to extend much farther into the basin than previously known. The expansion of Atlantic water into the Arctic could be the result of global change in response to a warming climate, or a temporary change in circulation due to factors not associated with climate. The data collected on this cruise will fill in an important gap in the Arctic Ocean so that future studies may observe the persistence of the change in circulation within a global change context.
The award is to support a planning workshop to develop a science plan for studies of the physical and biogeochemical interactions of Arctic Ocean shelves. The ShelfBasin Interactions initiative to be developed by the workshop participants will identify a research program that may be conducted to address the question of the fate of organically derived material from the shelf that is transported to the deep basin in response to global change. The fate of the organic material must be determined in order to improve models for estimating the volume of carbon dioxide exchange with the atmosphere during global warming. At present, the carbon exchange from shelf to basin is largely unknown in the Arctic Ocean, and must be investigated if accurate estimates of the impact of global change on the climatically sensitive Arctic region is to be determined. The workshop will produce a science plan for conducting a research program.
The PIs will develop an Arctic Ocean circulation model coupled to a sea-ice model on two spatial grids. The model numerical will allow the researchers to investigate the input of Pacific Ocean water and the outflow of Arctic Ocean water to the Atlantic so that not only the circulation within the Arctic Ocean is simulated but also the important inputs and outputs are derived. The model should produce a very realistic circulation that may be examined for changing climatic conditions to determine the climatic effect on both Arctic Ocean circulation and the effects of that circulation on the North Atlantic Ocean. The model will provide a framework for other studies in the Arctic that require a predictive capability for ocean circulation in areas of the Arctic Ocean where no observational data exists.
This is a joint proposal to support the (OAII) Science Management Office ((SMO)) and Science Steering Committee (SSC). The SMO will be located at Old Dominion University and the chair of the SSC will be at the University of Tennessee. The (SMO) will support the activities of the (OAII) SSC (e.g., workshops, planning meetings and coordination with international science projects), publish a newsletter, promote correspondence of (OAII) results at national meetings and between PIs, facilitate logistical arrangements and promote integration of (OAII) activities with other components of the Arctic System Science (ARCSS) Program. The SSC will conduct planning meetings for future (OAII) science projects, appoint working groups to conduct workshops for development of science plans for new initiatives and provide the (ARCSS) Program with an assessment on priorities for (OAII) global change initiatives/projects in the Arctic that are developed through the workshops.
A jointly supported NASA/NSF workshop will examine bipolar processes of climate change. Research results and climate models suggest that climate changes observed in Antarctic and Arctic records have occurred similarly in both polar regions. The workshop participants will examine the recent results collected separately at the two poles and discuss a strategy for modeling climate changes that involve bipolar interactions of the climate. The increased communication between scientists separately studying Antarctic or Arctic climates will foster development of better models and enhanced collaboration that will lead to improved understanding of global climate changes.
The PIs propose to examine the iceberg keel depth data taken on U.S. nuclear submarines under the Arctic pack ice for a record of temporal changes in ice thickness in the Arctic Ocean. These data provide the only means of looking at the historical record of ice thickness for the past 30 years and, as such, are an excellent recorder of the possible impact of global change on the Arctic. The results of this study are very important for understanding the persistence of the pack ice in the past with the possibility of predicting changes that could occur in the near future. The results will be a valuable test of predictions from climate models that indicate a magnified global warming effect in the Arctic that might result in the disappearance of the pack ice.
This action provides support for the U.S. Navy Arctic Submarine Laboratory for baseline and special data acquisition during an extended scientific cruise of a submarine under the Arctic Ocean ice cover in the summer of 1995. The basis for this support is a Memorandum of Agreement among four operational units of the Navy and three civilian federal agencies: the National Oceanic and Atmospheric Administration, the U.S. Geological Survey and the NSF.
This award supports a project under (PALE), a program that focuses on the timing, magnitude and rates of change in Arctic climates during the late Quaternary. Understanding the complex regional responses to past shifts in global climate requires: (1) the compilation of numerous well-dated records of paleoclimate indicators (e.g., pollen); (2) the calibration of these proxies by defining their modern climatic relationships; and (3) the comparison of climatic histories inferred from the paleodata to qualitative or quantitative paleoclimatic models. Although such data sets are available from lakes in many areas of the North American and European Arctic, comparable information is virtually absent from northern Siberia. This award supports a project designed to analyze pollen, spores, plant macrofossils and sediment geochemistry of lake cores to reconstruct the late Quaternary vegetation and climate of Western Beringia (northeast Siberia). These histories will be reconstructed for six study areas, which today encompass the range of vegetation and climate in far northeast Russia. Analyses of surficial lake muds will improve the definition of modern pollenvegetationclimate relationships and aid the paleoclimatic interpretation of fossil data. The new Russian data will allow a more detailed description of trans-Beringian paleovegetational patterns and inferred paleoclimates. Definition of such broad-scale patterns will help paleodata/GCM comparisons for the Arctic, thereby improving the understanding of high-latitude responses to global climatic changes.
