Clearer picture of the Antarctic ice cap in the mid-Miocene – sciencedaily

Last month, the average concentration of atmospheric carbon dioxide (CO2) soared to nearly 418 parts per million, a level not seen on Earth in millions of years. In order to get an idea of ​​what our future might hold for us, scientists looked to the deep past. Now, new research from the University of Massachusetts at Amherst, which combines climate model, ice cap and vegetation simulations with a suite of different climatic and geological scenarios, opens the clearest window to date on the deep history of the Antarctic ice cap and what our planetary future might hold.

The Antarctic ice sheet has aroused particular interest in the scientific community because it is “a backbone of the Earth’s climate system, affecting everything from ocean circulation to climate,” says Anna Ruth Halberstadt, PhD student in geosciences and responsible for the author article , recently published in the newspaper Earth and Planetary Science Letters. In addition, the ice sheet contains enough frozen water to raise the current sea level by 57 meters.

Yet it has been difficult to accurately reconstruct the Miocene Antarctic climate. Researchers can run models, but without geological data to verify models, it is difficult to choose which simulation is correct. Conversely, researchers can extrapolate from geological data, but these data points only offer local snapshots, not a broader climate context. “We need both models and geological data to know anything,” says Halberstadt. There is one final complicating factor: geology. Antarctica is cut in half by the Transantarctic Mountains, and any clear picture of Antarctica’s deep history must be able to capture the continent’s slowly rising mountain range. “Without knowing the elevation,” says Halberstadt, “it is difficult to interpret geological data”.

Halberstadt and his colleagues, including researchers in New Zealand and the UK, devised a unique approach in which they coupled an ice cap model to a climate model, while simulating the types of vegetation that grow in each. climate model scenario. The team used historical geological data sets that included known paleoclimatic data points such as past temperature, vegetation, and glacial proximity, to compare their modeled climates. Next, the team used their benchmark model runs to make inferences about CO2 and tectonic model scenarios satisfying known geological constraints. Finally, Halberstadt and his colleagues extrapolated glacial conditions to the scale of the continent.

The research, which was supported by the NSF, reconstructed a thick but diminished ice cap under the warmest environmental conditions of the mid-Miocene. In this model, although the margins of the Antarctic ice sheet have retreated considerably, more precipitation has led to thickening of the interior regions of the ice sheet. The team’s modeling further suggests that the ice over the Wilkes Basin region of Antarctica advanced during ice ages and retreated during interglacials. The Wilkes Basin is the region considered particularly sensitive to future warming and could contribute to future sea level rise.

“The Antarctic paleoclimate,” says Halberstadt, “is fundamental to understanding the future”.

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