scholarly journals Seasonal variability of the circulation system in a west Greenland tidewater outlet glacier fjord, Godthåbsfjord (64°N)

2014 ◽  
Vol 119 (12) ◽  
pp. 2591-2603 ◽  
Author(s):  
J. Mortensen ◽  
J. Bendtsen ◽  
K. Lennert ◽  
S. Rysgaard
Keyword(s):  
Seasonal Variability ◽  
Circulation System ◽  
Outlet Glacier ◽  
West Greenland

scholarly journals Local Coastal Water Masses Control Heat Levels in a West Greenland Tidewater Outlet Glacier Fjord

2018 ◽  
Vol 123 (11) ◽  
pp. 8068-8083 ◽  
Author(s):  
J. Mortensen ◽  
S. Rysgaard ◽  
K. E. Arendt ◽  
T. Juul-Pedersen ◽  
D. H. Søgaard ◽  
...  
Keyword(s):  
Coastal Water ◽  
Water Masses ◽  
Outlet Glacier ◽  
West Greenland

scholarly journals Subannual and Seasonal Variability of Atlantic-Origin Waters in Two Adjacent West Greenland Fjords

2018 ◽  
Vol 123 (9) ◽  
pp. 6670-6687 ◽  
Author(s):  
D. Carroll ◽  
D. A. Sutherland ◽  
B. Curry ◽  
J. D. Nash ◽  
E. L. Shroyer ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
West Greenland ◽  
Atlantic Origin

scholarly journals Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

2020 ◽  
Vol 14 (1) ◽  
pp. 261-286 ◽  
Author(s):  
Kelly A. Hogan ◽  
Martin Jakobsson ◽  
Larry Mayer ◽  
Brendan T. Reilly ◽  
Anne E. Jennings ◽  
...  
Keyword(s):  
Sediment Flux ◽  
Outlet Glacier ◽  
Glacial Sediment ◽  
West Greenland ◽  
North West ◽  
Erosion Rates ◽  
Nares Strait ◽  
Ice Stream ◽  
Ice Retreat ◽  
Acoustic Facies

Abstract. Petermann Fjord is a deep (>1000 m) fjord that incises the coastline of north-west Greenland and was carved by an expanded Petermann Glacier, one of the six largest outlet glaciers draining the modern Greenland Ice Sheet (GrIS). Between 5 and 70 m of unconsolidated glacigenic material infills in the fjord and adjacent Nares Strait, deposited as the Petermann and Nares Strait ice streams retreated through the area after the Last Glacial Maximum. We have investigated the deglacial deposits using seismic stratigraphic techniques and have correlated our results with high-resolution bathymetric data and core lithofacies. We identify six seismo-acoustic facies in more than 3500 line kilometres of sub-bottom and seismic-reflection profiles throughout the fjord, Hall Basin and Kennedy Channel. Seismo-acoustic facies relate to bedrock or till surfaces (Facies I), subglacial deposition (Facies II), deposition from meltwater plumes and icebergs in quiescent glacimarine conditions (Facies III, IV), deposition at grounded ice margins during stillstands in retreat (grounding-zone wedges; Facies V) and the redeposition of material downslope (Facies IV). These sediment units represent the total volume of glacial sediment delivered to the mapped marine environment during retreat. We calculate a glacial sediment flux for the former Petermann ice stream as 1080–1420 m3 a−1 per metre of ice stream width and an average deglacial erosion rate for the basin of 0.29–0.34 mm a−1. Our deglacial erosion rates are consistent with results from Antarctic Peninsula fjord systems but are several times lower than values for other modern GrIS catchments. This difference is attributed to fact that large volumes of surface water do not access the bed in the Petermann system, and we conclude that glacial erosion is limited to areas overridden by streaming ice in this large outlet glacier setting. Erosion rates are also presented for two phases of ice retreat and confirm that there is significant variation in rates over a glacial–deglacial transition. Our new glacial sediment fluxes and erosion rates show that the Petermann ice stream was approximately as efficient as the palaeo-Jakobshavn Isbræ at eroding, transporting and delivering sediment to its margin during early deglaciation.

scholarly journals Change Points Detected in Decadal and Seasonal Trends of Outlet Glacier Terminus Positions across West Greenland

2020 ◽  
Vol 12 (21) ◽  
pp. 3651
Author(s):  
Ashley V. York ◽  
Karen E. Frey ◽  
Sadegh Jamali ◽  
Sarah B. Das
Keyword(s):  
Sea Surface ◽  
Change Points ◽  
Change Point Analysis ◽  
Landsat Images ◽  
Sea Ice Concentration ◽  
Outlet Glacier ◽  
West Greenland ◽  
Glacier Terminus ◽  
Point Analysis ◽  
Ice Concentration