Ice core and other paleoclimatic records from the High Arctic suggest that summer temperatures reached minimum levels for the entire Holocene during the last 500 years, but underwent a dramatic reversal in the last 100 years. This award, under the (PALE) program, is designed to study lake sediments from a number of sites to determine if this hypothesis is supported by the sedimentary record. To better understand the paleoclimatic signal in the sediments, a three-year process-based study is planned to determine the primary controls on sediment flux and varved sediment formation in Sophia Lake, a High Arctic hypersaline, meromictic lake. Sophia Lake provides a simple topographic environment, which will facilitate efforts to isolate the primary climatic forcing. Sediments from lakes on the margin of Agassiz Ice Cap also will be recovered in order to link the paleoclimatic record of ice cores from the ice cap to sedimentary records from the glacier margin.
This award supports a PALE/(ARCSS) effort to construct a high-quality data set for surficial lake sediment calibration in the eastern Canadian Arctic. A detailed sampling and analysis program will allow the development of new calibration data for fossil pollen and isotopic and palelimnological proxies. Modern numerical analysis will be applied to existing lake-based fossil pollen records to produce a new generation of quantitative paleoclimate estimates. This work will result in a large public domain database, and will make a collection of surface lake sediments available to the paleoclimate community for additional research.
These funds support a cooperative agreement for the National Center for Atmospheric Research: Arctic System Science Program support for the PALE program.
Beringia (far northwest Canada, Alaska, and northeast Siberia) is an important region of paleoclimate study for the NSF (PALE) program because it remained unglaciated during the late Quaternary and experienced extensive changes in paleogeography due to changing sea levels. This research is designed to describe the late Quaternary climate history of the North Slope (ca. 150,000 years BP to present) through the analysis of proxy climate indicators in a suite of lake sediment cores on the Alaskan North Slope. The research will: (1) describe temporal and spatial variations in the pollen, spores, plant macrofossils and selected geochemical properties; (2) interpret variations in paleoclimate from proxy indicators (using analytical approaches and large modern calibration data sets for the interpretation of pollen data); and (3) infer potential causes of paleoclimatic variations using a conceptual framework of large-scale controls of eastern Beringian climate and climate model simulations as part of ongoing (PALE) paleoclimate projects. Results of the proposed research will contribute directly to PALE's goal of documenting circumarctic paleoclimate variability.
The sensitivity of the polar regions to increased greenhouse gases is described by global circulation models. Rapid changes in Arctic boundary conditions that influence climate, such as vegetation type (especially tundra versus boreal forest), extent and duration of sea ice and seasonal snow cover, and continental ice thickness/iceberg discharge may have had dramatic impacts outside the Arctic in the past, and may have similar future impacts. These impacts underlie current interest in the role of the Arctic in the global climate system. A primary objective of (PALE) is to obtain and analyze a series of lake sediment cores that span the circumarctic region. This project focuses on the 020,000-year time period, with opportunistic sampling of older records and high-resolution younger records where encountered. Research will continue lake-coring research efforts, including the interpretation of pollen, diatom, sedimentological and isotopic analyses. additional proxies for past climate utilizing the isotopic composition (C and O isotopes) of aquatic macrofossils and specific classes of dissolved organic matter preserved in lake sediments and changes in diatom floral assemblages.
This award supports activities that are central to the success of (PALE), a project within the Arctic Systems Science (ARCSS) Program, but which are beyond the scope of individually funded research projects. The general contribution of (PALE) to the (ARCSS) program is the description of temporal and spatial variations in late Quaternary (150,000 years to present). Arctic climates are determined by multiple proxy indicators preserved in lacustrine and estuarine sediment records. These data, when coupled with paleoclimatic models, provide a fuller understanding of possible mechanisms and feedback that affect both circumarctic and regional high-latitude climate changes. Such knowledge improves predictive capabilities for assessing possible environmental responses to future climatic fluctuations. This award will support the activities of the (PALE) Steering Committee for coordination among national and international scientific programs. A data coordinator is also supported as being vital to (PALE) as the major facilitator for compilation, storage and exchange of data with other paleoclimatic programs. Support for radiocarbon analyses will ensure the high quality chronologies necessary to (PALE).
Iceland is located on the eastern side of Denmark Strait in a region where changes in the extent and duration of sea ice have major impacts on both the marine and terrestrial environments. This area monitors the relative strength of both the northward advection of Atlantic water and the southward flux of sea ice and freshwater in the East Greenland Current. This PALE/ARCSS award supports the recovery of a series of sediment cores from lakes in Northwest Iceland and compares their proxy records of climate with proxy records from marine cores taken from fjords and shelf-troughs off Northwest Iceland. Based on earlier (PALE) studies, decadal/centennial sampling resolution is realistic in both environments, and correlations within systems and between lakes and the offshore are enhanced by an abundance of regional tephras. A major Icelandic contribution to the grant will include ship-time to carry out coring along three fjord shelf transects in Northwest Iceland.
