Circulation induced by subglacial discharge in glacial fjords: Results from idealized numerical simulations

Salcedo-Castro, Julio; Bourgault, D.; deYoung, Brad

doi:10.1016/j.csr.2011.06.002

Cited by 14 publications

(13 citation statements)

References 32 publications

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“…Numerous studies indicate that subglacial discharge at the grounding line of Greenland's glaciers drives a turbulent plume that rises along or near the ice face (Motyka et al 2003;Salcedo-Castro et al 2011;Xu et al 2012Xu et al , 2013Sciascia et al 2013). The turbulent plume entrains warm Atlantic-origin water (AW) at depth, providing a mechanism for delivering heat to the ice face.…”

Section: Introductionmentioning

confidence: 99%

“…Current models include 1D theory-based models (Jenkins 2011), 2D numerical simulations (Salcedo-Castro et al 2011), more complex general circulation models (GCMs) (Xu et al 2012(Xu et al , 2013Sciascia et al 2013Sciascia et al , 2014, and finiteelement methods (FEMs) (Kimura et al 2014). Current models include 1D theory-based models (Jenkins 2011), 2D numerical simulations (Salcedo-Castro et al 2011), more complex general circulation models (GCMs) (Xu et al 2012(Xu et al , 2013Sciascia et al 2013Sciascia et al , 2014, and finiteelement methods (FEMs) (Kimura et al 2014).…”

Section: Introductionmentioning

confidence: 99%

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Modeling Turbulent Subglacial Meltwater Plumes: Implications for Fjord-Scale Buoyancy-Driven Circulation

Carroll

Sutherland

Shroyer

et al. 2015

Journal of Physical Oceanography

127

194

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Fjord-scale circulation forced by rising turbulent plumes of subglacial meltwater has been identified as one possible mechanism of oceanic heat transfer to marine-terminating outlet glaciers. This study uses buoyant plume theory and a nonhydrostatic, three-dimensional ocean-ice model of a typical outlet glacier fjord in west Greenland to investigate the sensitivity of meltwater plume dynamics and fjord-scale circulation to subglacial discharge rates, ambient stratification, turbulent diffusivity, and subglacial conduit geometry. The terminal level of a rising plume depends on the cumulative turbulent entrainment and ambient stratification. Plumes with large vertical velocities penetrate to the free surface near the ice face; however, midcolumn stratification maxima create a barrier that can trap plumes at depth as they flow downstream. Subglacial discharge is varied from 1-750 m 3 s 21 ; large discharges result in plumes with positive temperature and salinity anomalies in the upper water column. For these flows, turbulent entrainment along the ice face acts as a mechanism to vertically transport heat and salt. These results suggest that plumes intruding into stratified outlet glacier fjords do not always retain the cold, fresh signature of meltwater but may appear as warm, salty anomalies. Fjordscale circulation is sensitive to subglacial conduit geometry; multiple point source and line plumes result in stronger return flows of warm water toward the glacier. Classic plume theory provides a useful estimate of the plume's outflow depth; however, more complex models are needed to resolve the fjord-scale circulation and melt rates at the ice face.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling Turbulent Subglacial Meltwater Plumes: Implications for Fjord-Scale Buoyancy-Driven Circulation

Carroll

Sutherland

Shroyer

et al. 2015

Journal of Physical Oceanography

127

194

View full text Add to dashboard Cite

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“…Subglacial fresh water (SgFW) includes basal as well as surface runoff and is injected into the fjords at distinct portals at depth in the calving front. SgFW is very difficult to measure in its original state due to the vigorous mixing which occurs on its injection from the portal (Salcedo-Castro et al, 2011;Xu et al, 2012Xu et al, , 2013. Hence, SgFW is reasonably assumed to have the basic characteristics of θ = 0 • C and S = 0 PSU (Mortensen et al, 2013;Straneo et al, 2012).…”

Section: Water Types Present At the Glacier Frontmentioning

confidence: 99%

“…To date, several processes of interaction between fjord water and tidewater calving fronts have been observed, modelled and/or speculated upon including forced convection caused by buoyant subglacial fresh water (SgFW) discharged at depth and entraining AW as it rises (Jenkins, 2011;Mugford and Dowdeswell, 2011;Salcedo-Castro et al, 2011;Sciascia et al, 2013;Sole et al, 2012;Xu et al, 2012Xu et al, , 2013 as well as wind stress and tide-driven fjord circulation Sole et al, 2012;Straneo et al, 2010;Sutherland and Straneo, 2012). Furthermore, it is emerging that circulation in Greenland's deep fjords is more complex than the single convective cell (estuarine-like) circulation model that has been assumed previously in energymass balance calculations (Motyka et al, 2003;Rignot et al, 2010).…”

Section: N Chauché Et Al: Ice-ocean Interaction and Calving Front Mmentioning

confidence: 99%

Ice–ocean interaction and calving front morphology at two west Greenland tidewater outlet glaciers

et al. 2014

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Abstract. Warm, subtropical-originating Atlantic water (AW) has been identified as a primary driver of mass loss across the marine sectors of the Greenland Ice Sheet (GrIS), yet the specific processes by which this water mass interacts with and erodes the calving front of tidewater glaciers is frequently modelled and much speculated upon but remains largely unobserved. We present a suite of fjord salinity, temperature, turbidity versus depth casts along with glacial runoff estimation from Rink and Store glaciers, two major marine outlets draining the western sector of the GrIS during 2009 and 2010. We characterise the main water bodies present and interpret their interaction with their respective calving fronts. We identify two distinct processes of iceocean interaction which have distinct spatial and temporal footprints: (1) homogenous free convective melting which occurs across the calving front where AW is in direct contact with the ice mass, and (2) localised upwelling-driven melt by turbulent subglacial runoff mixing with fjord water which occurs at distinct injection points across the calving front. Throughout the study, AW at 2.8 ± 0.2 • C was consistently observed in contact with both glaciers below 450 m depth, yielding homogenous, free convective submarine melting up to ∼ 200 m depth. Above this bottom layer, multiple interactions are identified, primarily controlled by the rate of subglacial fresh-water discharge which results in localised and discrete upwelling plumes. In the record melt year of 2010, the Store Glacier calving face was dominated by these runoff-driven plumes which led to a highly crenulated frontal geometry characterised by large embayments at the subglacial portals separated by headlands which are dominated by calving. Rink Glacier, which is significantly deeper than Store has a larger proportion of its submerged calving face exposed to AW, which results in a uniform, relatively flat overall frontal geometry.

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“…The plumes upwell and then, depending on their entrainment rate, either reach the surface or outflow subsurface (e.g. Salcedo-Castro et al, 2011;Sciascia et al, 2013;Stevens et al, 2015). These glacial plumes enter fjords that are typically deep, strongly stratified and composed of the two water masses from the shelf: warm, salty Atlantic-origin water at depth and cooler, fresher Polar-water at the surface .…”

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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Circulation induced by subglacial discharge in glacial fjords: Results from idealized numerical simulations

Cited by 14 publications

References 32 publications

Modeling Turbulent Subglacial Meltwater Plumes: Implications for Fjord-Scale Buoyancy-Driven Circulation

Modeling Turbulent Subglacial Meltwater Plumes: Implications for Fjord-Scale Buoyancy-Driven Circulation

Ice–ocean interaction and calving front morphology at two west Greenland tidewater outlet glaciers

Dynamics of Greenland�s glacial fjords

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