We investigated the change in terminus position between 1985 and 2015 of 17 marine-terminating glaciers that drain into Disko and Uummannaq Bays, West Greenland, by manually digitizing over 5000 individual frontal positions from over 1200 Landsat images. We find that 15 of 17 glacier termini retreated over the study period, with ~80% of this retreat occurring since 2000. Increased frequency of Landsat observations since 2000 allowed for further investigation of the seasonal variability in terminus position. We identified 10 actively retreating glaciers based on a significant positive relationship between glaciers with cumulative retreat >300 m since 2000 and their average annual amplitude (seasonal range) in terminus position. Finally, using the Detecting Breakpoints and Estimating Segments in Trend (DBEST) program, we investigated whether the 2000–2015 trends in terminus position were explained by the occurrence of change points (significant trend transitions). Based on the change point analysis, we found that nine of 10 glaciers identified as actively retreating also underwent two or three periods of change, during which their terminus positions were characterized by increases in cumulative retreat. Previous literature suggests potential relationships between our identified change dates with anomalous ocean conditions, such as low sea ice concentration and high sea surface temperatures, and our change durations with individual fjord geometry.

Late-Holocene diatom derived seasonal variability in hydrological conditions off Disko Bay, West Greenland

2013 ◽  
Vol 67 ◽  
pp. 93-104 ◽  
Author(s):  
Diana W. Krawczyk ◽  
Andrzej Witkowski ◽  
Jeremy Lloyd ◽  
Matthias Moros ◽  
Jan Harff ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
Late Holocene ◽  
West Greenland ◽  
Hydrological Conditions

scholarly journals Linking catchment-scale subglacial discharge to subsurface glacially modified waters near the front of a marine terminating outlet glacier using an autonomous underwater vehicle

2015 ◽  
Vol 9 (5) ◽  
pp. 4583-4624 ◽  
Author(s):  
L. A. Stevens ◽  
F. Straneo ◽  
S. B. Das ◽  
A. J. Plueddemann ◽  
A. L. Kukulya ◽  
...  
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Underwater Vehicle ◽  
Catchment Scale ◽  
Outlet Glacier ◽  
West Greenland ◽  
Plume Model ◽  
Fjord System

Abstract. Measurements of near-ice (< 200 m) hydrography and near-terminus subglacial hydrology are lacking due in large part to the difficulty in working at the margin of calving glaciers. Here we pair detailed hydrographic and bathymetric measurements collected with an Autonomous Underwater Vehicle as close as 150 m from the ice/ocean interface of the Sarqardliup sermia/Sarqardleq Fjord system, West Greenland, with modeled and observed subglacial discharge locations and magnitudes. We find evidence of two main types of subsurface glacially modified water localized in space and with distinct properties that are consistent with runoff discharged at two locations along the grounded margin. These locations, in turn, correspond with two prominent subglacial subcatchments beneath Sarqardliup sermia. Thus, near-ice observations and subglacial discharge routing indicate that subglacial discharge from this glacier occurs at only two primary locations and gives rise to two distinct glacially modified waters. Furthermore, we show that the location with the largest discharge flux is associated with the lighter, fresher glacially modified watermass. This is qualitatively consistent with results from an idealized plume model.

scholarly journals Seismic-reflection evidence for a deep subglacial trough beneath Jakobshavns Isbræ, West Greenland

1996 ◽  
Vol 42 (141) ◽  
pp. 219-232 ◽  
Author(s):  
Ted S. Clarke ◽  
Keiih Echelmeyer
Keyword(s):  
Seismic Reflection ◽  
Dominant Role ◽  
Ice Thickness ◽  
Shear Stresses ◽  
Outlet Glacier ◽  
West Greenland ◽  
Ice Stream ◽  
Surface Slopes ◽  
Radio Echo Sounding ◽  
Basal Shear

AbstractSeismic-reflection methods were used to determine the ice thickness and basal topography of Jakobshavns Isbræ, a large, fast-moving ice stream/outlet glacier in West Greenland. A method of data analysis was developed which involves the pointwise migration of data from a linear seismic array and a single explosive source; the method yields the depth, horizontal position and slope of the basal reflector. A deep U-shaped subglacial trough was found beneath the entire length of the well-defined ice stream. The trough is incised up to 1500 m into bedrock, and its base lies 1200–1500 m below sea level for at least 70 km inland. Center-line ice thickness along most of the channel is about 2500 m, or about 2.5 times that of the surrounding ice sheet. This prominent bedrock trough was not apparent in existing radio-echo-sounding data. Reflection coefficients indicate that much of the basal interface is probably underlain by compacted, non-deforming sediment. The large ice thickness, coupled with relatively steep surface slopes, leads to high basal shear stresses (200–300 k Pa) along the ice stream. The large shear stresses and lack of a deformable bed imply that internal deformation plays a dominant role in the dynamics of Jakobshavns Isbræ.