The climate system of the Arctic is a key component of the global system, and an understanding of the nature of paleoclimatic variations in the Arctic is therefore an important element in predicting how that region may respond to changes in the large-scale controls of climate. This PALE/(ARCSS) award supports the analysis of Quaternary paleoecological records from Beringia to: (1) document the nature and magnitude of past climatic changes; (2) test hypotheses about the controls of regional climatic variations, and how changes in those controls are expressed at the regional and local levels; and (3) exploit the growing number of paleoenvironmental records from this region for use in the examination of paleoclimatic variations along key transects, and for application in model-validation studies. This analysis requires the compilation of modern sets of climate and vegetation data from the region, and their use to establish relationships between vegetation and climate. These relationships can then be applied to: (1) interpret fossilpollen data in climate terms, thereby illustrating the range of past climate changes; (2) test specific hypotheses about the controls of past climatic variations by comparing the "observed" record of vegetation change with that implied by the hypotheses; and (3) validate climate model simulations of Arctic paleoclimates.
The aim of this grant is to synthesize and quantify paleoclimate reconstructions on the basis of fossil insect data from Eastern Beringia (Alaska, the Yukon Territory) and the Bering Land Bridge, using the Mutual Climate Range method. The Quaternary insect fossil record is a source of proxy data that provides sensitive, accurate paleoclimatic reconstructions for terrestrial ecosystems. As with any single source of proxy data, fossil insect interpretations cannot provide the complete paleoenvironmental picture. This investigation will promote interdisciplinary cooperation by generating calibrated, quantitative paleotemperature data for fossil beetle assemblages that will be more readily comparable to the reconstructions based on the interpretation of other proxy data, such as pollen response surfaces and transfer functions. A principal objective of this investigation will be to establish the nature, timing and intensity of the major climatic transitions of the late Pleistocene. Secondly, this method will be applied in Eastern Beringia to calibrate existing data and provide seasonal temperature reconstructions.
It is poorly known how dramatic changes in deglacial and Holocene climates in the North Atlantic region propagated into the Eurasian Arctic. Lacustrine and estuarine records from the Kola Peninsula, adjacent to the North Cape Current, the easternmost limb of the North Atlantic Current, provide archives to assess postglacial and Holocene variations in lakes, vegetation and tree line and inferred changes in atmospheric and oceanic circulation. Extant cores from the northern Kola Peninsula provide estuarine and lacustrine records spanning at least the last 12,000 years. Preliminary analyses demonstrate that these sediments are rich in biologic remains, ideal for securing a reliable radiocarbon chronology and for determining environmental changes. This PALE/(ARCSS) award supports lake coring on a transect from the tundra-dominated northern coast to the forested center of the Kola Peninsula. This research will utilize an array of paleoecological techniques such as pollen, diatom, macrofossil and sediment analyses, augmented by recent advances in stomate, chironomid and cellulose stable isotope analyses. To strengthen the paleoenvironmental interpretations of the cores, modern sediment samples will be collected from lakes to statistically calibrate pollen, stomate, diatom and chironomid records with present climatic, edaphic and vegetation conditions. The research will provide new late glacial and Holocene records from the western Russian Arctic, currently a void in global paleoclimatic time series.
This Small Grants for Exploratory Research (SGER) award supports a pilot study of Elgygytgyn Lake, a large lacustrine basin located 100 km north of the Arctic Circle in northeast Russia. This lake was created by a meteorite impact that generated a crater roughly 23 km in diameter. The lack of glaciation in this basin makes it highly likely that the modern lake contains a continuous paleoenvironmental record of at least the last 250,000 years, but probably back to the time of impact. It is believed that an international, multidisciplinary project to collect and analyze core materials from this lake will provide a paleoclimate record unparalleled in northern Asia. The objectives in this project are intended to test the hypothesis that this large, but morphologically simple lacustrine system contains a high-resolution sediment archive extending through the Holocene and well into the late Pleistocene. If successful, these cores will provide the impetus for a major deep drilling program to retrieve the entire record in the future.
This (SGER) awards supports the exploration of two small lakes in the Denali area of Alaska for their potential to yield a continuous environmental record of the last 60,000 years. Field work will include the documentation of basin bathymetry, structure of the sediment fill through acoustic profiling and nature of the sediment infill. If successful, these basins could provide a key record of paleoclimate for the glacial period.
This research will analyze the pollen from selected peat cores from the tundra of Beringia, the ancient subcontinent which now includes Alaska and northeastern Siberia. The Arctic tundra is a major ecosystem which plays a significant role as a major repository of the world's carbon. Whether northern peat is still accumulating soil carbon or may actually be losing carbon is a question with important consequences for global change scenarios. This work will use plant ecology and soil studies to interpret pollen records. Pollen analysis offers ecologists a long-term perspective on vegetation change in this complex environment. Interactive activities include teaching a course directly related to this research, and introducing students to the tools and methods used to understand past environmental change. In addition, a seminar will be offered, entitled Women in Prehistoric Society. This course is an exploration of the traditional biases toward gender roles in prehistory, which will enable the PI to extend her visibility and contribution to other departments at the University of Alaska.
