Connections Between Increased Incidence of US Summer Heat Waves and Sea Ice Decline in Hudson Bay

Recent studies point to a significant rise in the number of summer extreme weather events that correspond with the presence of amplified quasi-stationary mid-tropospheric planetary waves and overall weakened atmospheric circulation in the Northern Hemisphere and also coincide with reduced summer Arctic sea ice cover. This study explores the interannual connections between 1979-2016 summer heat wave frequency across the United States and relatively low summer sea ice cover in the Hudson Bay region. Increased frequencies of summer heat waves coincide with unseasonably warm conditions developed and sustained by the presence of an omega blocking pattern situated over the southern U.S. throughout summer. The block appears immediately following anomalous atmospheric warming and reduced mean zonal winds observed throughout spring over northeastern Canada, the northwestern Atlantic basin, and Greenland. Spring pre-conditioning of the low summer ice cover on Hudson Bay is favored by the presence of a strong negative phase of the North Atlantic Oscillation and positive Greenland Blocking Index with unseasonably warm sea surface temperatures throughout north Atlantic Arctic waters reflective of the positive phase of the Atlantic Multidecadal Oscillation.