Abstract
In this paper, we examine sea surface temperatures (SSTs) and sea ice conditions in the Hudson Bay Complex as a baseline evaluation for the BaySys 2016–2018 field program time frame. Investigated in particular are spatiotemporal patterns in SST and sea ice state and dynamics, with rankings of the latter to highlight extreme conditions relative to the examined 1981–2010 climatology. Results from this study show that SSTs in northwestern Hudson Bay from May to July, 2016–2018, are high relative to the climatology for SST (1982–2010). SSTs are also warmer in 2016 and 2017 than in 2018 relative to their climatology. Similarly, unusually low sea ice cover existed from August to December of 2016 and July to September of 2017, while unusually high sea ice cover existed in January, February, and October of 2018. The ice-free season was approximately 20 days longer in 2016 than in 2018. Unusually high ice-drift speeds occurred in April of 2016 and 2017 and in May of 2018, coinciding with strong winds in 2016 and 2018 and following strong winds in March 2017. Strong meridional circulation was observed in spring of 2016 and winter of 2017, while weak meridional circulation existed in 2018. In a case study of an extreme event, a blizzard from 7 to 9 March 2017, evaluated using Lagrangian dispersion statistics, is shown to have suppressed sea ice deformation off the coast of Churchill. These results are relevant to describing and planning for possible future pathways and scenarios under continued climate change and river regulation.
Highlights
In a companion paper (Lukovich et al, 2021), we examined atmospheric and river discharge conditions in the Hudson Bay Complex (HBC) from 2016 to 2018 relative to the 1981–2010 climatology as “input” to the Arctic and Northern Hemisphere Atlantic configuration of the Nucleus for European Modelling of the Ocean (NEMO)/ LIM2 ice-ocean model and the Hudson Bay System Study (BaySys)
Freshwater and heat budgets are central to an understanding of changes in Hudson Bay (HB), with water mass balance determined by input from Arctic waters, river discharge, and sea ice melt (Prinsenberg, 1984; Ingram and Prinsenberg, 1998; St-Laurent et al, 2012; Carmack et al, 2016)
Hochheim and Barber (2010) showed that fall freeze-up/sea ice formation begins near Week 45 until complete ice coverage, exceeding 20%–30%, in Week 48; spring breakup occurs near Week 23, with variability between years due to differences in summer and autumn winds, air temperature, cloud cover, and snow cover (Hochheim et al, 2011)
Summary
In a companion paper (Lukovich et al, 2021), we examined atmospheric and river discharge conditions in the Hudson Bay Complex (HBC) from 2016 to 2018 relative to the 1981–2010 climatology as “input” to the Arctic and Northern Hemisphere Atlantic configuration of the Nucleus for European Modelling of the Ocean (NEMO)/ LIM2 ice-ocean model and the Hudson Bay System Study (BaySys). Hochheim and Barber (2010) showed that fall freeze-up/sea ice formation begins near Week 45 until complete ice coverage, exceeding 20%–30%, in Week 48; spring breakup occurs near Week 23, with variability between years due to differences in summer and autumn winds, air temperature, cloud cover, and snow cover (Hochheim et al, 2011) Highlighted in both studies was east–west asymmetry in SIC anomalies associated with surface winds. Because the magnitude of density-driven currents is proportional to the runoff rate, Prinsenberg (1983) noted that hydroelectric developments that increase winter runoff will increase winter circulation In this baseline study, we examine sea ice and oceanographic conditions during the BaySys time frame using reanalysis products. The case study for the March 2017 blizzard is presented in Section 3.3, as an example of an extreme event which, in a storylines approach to describing possible future pathways and scenarios based on an assessment of a range in plausible outcomes and compound extreme events including windstorms with heavy precipitation (Shepherd et al, 2018), is relevant to climate change impact considerations and planning
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