Introduction The Hudson Bay Drainage Basin (HBDB) comprises over a third of the Canadian landmass, contains important hydroelectric infrastructure and agricultural lands, and accounts for over a fifth of freshwater exports into the pan-arctic ocean system via the Hudson Bay Complex (HBC comprised of Hudson Bay, James Bay, Ungava Bay, Foxe Basin, and Hudson Strait; McClelland et al., 2006). The HBC itself is important to Arctic marine wildlife, and as a shipping route for Canada. It is a large region of primary production, influenced mainly by the timing of freshwater inputs (largely meltwater). Changing freshwater inputs are essential to the annual formation, decay and break up of sea ice, with seasonal ice cover being important for the HBC pelagic life (Manak and Mysak, 1989; Saucier et al. 1998, 2004). HBDB terrestrial discharge influences Arctic Ocean circulation, sea ice dynamics, biological and biogeochemical processes within the HBC. Due to the importance of terrestrial freshwater fluxes into the HBC for bay-wide circulation and ice-formation, continental-scale hydrologic modeling is key to the combined modeling/observation BaySys group of projects (Barber, 2014). The importance of the HBDB necessitates a comprehensive hydrological monitoring and prediction framework. Although hydrometric gauges remain relatively dense in southern, lower-latitude regions of the basin, higher-latitude counterparts remain poorly gauged. Additionally, the number of hydrometric gauges has declined across Canada in recent decades (Coulibaly et al., 2013; Mlynowski et al., 2011). As of 2013, 40% of the HBDB is ungauged and 27% has never been gauged. Hydrological modeling is required to fill spatial and temporal gaps in the observational record, and for making long-term streamflow projections. Over the same period this basin has undergone significant climate change impacting the distribution and
The pan-Arctic domain is undergoing some of Earth’s most rapid and significant changes resulting from anthropogenic and climate-induced alteration of freshwater distribution. Changes in terrestrial freshwater discharge entering the Arctic Basin from pan-Arctic watersheds significantly impact oceanic circulation and sea ice dynamics. Historical streamflow records in high-latitude basins are often discontinuous (seasonal or with large temporal gaps) or sparse (poor spatial coverage), however, making trends from observed records difficult to quantify. Our objectives were to generate a more continuous 90-year record (1981–2070) of spatially distributed freshwater flux for the Arctic Basin (all Arctic draining rivers, including the Yukon), suitable for forcing ocean models, and to analyze the changing simulated trends in freshwater discharge across the domain. We established these data as valid during the historical period (1971–2015) and then used projected futures (preserving uncertainty by running a coupled climate-hydrologic ensemble) to analyze long-term (2021–2070) trends for major Arctic draining rivers. When compared to historic trends reported in the literature, we find that trends are projected to nearly double by 2070, with river discharge to the Arctic Basin increasing by 22% (on average) by 2070. We also find a significant trend toward earlier onset of spring freshet and a general flattening of the average annual hydrograph, with a trend toward decreasing seasonality of Arctic freshwater discharge with climate change and regulation combined. The coupled climate-hydrologic ensemble was then used to force an ocean circulation model to simulate freshwater content and thermohaline circulation. This research provides the marine research community with a daily time series of historic and projected freshwater discharge suitable for forcing sea ice and ocean models. Although important, this work is only a first step in mapping the impacts of climate change on the pan-Arctic region.
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).
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