More ice cover may lead to higher water levels
Near record level ice cover topping 90 percent recently over the Great Lakes could help reduce evaporation and contribute to higher lake levels. NOAA and the U.S. Army Corps of Engineers this week forecast that Great Lake water levels will be closer to average over the next six months and higher than last year on most of the lakes. A similar pattern occurred in 1996 when the Great Lakes experienced severe ice cover of more than 80 percent. Water levels were higher in 1997 on all but Lake Superior where they were largely unchanged. To get the latest ice cover click here. To learn more about how Great Lakes ice affects water levels click here.
As people who live along our nation’s coast experience rising sea levels, residents along the Great Lakes – the Earth’s largest lake system – are adapting to the opposite problem: chronic low water levels and a receding shoreline.
In a perspective now running in Science magazine, Drew Gronewold, a hydrologist at NOAA’s Great Lakes Environmental Research Laboratory, says “the record low water levels in Lake Michigan-Huron in the winter of 2012 to 2013 raise important questions about the driving forces behind water level fluctuations and how water resource management planning decisions can be improved.”
Answers to these questions are in high demand given the profound impact low water levels have on the Great Lakes region and the North American economy. Low levels limit navigability of shipping channels, reduce hydropower capacity, (e.g. at Niagara Falls, the largest electricity producer in New York state), impede tourism and recreational activities, and increase operational risks for industries that rely on the lakes as a source of process and cooling water.
A key question is what is causing the recent record low water levels. Answering this question can help planners adapt to these fluctuations and plan appropriate strategies. Research led by Gronewold and the hydrology team at NOAA’s Great Lakes Environmental Lab focuses on differentiating the range of drivers behind the recent record low water levels. Gronewold notes that most of the episodic changes in Great Lakes water levels over the past century closely correspond to changes in annual precipitation. However, the abrupt and sustained water level drop in the late 1990s is more closely related to increased lake surface water temperature and greater evaporation, both of which coincided with one of the strongest El Niño events on record. Strong El Nino events typically lead to abnormally mild winters and warmer surface waters in the Great Lakes.
Water levels dropping
Rising water temperature and evaporation contributes to decline in lake levels. The vertical gray bar represents the period of El Niño influenced warming. (NOAA)
The important question today is whether the recent water level drops are due to El Nino, part of a progressive decline resulting from global climate change or linked to engineering modifications of the Great Lakes. To get at answers, NOAA-GLERL works as part of a regional team to improve historical estimates, real-time measurement, and projections of Great Lakes over-lake evaporation and lake-wide surface water temperature. Scientists have based their analysis on computer models using measurements from a relatively sparse network of shore-line based stations and off-shore buoy- and island-based stations. Of the off-shore stations, many are seasonal buoys deployed between May and November.
A network of monitoring stations records water temperatures and data to estimate evaporation. It includes shoreline (red) and off-shore (yellow) stations. (NOAA)
“We’ll be reducing the uncertainties due to relatively sparse over-lake stations by expanding our network of year round off-shore monitoring stations, including buoy-, lighthouse-, and vessel-based sensors to track meteorological and atmospheric conditions,” Gronewold says. Within the past five years, for example, six monitoring towers have been installed on remote lighthouses across the Great Lakes to increase our capacity to measure water loss from evaporation. Scientists have explored – though not yet routinely implemented – buoy-based sensors that could increase the spatial resolution of evaporation-related measurements substantially. Findings from these new monitoring platforms may help to improve our understanding of the water budget and of the drivers of water loss from Lakes Superior and Michigan-Huron.
“As the need intensifies to adapt to climate-induced changes, so does the need for better tracking and forecasting the Great Lakes water level fluctuations to support water resource managers and ultimately the region’s economy,” Gronewold says.
Click here to read the Perspective in Science on Great Lakes water levels.
For more information, please contact Monica Allen, director of public affairs for NOAA Research at 301-734-1123 or by email at email@example.com