1. Mixing, Water Transformation, and Melting Close to a Tidewater Glacier.
- Author
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Inall, Mark E., Sundfjord, Arild, Cottier, Finlo, Korte, Marie‐Louise, Slater, Donald A., Venables, Emily J., and Coogan, James
- Subjects
VERTICAL mixing (Earth sciences) ,GLACIAL melting ,ICE sheets ,FRESH water ,ICE calving ,MELTWATER ,GLACIERS - Abstract
Marine‐terminating glacier fjords play a central role in the transport of oceanic heat toward ice sheets, regulating their melt. Mixing processes near glacial termini are key to this circulation but remain poorly understood. We present new summer measurements of circulation and mixing near a marine‐terminating glacier with active sub‐glacial discharge. 65% of the fjord's vertical overturning circulation is driven by the buoyant plume, however we newly report intense vertical and horizontal mixing in the plume's horizontal spreading phase, accounting for the remaining 35%. Buoyant plume theory supports 2%–5% of total glacial melt. Thus, most of the heat associated with vertical overturing short‐circuits the glacial front. We find however that turbulence in the horizontal spreading phase redistributes the short‐circuited heat back into the surface waters of the near‐glacial zone. Our findings highlight the need for further research on the complex mixing processes that occur near the glacier terminus. Plain Language Summary: Melting of glacial ice is the single largest contributor to global sea‐level rise. Many glaciers flow into the ocean where the near‐vertical ice wall is bathed in relatively warm sea water. Freshwater from ice surface melting seeps down through cracks and crevasses in the glacier to be discharged at the base of the ice wall, many tens to hundreds of meters below the sea surface. This fresh water rises from the depths as a highly turbulent plume, drawing in and pushing upwards the surrounding seawater, eventually spreading horizontally as a mixture of fresh discharge and mixed‐in seawater. Few measurements exist in the dangerous zone where iceberg often calve. Using data from a robotic platform we show that the vertical rise and the horizontal spreading of fresh water both play important roles in the total ocean‐induced melting of the glacial face in this type of system. Key Points: Entrainment into the buoyant plume drives ∼65% of fjord vertical overturning circulationIntense turbulent mixing in the horizontal spreading phase of the plume drives the remaining ∼35%95%–98% of the heat in the rising plume short‐circuits the glacier, to be redistributed into glacial proximal waters by horizontal mixing [ABSTRACT FROM AUTHOR]
- Published
- 2024
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