On assessment of the relationship between changes of sea ice extent and climate in the Arctic

An increase of surface air temperature (SAT) in the marine Arctic (a part of the Arctic covered with sea ice in winter) shows a good relationship with reduction of sea ice extent (SIE) in summer. For instance, a strong correlation (a coefficient equal to -0.93) was found between the summer SAT in the marine Arctic and satellite-derived 1980-2014 September sea ice index (the average of SIE in the Arctic since 1978, in millions of km(2)). Based on this finding, anomalies of Arctic September SIE were reconstructed from the beginning of 20th century using a linear regression relationship. This reconstructed SIE shows a substantial decrease in the 1930-1940s with a minimum occurring in 1936, which, however, is only a half of the decline in 2012. The strong relationship between the summer SAT and September SIE was used to assess the onset of summer sea ice disappearance in the Arctic Ocean. According to the estimates made with a simple regression model, we can expect a seasonally ice-free Arctic Ocean as early as in the mid-2030s. An impact of the inflow of warm and salty Atlantic water (AW) on winter SIE was evaluated as an example for the Barents Sea. This evaluation reveals a coherent spatial pattern of the AW spreading, presented by surface salinity distribution, and the position of sea ice edge, and significant correlation between the inflow of the AW and maximal SIE. This publication presents a revised version of an 'Arctic sea ice extent in changing climate' report (Alekseev et al., 2015).