A baseline evaluation of oceanographic and sea ice conditions in the Hudson Bay Complex during 2016–2018

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.

Understanding the Physical Forcings Behind the Biogeochemical Productivity of the Hudson Bay Complex

“…The HBC experiences a cyclonic circulation for most of the year, with a seasonal variation in the currents due to the river runoff dynamics and anticyclonic wind patterns more prevalent during summer (Dmitrenko et al., 2020; Ridenour, Hu, Sydor, et al., 2019; St‐Laurent et al., 2011). The sea‐ice dynamics involve full ice cover from December to May and open water from July to September, with the presence of a large polynya in the north west of HB forming in late winter, and early spring due to wind patterns (Bruneau et al., 2021; Gagnon & Gough, 2005; Gupta et al., 2022; Landy et al., 2017; Lukovich et al., 2021; Markham, 1986; Prinsenberg, 1988; Wang et al., 1994). These winds continuously push the ice cover toward the east and southeast, where large quantities are accumulated until early summer when, eventually, all of it melts (Barber et al., 2021; Gupta et al., 2022; Kirillov et al., 2020; Landy et al., 2017; Lukovich et al., 2021).…”

A contrast in sea ice drift and deformation between winter and spring of 2019 in the Antarctic marginal ice zone

“…The absolute dispersion is used to characterise ice motion, and for an ice buoy in an ensemble of buoys, it is defined as (Taylor, 1922;Lukovich et al, 2017Lukovich et al, , 2021)…”

“…Lagrangian dispersion statistics applied to ice-buoy trajectories have been used extensively to quantify ice drift and deformation in the Arctic (e.g. Rampal et al, 2008Rampal et al, , 2009Girard et al, 2009;Lukovich et al, 2011Lukovich et al, , 2015Lukovich et al, , 2017Lukovich et al, , 2021. However, to our knowledge, only absolute dispersion has been considered in the Antarctic by Womack et al (2022), and only for a single-buoy trajectory.…”

“…However, to our knowledge, only absolute dispersion has been considered in the Antarctic by Womack et al (2022), and only for a single-buoy trajectory. In general, absolute dispersion provides a signature of circulation and organised structure in the flow field (Lukovich et al, 2021). It also estimates the linear time dependence of the fluctuating velocity variance, characteristic of turbulent diffusion theory (Taylor, 1922).…”

Atmospheric drivers of a winter-to-spring Lagrangian sea-ice drift in the Eastern Antarctic marginal ice zone

“…This indicates that, while drifting within >80% SIC, the buoy was characterised predominantly by a super-diffusive regime, denoting organised structure in the flow field. However, during the three groups of cyclones, sea-ice dispersion was rather characterised by a sub-diffusive regime β < 1, which captures interruptions in organised flow due to ice-ice interactions (Lukovich andothers, 2017, 2021). These interruptions or 'trapping' events would have resulted in the three large loops as the ice cover was compressed by the meridional winds and the displacement of the buoy was limited.…”