This award is for support for a study to continue development of a chronology, reconstruct paleoenvironments and understand the processes associated with major ice sheet instability (Heinrich events) of the eastern sector of the Laurentide Ice Sheet over the last glacial cycle. During the continental glaciation of North America, Hudson Strait drained one-quarter to one-third of the Laurentide Ice Sheet and was the major conduit for the transport of water, sediment and icebergs from the ice sheet into the North Atlantic. The fluxes of these materials into the Labrador Sea and North Atlantic would have had a dramatic effect on the global climate system. A number of cores have been identified for study that will provide high-resolution records of ice sheet (Heinrich) events on centurial-to-decadal time scales.
This project seeks to develop a dynamic model to describe the potential impact of climate variation on the tropic structure of a coastal Alaskan ecosystem by assessing the degree to which climate change influences habitat structure and availability with the population dynamics of a colonially nesting bird, the Pacific brant. The area of study, the YukonKuskokwim Delta, has been traditionally exploited by Yup'ik people, and geese are a seasonally important resource. A parallel study of native oral history will be conducted in order to access traditional knowledge of the ecology of this region.
This project is a significant contribution to the Arctic System Science (ARCSS) LandAtmosphereIce Interactions (LAII) study. The research proposed will determine CO2 and water, momentum, and energy fluxes at three spatial scales (plot, landscape and mesoscale) using chamber, tower-based eddy correlation techniques, and aircraft-based eddy correlation techniques. The information obtained from each of these techniques will be analyzed and compared, especially in light of defining the most efficient approaches for estimating large spatial scale CO2 flux in the Arctic. Remotely sensed spectral indices, geographic information system (GIS), process model, and phenomenological models will be used to develop a methodology for efficiently estimating ecosystem CO2 flux over meso- and global scales. Initial testing of the applicability of these methods will be undertaken during 19931996. The research will yield the current CO2 flux for the area studied (east-central North Slope of Alaska), the contribution to CO2 flux of various elements of the landscape, the sensitivity of net ecosystem CO2 flux to altered environmental conditions, models and methodology to predict CO2 flux in the Arctic and efficient techniques for estimating meso- and global scale CO2 and other trace gas fluxes.
The research, a part of the (ARCSS) (LAII) Study, will take place in Arctic Alaska in the headwaters of the Kuparuk River. There are four parts: (1) the measurements of flux of carbon as CO2 and organic matter from groundwater/land to streams and lakes and eventually, in the case of CO2, to the atmosphere (calibrations to be carried out with the help of the Chapin project); (2) the measurement of the concentration of nutrients (PO4, NO3, NH4) and dissolved and particulate organic matter in the Kuparuk River in order to calculate flux to the ocean; (3) the enhancement of a General Ecosystem Model (GEM) to include anaerobic conditions and phosphorus cycling in order to understand and predict the interactions of variations in vegetation, soil, and carbon cycling on CO2 and methane transfer to the atmosphere; and (4) The enhancement of a Terrestrial Ecosystem Model (TEM) to include permafrost in the soil moisture calculations in order to make spatially explicit regional estimates of CO2 exchange between vegetation/soil and the atmosphere.
This component of the Arctic System Science (ARCSS) (LAII) Flux Study will: (1) develop (GIS) databases at five scales (1:10, 1:500, 1:5000, 1:25,000 and 1:250,000) and at five sites; (2) develop an understanding of the relationship between vegetation signals and key terrain parameters; and (3) develop a method to use remotely-sensed images and (GIS) variables to distinguish key vegetation parameters for spatial models of trace gas fluxes. One task will be the development of methane and CO2 flux maps at multiple scales of the Toolik LakeImnavait Creek region, using an empirical approach based on field measurements of trace gas fluxes in a hierarchy of vegetation types, and a modeled approach using a variety of remotely-sensed satellite data. Measurements of vegetation, biomass, soil, site and spectral reflectance characteristics will be made at permanent study plots representing the majority of landscape variation. Trace gas measurements by other investigators at the same sites and (GIS) databases will be used to extrapolate this information to landscape and regional scales. Permanently marked 1 km x 1 km grids at the five study areas will be used as a sampling framework for much of this research (e.g., monitoring trends in species composition and canopy structure in relation to landscape variables and climate change) and other research within the project. Data from (GIS) databases also will be used by other investigators in hydrology models, terrain models of trace gas fluxes and algorithms to scale plot level measurements to regional scales.
The goals of the CH4 component of the Arctic System Science (ARCSS) (LAII) Flux Study are to produce regional CH4 flux estimates and perform field experiments that will elucidate the controls and feedback on CH4 and CO2 emission from tundra environments. The region flux estimates will be made using time series chamber measurements of CH4 flux at permanent sites along a transect covering a range of physiographic provinces. The locations and times of measurements will be coordinated with atmospheric CO2 studies, with vegetation mapping studies, and with soil chemistry studies. The field experiments will involve manipulations of soil temperature and water table level, jar and core experiments at a range of temperatures and moisture contents and a series of isotope labeling experiments. The experiments will provide information on CH4 oxidation to temperature and moisture changes, and the role of recently fixed carbon in CH4 and CO2 emissions. These experiments will be performed in collaboration with other (LAII) investigators.
