Marine geophysical evidence for former expansion and flow of the Greenland Ice Sheet across the north-east Greenland continental shelf

All available mean annual accumulation data on the Greenland ice sheet (excluding the Thule peninsula) have been collected and analyzed using multiple regression techniques to develop equations capable of predicting mean annual accumulation. The analysis was carried out for north Greenland, south Greenland, and for the transition zone between the two major regions. The resulting equations show that mean annual accumulation can be predicted from the independent parameters latitude, longitude and elevation. The patterns of accumulation are shown in a series of isohyetal (contours of accumulation in terms of water) maps. The major feature shown is a well defined asymmetry in accumulation; a pronounced east-slope maximum in south Greenland and an equally pronounced west-slope maximum in north Greenland. Poleward of lat. 69° N., isohyets decrease in elevation to the north. Mean annual accumulation ranges from >90 g./cm.2in south-east Greenland to <15 g./cm.2in north-east Greenland. A brief discussion of mass balance estimates of the Greenland ice sheet and of the relevance of this study to them is included.

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Calculated Patterns of Accumulation on the Greenland Ice Sheet

Journal of Glaciology ◽

10.3189/s0022143000020104 ◽

1967 ◽

Vol 6 (48) ◽

pp. 795-803 ◽

Cited By ~ 3

Author(s):

Steven J. Mock

Keyword(s):

Mass Balance ◽

Transition Zone ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

East Greenland ◽

North East ◽

The North ◽

Regression Techniques ◽

Independent Parameters ◽

North Greenland

All available mean annual accumulation data on the Greenland ice sheet (excluding the Thule peninsula) have been collected and analyzed using multiple regression techniques to develop equations capable of predicting mean annual accumulation. The analysis was carried out for north Greenland, south Greenland, and for the transition zone between the two major regions. The resulting equations show that mean annual accumulation can be predicted from the independent parameters latitude, longitude and elevation. The patterns of accumulation are shown in a series of isohyetal (contours of accumulation in terms of water) maps. The major feature shown is a well defined asymmetry in accumulation; a pronounced east-slope maximum in south Greenland and an equally pronounced west-slope maximum in north Greenland. Poleward of lat. 69° N., isohyets decrease in elevation to the north. Mean annual accumulation ranges from >90 g./cm.2 in south-east Greenland to <15 g./cm.2 in north-east Greenland. A brief discussion of mass balance estimates of the Greenland ice sheet and of the relevance of this study to them is included.

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The Nioghalvfjerdsfjorden glacier project, North-East Greenland: a study of ice sheet response to climatic change

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/ggub.v176.5073 ◽

1997 ◽

pp. 95-103 ◽

Cited By ~ 5

Author(s):

Henrik Højmark Thomsen ◽

Niels Reeh ◽

Ole B. Olesen ◽

Carl Egede Bøggilde ◽

Wolfgang Starzer ◽

...

Keyword(s):

Climatic Change ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

East Greenland ◽

Changing Climate ◽

North East ◽

Integrated Research ◽

Research Themes ◽

Advance Research ◽

Inland Ice

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Højmark Thomsen, H., Reeh, N., Olesen, O. B., Egede Bøggilde, C., Starzer, W., Weidick, A., & Higgins, A. K. (1997). The Nioghalvfjerdsfjorden glacier project, North-East Greenland: a study of ice sheet response to climatic change. Geology of Greenland Survey Bulletin, 176, 95-103. https://doi.org/10.34194/ggub.v176.5073 _______________ Glaciological research was initiated in 1996 on the floating glacier tongue filling Nioghalvfjerdsfjorden in NorthEast Greenland (Fig. 1), with the aim of acquiring a better understanding of the response of the Greenland ice sheet (Inland Ice) to changing climate, and the implications for future sea level. The research is part of a three year project (1996–98) to advance research into the basic processes that contribute to changes in the ocean volume with a changing climate. Five nations are participants in the project, which is supported by the European Community (EC) Environment and Climate Programme. The Geological Survey of Denmark and Greenland (GEUS) and the Danish Polar Center are the Danish partners in the project, both with integrated research themes concentrated on and around Nioghalvfjerdsfjorden.

