scholarly journals A first constraint on basal melt-water production of the Greenland ice sheet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nanna B. Karlsson ◽  
Anne M. Solgaard ◽  
Kenneth D. Mankoff ◽  
Fabien Gillet-Chaulet ◽  
Joseph A. MacGregor ◽  
...  
Keyword(s):  
Mass Loss ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Recent Change ◽  
The Arctic ◽  
Water Production ◽  
Ice Flow ◽  
Fjord Circulation ◽  
Current Mass ◽  
Basal Melting

AbstractThe Greenland ice sheet has been one of the largest sources of sea-level rise since the early 2000s. However, basal melt has not been included explicitly in assessments of ice-sheet mass loss so far. Here, we present the first estimate of the total and regional basal melt produced by the ice sheet and the recent change in basal melt through time. We find that the ice sheet’s present basal melt production is 21.4 +4.4/−4.0 Gt per year, and that melt generated by basal friction is responsible for about half of this volume. We estimate that basal melting has increased by 2.9 ± 5.2 Gt during the first decade of the 2000s. As the Arctic warms, we anticipate that basal melt will continue to increase due to faster ice flow and more surface melting thus compounding current mass loss trends, enhancing solid ice discharge, and modifying fjord circulation.

scholarly journals A new programme for monitoring the mass loss of the Greenland ice sheet

2008 ◽  
Vol 15 ◽  
pp. 61-64 ◽  
Author(s):  
Andreas P. Ahlstrøm ◽  
* PROMICE project team
Keyword(s):  
Mass Loss ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Arctic Region ◽  
Decision Makers ◽  
The Arctic ◽  
National Space ◽  
Ice Caps ◽  
Political Concern ◽  
Global Sea Level

The Greenland ice sheet has been losing mass at a dramatic rate in recent years, raising political concern worldwide due to the possible impact on global sea level rise and climate dynamics (Luthcke et al. 2006; Rignot & Kanagaratnam 2006; Velicogna & Wahr 2006; IPCC 2007; Shepherd & Wingham 2007). The Arctic region as a whole is warming up much more rapidly than the globe at large (ACIA 2005) and it is desirable to quantify these changes in order to provide the decision-makers with a firm knowledge base. To cover this need, the Danish Ministry of Climate and Energy has now launched a new Programme for Monitoring of the Green- land Ice Sheet (PROMICE), designed and operated by the Geological Survey of Denmark and Greenland (GEUS) in collaboration with the National Space Institute at the Tech nical University of Denmark and Asiaq (Greenland Survey). The aim of the programme is to quantify the annual mass loss of the Greenland ice sheet, track changes in the extent of local glaciers and ice caps, and track changes in the position of the ice-sheet margin.

scholarly journals Ice flow around large obstacles as indicated by basal ice exposed at the margin of the Greenland ice sheet

1994 ◽  
Vol 40 (135) ◽  
pp. 359-367 ◽  
Author(s):  
Peter G. Knight ◽  
David E. Sugden ◽  
Christopher D. Minty
Keyword(s):  
Empirical Model ◽  
Basal Layer ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Flow ◽  
Subglacial Environment ◽  
Basal Ice ◽  
Convergence And Divergence ◽  
Basal Melting ◽  
Marginal Environment

AbstractSpatial variations in the debris-bearing basal ice layer exposed at the ice-sheet margin in West Greenland reflect the geography of basal melting and ice flow around large obstacles close to the margin. This paper demonstrates the character of the basal ice layer, which comprises fine material incorporated in an interior, subglacial environment and coarser material entrained in an ice-marginal environment. We develop an empirical model of ice flow close to a lobate margin of the ice sheet in which ice convergence and divergence, and limited subglacial melting affect the character and distribution of the basal ice at the margin. There is a tendency for the convergence and divergence to thicken the basal layer in lobate areas and to thin it in inter-lobate areas. Under certain circumstances, basal melting may remove much of the layer from beneath the snouts of larger lobes, thus causing the basal layer to be thickest in an intermediate location.

The ocean response to changes of the Greenland Ice sheet in a warming climate

2020 ◽  
Author(s):  
Marianne S. Madsen ◽  
Shuting Yang ◽  
Christian Rodehacke ◽  
Guðfinna Aðalgeirsdóttir ◽  
Synne H. Svendsen ◽  
...  
Keyword(s):  
Mass Loss ◽  
Ocean Circulation ◽  
Large Scale ◽  
Climate Model ◽  
Variable Mass ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Model System ◽  
Meridional Overturning Circulation ◽  
The Arctic

