scholarly journals Calculated Patterns of Accumulation on the Greenland Ice Sheet

1967 ◽  
Vol 6 (48) ◽  
pp. 795-803 ◽  
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.

scholarly journals Calculated Patterns of Accumulation on the Greenland Ice Sheet

1967 ◽  
Vol 6 (48) ◽  
pp. 795-803 ◽  
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 &gt;90 g./cm.2in south-east Greenland to &lt;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.

scholarly journals Recent North Greenland temperature warming and accumulation

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.

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

2009 ◽  
Vol 24 (3) ◽  
pp. 279-293 ◽  
Author(s):  
Jeffrey Evans ◽  
Colm Ó Cofaigh ◽  
Julian A. Dowdeswell ◽  
Peter Wadhams
Keyword(s):  
Continental Shelf ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
East Greenland ◽  
North East ◽  
The North

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

1997 ◽  
pp. 95-103 ◽  
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.

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

2007 ◽  
Vol 1 (1) ◽  
pp. 41-76 ◽  
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.

scholarly journals Modelling snow accumulation on Greenland in Eemian, glacial inception and modern climates in a GCM

2012 ◽  
Vol 8 (2) ◽  
pp. 1523-1565 ◽  
Author(s):  
H. J. Punge ◽  
H. Gallée ◽  
M. Kageyama ◽  
G. Krinner
Keyword(s):  
Mass Balance ◽  
Ocean Circulation ◽  
Accumulation Rate ◽  
High Surface ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Local Climate ◽  
North East ◽  
Surface Climate

Abstract. Changing climate conditions on Greenland influence the snow accumulation rate and surface mass balance (SMB) on the ice sheet and, ultimately, its shape. This can in turn affect local climate via orography and albedo variations and, potentially, remote areas via changes in ocean circulation triggered by melt water or calving from the ice sheet. Examining these issues in the IPSL global model requires improving the representation of snow at the ice sheet surface. In this paper, we present the new snow scheme implemented in LMDZ, the atmospheric component of the IPSL coupled model. We analyze surface climate and SMB on the Greenland ice sheet under insolation and oceanic boundary conditions for modern, but also for two different past climates, the last glacial inception (115 kyr BP) and the Eemian (126 kyr BP). While being limited by the low resolution of the GCM, present-day SMB is on the same order of magnitude as recent regional model findings. It is affected by a moist bias of the GCM in Western Greenland and a dry bias in the north-east. Under Eemian conditions, the SMB diminishes largely, and melting affects areas with today high surface altitude including recent ice core drilling sites as NEEM. In contrast, glacial inception conditions lead to a higher mass balance overall due to the reduced melting in the colder summer climate. Compared to the widely applied positive degree day (PDD) parameterization of SMB, our direct modelling results suggest a weaker sensitivity of SMB to changing climatic forcing. In addition, significant differences in surface climate and SMB are found between simulations using monthly climatological mean and actual interannually varying monthly mean forcings for the ocean surface temperature and sea ice cover, in particular for the Eemian.

scholarly journals Small impact of surrounding oceanic conditions on 2007–2012 Greenland Ice Sheet surface mass balance

2014 ◽  
Vol 8 (2) ◽  
pp. 1453-1477 ◽  
Author(s):  
B. Noël ◽  
X. Fettweis ◽  
W. J. van de Berg ◽  
M. R. van den Broeke ◽  
M. Erpicum
Keyword(s):  
Mass Balance ◽  
North Atlantic ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Katabatic Winds ◽  
Surface Mass ◽  
The North ◽  
The North Atlantic ◽  
Surface Melt

Abstract. During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North-Atlantic Oscillation (NAO), favouring warmer than normal conditions over the GrIS. In addition, it has been suggested that significant anomalies in sea ice cover (SIC) and sea surface temperature (SST) may partially explain recent anomalous GrIS surface melt. To assess the impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR. These simulations suggest that changes in SST and SIC in the seas surrounding Greenland do not significantly impact GrIS SMB, due to the katabatic winds blocking effect. These winds are strong enough to prevent oceanic near-surface air, influenced by SIC and SST variability, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds are weaker. However, anomalies in SIC and SST could have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, favouring more frequent warm air advection to the GrIS.

Chapter 16 Devonian history

1997 ◽  
Vol 17 (1) ◽  
pp. 289-309 ◽  
Author(s):  
W. Brian Harland
Keyword(s):  
Early Devonian ◽  
East Greenland ◽  
Red Sandstone ◽  
North East ◽  
The North ◽  
Fossil Fish ◽  
Red Bay ◽  
The Many ◽  
Orogenic Events ◽  
North Greenland

