Seasonal variations of outlet glacier terminus position in Greenland

Schild, K. M.; Hamilton, G. S.

doi:10.3189/2013jog12j238

Cited by 75 publications

(113 citation statements)

References 47 publications

(121 reference statements)

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“…At Store Glacier, frontal mass loss during both summers is greater on the southern flank, where a large embayment between two headlands coincides with an upwelling plume visible at the surface. These observations suggest that in addition to the fjord geometrical control on the glacier calving processes (McFadden et al, 2011;Schild and Hamilton, 2013), the presence of warm, subpolar-originating water bodies at the glacier front, along with the presence of sills and inner basins in the fjord, also has a considerable impact on the calving dynamics, and thus on the shape of the calving front. We hypothesise that deep tidewater glaciers, such as Rink (∼ 750 m), which are exposed significantly to warm AW at their base (∼ 75 % at Rink), will be influenced by widespread, submarine melting, which would favour a relatively flat calving face (Fig.…”

Section: Oceanic and Bathymetric Influence On Glacier Front Behaviourmentioning

confidence: 97%

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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Section: Oceanic and Bathymetric Influence On Glacier Front Behaviourmentioning

confidence: 97%

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

et al. 2014

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“…Enderlin and others, 2014) or a change in glacier calving style (full-thickness tabular vs smaller sub-thickness icebergs) (e.g. Schild and Hamilton, 2013), will likely result in a change in the magnitude of the distributed freshwater flux from submarine melting of icebergs. Using the DEMdifferencing approach described here, we may be able to quantify spatial and temporal changes in freshwater fluxes in the absence of detailed hydrographic surveys.…”

Section: Discussionmentioning

confidence: 99%

Estimates of iceberg submarine melting from high-resolution digital elevation models: application to Sermilik Fjord, East Greenland

Enderlin¹,

Hamilton

2014

J. Glaciol.

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ABSTRACT. Observed increases in iceberg discharge from Greenland's marine-terminating glaciers over the past two decades have altered the freshwater flux from glacial fjords into surrounding ocean basins. Although variations in freshwater flux due to ice-sheet discharge change have been investigated on a broad scale, the distribution of the freshwater flux due to melting of calved glacier ice (i.e. icebergs) has not been examined. Logistical challenges to collecting in situ data in glacial fjords have so far prevented a detailed examination of freshwater fluxes arising from melting beneath the waterline (i.e. submarine melting). Here we demonstrate that submarine melting of icebergs can be quantified using repeat digital elevation models derived from very high-resolution stereo satellite images. Analysis of volume changes for icebergs in Sermilik Fjord, East Greenland, yield area-averaged submarine melt rates of �0.39 m d -1. These rates are in relatively good agreement with simulated winter melt rates along the submerged portion of the Helheim Glacier terminus, providing independent validation of the applied technique. Further, the volume flux of fresh water from iceberg melting scales with surface and submerged iceberg areas, which suggests that iceberg meltwater may be an important freshwater component in fjords with high iceberg concentrations and/or expansive ice melange.

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“…In lieu of attempting to quantify meltwater run-off, we use positive degree days (PDDs) as a proxy for meltwater availability at Kronebreen and Tunabreen (Hock 2003;Bartholomew et al 2010;Chu et al 2012;Schild and Hamilton 2013). We calculate the daily PDD values using the average daily temperature measurements collected from automatic weather station at Ny-Ålesund (78.92°N, 11.93°E, 8 masl), 15 km west of Kronebreen, and Pyramiden (78.65°N, 16.35°E, 20 masl), 32 km north of Tunabreen.…”

Section: Meltwatermentioning

confidence: 99%

“…We calculate the daily PDD values using the average daily temperature measurements collected from automatic weather station at Ny-Ålesund (78.92°N, 11.93°E, 8 masl), 15 km west of Kronebreen, and Pyramiden (78.65°N, 16.35°E, 20 masl), 32 km north of Tunabreen. Following the methods of Schild and Hamilton (2013), the daily average temperature after the onset of melt is defined as the PDD value for each day. To take into account lags in the hydraulic system introduced by finite transit time of meltwater through the glacier system and potential subglacial storage, we construct a 'lag index' using accumulated PDDs.…”

Section: Meltwatermentioning

confidence: 99%

Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

Schild

Hawley

Chipman

et al. 2017

International Journal of Remote Sensing

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Marine-terminating outlet glaciers discharge mass through iceberg calving, submarine melting, and meltwater run-off. While calving can be quantified by in situ and remote-sensing observations, meltwater run-off, the subglacial transport of meltwater, and submarine melting are not well constrained due to inherent difficulties observing the subglacial and proglacial environments at tidewater glaciers. Remote-sensing and in situ measurements of surface sediment plumes, and their suspended sediment concentration (SSC), have been used as a proxy for glacier meltwater run-off. However, this relationship between satellite reflectance and SSC has predominantly been established using land-terminating glaciers. Here, we use two Svalbard tidewater glaciers to establish a well-constrained relationship between Landsat-8 surface reflecance and SSC and argue that it can be used to measure relative meltwater runoff at tidewater glaciers throughout a summer melt season. We find the highest correlation between SSCs and Landsat-8 surface reflectance by using the red + NIR band combination (r 2 = 0.76). The highest correlation between SSCs and in situ field spectrometer measurements is in the 740-800 nm wavelength range (r 2 = 0.85), a spectral range not currently measured by Landsat. Additionally, we find that in situ and Landsat-8 measurements for surface reflectance of SSCs are not interchangeable and therefore establish a relationship for each detection method. We then use the Landsat-8 relationship to calculate total surface sediment load, finding a strong correlation between total surface sediment load and a proxy for meltwater run-off (r 2 ≥ 0.89). Our results establish a new metric to calculate SSCs from Landsat-8 surface reflectance and demonstrate how the SSC of subglacial sediment plumes can be used to monitor relative seasonal meltwater discharge at tidewater glaciers. ARTICLE HISTORY

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Seasonal variations of outlet glacier terminus position in Greenland

Cited by 75 publications

References 47 publications

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

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

Estimates of iceberg submarine melting from high-resolution digital elevation models: application to Sermilik Fjord, East Greenland

Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

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