Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice

Warming of the north and tropical Atlantic Ocean, which is associated in part with the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability), is shown to affect sea-level pressure in the Amundsen Sea, explaining the accelerated warming of and sea-ice redistribution around the Antarctic Peninsula. An Atlantic influence on Antarctic climate The Antarctic climate is known to be influenced by distant climate conditions, particularly in the Pacific Ocean. So far, however, the causes of the accelerated warming on the Antarctic Peninsula and the redistribution of Antarctic sea ice have remained unclear. Xichen Li and colleagues now show that sea-level pressure changes in the Amundsen Sea — which affect temperature on the Peninsula and sea-ice distributions — can be traced to sea-surface temperature variations caused by the Atlantic Multidecadal Oscillation, a persistent driver of climate variability in the tropical and north Atlantic. In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming 1 , 2 of any region on the planet, causing rapid changes in land ice 3 , 4 . Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution 5 , 6 . Antarctic climate is influenced by, among other factors, changes in radiative forcing 7 and remote Pacific climate variability 8 , 9 , but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation 10 , 11 (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen–Bellingshausen–Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation 6 and sea-level change 3 , 12 .