|Manu||Date: Thursday, 26-November-2020, 3:53 AM | Message # 1|
|Ice sheets on the move: Evidence of the interconnectedness of global climate|
by Harvard University
To see how deeply interconnected the planet truly is look no further than the massive ice sheets on the Northern Hemisphere and South Pole.
Thousands of kilometers apart, they are hardly next-door neighbors, but according to new research from a team of international scientists—led by alumna Natalya Gomez Ph.D.'14, and including Harvard professor Jerry X. Mitrovica—what happens in one region has a surprisingly direct and outsized effect on the other, in terms of ice expanding or melting.
The analysis, published in Nature, shows for the first time that changes in the Antarctic ice sheet were caused by the melting of ice sheets in the Northern Hemisphere. The influence was driven by sea-level changes caused by the melting ice in the north during the past 40,000 years. Understanding how this works can help climate scientists grasp future changes and instability as global warming increases the melting of major ice sheets and ice caps, researchers said.
The study models how this seesaw effect works. They found that when ice on the Northern Hemisphere stayed frozen during the last peak of the Ice Age, about 20,000 to 26,000 years ago, it led to reduced sea-levels in Antarctica and a growth of the ice sheet there. When the climate warmed after that peak, the ice sheets in the north started melting, causing sea-levels in the southern hemisphere to rise. This rising ocean triggered the ice in Antarctica to retreat quickly to about the size it is today over thousands of years.
The question of what caused the Antarctic ice sheet to melt so rapidly during this warming period has been a long-standing enigma.
"That's the really exciting part of this," said Mitrovica, the Frank Baird Jr. Professor of Science in the Department of Earth and Planetary Sciences. "What was driving these dramatic events in which the Antarctic released huge amounts of ice mass? This research shows that the events weren't ultimately driven by anything local. They were driven by sea level rising locally but in response to the melting of ice sheets very far away. The study establishes an underappreciated connection between the stability of the Antarctic ice sheet and significant periods of melting in the Northern Hemisphere."
The retreat was consistent with the pattern of sea level change predicted by Gomez, now an assistant professor of earth and planetary sciences at McGill University, and colleagues in earlier work on the Antarctic continent. The next step is expanding the study to see where else ice retreat in one location drives retreat in another. That can provide insight on ice sheet stability at other times in the history and perhaps the future.
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