Abstract
In this analysis, we examine relative contributions from climate change and river discharge regulation to changes in marine conditions in the Hudson Bay Complex using a subset of five atmospheric forcing scenarios from the Coupled Model Intercomparison Project Phase 5 (CMIP5), river discharge data from the Hydrological Predictions for the Environment (HYPE) model, both naturalized (without anthropogenic intervention) and regulated (anthropogenically controlled through diversions, dams, reservoirs), and output from the Nucleus for European Modeling of the Ocean Ice-Ocean model for the 1981–2070 time frame. Investigated in particular are spatiotemporal changes in sea surface temperature, sea ice concentration and thickness, and zonal and meridional sea ice drift in response to (i) climate change through comparison of historical (1981–2010) and future (2021–2050 and 2041–2070) simulations, (ii) regulation through comparison of historical (1981–2010) naturalized and regulated simulations, and (iii) climate change and regulation combined through comparison of future (2021–2050 and 2041–2070) naturalized and regulated simulations. Also investigated is use of the diagnostic known as e-folding time spatial distribution to monitor changes in persistence in these variables in response to changing climate and regulation impacts in the Hudson Bay Complex. Results from this analysis highlight bay-wide and regional reductions in sea ice concentration and thickness in southwest and northeast Hudson Bay in response to a changing climate, and east-west asymmetry in sea ice drift response in support of past studies. Regulation is also shown to amplify or suppress the climate change signal. Specifically, regulation amplifies sea surface temperatures from April to August, suppresses sea ice loss by approximately 30% in March, contributes to enhanced sea ice drift speed by approximately 30%, and reduces meridional circulation by approximately 20% in January due to enhanced zonal drift. Results further suggest that the offshore impacts of regulation are amplified in a changing climate.
Highlights
In this study, we examined simulated climate change and river discharge regulation and their combined impact on marine conditions in Hudson Bay (HB) as a contribution to BaySys, a collaborative project between Manitoba Hydro, the University of Manitoba, the University of Alberta, and Ouranos
We explored the relative and combined impacts of climate change and regulation on sea ice state and dynamics in the Hudson Bay Complex (HBC) and examined questions including: How is the annual cycle in sea ice and ocean conditions influenced by the impacts of climate change and regulation? Does regulation enhance or decrease climate change impacts? How will persistence in sea ice conditions be influenced by climate change and regulation impacts combined? Will a more diffusive sea ice cover be attained? To address these questions in the context of BaySys objectives, we analyze output from simulations implemented for the BaySys project
For the f1 (f2) time frame, maximum decreases in sea ice area on the order of 2 À 4ð4 À 6Þ Â 105km2 are evident in December/January, while simulations suggest a maximum decline in sea ice volume on the order of 1–2 (3–5) Â 105 km3, with a large spread among models and larger decreases for the highemissions (RCP8.5) scenario (Figure 2)
Summary
We examined simulated climate change and river discharge regulation and their combined impact on marine conditions in Hudson Bay (HB) as a contribution to BaySys, a collaborative project between Manitoba Hydro, the University of Manitoba, the University of Alberta, and Ouranos. Lukovich et al: Climate change and regulation impacts on marine conditions in Hudson Bay. Climate change impacts on Arctic sea ice and sea surface temperatures (SSTs) are evidenced in the correspondence between increasing temperatures, associated with global CO2 increases, and sea ice decline, as demonstrated in Mahlstein and Knutti (2012), Stroeve and Notz (2015), and Notz and Stroeve (2016). Within the Hudson Bay Complex (HBC), future warming trends have been estimated under various greenhouse gas emission scenarios, with mean multimodel ensemble trends of 0.22 + 0.08C per decade for representative concentration pathway RCP4.5, and 0.31 + 0.07C per decade for RCP8.5 during the 2012–2064 time frame (Lavoie et al, 2013). Seasonal difference maps show enhanced warming in southeastern HB in summer and fall (Joly et al, 2011)
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