Arctic Sea Ice and Large-Scale Atmospheric Teleconnections Associated with Greenland Blocking
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Sea ice is a critical component of the cryosphere (regions of the Earth where water exists as ice) as it helps to maintain Earth’s heat and energy balance, in part, through reflecting incoming shortwave radiation during summer back into space. Due to global warming, Arctic (≥60°N) temperatures are increasing at twice the rate of the rest of the world, a phenomenon known as Arctic Amplification (AA), and because of this, both the Arctic sea ice and atmosphere have experienced greater variability and extreme conditions. Sea ice extent (SIE) and area (SIA) have steadily diminished since the 1970s, but more persistent and accelerated rates of sea ice loss have been observed since the mid-1990s. The loss of sea ice has affected the Arctic climate, but also has implications for regions of the Northern Hemisphere (NH), including the mid-latitudes (30°–60°N). Atmospheric circulation changes have been observed and associated with the loss of sea ice. These changes have been linked with increased extreme weather such as cold air outbreaks over regions of North America (NA), and more frequent blocking episodes over Greenland and the North Atlantic Ocean.
The goal of this research was to assess the potential for Arctic sea ice influence on mid-latitude weather extremes via Greenland blocking. This study is comprised of two parts: the first tested monthly associations between regional Arctic SIE and SIA, and the Greenland blocking time series (as represented by the Greenland Blocking Index; GBI); and the second examined GBI linkages with anomalous weather patterns across NA in those years with extreme sea ice and GBI conditions. Statistical associations from part one were further analyzed in part two through composites of synoptic atmospheric circulation variables (i.e. geopotential height, surface air pressure and temperature, and precipitable water) to draw physical associations to the co-variability of sea ice, blocking patterns, and southward climate conditions over NA.
It was found that two Arctic marginal seas, Baffin Bay and the Beaufort Sea, produced the greatest and second greatest number of months with statistically significant associations, respectively. The composite analyses for minimum sea ice and maximum GBI for both Baffin Bay and the Beaufort Sea produced greater instances of anomalously negative values for geopotential height, and surface air pressure and temperature in the mid-latitude region, while precipitable water shows a more mixed response; and greater instances of anomalously positive values for regions of the Arctic for all variables. This study concluded that there are not only statistical links between changing sea ice patterns over certain Arctic marginal seas with increased Greenland blocking episodes, but also that those years of sea ice and blocking extremes can affect mid-latitude weather variables in some months of the year.