The two polar regions of the Arctic and Antarctic are actually two very different regions and are also almost 40,000 kilometres apart. The two regions also react differently to the current climatic changes. While the Arctic is melting away almost uniformly, West and East Antarctica show different reactions. East Antarctica in particular, with its larger ice sheet, still seems to be more stable. But what is happening in the Arctic is affecting the ice sheet stronger than previously thought, as two independent studies show.
Both studies, published shortly after each other, showed that in the past, the melting of Arctic glaciers due to climate changes had also negatively affected the Antarctic ice sheets. The main factor was the sea level, which rose rapidly due to the melting of glaciers in the Arctic. As a result, warmer water reached Antarctica and melted the edges of the ice sheets from below. Thereby, huge icebergs broke off and melted in the surrounding Southern Ocean and thus amplifying the effect.
The study, published last week by Natalya Gomez of McGill University and her colleagues in the journal Nature, simulated the behavior of ice sheets and sea levels using numerous geological data from sediment samples from the Antarctic seabed and soil samples and data of exposed soils in Antarctica. They mainly focused on the period from 26,000 to 20,000 years. That was the time period when the last ice age had built up. “We found a very variable signal of ice-mass loss over the last 20,000 years, left behind by icebergs breaking off Antarctica and melting down in the surrounding oceans,” explains co-author Michael Weber from the University of Bonn. “This evidence could hardly be reconciled with existing models until we accounted for how the ice sheets in both hemispheres interact with one another across the globe.” Their simulation proved that sea level was the link between events in the Arctic and Antarctic. “Ice sheets can influence each other over great distances due to the water that flows between them,” explains Natalya Gomez. “It’s as though they were talking to one another through sea level changes.”
The second study, conducted by Dr. Kim Jakob and a german-British team, examined sediment samples from the Atlantic that had been obtained as part of a multidisciplinary drilling program. Using these samples, the group was able to reconstruct changes in global sea level over the period between 2.8–2.4 million years ago. During this period, CO2 concentrations had dropped from soon-to-reach levels to levels in line with our pre-industrialised world. The results showed that sea levels had peaked at the beginning, primarily due to the melting of glaciers in the northern hemisphere. At the same time, the researchers found that the East Antarctic ice sheet also melted during this time. As global sea levels rose again, the ice sheet stabilized. Their models showed that not only the sun’s radiation and the CO2 concentration could be considered as a factor for this behavior, but also the sea level. Because, as the sea level drops, the authors write, the edges of the ice sheet were less exposed to the warm water masses. Both studies warn that the current situation may destabilize the Antarctic ice sheets again.
Dr Michael Wenger, PolarJournal
Links to the studies:
K.A. Jakob, P.A. Wilson, J. Pross, T.H.G. Ezard, J. Fiebig, J. Repschläger, O. Friedrich: A new sea-level record for the Neogene/Quaternary boundary reveals transition to a more stable East Antarctic Ice Sheet. PNAS (2020). https://doi.org/10.1073/pnas.2004209117
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