Asymmetry in the seasonal cycle of Antarctic sea ice driven by insolation

• Published in: Nature Geoscience
• Other Authors: Roach, Lettie A. (author), Eisenman, I. (author), Wagner, T.J.W. (author), Blanchard-Wrigglesworth, E. (author), Bitz, Cecilia M. (author)
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: Antarctic; Antarc*; Sea ice
• Online Access: https://doi.org/10.1038/s41561-022-00913-6

The mean seasonal cycle of Antarctic sea-ice extent is asymmetric, with the period of ice retreat being approximately two months shorter than the period of ice advance. This feature is largely consistent in observations from year to year and across different satellite products. The asymmetry is also broadly reproduced by comprehensive climate models across generations from CMIP3 to CMIP6, with limited impacts from internal variability. Using a range of idealized climate models of varying complexity, we show that the seasonal cycle in top-of-atmosphere incident solar radiation drives the asymmetry. Because insolation in southern high latitudes departs from a sinusoid by having a narrow peak of intense brightness in summer and a long period of low light in winter, there is rapid summer ice retreat and gradual winter ice advance. This simple physical explanation is markedly different from those proposed in previous studies. NA18NWS4620043B