<p>During recent decades, increased and highly variable mass loss from the Greenland ice sheet has been observed, implying that the ice sheet can respond to changes in ocean and atmospheric conditions on annual to decadal time scales. Changes in ice sheet topography and increased mass loss into the ocean may impact large scale atmosphere and ocean circulation. Therefore, coupling of ice sheet and climate models, to explicitly include the processes and feedbacks of ice sheet changes, is needed to improve the understanding of ice sheet-climate interactions.</p><p>Here, we present results from the coupled ice sheet-climate model system, EC-Earth-PISM. The model consists of the atmosphere, ocean and sea-ice model system EC-Earth, two-way coupled to the Parallel Ice Sheet Model, PISM. The surface mass balance (SMB) is calculated within EC-Earth, from the precipitation, evaporation and surface melt of snow and ice, to ensure conservation of mass and energy. The ice sheet model, PISM, calculates ice dynamical changes in ice discharge and basal melt as well as changes in ice extent and thickness. Idealized climate change experiments have been performed starting from pre-industrial conditions for a) constant forcing (pre-industrial control); b) abruptly quadrupling the CO<sub>2</sub> concentration; and c) gradually increasing the CO<sub>2</sub> concentration by 1% per year until 4xCO<sub>2</sub> is reached.  All three experiments are run for 350 years.</p><p>Our results show a significant impact of the interactive ice sheet component on heat and fresh water fluxes into the Arctic and North Atlantic Oceans. The interactive ice sheet causes freshening of the Arctic Ocean and affects deep water formation, resulting in a significant delay of the recovery of the Atlantic Meridional Overturning Circulation (AMOC) in the coupled 4xCO<sub>2</sub> experiments, when compared with uncoupled experiments.</p>

scholarly journals Impact of ice-shelf basal melting on inland ice-sheet thickness: a model study

2012 ◽  
Vol 53 (60) ◽  
pp. 129-135 ◽  
Author(s):  
Jürgen Determann ◽  
Malte Thoma ◽  
Klaus Grosfeld ◽  
Sylvia Massmann
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Ice Shelf ◽  
Ice Flow ◽  
Ice Shelves ◽  
Ice Volume ◽  
Basal Melting ◽  
The Impact

AbstractIce flow from the ice sheets to the ocean contains the maximum potential contributing to future eustatic sea-level rise. In Antarctica most mass fluxes occur via the extended ice-shelf regions covering more than half the Antarctic coastline. The most extended ice shelves are the Filchner–Ronne and Ross Ice Shelves, which contribute ~30% to the total mass loss caused by basal melting. Basal melt rates here show small to moderate average amplitudes of <0.5ma–1. By comparison, the smaller but most vulnerable ice shelves in the Amundsen and Bellinghausen Seas show much higher melt rates (up to 30 ma–1), but overall basal mass loss is comparably small due to the small size of the ice shelves. The pivotal question for both characteristic ice-shelf regions, however, is the impact of ocean melting, and, coevally, change in ice-shelf thickness, on the flow dynamics of the hinterland ice masses. In theory, ice-shelf back-pressure acts to stabilize the ice sheet, and thus the ice volume stored above sea level. We use the three-dimensional (3-D) thermomechanical ice-flow model RIMBAY to investigate the ice flow in a regularly shaped model domain, including ice-sheet, ice-shelf and open-ocean regions. By using melting scenarios for perturbation studies, we find a hysteresis-like behaviour. The experiments show that the system regains its initial state when perturbations are switched off. Average basal melt rates of up to 2 ma–1 as well as spatially variable melting calculated by our 3-D ocean model ROMBAX act as basal boundary conditions in time-dependent model studies. Changes in ice volume and grounding-line position are monitored after 1000 years of modelling and reveal mass losses of up to 40 Gt a–1.

scholarly journals Increasing mass loss from Greenland's Mittivakkat Gletscher

2011 ◽  
Vol 5 (2) ◽  
pp. 341-348 ◽  
Author(s):  
S. H. Mernild ◽  
N. T. Knudsen ◽  
W. H. Lipscomb ◽  
J. C. Yde ◽  
J. K. Malmros ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Winter Precipitation ◽  
The Arctic ◽  
Surface Mass ◽  
Glacier Changes ◽  
Temperature Records ◽  
Current Area

Abstract. Warming in the Arctic during the past several decades has caused glaciers to thin and retreat, and recent mass loss from the Greenland Ice Sheet is well documented. Local glaciers peripheral to the ice sheet are also retreating, but few mass-balance observations are available to quantify that retreat and determine the extent to which these glaciers are out of equilibrium with present-day climate. Here, we document record mass loss in 2009/10 for the Mittivakkat Gletscher (henceforth MG), the only local glacier in Greenland for which there exist long-term observations of both the surface mass balance and glacier front fluctuations. We attribute this mass loss primarily to record high mean summer (June–August) temperatures in combination with lower-than-average winter precipitation. Also, we use the 15-yr mass-balance record to estimate present-day and equilibrium accumulation-area ratios for the MG. We show that the glacier is significantly out of balance and will likely lose at least 70% of its current area and 80% of its volume even in the absence of further climate changes. Temperature records from coastal stations in Southeast Greenland suggest that recent MG mass losses are not merely a local phenomenon, but are indicative of glacier changes in the broader region. Mass-balance observations for the MG therefore provide unique documentation of the general retreat of Southeast Greenland's local glaciers under ongoing climate warming.

scholarly journals Sensitivity of ice loss to uncertainty in flow law parameters in an idealized one-dimensional geometry

