Role of River Runoff and Sea Ice Brine Rejection in Controlling Stratification Throughout Winter in Southeast Hudson Bay

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dc.contributor.author Eastwood, Rosemary Ann
dc.contributor.author Macdonald, R.W.
dc.contributor.author Ehn, J.K
dc.contributor.author Heath, J.
dc.contributor.author Arragutainaq, L.
dc.contributor.author Myers, P.G.
dc.contributor.author Barber, D.G.
dc.contributor.author Kuzyk, Z.A.
dc.date.accessioned 2020-07-10T17:39:42Z
dc.date.available 2020-07-10T17:39:42Z
dc.date.issued 2020-03-09
dc.date.submitted 2020-07-10T17:39:42Z en_US
dc.identifier.citation Eastwood, R.A., Macdonald, R.W., Ehn, J.K. et al. Role of River Runoff and Sea Ice Brine Rejection in Controlling Stratification Throughout Winter in Southeast Hudson Bay. Estuaries and Coasts 43, 756–786 (2020). https://doi.org/10.1007/s12237-020-00698-0 en_US
dc.identifier.uri http://hdl.handle.net/1993/34772
dc.description.abstract The Hudson Bay system is undergoing climate-driven changes in sea ice and freshwater inflow and has seen an increase in winter river inflow since the 1960s due in part to flow regulation for hydropower production. Southeast Hudson Bay and adjacent James Bay are at the forefront of these changes, with more than 1-month shortening of the season of sea ice cover as defined using satellite data, increases in winter inflow from the regulated La Grande River complex, and changes in coastal ice and polynya behavior described by Belcher Islands’ Inuit. In summer, there is a fresh coastal domain in southeastHudson Bay fueled by river runoff and sea icemelt. To investigate winter oceanographic conditions and potential interactions between runoff and ice melt or brine in southeast Hudson Bay, we initiated the first winter study of the shallow waters surrounding the Belchers, collecting conductivity-temperature-depth (CTD) profiles and conductivity-temperature (CT) time series using under-icemoorings, and collecting water samples and ice cores during four campaigns between January 2014 and March 2015. Tandem measurements of salinity and δ18O were made for the water and ice samples to discriminate between freshwater sources (river runoff and sea ice melt). We find that southeast Hudson Bay, and particularly the nearshore domain southeast of the Belchers, is distinguished in winter by the presence of river water and strong surface stratification, which runs counter to expectations for a system in which local freshwater remains frozen on land until spring freshet (May–June) and sea ice growth is adding brine to surface waters. The amount of river water around the Belcher Islands increased significantly from fall through to late winter according to δ18O records of ice. The accumulation of river water in surface waters during the winter is directly associated with an accumulation of brine, which considerably exceeds the capacity of local ice formation to produce brine.We therefore infer that brine is advected into the study area together with river water, and that interplay between these properties establishes and maintains the level of surface stratification throughout winter.With reference to a NEMO ocean model simulation of winter circulation in the study area, we propose a conceptual model in which winter river inflow into James Bay drives the northward transport of both river water and brine captured near the surface, with reductions in brine-driven deep convection in the area’s flaw leads. While past changes in winter oceanographic conditions and sea ice cannot be reconstructed from the few available scientific data, the presence of significant runoff inwinter in southeast Hudson Bay implies heightened sensitivity to delayed freeze-up under a warmer climate, which will have the effect of reducing brine early in the winter, also promoting increased stratification and river plume transport. en_US
dc.language.iso en en_US
dc.publisher Springer Nature en_US
dc.rights info:eu-repo/semantics/openAccess
dc.subject River Inflow en_US
dc.subject Sea Ice en_US
dc.subject Brine en_US
dc.subject Stratification en_US
dc.subject Polynyas en_US
dc.subject Flaw leads en_US
dc.subject Hudson Bay en_US
dc.subject James Bay en_US
dc.subject Freshwater en_US
dc.subject Oxygen isotopes en_US
dc.subject Environmental change en_US
dc.title Role of River Runoff and Sea Ice Brine Rejection in Controlling Stratification Throughout Winter in Southeast Hudson Bay en_US
dc.type Technical Report en_US
dc.type info:eu-repo/semantics/report
dc.identifier.doi https://doi.org/10.1007/s12237-020-00698-0

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