The three major aspects of this project are: (1) comparison of CO2, water and energy fluxes in different vegetation types and climates; (2) evaluating the roles of water and energy fluxes as components of the coupled landatmosphere system; and (3) determining the relative importance of soil, root and above-ground components of net ecosystem CO2 flux. Fluxes will be measured in reference vegetation types by other projects. The role of water and energy fluxes in regional climate will assessed by a land-surface model that can be coupled to a regional climate model. Sensitivity analysis with this land-surface model will determine the major ways in which regional climate affects water and energy fluxes. Labeling of soils with stable isotopes will be used to evaluate the relative importance of roots and soil in controlling CO2 flux from tundra. These experiments will be coordinated with measurements of soil organic matter content and quality and of ecosystem CO2 flux made by other projects in the Arctic System Science (ARCSS) (LAII) Flux Study.
The goal of this project is the implementation of a regional model of the Arctic atmosphereland system for use in the Flux Study of the ARCSS (LAII) program. Specific objectives are to simulate the landatmosphere interactions that control the hydrology and the trace gas fluxes over the northern Alaskan region, and to project changes in the climate and surface forcing of this region. The atmospheric simulations utilize the NCAR/Penn State mesoscale analyses to provide the lateral forcing. The surface exchanges will draw upon a coupling to soil-vegetation and hydrological models under development in other Flux Study projects. Mesoscale topography, vegetation and soil data also provided by other Flux Study projects will be incorporated into the model. The regional model provides the framework for scaling up the study's plot, tower and aircraft measurements of the surface fluxes. Finally, output from a global circulation model will be used to drive the regional model in a series of greenhouse-induced climate change experiments, thereby providing high-resolution scenarios of regional climate change for assessments of future trace gas fluxes.
The major objective of this research is to assess the quantity and quality of soil organic matter (SOM) and to test the roles of the active fractions of (SOM) in CO2 and CH4 production in the Arctic ecosystem. The first phase of this project involves the sampling and full characterization of soils on the flux study sites which were jointly selected by all PIs involved in this collaborative proposal. The soil characterization will provide a database for extrapolating the results of gas flux studies over a geographic base. The second phase involves the isolation and characterization of the inactive and active organic fractions in soils and soil solutions; then identification of the microbial active fractions by using respiration experiments under controlled conditions and the identification of active components as substrates for gas flux (both CO2 and CH4) by using carbon labeling experiments. It is hypothesized that the major sources of CO2 and CH4 production are the active fractions in (SOM). The composition, quantity of active and inactive organic carbon fraction and their turnover rate are expected to closely relate to gas flux on different arctic ecosystems. This project is part of the larger integrated (LAII) Flux Study.
Development of climatic models has intensely highlighted the fact that almost all of the important processes controlling climate are interactive, and that it is vital to understand the linkages between these processes; for example, what is the role of the hydrologic system in connecting atmospheric and terrestrial processes? As a component of the (ARCSS) (LAII) Flux Study, the objective of this project is to improve the understanding of the linkages between atmospheric, terrestrial and aquatic systems. Specifically, this means developing a quantitative understanding of the energy and mass transfer processes of the hydrologic regime. A primary component of this study is a field measurement program to quantify the water balance of watersheds that are physically quite different (e.g., watersheds in the foothills compared to those on the coastal plain) and an energy balance of the entire region from the Arctic Ocean to the Brooks Range. One goal is to develop a physically based, spatially distributed hydrologic model that, when combined with the results of cooperating (LAII) researchers, can be coupled with the biogeochemical processes of a watershed. Other goals are to develop an understanding of the mechanisms which impact snow distribution and a working model of lateral and vertical fluxes of water and energy in the entire Kuparuk watershed.
Global warming will substantially increase the length of the active season for high-latitude ecosystems, but many plant species in these areas have phenological patterns adapted to short growing seasons. Some, but not all, of the factors that affect phenological stages will change with global warming. Those species constrained by cues that will be unchanged with global warming, such as photoperiod, will be unable to respond to extended season length. As a result, species composition, productivity and carbon fluxes from these ecosystems will change substantially. Using Alaskan tundra as a model system, this project addresses the questions: (1) What are the constraints on phenological patterns for the dominant species? (2) What physiological adjustments will species make in response to an extended period of resource availability? (3) How will growth of the dominant species, ecosystem productivity and ecosystem carbon fluxes change under field-simulated extended seasons? These questions will be addressed using a combination of controlled-environment studies and field manipulations of season length. Growth chamber studies will examine the effects of photoperiod, soil and air temperature, and leaf age on phenological patterns and carbon gain of selected species of the dominant growth forms. Field studies will examine the effects of extended active period on phenology, growth, productivity and ecosystem carbon balance. Results from this study will be used to develop a model of phenological patterns of tundra plants that can be used to evaluate species' responses to extended growing season.