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The effect of the north-east ice stream on the Greenland ice sheet in changing climates

The Cryosphere Discussions ◽

10.5194/tcd-1-41-2007 ◽

2007 ◽

Vol 1 (1) ◽

pp. 41-76 ◽

Cited By ~ 10

Author(s):

R. Greve ◽

S. Otsu

Keyword(s):

Large Scale ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Simulation Code ◽

North East ◽

The North ◽

Ice Stream ◽

Basal Sliding ◽

Speed Up ◽

Fast Flow

Abstract. The north-east Greenland ice stream (NEGIS) was discovered as a large fast-flow feature of the Greenland ice sheet by synthetic aperture radar (SAR) imaginary of the ERS-1 satellite. In this study, the NEGIS is implemented in the dynamic/thermodynamic, large-scale ice-sheet model SICOPOLIS (Simulation Code for POLythermal Ice Sheets). In the first step, we simulate the evolution of the ice sheet on a 10-km grid for the period from 250 ka ago until today, driven by a climatology reconstructed from a combination of present-day observations and GCM results for the past. We assume that the NEGIS area is characterized by enhanced basal sliding compared to the "normal", slowly-flowing areas of the ice sheet, and find that the misfit between simulated and observed ice thicknesses and surface velocities is minimized for a sliding enhancement by the factor three. In the second step, the consequences of the NEGIS, and also of surface-meltwater-induced acceleration of basal sliding, for the possible decay of the Greenland ice sheet in future warming climates are investigated. It is demonstrated that the ice sheet is generally very susceptible to global warming on time-scales of centuries and that surface-meltwater-induced acceleration of basal sliding can speed up the decay significantly, whereas the NEGIS is not likely to dynamically destabilize the ice sheet as a whole.

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Simulation of the Greenland Ice sheet over two glacial cycles: Investigating a sub-ice shelf melt parameterisation and relative sea level forcing in an ice sheet-ice shelf model

10.5194/cp-2017-132 ◽

2017 ◽

Cited By ~ 1

Author(s):

Sarah L. Bradley ◽

Thomas J. Reerink ◽

Roderik S. W. van de Wal ◽

Michiel M. Helsen

Keyword(s):

Continental Shelf ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Shelf ◽

Temporal Behaviour ◽

The North ◽

Non Local ◽

Continental Shelf Break

Abstract. Observational evidence, including offshore moraines and sediment cores confirm that at the Last Glacial maximum (LGM) the Greenland ice sheet (GrIS) grew to a significantly larger spatial extent than seen at present, grounding into Baffin Bay and to the continental shelf break. Given this larger spatial extent and it is close proximity to the neighboring Laurentide (LIS) and Innuitian Ice sheet (IIS), it is likely these ice sheets will have had a strong non-local influence on the spatial and temporal behaviour of the GrIS. Most previous paleo ice sheet modelling simulations recreated an ice sheet that either did not extend out onto the continental shelf; or utilized a simplified marine ice parametersiation and therefore did not fully include ice shelf dynamics, and or the sensitivity of the GrIS to this non-local signal from the surrounding ice sheets. In this paper, we investigated the evolution of the GrIS over the two most recent glacial-interglacial cycles (240 kyr BP to present day), using the ice sheet-ice shelf model, IMAU-ICE and investigated the influence of the LIS and IIS via an offline relative sea level (RSL) forcing generated by a GIA model. This RSL forcing controlled via changes in the water depth below the developing ice shelves, the spatial and temporal pattern of sub-ice shelf melting, which was parametrised in relation to changes in water depth. In the suite of simulations, the GrIS at the glacial maximums coalesced with the IIS to the north, expanded to the continental shelf break to the south west but remained too restricted to the north east. In terms of an ice-volume equivalent sea level contribution, at the Last Interglacial (LIG) and LGM the ice sheet added 1.46 m and −2.59 m to the budget respectively. The estimated lowering of the sea level by the Greenland contribution is considerably more (1.26 m) than most previous studies indicated whereas the contribution to the LIG high stand is lower (0.7 m). The spatial and temporal behaviour of the northern margin was highly variable in all simulations, controlled by the sub surface melt (SSM), which was dictated by the RSL forcing and the glacial history of the IIS and LIS. In contrast, the southwestern part of the ice sheet was insensitive to these forcing’s, with a uniform response in an all simulations controlled by the surface air temperature (SAT) forcing, derived from ice cores.

