Abstract
Subglacial discharge plumes increase submarine melting of marine-terminating glaciers significantly; however, in-situ data on their properties and behaviour are limited. We present oceanographic data collected by ringed seals (Pusa hispida) instrumented with GPS-equipped conductivity-temperature-depth satellite relay data loggers (GPS-CTD-SRDLs) in Kongsfjorden, Svalbard, during 2012. The seals foraged just outside the plumes and collected hydrographic data from within the plumes’ upwelling cores as they returned to the surface. The seals encountered water with fractions of subglacial discharge as high as 27% at 60 m below the ocean surface. The ringed seals responded rapidly to spatial and temporal variations in subglacial discharge at the glacier terminus, suggesting that prey becomes available quickly following the appearance of plumes. The seals’ dive locations were used to monitor the presence of plumes over a four-month period. High surface runoff from Kronebreen catchment created strong plumes, but weak plumes were present even during periods of low surface runoff. The continued retreat of Kronebreen, and other tidewater glaciers, will lead to the loss of these marine-termini as the glaciers retreat onto land. The techniques presented here improve our understanding of the drivers of glacial retreat and the implications of future habitat loss for glacier-associated birds and mammals.
Highlights
Subglacial discharge plumes are frequently observed at the fronts of marine-terminating glaciers
There is only a limited amount of field data available to incorporate into modelling efforts, and plumes are difficult to include in existing large-scale models of either ice or fjord dynamics
We present data collected from ringed seals instrumented with GPS-equipped conductivitytemperature-depth satellite relay data loggers[26] (GPS-CTD-SRDLs) that foraged close to glacier fronts in Kongsfjorden, Svalbard during 2012
Summary
Subglacial discharge plumes are frequently observed at the fronts of marine-terminating glaciers. Kittiwakes (Rissa tridactyla) and fulmars (Fulmarus glacialis), focus their foraging in the so-called “brown-zone”, where sediment-laden water contained in plumes reaches the surface[11,12,13] Marine mammals, such as white whales (Delphinapterus leucas) and ringed seals (Pusa hispida), preferentially forage close to glacier fronts[14,15], though no specific link to subglacial discharge plumes has yet been established. A recent modelling study of Kongsfjorden[25], which did not include a fully-developed plume representation, showed that the simulated fjord circulation is likely incorrectly represented in the peak runoff season This was most noticeable in the vicinity of the glacier fronts, but may have affected the exchanges with the open ocean, even after the subglacial discharges cease at the end of summer. Kongsbreen South, on the other hand, has retreated onto land but is still characterised by large sediment plumes that are largely driven by surface inputs of glacial discharge
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