2020 ◽  
Vol 14 (10) ◽  
pp. 3537-3550
Author(s):  
Maria Zeitz ◽  
Anders Levermann ◽  
Ricarda Winkelmann
Keyword(s):  
Mass Loss ◽  
Flow Line ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Flow ◽  
Surface Mass ◽  
Scientific Debate ◽  
Flow Parameters ◽  
Flow Law

Abstract. Acceleration of the flow of ice drives mass losses in both the Antarctic and the Greenland Ice Sheet. The projections of possible future sea-level rise rely on numerical ice-sheet models, which solve the physics of ice flow, melt, and calving. While major advancements have been made by the ice-sheet modeling community in addressing several of the related uncertainties, the flow law, which is at the center of most process-based ice-sheet models, is not in the focus of the current scientific debate. However, recent studies show that the flow law parameters are highly uncertain and might be different from the widely accepted standard values. Here, we use an idealized flow-line setup to investigate how these uncertainties in the flow law translate into uncertainties in flow-driven mass loss. In order to disentangle the effect of future warming on the ice flow from other effects, we perform a suite of experiments with the Parallel Ice Sheet Model (PISM), deliberately excluding changes in the surface mass balance. We find that changes in the flow parameters within the observed range can lead up to a doubling of the flow-driven mass loss within the first centuries of warming, compared to standard parameters. The spread of ice loss due to the uncertainty in flow parameters is on the same order of magnitude as the increase in mass loss due to surface warming. While this study focuses on an idealized flow-line geometry, it is likely that this uncertainty carries over to realistic three-dimensional simulations of Greenland and Antarctica.

scholarly journals The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6

2020 ◽  
Author(s):  
Heiko Goelzer ◽  
Sophie Nowicki ◽  
Anthony Payne ◽  
Eric Larour ◽  
Helene Seroussi ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Model Uncertainty ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Global Climate Models ◽  
Climate Forcing ◽  
The Arctic

Abstract. The Greenland ice sheet is one of the largest contributors to global-mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater runoff and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of CMIP5 global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100 with contributions of 89 ± 51 mm and 31 ± 16 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the southwest of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against a unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40 mm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 mm and 19 mm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean.

scholarly journals <i>Brief Communication</i> "Expansion of meltwater lakes on the Greenland ice sheet"

2012 ◽  
Vol 6 (5) ◽  
pp. 4447-4454 ◽  
Author(s):  
I. M. Howat ◽  
S. de la Peña ◽  
J. H. van Angelen ◽  
J. T. M. Lenaerts ◽  
M. R. van den Broeke
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Satellite Imagery ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Equilibrium Line ◽  
Ice Flow ◽  
West Greenland ◽  
Physical Limit

Abstract. Forty years of satellite imagery reveal that meltwater lakes on the margin of the Greenland Ice Sheet have expanded substantially inland to higher elevations with warming. These lakes are important because they provide a mechanism for bringing water to the ice bed, warming the ice and causing sliding. Inland expansion of lakes could accelerate ice flow by bringing water to previously frozen bed, potentially increasing future rates of mass loss. Increasing lake elevations in West Greenland closely follow the rise of the mass balance equilibrium line, suggesting no physical limit on lake expansion there. This is not included in ice sheet models.

scholarly journals The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6

2020 ◽  
Vol 14 (9) ◽  
pp. 3071-3096 ◽  
Author(s):  
Heiko Goelzer ◽  
Sophie Nowicki ◽  
Anthony Payne ◽  
Eric Larour ◽  
Helene Seroussi ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Model Uncertainty ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Climate Forcing ◽  
The Arctic ◽  
Model Intercomparison ◽  
Intercomparison Project

Abstract. The Greenland ice sheet is one of the largest contributors to global mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater run-off and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of the Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100, with contributions of 90±50 and 32±17 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the south-west of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against an unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40 mm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 and 19 mm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean.

scholarly journals Ice flow around large obstacles as indicated by basal ice exposed at the margin of the Greenland ice sheet

1994 ◽  
Vol 40 (135) ◽  
pp. 359-367 ◽  
Author(s):  
Peter G. Knight ◽  
David E. Sugden ◽  
Christopher D. Minty
Keyword(s):  
Empirical Model ◽  
Basal Layer ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Flow ◽  
Subglacial Environment ◽  
Basal Ice ◽  
Convergence And Divergence ◽  
Basal Melting ◽  
Marginal Environment

AbstractSpatial variations in the debris-bearing basal ice layer exposed at the ice-sheet margin in West Greenland reflect the geography of basal melting and ice flow around large obstacles close to the margin. This paper demonstrates the character of the basal ice layer, which comprises fine material incorporated in an interior, subglacial environment and coarser material entrained in an ice-marginal environment. We develop an empirical model of ice flow close to a lobate margin of the ice sheet in which ice convergence and divergence, and limited subglacial melting affect the character and distribution of the basal ice at the margin. There is a tendency for the convergence and divergence to thicken the basal layer in lobate areas and to thin it in inter-lobate areas. Under certain circumstances, basal melting may remove much of the layer from beneath the snouts of larger lobes, thus causing the basal layer to be thickest in an intermediate location.

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