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The Greenland ice sheet - a model for its culmination and decay during and after the last glacial maximum

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1995-42-12 ◽

1996 ◽

Vol 42 ◽

pp. 137-152 ◽

Cited By ~ 1

Author(s):

Svend Funder ◽

Louise Hansen

Keyword(s):

Frequency Distribution ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Field Work ◽

East Greenland ◽

Nares Strait ◽

The North ◽

Field Evidence ◽

Insolation Maximum ◽

The Last Glacial

Ice margin reconstructions of the Greenland ice sheet during LGM (c. 21-16 ka) and 10 ka are based on published onshore field evidence supplemented with recent studies on the East Greenland shelf and results of current field work in the Scoresby Sund area Additional evidence comes from the pattern of Holocene uplift and the frequency distribution of more than 1000 14C-dates. During LGM, only southern Greenland (south of lat. 69°-72°N) saw a major expansion of the ice sheet with thick cover over the present coastline and onto the shelf. In the north, outlet glaciers filled fjord basins, including the Nares Strait between Canada and Greenland, and piedmont glaciers descended from coastal mountains onto the coastline, but the glaciers did not cover the shelf. Break up probably began after c. 15 ka, and took place in two discrete steps. First, the shelf and major inlets were cleared of marine based ice. There was little thinning of the ice on land, and in the northern parts there was little change at all. The driving factor during this step was calving caused by rising sea level. This lasted until c. 10 ka, but may have been consumated before the Younger Dry as. The second step began with a glacier-readvance between 10 and 9.5 ka, and after this the fjord glaciers began to retreat rapidly. Within a few millenia all the presently ice free land was exposed. The frequency distribution of 14C-dates show that the nearshore marine and terrestrial biotopes emerged in this period. The discharge of ice was both by calving and melting, and the driving force was probably increased insolation. Maximum Holocene uplift was attained in areas of the 10 ka ice margin, indicating that the uplift is essentially a response to the melting and unloading of ice that began at this time. In suppport of this, recent results in West, North and East Greenland indicate that the age of the marine limits decline towards the outer coasts, away from the 10 ka ice margin.

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Heat flux and the North East Greenland Ice Stream

10.5194/egusphere-egu21-13450 ◽

2021 ◽

Author(s):

Paul D. Bons ◽

Tamara de Riese ◽

Steven Franke ◽

Maria-Gema Llorens ◽

Till Sachau ◽

...

Keyword(s):

Heat Flux ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Heat Fluxes ◽

High Heat Flux ◽

Geothermal Heat ◽

Radiogenic Heat ◽

East Greenland ◽

North East ◽

Ice Stream

The prominent North East Greenland Ice Stream (NEGIS) is an exceptionally large ice stream in the Greenland Ice sheet. It is over 500 km long, originates almost at the central ice divide, and contributes significantly to overall ice drainage from the Greenland Ice sheet. Surface velocities in the inland part of the ice stream are several times higher inside NEGIS than in the adjacent ice sheet. Modelling NEGIS is still a challenge as it remains unclear what actually causes and controls the ice stream.An elevated geothermal heat flux is one of the factors that are being considered to trigger or drive the fast flow inside NEGIS. Unfortunately, the geothermal heat flux below NEGIS and its upstream area is poorly constrained and estimates vary from close to the global average for continental crust (ca. 60 mW/m2) to values as high as almost 1000 mW/m2. The latter would cause about 10 cm/yr of melting at the base of the ice sheet.We present a brief survey of global geothermal heat flux data, especially from known hotspots, such as Iceland and Yellowstone. Heat fluxes in these areas that are known to be among the hottest on Earth rarely, if ever, exceed 300 mW/m2. A plume hotspot or its trail can therefore not cause heat fluxes at the high end of the suggested range. Other potential factors, such as hydrothermal fluid flow and radiogenic heat, also cannot raise the heat flux significantly. We conclude that the heat flux at NEGIS is very unlikely to exceed 100-150 mW/m2, and future modelling studies on NEGIS should thus be mindful of implementing realistic geothermal heat flux values. If NEGIS is not the result of an exceptionally high heat flux, we are left with the exciting challenge to find the true trigger of this fascinating structure.

