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TitleHyperpycnal flows control the persistence and flushing of hypoxic high conductivity bottom water in a High Arctic lake
AuthorLewis, T; Lamoureux, S F; Normandeau, A; Dugan, H A
SourceArctic Science vol. 0, 2017., https://doi.org/10.1139/AS-2017-0022 (Open Access)
Year2017
Alt SeriesNatural Resources Canada, Contribution Series 20170098
PublisherCanadian Science Publishing
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut
NTS78F/15; 78F/16; 78G/01; 78G/02
AreaCape Bounty; Melville Island; West Lake
Lat/Long WENS-112.0000 -108.0000 76.0000 74.5000
Subjectshydrogeology; conductivity surveys; conductivity; oxygen; water geochemistry; lake water geochemistry; lake water; flow trajectories; fluvial deposits; fluvial transport; hypoxic water; dissolved oxygen; hyperpycnal flows
Illustrationslocation maps; bathymetric profiles; graphs
Released2017 08 16
AbstractIn the deepest portions of many lakes, zones of high conductivity bottom water (HCBW) depleted in dissolved oxygen (DO) are present. HCBW and DO are important for benthic organism and deep pelagic habitat, the cycling of nutrients and contaminants, understanding the long-term evolution of lakes, and for paleoenvironmental studies. Here, we investigate the persistence and removal of HCBW and replenishment of DO over a four melt season monitoring period in an Arctic lake at Cape Bounty, Melville Island, using physical properties and flow velocity data collected from the deepest part of the lake, along with hydrometric and suspended sediment data from the lake inflow ('West River'). During the monitoring period, HCBW were removed in 2007 and 2008, but largely remained in place in 2009 and 2010. In 2007, major landscape disturbances occurred in the watershed, increasing suspended sediment concentrations (SSC) in the inflowing river in 2007 and 2008. In the later two years of monitoring (2009-2010), fluvial sediment availability relaxed to pre-disturbance levels. High SSC in 2007 and 2008 caused by landscape disturbances formed sustained hyperpycnal flows (or underflows) during the melt period, which we link to the removal of HCBW.
Summary(Plain Language Summary, not published)
In the deepest portions of many lakes, zones of high conductivity bottom water (HCBW) depleted in dissolved oxygen (DO) are present. HCBW and DO are important for benthic organism and deep pelagic habitat, the cycling of nutrients and contaminants, understanding the long-term evolution of lakes, and for paleoenvironmental studies. We found that high suspended sediment concentration in High Arctic rivers in 2007 and 2008 caused by landscape disturbances formed sustained hyperpycnal flows (density current at river mouths) in Cape Bounty's West Lake (Melville island) during the melt period, which we link to the removal of HCBW. Increase in fluvial suspended sediment concentrations in the future will likely become an increasingly important control on the balance between river and lake water density. We therefore suggest that hyperpycnal flow frequency will increase in the future, and HCBW persistence will decrease in this system.
GEOSCAN ID302733