Rising levels of greenhouse gases are expected to bring about a host of changes in climate and terrestrial ecosystems. These changes are expected to be greatest at high-latitudes. This project will assess the capacity of three important arctic plant species to adapt to new environments that may arise as a consequence of climate change. Because the exact nature of future climate change is, at present, unclear, this research will focus on plant response to multiple environmental factors including temperature, moisture, CO2 and nutrients. In this way, models of evolutionary response will be developed that have predictive value among a range of alternative scenarios of climate change. A series of experiments will focus on plant growth rate and morphological traits, relationships between traits and growth, and quantitative genetic analysis. This research is expected to produce evolutionary models of each species that describe the capacity of arctic plant populations to adapt to new environments and the patterns of morphological and physiological changes that would be favored by natural selection in these altered environments.
This project will evaluate the ecological consequences of climate change in moist and dry Arctic tundra with field manipulations of winter precipitation and summer temperature. Project scientists will investigate effects on species performance, community structure and ecosystem C and N dynamics. They will erect snow fences to increase snowpack and use small greenhouses to warm air and soil temperatures. Growth rings and annual stem increments of wood species and physiological plant performance will be compared with historical temperature and precipitation records. Experimental findings also will be compared to natural vegetation patterns along snow gradients and areas where long-term anthropogenic increases in snow cover have occurred. Simulation modeling will be used to extend their findings with a focus on net ecosystem carbon budgets. The main effort will be to quantify and understand the magnitude and direction of the transient response of Arctic tundra to a series of climate change scenarios. The experimental infrastructure will permit more detailed investigations by other investigators in future years if the response is, as we anticipate, of sufficient magnitude to be of importance for evaluation effects of climate change to arctic ecosystems. The project is a U.S. contribution of the International Tundra Experiment (ITEX).
The (LAII) Science Management Office, located at the University of AlaskaFairbanks, is part of the (LAII) Flux Study, but it also is involved in the integration and coordination of the Flux Study within the broader aspects of (LAII), and indeed the entire Arctic System Science program of the NSF. The (SMO) will also establish connections to other international programs of global change research in the Arctic. The (SMO) will facilitate project planning and integration by providing active scientific leadership and coordination service to the (LAII) projects, by holding science planning and synthesis meetings, providing communications between PIs and ensuring linkages to related programs. Specifically, long-term science plans for the Flux Study will be developed, modeling and data management requirements will be specified in the context of the overall (ARCSS) program, and logistics needs will be coordinated. The (SMO) will be advised by an Executive Committee of four, including the director of the (SMO), and a Steering Committee of both external members and (LAII) PIs. The establishment of the (LAII) (SMO) is in response to a recommendation from the NSF review panel for the (LAII) Flux Study.
A combined program of field measurements and modeling of the Arctic snow cover is proposed as an addition to the (LAII) component of the Arctic System Science Program. The objective of the proposed program is to understand the role of the Arctic snow cover in governing the winter heat and mass exchange between the ground and the atmosphere. The justification for studying the Arctic snow cover is that it is one of the dominant features of the Arctic system and needs to be accurately incorporated in an Arctic system model. Studies have shown that long-term changes in the depth and thermal properties of the snow that could accompany a change in climate would affect plants under the snow as well as the temperature. Furthermore, thawing of carbon-rich permafrost may release CO2 to the atmosphere, providing a strong feedback mechanism for local and global warming. Predicting how the Arctic will respond to a changing climate will require understanding the role of the winter snow cover. The core of the proposed program is a series of over-snow traverses during which extensive measurements of the physical and thermal properties of the snow will be made. Traverse measurements, along with knowledge of the physical process that affect the Arctic snow cover, will be used to develop an Arctic snow distribution model. The validated snow distribution model can be incorporated in both climate and surface process models being developed under other (LAII) projects.
The aim of this research is to analyze the role of temperature, light and nutrient availability in regulating primary production of Arctic tundra ecosystems at several levels of ecological organization and at different time scales. The research is organized around three general hypotheses about the mechanisms reevaluating adjustments of primary production in response to short- and long-term variation in climate. The basic idea is that different mechanisms control the responses to climate at different levels of ecological organization and at different time scales. In order to obtain useful predictions of the effects of climate change on primary production, a better understanding of relationships between these interacting mechanisms of adjustment to climate change is needed. To test the three general hypotheses, this five-year program of research will focus on an integrated series of field experiments in moist tussock tundra at Toolik Lake, Alaska. The mechanisms to be studied include those operating at the physiological level (e.g., photosynthesis), the whole-plant level (storage and recycling, changes in allocation and biomass turnover), the species and ecotype levels (constraints on nutrient use efficiency and growth rates), and the whole-ecosystem level (climate controls on soil nutrient supply). This project is part of the International Tundra Experiment (ITEX). Collaboration with other ecologists working at Toolik Lake and at other Arctic sites, as part of the Long-Term Ecological Research (LTER) and Global Change in Terrestrial Ecosystems (GCTE) Programs, will increase the application and impact of this research.
