Abstract
Abstract. The record sea ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric thermodynamics. Here, we facilitate comparisons in the evolution of the thermodynamic state of the Arctic atmosphere during these two SIM events using a decade-long AIRS observational record (2003–2012). It is shown that the meteorological conditions during 2012 were not extreme, but three factors of preconditioning from winter through early summer played an important role in accelerating sea ice melt. First, the marginal sea ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea ice melt. All these factors may have lead the already thin and declining sea ice cover to pass below the previous sea ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea ice melting events in the Arctic.
Highlights
Context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA’s Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric thermodynamics
The results suggest that sateMllietet-hbaosdedsmaonnidtoring of atmospheric mation ipnrepcroenddicittiionnginegxtrceoDmulaedtsabeeaSaicycesrimttiecealmtlinssgouervceenotsf inforin the predictions of such extreme events in the future
It is important to investigate how the atmosphere manifests itself during record minimum events so as to understand commonalities and differences, which can further be exploited to improve prediction skills of such events and to study and model relevant processes
Summary
In the winter of 2006–2007, the Arctic Oscillation (AO), the most dominant mode of variability over the Arctic, was in the positive phase during December, January and March and was in the negative phase during February 2007. There were little significant surface temperature anomalies over northern Canada and the Canadian archipelago during December and January 2011–2012 (Fig. 3), consistent with the dominant low geopotential height anomalies over those regions (Fig. 2). These anomalies indicate that the significant warming signal observed at the surface during 2011–2012 over the Eurasian regions exceeded the 1-sigma level from the surface up to 400 hPa, and the cooling over the North American continent was present through a majority of the atmosphere (Fig. 4). Unlike 2011–2012, the significant surface warming during January 2007 over Eurasia extended vertically but over a shallower atmospheric layer above the surface, while the same region experienced a deep anomalous cooling during the following month of February (Fig. 4). This resulted in a warmer and moister Eurasia and neighbouring seas and a cooler, drier atmosphere over North American neighbouring seas during winter 2011–2012
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