scholarly journals Are seasonal calving dynamics forced by buttressing from ice mélange or undercutting by melting? Outcomes from full-Stokes simulations of Store Glacier, West Greenland

2014 ◽  
Vol 8 (6) ◽  
pp. 2353-2365 ◽  
Author(s):  
J. Todd ◽  
P. Christoffersen
Keyword(s):  
The Other ◽  
Subgrid Scale ◽  
Outlet Glacier ◽  
West Greenland ◽  
Oceanic Forcing ◽  
Calving Rate ◽  
Forcing Mechanisms ◽  
D Model ◽  
Shed Light ◽  
Limited Sensitivity

Abstract. We use a full-Stokes 2-D model (Elmer/Ice) to investigate the flow and calving dynamics of Store Glacier, a fast-flowing outlet glacier in West Greenland. Based on a new, subgrid-scale implementation of the crevasse depth calving criterion, we perform two sets of simulations: one to identify the primary forcing mechanisms and another to constrain future stability. We find that the mixture of icebergs and sea ice, known as ice mélange or sikussak, is principally responsible for the observed seasonal advance of the ice front. On the other hand, the effect of submarine melting on the calving rate of Store Glacier appears to be limited. Sensitivity analysis demonstrates that the glacier's calving dynamics are sensitive to seasonal perturbation, but are stable on interannual timescales due to the strong topographic control on the flow regime. Our results shed light on the dynamics of calving glaciers and may help explain why neighbouring glaciers do not necessarily respond synchronously to changes in atmospheric and oceanic forcing.

scholarly journals Change in position and altitude of a small outlet glacier during the period 1943–92: Leverett Glacier, West Greenland

1995 ◽  
Vol 21 ◽  
pp. 251-258
Author(s):  
Frank G.M. Van Tatenhove ◽  
Chris M. Roelfsema ◽  
Geert Blommers ◽  
Anton Van Voorden
Keyword(s):  
Greenland Ice Sheet ◽  
Maximum Error ◽  
Meteorological Conditions ◽  
Control Points ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
West Greenland ◽  
Exposed Rock ◽  
Time Period ◽  
Climate Station

Fluctuations in the position and surface altitude of Leverett Glacier, a small outlet glacier at the western margin of the Greenland ice sheet, are determined from a photogrammetric analysis. During the Greenland Ice-Margin Experiment (GIMEX) 1992 expedition, six control points were measured on the exposed rock surrounding Leverett Glacier, using a distancemeter (AGA 220 Geodimeter) and theodolite (Wild T2). Photogrammetric measurements were carried out on an analytical plotter (Zeiss Planicomp C100). The altitude of points could be photogrammetrically measured with a maximum error of 0.86 m.The data on the altitude changes of Leverett Glacier presented here are the first in West Greenland that span a time period of nearly 50 years. During the period 1943–68 the rate of altitude change was –0.6 m w.e.a−1. The thickening rate during the period 1968–85 was + 1.2 m w.e.a−1. Thickening continued dining the period 1985–92 at a rate of + 0.4 m w.e.a−1. This recent thickening is significant when compared to year-to-year variation in ablation. Trends in air temperature from the nearby climate station at Kangerlussuaq are consistent with the possibility that observed changes in the altitude of the glacier surface are the result of local changes in meteorological conditions determining ablation rates.

scholarly journals Variability in ice motion at a land-terminating Greenlandic outlet glacier: the role of channelized and distributed drainage systems

2016 ◽  
Vol 62 (233) ◽  
pp. 451-466 ◽  
Author(s):  
TOM COWTON ◽  
PETER NIENOW ◽  
ANDREW SOLE ◽  
IAN BARTHOLOMEW ◽  
DOUGLAS MAIR
Keyword(s):  
Seasonal Variability ◽  
Close Agreement ◽  
Water Pressure ◽  
Cavity Expansion ◽  
Field Observations ◽  
Coupled Models ◽  
Outlet Glacier ◽  
Basal Ice ◽  
Ice Velocity

ABSTRACTWe use a combination of field observations and hydrological modelling to examine the mechanisms through which variability in meltwater input affects ice motion at a land-terminating Greenlandic outlet glacier. We find a close agreement between horizontal ice velocity, vertical ice velocity and modelled subglacial water pressure over the course of a melt season. On this basis, we argue that variation in horizontal and vertical ice velocity primarily reflects the displacement of basal ice during periods of cavity expansion and contraction, a process itself driven by fluctuations in basal water pressure originating in subglacial channels. This process is not captured by traditional sliding laws linking water pressure and basal velocity, which may hinder the simulation of realistic diurnal to seasonal variability in ice velocity in coupled models of glacial hydrology and dynamics.

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