Weltnachrichten – AU – Ice sheets in motion: How the north and south poles connect

PICTURE: Polar ice sheets develop on different time scales and are in constant flux, with the ice growing and retreating depending on the climate and the surrounding water levels. RECOGNITION:. . .

In the last 40. 000 years ago, ice sheets that are thousands of kilometers apart have influenced each other due to changes in sea level, according to research published today in Nature. The new modeling of ice sheet changes during the last glacier cycle by a team led by McGill provides a clearer understanding of the mechanisms that drive change than before and explains newly available geological records. The study shows for the first time that changes in the Antarctic ice sheet during this time were caused by the melting ice sheets in the northern hemisphere.

As the climate cooled, water was trapped in the land ice of the northern hemisphere during the last ice age, causing the sea level in Antarctica to drop and the ice sheet to grow as a result. As the climate warmed, the retreating ice in the northern hemisphere, as in the time of de-icing, led to a rise in the water level in Antarctica, which in turn led to a retreat of the Antarctic ice cover.

« Ice sheets can interact over great distances because of the water flowing between them, » explains senior author Natalya Gomez of the McGill Department of Earth and Planetary Sciences. « It’s like talking to each other through changes in sea level. « 

« Polar ice sheets are not just large, static icebergs. They develop on different time scales and are in constant flux, with the ice growing and retreating depending on the climate and the surrounding water level, « explains Gomez. « They gain ice when snow accumulates on them, then spreads outward under their own weight and flows into the surrounding ocean, where their edges break off into icebergs. « 

To examine the mechanisms that drive changes in the Antarctic ice sheet across geological time scales, the study relies on numerical models and a wide range of geological records, from sediment cores from the seabed near Antarctica to records of land exposure and past coasts.

With this information, the researchers were able to identify changes in sea level and ice dynamics in both hemispheres for the first time in the last 40. Simulate 000 years simultaneously. This timeframe provides the basis for a comprehensive understanding of the effects of climate factors on the ice cover, as it covers the period up to the height of the last ice age between 26. 000 and 20. 000 years to date.

The records suggest that there ice loss from the Antarctic ice sheet was significant during this period, with intermittent periods of accelerated retreat. The researchers found that the only mechanism that could explain this response was changes in sea level in Antarctica caused by changes in the ice sheet in the northern hemisphere.

« We have in the last 20. 000 years ago, we found a very variable signal for the loss of the ice mass left by icebergs that break off the Antarctic and melt in the surrounding oceans, « says Michael Weber from the Department of Geochemistry and Petrology at the University of Bonn. « This evidence could hardly be reconciled with existing models until we explained how the ice sheets in both hemispheres interact with each other around the world. « 

« The extent and complexity of the ice sheets and oceans, as well as the mysteries of Earth’s past climates contained in the geological records, are fascinating and inspiring, » Gomez concludes. « Our results show how closely the Earth system is interconnected, with changes in one part of the planet causing changes in another. In modern times we have not seen the kind of great ice sheet retreat that we might see in our future warming world. A look at records and models of changes in the earth’s history can tell us about this. «  »

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Ice cover of Antarctica, sea level rise, climate change, Antarctica