Atmosphere and Ocean Impacts on Recent Western Arctic Summer Sea Ice Melt

Abstract

Summer sea ice in the western Arctic, specifically in the Chukchi and Beaufort Seas, has been rapidly declining during the last several decades. Annual minima in six recent Septembers (2007–2012) have witnessed the lowest western Arctic sea ice extents of the modern satellite era. The western Arctic summer sea ice has become less extensive amidst a fundamental transition from once widely prevalent and thick multi‐year ice to a thinner and readily melted first‐year ice cover. Questions remain for the Arctic climate research community involving the combination of factors that may be forcing these negative sea ice trends, particularly as current understanding of these complex ice–climate interactions evolves. Interannual variations of atmospheric pressure systems such as the Beaufort Sea High help determine the overlying wind direction and strength as well as the severity of summer ice cover. Atmospheric circulation teleconnections are important in sea ice variability but the role of some, such as the Arctic Oscillation, may in fact have changed as the western Arctic transitioned to a thinner ice cover. Reductions in summer sea ice extent became noticeable from 1998 onward and can be partly attributed to oceanic warming in the northern Pacific across the Bering Strait into the western Arctic. Warming of the northern Atlantic has had dramatic impacts in the Eurasian Arctic but a viable physical mechanism by which it can produce western Arctic ice melt is not yet established. Arctic warming induced by forcing from greenhouse gases is estimated to rival the impact of atmospheric teleconnections and helps produce the “Arctic amplification” of air temperatures that enhances summer sea ice melt. Late summer open water may in turn be altering the atmospheric circulation, weather and climate of subsequent autumn and winter seasons throughout the middle latitudes.

Assessing the climatic and environmental impacts of mid‐tropospheric anticyclones over Alaska

“…Additionally, low‐frequency fluctuations in North Pacific sea surface temperatures (SSTs), broadly characterized by the Pacific Decadal Oscillation (PDO), affect the Pacific Arctic climate (e.g. Liu et al ., ; Overland et al ., ; Ballinger and Rogers, ; Bieniek et al ., ; Screen and Francis, ), including 500 hPa height field behaviours over Alaska (Hartmann and Wendler, ), and therefore may relate to the incidence and intensity of upper‐air blocking patterns in the region.…”

Assessing trends in atmospheric circulation patterns across North America

“…The North region, centred on Alaska and the Yukon, is a region that has experienced large changes in atmospheric circulation in recent decades (Figure 7; McLeod et al ., 2018). In addition to the downstream implications of variability in this region, changes in CPs in this region are thought to be contributing to large sea‐ice loss in the Bering, Beaufort, and Chukchi Seas (Ballinger and Rogers, 2013; Ballinger and Sheridan, 2014; Walsh et al ., 2017; Ballinger et al ., 2019). While both the NARR and ERA5 show a decrease in winter‐dominant CPs, only the change in CP 23 is significant.…”

Resolving the Beaufort Sea High using synoptic climatological methods

“…The Beaufort Sea High (BSH) plays an important role in modulating lower troposphere temperatures and sea ice variability over the western Arctic during the melt season (Drobot and Maslanik, ; Ballinger and Rogers, ). This semi‐permanent pressure feature is apparent in the annual, spring, and summer pressure fields over the region and is linked to various atmospheric teleconnections that affect large‐scale Arctic climate (Serreze and Barrett, ; Overland et al , ).…”