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Recent North Greenland temperature warming and accumulation

10.5194/tc-2020-337 ◽

2021 ◽

Author(s):

Helle Astrid Kjær ◽

Patrick Zens ◽

Ross Edwards ◽

Martin Olesen ◽

Ruth Mottram ◽

...

Keyword(s):

Mass Balance ◽

Climate Model ◽

Regional Climate ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Snow Accumulation ◽

Topographic Effects ◽

North East ◽

The North ◽

North Greenland

Abstract. In a warming climate concise knowledge of the mass balance of the Greenland ice sheet is of utter importance. Speculations that current warming will increase the snow accumulation and mitigate mass balance losses are unconstrained as accumulation data across large regions of the northern ice sheet are scarce. We reconstructed the accumulation from six north Greenland shallow firn cores (~10 m) and eight snow cores (~2 m) to constrain recent accumulation patterns in northern Greenland and calculated recent warming in the same area using borehole temperature measurements. We find an increase in temperatures in the north Greenland interior of 0.9 to 2.5 °C (method and site dependent) per decade over the past two decades in line with an Arctic amplified anthropogenic warming. We compare annual reconstructed accumulation from the firn cores (1966–2015) to radar estimates and to annual re-analysis data (1980–2016) of precipitation subtracted evaporation from the regional climate model HIRHAM5, operated by the Danish Meteorological Institute. The spatial variability resembles that observed in earlier estimates with a clear increase west of the topographic divide and a low accumulation area across the north-eastern ice sheet. Our accumulation results are comparable to earlier firn core estimates, despite being larger in the east. We only find a positive significant trend in the accumulation for the period 2000–2010 to the northwest. In the vicinity of the EGRIP deep ice core drilling site, we find variable accumulation patterns for two 15 km apart firn cores likely owing to local topographic effects as a result of the North East Greenland Ice Stream dynamics.

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A confined–unconfined aquifer model for subglacial hydrology and its application to the North East Greenland Ice Stream

10.5194/tc-2017-221 ◽

2017 ◽

Cited By ~ 2

Author(s):

Sebastian Beyer ◽

Thomas Kleiner ◽

Vadym Aizinger ◽

Martin Rückamp ◽

Angelika Humbert

Keyword(s):

Computational Cost ◽

Ice Sheet ◽

Unconfined Aquifer ◽

Ocean Modeling ◽

Model Parameters ◽

Efficient System ◽

East Greenland ◽

North East ◽

The North ◽

Ice Stream

Abstract. Subglacial hydrology plays an important role in the ice sheet dynamics as it determines the sliding velocity of ice sheets and also drives freshwater into the ocean. Modeling subglacial water has been a challenge for decades, and only recently new approaches have been developed such as representing subglacial channels and thin water sheets by separate layers of variable permeability. We extend this concept by modeling a confined and unconfined aquifer system (CUAS) in a single layer. The advantage of this formulation is that it prevents unphysical values of pressure at reasonable computational cost. We also performed sensitivity tests to investigate the effect of different model parameters. The strongest influence of model parameters was detected in terms governing the opening and closure of channels. Furthermore, we applied the model to the North East Greenland Ice Stream, where an efficient system independent of seasonal input was identified about 500 km downstream from the ice divide. Using the effective pressure from the hydrology model in the Ice Sheet System Model (ISSM) shows considerable improvements of modeled velocities in the coastal region.

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