Freshwater flux to Sermilik Fjord, SE Greenland

Mernild, Sebastian H.; Howat, I. M.; Ahn, Y.; Liston, Glen E.; Steffen, Konrad; Jakobsen, Bjarne Holm; Hasholt, Bent; Fog, Bjarne; As, Dirk van

doi:10.5194/tc-4-453-2010

Cited by 38 publications

(66 citation statements)

References 50 publications

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“…From September through May, shelf winds are strong along Greenland's southeast coast (Harden et al, 2011), and subglacial discharge is negligible as air temperatures drop below freezing (Mernild et al, 2010;Andersen et al, 2010). During summer, winds weaken, and subglacial discharge increases, becoming a larger freshwater source than submarine melt (Mernild et al, 2010;Andersen et al, 2010). This seasonality likely modulates the glacierdriven circulation and submarine melt rate; one modeling study estimated the summer melt rate at Helheim Glacier to be twice the non-summer rate due to variations in subglacial discharge (Sciascia et al, 2013).…”

Section: Settingmentioning

confidence: 99%

“…Surface runoff from the ice sheet will only form when air temperatures are above freezing, which is primarily June through August (e.g. Mernild et al, 2010). RACMO2.3 runoff into Sermilik (Fig.…”

Section: Seasonality: Summer Versus Non-summer Conditionsmentioning

confidence: 99%

“…Two smaller glaciers, Fernis and Midgård, also drain into the fjord in the north and northeast corners. Based on satellite-observed ice velocities and estimated ice thickness, the total ice discharges (iceberg calving plus submarine melting) from Helheim, Midgård, and Fernis are 821±82, 174±32, and 79±16 m 3 s −1 water equivalent, respectively, from 1999-2008 (Mernild et al, 2010).…”

Section: Background On Sermilik Fjord Regionmentioning

confidence: 99%

“…RACMO2.3 simulations from 1981 to 2013 were used to estimate the runoff flux into the upper half of Sermilik Fjord (i.e. the control volume, or north of our mooring locations) based on the catchment basins in Mernild et al (2010). The RACMO runoff time-series provides context for the seasonality of freshwater fluxes and a point of comparison for our inferred runoff flux.…”

Section: Background On Sermilik Fjord Regionmentioning

confidence: 99%

“…Runoff into proglacial fjords is not directly measured but estimated with regional models and reanalyses that often differ significantly (e.g. Mernild et al, 2010;Andersen et al, 2010;Van As et al, 2014). Second, the glacier-driven circulation from these inputs of freshwater is not well understood.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of Greenland�s glacial fjords

Jackson¹

2016

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Glacial fjords form conduits between glaciers of the Greenland Ice Sheet and the North Atlantic. They are the gateways for importing oceanic heat to melt ice and for exporting meltwater into the ocean. Submarine melting in fjords has been implicated as a driver of recent glacier acceleration; however, there are no direct measurements of this melting, and little is known about the fjord processes that modulate melt rates. Combining observations, theory, and modeling, this thesis investigates the circulation, heat transport, and meltwater export in glacial fjords.While most recent studies focus on glacial buoyancy forcing, there are other drivers -e.g. tides, local wind, shelf variability -that can be important for fjord circulation. Using moored records from two major Greenlandic fjords, shelf forcing (from shelf density fluctuations) is found to dominate the fjord circulation, driving rapid exchange with the shelf and large heat content variability near the glacier. Contrary to the conventional paradigm, these flows mask any glacier-driven circulation in the non-summer months. During the summer, when shelf forcing is reduced and freshwater forcing peaks, a mean exchange flow transports warm Atlantic-origin water towards the glacier and exports glacial meltwater.Many recent studies have inferred submarine melt rates from oceanic heat transport, but the fjord budgets that underlie this method have been overlooked. Building on estuarine studies of salt fluxes, this thesis presents a new framework for assessing glacial fjord budgets and revised equations for inferring meltwater fluxes. Two different seasonal regimes are found in the heat/salt budgets for Sermilik Fjord, and the results provide the first time-series of submarine meltwater and subglacial discharge fluxes into a glacial fjord.Finally, building on the observations, ROMS numerical simulations and two analytical models are used to investigate the dynamics of shelf-driven flows and their importance relative to local wind forcing across the parameter space of Greenland's fjords. The fjord response is found to vary primarily with the width relative to the deformation radius and the fjord adjustment timescale relative to the forcing timescale. Understanding these modes of circulation is a step towards accurate modeling of ocean-glacier interactions.

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Section: Settingmentioning

confidence: 99%

Section: Seasonality: Summer Versus Non-summer Conditionsmentioning

confidence: 99%

Section: Background On Sermilik Fjord Regionmentioning

confidence: 99%

Section: Background On Sermilik Fjord Regionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamics of Greenland�s glacial fjords

Jackson¹

2016

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Quantifying flow regimes in a Greenland glacial fjord using iceberg drifters

Sutherland

Roth

Hamilton

et al. 2014

Geophysical Research Letters

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Large, deep-keeled icebergs are ubiquitous in Greenland's outlet glacial fjords. Here we use the movement of these icebergs to quantify flow variability in Sermilik Fjord, southeast Greenland, from the ice mélange through the fjord to the shelf. In the ice mélange, a proglacial mixture of sea ice and icebergs, we find that icebergs consistently track the glacier speed, with slightly faster speeds near terminus and episodic increases due to calving events. In the fjord, icebergs accurately capture synoptic circulation driven by both along-fjord and along-shelf winds. Recirculation and in-/out-fjord variations occur throughout the fjord more frequently than previously reported, suggesting that across-fjord velocity gradients cannot be ignored. Once on the shelf, icebergs move southeastward in the East Greenland Coastal Current, providing wintertime observations of this freshwater pathway.

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Impact of periodic intermediary flows on submarine melting of a Greenland glacier

et al. 2014

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The submarine melting of a vertical glacier front, induced by an intermediary circulation forced by periodic density variations at the mouth of a fjord, is investigated using a nonhydrostatic ocean general circulation model and idealized laboratory experiments. The idealized configurations broadly match that of Sermilik Fjord, southeast Greenland, a largely two layers system characterized by strong seasonal variability of subglacial discharge. Consistent with observations, the numerical results suggest that the intermediary circulation is an effective mechanism for the advection of shelf anomalies inside the fjord. In the numerical simulations, the advection mechanism is a density intrusion with a velocity which is an order of magnitude larger than the velocities associated with a glacier-driven circulation. In summer, submarine melting is mostly influenced by the discharge of surface runoff at the base of the glacier and the intermediary circulation induces small changes in submarine melting. In winter, on the other hand, submarine melting depends only on the water properties and velocity distribution at the glacier front. Hence, the properties of the waters advected by the intermediary circulation to the glacier front are found to be the primary control of the submarine melting. When the density of the intrusion is intermediate between those found in the fjord's two layers, there is a significant reduction in submarine melting. On the other hand, when the density is close to that of the bottom layer, only a slight reduction in submarine melting is observed. The numerical results compare favorably to idealized laboratory experiments with a similar setup.

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Freshwater flux to Sermilik Fjord, SE Greenland

Cited by 38 publications

References 50 publications

Dynamics of Greenland�s glacial fjords

Dynamics of Greenland�s glacial fjords

Quantifying flow regimes in a Greenland glacial fjord using iceberg drifters

Impact of periodic intermediary flows on submarine melting of a Greenland glacier

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