The Effect of Meltwater Plumes on the Melting of a Vertical Glacier Face

Kimura, Satoshi; Holland, Paul R.; Jenkins, Adrian; Piggott, Matthew D.

doi:10.1175/jpo-d-13-0219.1

Cited by 82 publications

(127 citation statements)

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“…While the largest discharge outlet at the terminus prow is associated with predicted subglacial flowpaths, persistent sediment plumes, and anticipated large submarine melt [Xu et al, 2013;Kimura et al, 2014], we also demonstrate that the near-terminus, distributed hydrologic system drives significant submarine melt through minor discharge outlets elsewhere. We observe melt rates exceeding 3.0 m d À1 at smaller, secondary discharge outlets outside of the main subglacial channel system, particularly along the southern terminus face.…”

Section: Discussionmentioning

confidence: 53%

Distributed subglacial discharge drives significant submarine melt at a Greenland tidewater glacier

Fried

Catania

Bartholomaus

et al. 2015

Geophysical Research Letters

169

206

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Submarine melt can account for substantial mass loss at tidewater glacier termini. However, the processes controlling submarine melt are poorly understood due to limited observations of submarine termini. Here at a tidewater glacier in central West Greenland, we identify subglacial discharge outlets and infer submarine melt across the terminus using direct observations of the submarine terminus face. We find extensive melting associated with small discharge outlets. While the majority of discharge is routed to a single, large channel, outlets not fed by large tributaries drive submarine melt rates in excess of 3.0 m d−1 and account for 85% of total estimated melt across the terminus. Nearly the entire terminus is undercut, which may intersect surface crevasses and promote calving. Severe undercutting constricts buoyant outflow plumes and may amplify melt. The observed morphology and melt distribution motivate more realistic treatments of terminus shape and subglacial discharge in submarine melt models.

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Section: Discussionmentioning

confidence: 53%

Distributed subglacial discharge drives significant submarine melt at a Greenland tidewater glacier

Fried

Catania

Bartholomaus

et al. 2015

Geophysical Research Letters

169

206

View full text Add to dashboard Cite

show abstract

“…The current model-based estimates of submarine melt rates at tidewater glaciers and their sensitivity to external forcings of the near-ice environment are highly uncertain. The uncertainty in these estimates is due to plume models using ice/ocean boundary parameterizations forced by far field (>1 km) ocean property measurements and largely unknown subglacial discharge magnitude and distribution [Jenkins, 2011;Xu et al, 2012Xu et al, , 2013Sciascia et al, 2013;Kimura et al, 2014;Slater et al, 2015]). …”

Section: 5! Ice-ocean Interactions At Marine-terminating Outlet Glamentioning

confidence: 99%

Influence of meltwater on Greenland Ice Sheet dynamics

Stevens¹

2017

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Seasonal fluxes of meltwater control ice-flow processes across the Greenland Ice Sheet ablation zone and subglacial discharge at marine-terminating outlet glaciers. With the increase in annual ice sheet meltwater production observed over recent decades and predicted into future decades, understanding mechanisms driving the hourly to decadal impact of meltwater on ice flow is critical for predicting Greenland Ice Sheet dynamic mass loss. This thesis investigates a wide range of meltwater-driven processes using empirical and theoretical methods for a region of the western margin of the Greenland Ice Sheet. I begin with an examination of the seasonal and annual ice flow record for the region using in situ observations of ice flow from a network of Global Positioning System (GPS) stations. Annual velocities decrease over the seven-year time-series at a rate consistent with the negative trend in annual velocities observed in neighboring regions. Using observations from the same GPS network, I next determine the trigger mechanism for rapid drainage of a supraglacial lake. In three consecutive years, I find precursory basal slip and uplift in the lake basin generates tensile stresses that promote hydrofracture beneath the lake. As these precursors are likely associated with the introduction of meltwater to the bed through neighboring moulin systems, our results imply that lakes may be less able to drain in the less crevassed, interior regions of the ice sheet. Expanding spatial scales to the full ablation zone, I then use a numerical model of subglacial hydrology to test whether model-derived effective pressures exhibit the theorized inverse relationship with melt-season ice sheet surface velocities. Finally, I pair near-ice fjord hydrographic observations with modeled and observed subglacial discharge for the Saqqardliup sermia-Sarqardleq Fjord system. I find evidence of two types of glacially modified waters whose distinct properties and locations in the fjord align with subglacial discharge from two prominent subcatchments beneath Saqqardliup sermia. Continued observational and theoretical work reaching across discipline boundaries is required to further narrow our gap in understanding the forcing mechanisms and magnitude of Greenland Ice Sheet dynamic mass loss.

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“…Furthermore, modeling studies have focused on the glacier's buoyancy driven circulation, both in the near-glacier region and at the fjord-scale (Xu et al, 2013;Sciascia et al, 2013;Kimura et al, 2014;Carroll et al, 2015). According to the conventional paradigm for Greenland's fjords as a buoyancy-driven regime, the freshwater inputs from glaciers control renewal of water and heat into the fjord, allowing for positive feedbacks between melting and heat transport.…”

Section: Unknown Dynamics In Glacial Fjordsmentioning

confidence: 99%

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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The Effect of Meltwater Plumes on the Melting of a Vertical Glacier Face

Cited by 82 publications

References 84 publications

Distributed subglacial discharge drives significant submarine melt at a Greenland tidewater glacier

Distributed subglacial discharge drives significant submarine melt at a Greenland tidewater glacier

Influence of meltwater on Greenland Ice Sheet dynamics

Dynamics of Greenland�s glacial fjords

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