A researcher at the University of California will conduct two workshops to examine trace gas feedback to global climates, water/energy feedback to climate and the role of vegetation structure and change in feedback to climate. The workshops will address the importance of biodiversity and vegetation structure to large-scale (regional to global) processes. The workshops will serve to integrate the results of several separate high-latitude programs into a comprehensive framework to determine the interactive roles of vegetation and ecosystem processes in the feedback of high-latitude ecosystems to global climate. Separate workshops are planned to summarize the vegetation and water feedback to climate. The workshops will constitute the U.S. contribution to the International GeosphereBiosphere Programme effort to coordinate North American high-latitude research in global change.
This project will examine the processes for transfer of heat from the atmosphere into the permafrost at the Barrow Environmental Observatory on the North Slope of Alaska. Data loggers will be installed at 3 m depth in the soil at numerous sites to monitor the effects of moisture on heat transfer during the seasonal freeze/thaw cycle of the upper permafrost layer. The data will be used to establish how moisture and climate affect the permafrost so that the potential effects of climate change on the permafrost layer may be predicted. The research will test a new theory about the way permafrost responds to seasonal temperature changes in order to examine the role that global warming may play on the surficial frozen soil layer in the Arctic. The results are critically important to planning for the potential impacts of proposed climate change on the construction of buildings, roads, and other infrastructure in the Arctic.
This project addresses the central hypotheses of the Arctic System Science (LAII) Flux Study by examining spatial (local and regional) and temporal (interannual to interdecadal) variations in soil active layer thickness. This is done on representative landscapes by using different probing and soil coring approaches (grids, transects, and point data). Standard 1-km x 1-km grids are located in different landscape units across the Alaska Arctic Slope. The (LAII) sites, which are shared by other Flux Study projects, were selected in most cases based on availability of long-term data sets, including soil thaw and local climate records. The study relies upon high-frequency, site-specific determination of active layer thickness as a function of climate, soil properties and landscape units (geobotanical complexes). The historical boundary between the base of the recelt soil thaw and the upper permafrost is established by coring the frozen ground and observing the distribution and morphology of the ground ice. The thaw-depth measurements are used to validate or modify active layer models and to assess climate change upon the Arctic tundra ecosystem. The carbon status of the soils and near-surface permafrost are established across landscape units and serve as a basis for carbon balance extrapolations to regional scales.
The goal of this project is to quantify and to improve understanding of changes in carbon storage in terrestrial Arctic ecosystems. The balance between canopy and soil carbon cycling processes, and the interactions between them and soil moisture, will help determine whether the Arctic develops as an important sink or source for carbon. This project will focus specifically on modeling canopy carbon and water exchange, and synthesize information gathered in experimental components of existing programs. A hierarchy of models will be employed that will produce robust regional models of canopy carbon and energy exchange, derived from validated process-based models. The project will integrate information collected from the Toolik Lake LTER site, make linkages that will facilitate the construction of simpler and coarsely-scaled models of canopy process and create suitably scaled representations of canopy process for use by other regional modeling efforts.
This study proposes to elucidate the role of high-latitude ecosystems in the global carbon cycle and to assess the sensitivity and uncertainty of terrestrial carbon storage responses to transient changes in climate. The study will synthesize and integrate data from investigations of carbon cycling at local, regional, and global scales with the Terrestrial Ecosystem Model ((TEM)). Once the TEM is tested, the model will be run for the historical transient climate to compare estimated temporal and spatial variations in terrestrial carbon storage with those estimated by analysis of the historical record of atmospheric carbon dioxide. The results will be useful for identifying the uncertainty in carbon storage responses of high-latitude ecosystems and for assessing the effects of climate change in terrestrial systems.
The research project will examine the fluctuations in fresh water input into the Arctic by utilizing output from historical weather prediction models in the Arctic as a means for predicting climate variables in the region. The model output will be validated using observed data. The resulting calibrated models of Arctic temperature and precipitation, for example, will be used to examine the relationship between climate variables and fresh water input, circulation fields and sea-ice extent. The results of this project will provide a very important set of predicted climate parameters for regions where observational data is scarce, or absent. Therefore, the output of the derived data will serve as input for other models that require closely spaced observational data that is not available directly.
Researchers will examine the role of climate forcing and landscape character on the evolution of vegetation cover and soil carbon storage in the central Arctic foothills of Alaska. A combination of field methods, modeling and paleoreconstruction will be used to determine the spatial variation of ecosystem processes on different age landscapes. The results of this study will provide an indication of expected changes to the carbon balance in the Arctic due to changes in tundra ecology as a result of global climate change. The study is important for understanding the role of tundra as a source or reservoir of terrestrial carbon that may be added to, or extracted from, the atmosphere under proposed greenhouse climate conditions.
