Revisiting the Linkages between the Variability of Atmospheric Circulations and Arctic Melt-Season Sea Ice Cover at Multiple Time Scales

The sharp decline of Arctic sea ice in recent decades has captured the attention of the climate science
community. A majority of climate analyses performed to date have used monthly or seasonal data. Here,
however, we analyze daily sea ice data for 1979–2016 using the self-organizing map (SOM) method to further
examine and quantify the contributions of atmospheric circulation changes to the melt-season Arctic sea ice
variability. Our results reveal two main variability modes: the Pacific sector mode and the Barents and Kara
Seas mode, which together explain about two-thirds of the melt-season Arctic sea ice variability and more
than 40% of its trend for the study period. The change in the frequencies of the two modes appears to be
associated with the phase shift of the Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation
(AMO). The PDO and AMO trigger anomalous atmospheric circulations, in particular, the
Greenland high and the North Atlantic Oscillation and anomalous warm and cold air advections into the
Arctic Ocean. The changes in surface air temperature, lower-atmosphere moisture, and downwelling longwave
radiation associated with the advection are consistent with the melt-season sea ice anomalies observed
in various regions of the Arctic Ocean. These results help better understand the predictability of Arctic sea ice
on multiple (synoptic, intraseasonal, and interannual) time scales.