Effects of Arctic Sea Ice Decline on Weather and Climate: A Review

Abstract

The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia.

The Impact of Regional Arctic Sea Ice Loss on Atmospheric Circulation and the NAO

“…The upward heat flux is driven by the large wintertime temperature gradient between ocean and atmosphere, which persists in our experiments, although the SST is allowed to cool below freezing. This key role of the turbulent heat flux and the related delayed warming agrees with several other studies of sea ice loss Screen et al 2013;Vihma 2014). Increased longwave loss from the surface also contributes to the surface-based warming, but the longwave flux change amounts to only one-third of the turbulent changes during winter (cf.…”

“…Previous studies have indeed indicated that the largescale circulation could be affected by sea ice loss (Bader et al 2011;Vihma 2014). Depending on the mechanisms behind potential remote changes, the different sea ice scenarios simulated here may lead to different circulation shifts.…”

“…Despite varying conclusions, there seems to be widespread agreement that Arctic sea ice loss favors the negative mode of the NAO (Vihma 2014). In our experiments, the NAO index shows no significantly different response to the varying patterns of sea ice loss (not shown), but further analysis reveals that the circulation pattern is indeed affected.…”

“…These characteristics mean that sea ice loss initiates feedbacks that contribute directly to Arctic amplification of near-surface warming (Serreze et al 2009;Screen and Simmonds 2010;Serreze and Barry 2011). Furthermore, Arctic sea ice loss has been linked to climatic changes at lower latitudes through shifts in the oceanic and atmospheric circulation (Bader et al 2011;Vihma 2014). The remote changes, however, remain challenging to interpret and the mechanisms are still subject to investigation (Francis and Vavrus 2012;Screen and Simmonds 2013;Barnes 2013;Wallace et al 2014).…”

Winter 2015/16: A Turning Point in ENSO-Based Seasonal Forecasts

“…A strong polar vortex is a plausible explanation for the poleward-displaced jet stream during winter 2015/16, despite a record strong El Niño that favors just the opposite response. Two of the proposed Arctic boundary influences on weather patterns in lower latitudes are changes in Arctic sea ice coverage (Honda et al, 2009;Overland et al, 2011;Vihma, 2014) and in Eurasian snow cover (Cohen and Entekhabi, 1999;Cohen et al, 2007;Allen and Zender, 2011). The atmospheric response most closely associated with these factors is variability in the strength of the Siberian high (Cohen et al, 2014a).…”