Investigators from the Marine Biological Laboratory and the University of Michigan propose to apply a new, computationally simple, modeling scheme to the problem of understanding the hydrological controls on terrestrial Arctic ecosystems. The model will allow researchers to calculate the flux of nutrients, gases and water through lakes, streams and entire watersheds so that the ecological response of the terrestrial vegetation may be examined. The development of a model to determine the flux of materials and water flow is urgently needed because the cost of observing and calculating the flow throughout the Arctic is prohibitive. The new model will be used in conjunction with global climate models to test the effects of changing climate scenarios on the response of vegetation in the Arctic. The Arctic is expected to feel the impact of global change to a greater degree than other places on Earth and the new modeling scheme will allow predictions of the ecosystem response on the landscape scale without the necessity to run complex models requiring prohibitively long computational times.
The proposed research will address a major problem in climate change research in the Arctic. The role of shifts in treeline due to past climate change will be examined using the relationships of modern treeline position with measured climate variables. The results from the study of predicted response of treeline position to climate changes in the past will then be used to examine changes that could take place due to proposed climate changes in the future. The consequences of feedback to climate change due to the movement of the treeline is important to ascertain so that management and policy decisions can be made concerning the impacts of global change and other disturbance factors on human use of forest resources in the Arctic.
The PIs propose to examine the climatic effects of a warming trend on the below-ground component of plant respiration. The results of this study will complement the results of a large study on the Alaskan North Slope that is examining the effects of global warming on the flux of carbon dioxide from plants and soil. The assessment of the below-ground component of the carbon dioxide flux will allow researchers to differentiate between the carbon dioxide flux due to respiration of living plants from that resulting from decay of organic matter incorporated into the frozen soil. This study will be an important component of ongoing studies relating the tundra ecosystem to climate in the Arctic.
The researchers will develop a new method for studying the annual cycle of glacial melting in relation to climate change. Satellite imagery will be used to examine large areas encompassing many glaciers rather than traditional methods of studying individual glaciers using time-consuming field measurements. The assessment of annual glacial melting rates is important because it may provide a precursor to climate change and the meltwater will contribute to a sea-level rise. That rise will have potentially serious effects on coastal human populations and must be examined if management policies are required to prepare for the rise.
The National Snow and Ice Data Center (NSIDC) proposes an (ARCSS) (Arctic System Science) Data Coordination Center to integrate management of data for (LAII), (OAII), GISP2, (PALE), and the emerging Arctic Archaeology component. In this three-year view, (NSIDC) envisions a distributed set of (ARCSS) data archives with data sets held in appropriate centers (including NSIDC), linked by NSIDC's "front end" coordination to ensure that (ARCSS)-funded researchers can easily obtain required data, and to guarantee archival of data they collect during (ARCSS). The "front end," or Data Coordination Center, will produce the results described below: (1) publishing of ARCSS and other Arctic data sets and products of importance to (ARCSS) science priorities in an (ARCSS) Catalog and in the Global Change Master Directory; (2) making (ARCSS) and other Arctic data sets and products easier to access and to use for research; (3) coordinating and managing (ARCSS) data sets within the framework of established and emerging U.S. and international data systems and centers; (4) establishing a data accession and archival system for (ARCSS) data sets and products at NSIDC; (5) developing and promulgating guidelines for data formats and documents, including (GIS) and model output data sets, within the (ARCSS) community; (6) delivering tailored data products, on CD-ROM, diskette, and via electronic file transfer delivering to (ARCSS) investigators; (7) working with the (ARCSS) Data Management Working Group, ARCSS Modeling Working Group, and (ARCSS) Science Steering Committees to identify data priorities for (ARCSS)-funded research; (8) facilitating exchange of information about data sets and data-related activities among members of the (ARCSS) community will be facilitation by an electronic bulletin board, newsletter, and information clearinghouse at NSIDC; and (9) initiating work on a geocryological database by capitalizing on recent opportunities to obtain data from the former Soviet Union.
With this award the Arctic Research Consortium of the United States (ARCUS) has entered into a three-year cooperative agreement with the NSF's Office of Polar Programs. This agreement will facilitate the continuing development, promotion and implementation of the Arctic System Science (ARCSS) Program, with special emphasis on integrating and synthesizing its various parts, and to broaden (ARCSS) so that it involves other presently neglected areas, such as the human aspect of global change. ARCUS will work to increase communication among Arctic researchers, academic institutions, federal agencies and logistical field facilities and projects; to inform policymakers, funding sources (federal agencies, private foundations and corporate bodies), and educators on the need, opportunities and benefits in Arctic research; and to improve offerings and programs in Arctic science education. ARCUS will facilitate an Arctic Week, combining several of these activities to increase participation of all interested Arctic groups and individuals, to foster interdisciplinary exchanges and to make the most effective use of available resources.
This award continues funding of the Polar Ice Coring Office at the University of Nebraska for support of scientific operations in Greenland and at other Arctic locations.