![]() "Our observation of this rapid volatility of the Antarctic ice sheets raises the interesting question of what's causing it," says Nick Sullivan, a 2022 UW-Madison PhD graduate who led the analysis for his dissertation research. ![]() That is much more rapidly than can be explained by periodic shifts in the planet's orbit and rotational axis, known as Milankovitch cycles, which typically advance slowly, altering Earth's climate and ice sheets over tens or hundreds of thousands of years. This new evidence, published recently in the Proceedings of the National Academy of Sciences, indicates that between about 19.2 and 18.8 million years ago, the ice sheets grew and receded multiple times over cycles of just a few thousand years. While fluctuations in Antarctica's ice sheets have, over the span of millions of years, grown and diminished at regular intervals tied to natural oscillations in Earth's journey in orbit, researchers at the University of Wisconsin-Madison and their collaborators around the world have uncovered evidence that Antarctica's ice sheets grew and shrank more frequently during the Miocene epoch than was previously known. Their fate has profound consequences for life nearly everywhere on Earth. Together, the ice sheets lock a volume of water equivalent to more than 50 meters of sea level rise and influence ocean currents that affect marine food webs and regional climates. Identifying how and why Antarctica's major ice sheets behaved the way they did in the early Miocene could help inform understanding of the sheets' behavior under a warming climate. ![]()
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