Svalbard is part of the Old Red Sandstone province with affinities in East Greenland, Norway, Appalachian North America and, of course, the British Isles where the Devonian Period was defined. This allows Devonian history in this region, controlled by Caledonian events, to form a neat and natural chapter, though not necessarily a global one. Old Red Sandstone environments in each area were already becoming established in Late Silurian time. Olaf Holtedahl was the prime author of both Caledonian tectogenesis in Svalbard and the Old Red Sandstone aftermath.Of the many and varied biotas of Svalbard the fossil fish have made remarkable and classic contributions to Spitsbergen geology.The earliest 'Old Red Sandstone' Spitsbergen strata have yet to yield evidence of age and so may be latest Silurian (Siktefjellet Group). But the earliest Devonian strata to be identified biostratigraphically begin with the Red Bay Group. Similarly the (major) Ny Friesland Orogeny and the various late orogenic granite emplacements, while initially Silurian, continued at least to cool in Devonian time. For convenience the orogenic events that may continue as early Devonian are treated in the Silurian chapter and the sedimentary events that may be Silurian are treated here.Devonian successions in Svalbard are known only from terranes which are postulated to have originated from the North East Greenland Province. No record has yet been established for Devonian strata in Svalbard either from the eastern terranes (East Greenland Province) or from the western terranes (North Greenland-Pearya Province). Moreover, the East Greenland succession lacks

Tectono-stratigraphic history of northern Amdrup Land, eastern North Greenland: implications for the northernmost East Greenland shelf

2000 ◽  
pp. 167-191
Author(s):  
Lars Stemmerik ◽  
Birgitte D. Larsen ◽  
Finn Dalhoff
Keyword(s):  
Plate Boundary ◽  
Southern Limit ◽  
East Greenland ◽  
North East ◽  
The North ◽  
Upper Proterozoic ◽  
Structural Style ◽  
History Of ◽  
Land Changes ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Stemmerik, L., Larsen, B. D., & Dalhoff, F. (2000). Tectono-stratigraphic history of northern Amdrup Land, eastern North Greenland: implications for the northernmost East Greenland shelf. Geology of Greenland Survey Bulletin, 187, 167-191. https://doi.org/10.34194/ggub.v187.5192 _______________ The NW–SE-oriented Sommerterrasserne fault in Amdrup Land marks the southern limit of Mesozoic compression related to the transform plate boundary between North Greenland and Svalbard. Structural style in Amdrup Land changes across the fault; Carboniferous, Permian and Jurassic sediments in northern Amdrup Land north-east of the fault are gently folded, with NE– SW-trending fold axes, whereas they are gently dipping south of the fault. The Sommerterrasserne fault is regarded as the south-eastern extension of the Trolle Land fault zone of eastern Peary Land. Upper Moscovian carbonates of the Foldedal Formation rest unconformably on isoclinally folded Upper Proterozoic sediments of the Independence Fjord Group in northern Amdrup Land and are conformably overlain by chert-rich limestones of the Permian Kim Fjelde and Midnatfjeld Formations. Locally, up to 70 m of Jurassic sandstone and siltstone are preserved in the axes of the synclines, resting conformably on Permian limestones; the folding thus post-dates their deposition. The folding of the sediments to the north-east of the Sommerterrasserne fault most likely took place during the latest Cretaceous; it is post-dated by a post- Paleocene extensional event.

scholarly journals Probabilistic parameterisation of the surface mass balance–elevation feedback in regional climate model simulations of the Greenland ice sheet

2014 ◽  
Vol 8 (1) ◽  
pp. 181-194 ◽  
Author(s):  
T. L. Edwards ◽  
X. Fettweis ◽  
O. Gagliardini ◽  
F. Gillet-Chaulet ◽  
H. Goelzer ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Mass Balance ◽  
Sea Level ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
The North

Abstract. We present a new parameterisation that relates surface mass balance (SMB: the sum of surface accumulation and surface ablation) to changes in surface elevation of the Greenland ice sheet (GrIS) for the MAR (Modèle Atmosphérique Régional: Fettweis, 2007) regional climate model. The motivation is to dynamically adjust SMB as the GrIS evolves, allowing us to force ice sheet models with SMB simulated by MAR while incorporating the SMB–elevation feedback, without the substantial technical challenges of coupling ice sheet and climate models. This also allows us to assess the effect of elevation feedback uncertainty on the GrIS contribution to sea level, using multiple global climate and ice sheet models, without the need for additional, expensive MAR simulations. We estimate this relationship separately below and above the equilibrium line altitude (ELA, separating negative and positive SMB) and for regions north and south of 77° N, from a set of MAR simulations in which we alter the ice sheet surface elevation. These give four "SMB lapse rates", gradients that relate SMB changes to elevation changes. We assess uncertainties within a Bayesian framework, estimating probability distributions for each gradient from which we present best estimates and credibility intervals (CI) that bound 95% of the probability. Below the ELA our gradient estimates are mostly positive, because SMB usually increases with elevation: 0.56 (95% CI: −0.22 to 1.33) kg m−3 a−1 for the north, and 1.91 (1.03 to 2.61) kg m−3 a−1 for the south. Above the ELA, the gradients are much smaller in magnitude: 0.09 (−0.03 to 0.23) kg m−3 a−1 in the north, and 0.07 (−0.07 to 0.59) kg m−3 a−1 in the south, because SMB can either increase or decrease in response to increased elevation. Our statistically founded approach allows us to make probabilistic assessments for the effect of elevation feedback uncertainty on sea level projections (Edwards et al., 2014).

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