Atmospheric forcing of sea ice in Hudson Bay during the spring period, 1980–2005

In this study we show recent trends in sea ice concentration (SIC) and sea ice extent (SIE) in Hudson Bay (HB) using Canadian Ice Service (CIS) data and passive microwave (PMW) data for the spring period, week of year (WOY) 24–30. Reductions in sea ice concentration and sea ice extent are examined in light of thermodynamic and dynamic forcing of sea ice.Results show surface air temperature (SAT) anomalies surrounding Hudson Bay have been increasing by 0.26 to 0.30 °C/decade from 1960 to 2005 accompanied by negative trends in SIC (− 15.1 to − 20.4%/decade) in western and southwestern Hudson Bay. SIE trends are negative with reductions ranging from − 8790 to − 10,035 km²/year depending on WOY.East–west asymmetry in SIC anomalies in Hudson Bay is investigated in the context of dynamic and thermodynamic phenomena, namely surface winds that drive sea ice circulation as monitored by relative vorticity, and SAT. Sea ice vorticity is linked to variations in atmospheric pressure and resultant changes in mean wind patterns over Hudson Bay. Variations in SIC across Hudson Bay are shown to be significantly related to spring and fall (lag − 1 year) SATs and the zonal (east–west) component of surface winds. Spring and fall SATs together with relative vorticity are also shown to be highly predictive of SIEs, while late in the melt season spring SAT anomalies are the most predictive.

Research highlights
► Spring surface air temperature (SAT) anomalies surrounding Hudson Bay have been increasing by 0.26 to 0.30 °C/decade from 1960 to 2005.
► Negative trends in SIC noted in western and southwestern Hudson Bay (− 15.1 to − 20.4%/decade), 1980–2005.
► An east–west asymmetry in sea ice concentrations across Hudson Bay is linked to relative vorticity of sea ice.
► Interannual sea ice extent in Hudson Bay a function of both fall (SON lag – 1 year) and spring SATs (AMJ) and relative vorticity of sea ice (R2 = 0.84).