From the CO2Science archive: In a recent study of Antarctic sea ice extent (SIE), Turner et al. (2016) note that Arctic sea ice reached a new record minimum extent in September 2012; but they also write that “during the same month sea ice over the Southern Ocean attained a new maximum extent,” citing Turner et al. (2013) and stating that “the differences in SIE between the two polar regions are getting larger.” And a further problem, as they continue, is that “the majority of coupled climate models when run over recent decades with observed forcings have Antarctic sea ice decreasing in a manner similar to Arctic Sea ice,” citing Eisenman et al. (2011) and suggesting, therefore, that “some process is not included in the current generation of climate models.” In further commenting on these findings, the five researchers say “the fact that the Southern Hemisphere sea ice has increased over the last 35 years while 95% of the climate model ‘historical’ runs over this period have sea ice decreasing is unexpected.” So what’s going on here?
Paper reviewed: Turner, J., Hosking, J.S., Marshall, G.J., Phillips, T. and Bracegirdle, T.J. 2016. Antarctic sea ice increase consistent with intrinsic variability of the Amundsen Sea Low. Climate Dynamics 46: 2391-2402.
Turner et al. logically speculate that “there may be some mechanism missing from the current generation of climate models that is critical in simulating the increase of Antarctic sea ice over recent decades.” But they note that quantifying the contributions from these different forcing factors and relating them to the observed changes since 1979 presents a number of problems,” especially since tropical high-latitude teleconnections are said by them to be “poorly represented in many climate models” and that “it is difficult to conduct experiments that isolate individual factors in a realistic manner.”
And so it is that the conundrum remains a conundrum.
Eisenman, I., Schneider, T., Battisti, D.S. and Birz, C.M. 2011. Consistent changes in the sea ice seasonal cycle in response to global warming. Journal of Climate 24: 5325-5335.
Turner, J., Bracegirdle, T.J., Phillips, T., Marshall, G.J. and Hosking, J.S. 2013. An initial assessment of Antarctic sea ice extent in the CMIP5 models. Journal of Climate 26: 1473-1484.