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Autonomous glider observations of specific conductance spatial variability in western Lake Superior.
Citation:
McKinney, P., T. Hollenhorst, J. Austin, AND J. Hoffman. Autonomous glider observations of specific conductance spatial variability in western Lake Superior. State of Lake Superior Conference, Houghton, MN, October 09 - 12, 2018.
Impact/Purpose:
Conductivity is a measure of water’s ability to conduct electrical current and varies according to the concentration of dissolved ions. In freshwater systems, it generally varies according to regional geology and land use, and each of the Great Lakes has a characteristic conductivity reflecting the surrounding geology and development within their watersheds. The conductivity of Lake Superior, based on annual observations from offshore monitoring stations, is relatively stable compared to the lower Great Lakes. This work presents high resolution autonomous glider observations that reveal this commonly measured parameter varies significantly over spatial scales of tens of kilometers in western Lake Superior, and demonstrates the utility of continuous sampling techniques for characterizing processes occurring at scales that coarser sampling programs overlook.
Description:
Slocum electric gliders are autonomous submersibles equipped with sensors that collect water quality data at fine spatial and temporal scales. Widely used in ocean studies, their use in freshwater systems is still relatively new, and presents a unique opportunity for characterizing processes in large lakes. The University of Minnesota Duluth Large Lakes Observatory and the US EPA Mid-Continent Ecology Laboratory have completed over 50 glider deployments since 2011, in four of the Great Lakes and Lake Tahoe, providing a rich dataset of observations for analysis. We use a multiyear subset of the high resolution glider data to investigate the spatial and temporal variability of specific conductance in Lake Superior’s western arm, including the Apostle Islands, in terms of landscape variability and individual tributary influences.