Abstract
Meltwater and sediment-laden plumes at tidewater
glaciers, resulting from the localized subglacial discharge of surface melt,
influence submarine melting of the glacier and the delivery of nutrients to
the fjord's surface waters. It is usually assumed that increased subglacial
discharge will promote the surfacing of these plumes. Here, at a western
Greenland tidewater glacier, we investigate the counterintuitive observation
of a non-surfacing plume in July 2012 (a year of record surface melting)
compared to the surfacing of the plume in July 2013 (an average melt year).
We combine oceanographic observations, subglacial discharge estimates and an
idealized plume model to explain the observed plumes' behavior and evaluate
the relative impact of fjord stratification and subglacial discharge on
plume dynamics. We find that increased fjord stratification prevented the
plume from surfacing in 2012, show that the fjord was more stratified in
2012 due to increased freshwater content and speculate that this arose from
an accumulation of ice sheet surface meltwater in the fjord in this record
melt year. By developing theoretical scalings, we show that fjord
stratification in general exerts a dominant control on plume vertical extent (and thus
surface expression), so that studies using plume surface expression as a
means of diagnosing variability in glacial processes should account for
possible changes in stratification. We introduce the idea that, despite
projections of increased surface melting over Greenland, the appearance of
plumes at the fjord surface could in the future become less common if the
increased freshwater acts to stratify fjords around the Greenland ice sheet.
We discuss the implications of our findings for nutrient fluxes, trapping of
atmospheric CO2 and the properties of water exported from Greenland's
fjords.
Original language | English |
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Pages (from-to) | 1951-1969 |
Number of pages | 19 |
Journal | The Cryosphere |
Volume | 14 |
Issue number | 6 |
DOIs | |
Publication status | Published - 18 Jun 2020 |
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Surface emergence of glacial plumes determined by fjord stratification (dataset)
Slater, D. A. (Creator), Arctic Research Centre , 2020
DOI: 10.18739/A2B853H78
Dataset