Abstract
Despite global warming and Arctic sea-ice loss, on average the Antarctic sea-ice extent has not declined since 1979 when satellite data became available. In contrast, climate model simulations tend to exhibit strong negative sea-ice trends for the same period. This Antarctic sea-ice paradox leads to low confidence in 21st-century sea-ice projections. Here we present multi-resolution climate change projections that account for Southern Ocean mesoscale eddies. The high-resolution configuration simulates stable September Antarctic sea-ice extent that is not projected to decline until the mid-21st century. We argue that one reason for this finding is a more realistic ocean circulation that increases the equatorward heat transport response to global warming. As a result, the ocean becomes more efficient at moderating the anthropogenic warming around Antarctica and hence at delaying sea-ice decline. Our study suggests that explicitly simulating Southern Ocean eddies is necessary for providing Antarctic sea-ice projections with higher confidence.
Highlights
Despite global warming and Arctic sea-ice loss, on average the Antarctic sea-ice extent has not declined since 1979 when satellite data became available
When considering the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble of models, we find evidence that simulated historical (1979–2018) sea-ice trends depend on the resolution of the ocean model used in the Southern Ocean
We show that a HR climate model is capable of simulating a stable Antarctic sea-ice cover over the past few decades in CMIP-type simulations—consistent with available satellite data
Summary
Despite global warming and Arctic sea-ice loss, on average the Antarctic sea-ice extent has not declined since 1979 when satellite data became available. 1979, previous studies have proposed various mechanisms such as decadal wind trends associated with the Southern Annular Mode (SAM)[10] and variability of the Amundsen Sea Low[11,12], dynamic sea-ice transport changes[13,14,15,16], recent absence of deep open-ocean convection[17,18], additional meltwater from the Antarctic ice sheet and ice shelves[19,20,21], and internal variability of tropical origin[22,23] While some of these factors are likely to contribute to the slightly positive real-world trend, here we argue that mesoscale dynamical processes in the ocean play a critical role for explaining a delayed
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