A baseline evaluation of atmospheric and river discharge conditions in the Hudson Bay Complex during 2016–2018

Abstract

In this article, we examine atmospheric and river discharge conditions within the Hudson Bay Complex for the BaySys 2016–2018 field program time frame. Investigated in particular is a subset of European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis - Interim (ERA-Interim) atmospheric forcing variables, namely 2-m surface temperature, 10-m surface winds, precipitation, and sea-level pressure, in addition to river discharge. Results from this assessment show that 2016 was characterized by unusually warm conditions (terrestrial and marine) throughout the annual cycle; 2017 by strong cyclone activity in March and high precipitation in January, October, and November; and 2018 by cold and windy conditions throughout the annual cycle. Evaluation of terrestrial conditions showed higher than normal land surface temperatures (the Hudson Bay physical watershed) for all of the 2016–2018 period (excluding a colder than normal spell August–November 2018), particularly in January (2016 and 2017), higher than normal precipitation in October (2016 and 2017), and higher than normal terrestrial discharge to the Hudson Bay Complex in March (2016 and 2017), with drier than average June through October (2016–2018).

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

“…For this study, as in the companion study (Lukovich et al, 2021), the 1981-2010 time frame was selected because it (i) falls after the establishment of river discharge regulation and (ii) coincides with a climatological and conventional normal time interval established by Environment and Climate Change Canada (2020). Variables examined (and selected based on available observational and reanalysis data) include SST, SIC, and sea ice drift.…”

“…Standardized monthly anomalies were computed using the technique described in Lukovich et al (2021, their Section 2) and equations provided in the Supplemental Material to illustrate spatial variability in sea ice conditions during the 2016-2018 BaySys time frame. The region of interest encompasses 50 -70 N and 95 -75 W (Figure 1).…”

“…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). In this additional baseline study, we examine oceanographic and sea ice conditions for the same time frame, as output from the NEMO model used by all BaySys teams, to provide an understanding and estimate of changes in physical and biogeochemical processes in response to relative climate change and impacts of the regulation of river discharge.…”

“…In an Eulerian analysis, sea ice area (SIA), drift speed, and meridional circulation index (MCI), as defined in the next section, are evaluated for the 2016-2018 BaySys time frame relative to the 1981-2010 climatology. In a Lagrangian analysis, sea ice deformation, computed from sea ice beacons deployed near Churchill in February 2017, is examined for the impacts of March 2017 storm, characterized in Lukovich et al (2021) by strong winds locally and high levels of precipitation regionally, based on the spatial and temporal evolution in triangular arrays.…”

“…Study objectives were thus to compare oceanographic and sea ice conditions for 2016-2018 relative to the 1981-2010 climatology and to examine the impact of the blizzard/extreme storm on sea ice dynamics in 2017 as a case study. We used standard anomaly maps, as in the companion paper on baseline atmospheric conditions (Lukovich et al, 2021), to assess spatial variability in SST and ice conditions relative to the 1981-2010 climatology (or 1982-2010 in the case of SST). Temporal changes are captured by monthly plots, while rankings depict extremes associated with SICs and drift.…”