Abstract
Abstract. After an unprecedented retreat, the total Arctic sea ice cover for the post-2007 period is characterized by low extent and a remarkable increase in annual cycle amplitude. We have identified the leading role of spring Bering Sea ice in explaining the changes in the amplitude of the annual cycle of total Arctic sea ice. In particular, these changes are related to the recent occurrence of multiyear variability in spring Bering Sea ice extent. This is due to the phase-locking of the North Pacific Gyre Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO) after about 2007, with a correlation coefficient reaching −0.6. Furthermore, there emerge notable changes in the sea level pressure and sea surface temperature patterns associated with the NPGO in the recent decade. After 2007, the NPGO is related to a quadrupole of sea level pressure (SLP) anomalies that is associated with the wind stress curl and Ekman pumping rate anomalies in the Bering deep basin; these account for the change in Bering Sea subsurface variability that contribute to the decadal oscillation of the spring Bering Sea ice extent.
Highlights
The Arctic sea ice is an integral part of the Arctic climate system as well as one of the strongest indicators of global climate change
During the 1999–2006 period sea ice declines with a dramatic rate of over −0.13 million km2 yr−1, such that the climatology of total Arctic sea ice extent drops from ∼ 13 million km2 for the 1979–1998 period to ∼ 11.6 million km2 for the post-2007 period
All these signals herald the transition to another Arctic climate regime, which is a hot topic in the climate research community (Livina and Lenton, 2013; Bathiany et al, 2016b)
Summary
The Arctic sea ice is an integral part of the Arctic climate system as well as one of the strongest indicators of global climate change. While previous studies mostly considered the signal of abrupt Arctic climate change in terms of rapid sea ice decline and the amplifying seasonal cycle, few of them focused on the regional and seasonal dependence of Arctic sea ice variations. Onarheim et al (2018) noted the distinct transformation of seasonal sea ice variability in various Arctic regional seas and predicted the increase and expansion of ice-free periods into the Arctic in the future These results indicate that Arctic sea ice variations are asymmetrical and strongly dependent on the local physical process, resulting in the complexity and difficulty in predicting the future Arctic climate change. It is urgent to understand the physical mechanisms accounting for the recent amplifying seasonal cycle of Arctic sea ice cover, so as to better foresee future Arctic climate change
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