Ocean-driven warming along western may be partly driven by natural climate variability
By Summit Voice
SUMMIT COUNTY — Temperature oscillations in the tropical Pacific have historically had a significant effect on the climate of the western Antarctic Peninsula, according to scientists who studied a 12,000-year fossil record to measure how much glacial ice melted into the sea during that span.
The research is important because the western Antarctic Peninsula is one of the fastest warming regions on the planet, and the fastest warming part of the Southern Hemisphere. The ice sheets of the region may be vulnerable to collapse, and would raise sea level by several meters if the melt.
The study, led by Cardiff University researchers, measured oxygen isotopes in microscopic marine algae fossils to trace glacial ice entering the ocean along the western Antarctic Peninsula. Based on the data, the study concluded that the atmospheric temperatures had a bigger factor than oceanic circulation on warming along the western Antarctic Peninsula than oceanic circulation in the late Holocene (from 3,500-250 years ago).
But that was not always the case. Prior to 3,500 years ago — and in the modern environment. According to the study, the late Holocene atmospheric warming was cyclic (400-500 year long cycles) and linked to the increasing strength of the El Niño – Southern Oscillation phenomenon demonstrating an equatorial influence on high latitude climate.
“Our research is helping to understand the past dynamic behavior of the Antarctic Peninsula Ice Sheet,” said Dr Jennifer Pike, with the Cardiff University School of Earth and Ocean Sciences. “The implications of our findings are that the modern observations of ocean-driven warming along the western Antarctic Peninsula need to be considered as part of a natural centennial timescale cycle of climate variability, and that in order to understand climate change along the Antarctic Peninsula, we need to understand the broader climate connections with the rest of the planet.”
Ice that forms on land has a distinctive signature of oxygen isotopes. When a large amount of glacial ice is discharged into the coastal ocean, its alters the oxygen isotope ratio of the sea water. That change leaves a clear imprint in the fossils, revealing the environmental conditions of the time.
The scientists used the oxygen isotope ratio of the fossils to reconstruct the amount of glacial ice entering the coastal ocean in the past 12,000 years, and to determine whether the variations in the amount of ice being discharged were the result of changes in the ocean or atmospheric environment.
“Technologically the analysis of the oxygen isotope composition of diatom silica is extremely difficult. the British Geological Survey is one of a very few research organizations in the world that can undertake this type of analysis,” said Professor Melanie Leng, from the British Geological Survey and Chair of Isotope Geosciences in the Department of Geology, University of Leicester.
She said the methodology for the research project has been developed over the last five years with the specific aim of investigating the different amounts of melting in the polar regions.
The study was published this week in Nature Geoscience.