Greenland ice sheet hydrology

Understanding Greenland ice sheet (GrIS) hydrology is essential for evaluating response of ice dynamics to a warming climate and future contributions to global sea level rise. Recently observed increases in temperature and melt extent over the GrIS have prompted numerous remote sensing, modeling, and field studies gauging the response of the ice sheet and outlet glaciers to increasing meltwater input, providing a quickly growing body of literature describing seasonal and annual development of the GrIS hydrologic system. This system is characterized by supraglacial streams and lakes that drain through moulins, providing an influx of meltwater into englacial and subglacial environments that increases basal sliding speeds of outlet glaciers in the short term. However, englacial and subglacial drainage systems may adjust to efficiently drain increased meltwater without significant changes to ice dynamics over seasonal and annual scales. Both proglacial rivers originating from land-terminating glaciers and subglacial conduits under marine-terminating glaciers represent direct meltwater outputs in the form of fjord sediment plumes, visible in remotely sensed imagery. This review provides the current state of knowledge on GrIS surface water hydrology, following ice sheet surface meltwater production and transport via supra-, en-, sub-, and proglacial processes to final meltwater export to the ocean. With continued efforts targeting both process-level and systems analysis of the hydrologic system, the larger picture of how future changes in Greenland hydrology will affect ice sheet glacier dynamics and ultimately global sea level rise can be advanced.

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Trends and projections in ice sheet mass balance

10.5194/egusphere-egu2020-20660 ◽

2020 ◽

Author(s):

Andrew Shepherd ◽

Keyword(s):

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Dynamics ◽

Surface Mass ◽

Sea Levels ◽

Global Sea Level

<p>In recent decades, the Antarctic and Greenland Ice Sheets have been major contributors to global sea-level rise and are expected to be so in the future. Although increases in glacier flow and surface melting have been driven by oceanic and atmospheric warming, the degree and trajectory of today&#8217;s imbalance remain uncertain. Here we compare and combine 26 individual satellite records of changes in polar ice sheet volume, flow and gravitational potential to produce a reconciled estimate of their mass balance. <strong>Since the early 1990&#8217;s, ice losses from Antarctica and Greenland have caused global sea-levels to rise by 18.4 millimetres, on average, and there has been a sixfold increase in the volume of ice loss over time. Of this total, 41 % (7.6 millimetres) originates from Antarctica and 59 % (10.8 millimetres) is from Greenland. In this presentation, we compare our reconciled estimates of Antarctic and Greenland ice sheet mass change to IPCC projection of sea level rise to assess the model skill in predicting changes in ice dynamics and surface mass balance. &#160;</strong>Cumulative ice losses from both ice sheets have been close to the IPCC&#8217;s predicted rates for their high-end climate warming scenario, which forecast an additional 170 millimetres of global sea-level rise by 2100 when compared to their central estimate.</p>

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Ice-dynamic projections of the Greenland ice sheet in response to atmospheric and oceanic warming

The Cryosphere ◽

10.5194/tc-9-1039-2015 ◽

2015 ◽

Vol 9 (3) ◽

pp. 1039-1062 ◽

Cited By ~ 57

Author(s):

J. J. Fürst ◽

H. Goelzer ◽

P. Huybrechts

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Flow Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Water Runoff ◽

Strong Impact ◽

Ice Dynamics ◽

Over Time ◽

Loss Rates

Abstract. Continuing global warming will have a strong impact on the Greenland ice sheet in the coming centuries. During the last decade (2000–2010), both increased melt-water runoff and enhanced ice discharge from calving glaciers have contributed 0.6 ± 0.1 mm yr−1 to global sea-level rise, with a relative contribution of 60 and 40% respectively. Here we use a higher-order ice flow model, spun up to present day, to simulate future ice volume changes driven by both atmospheric and oceanic temperature changes. For these projections, the flow model accounts for runoff-induced basal lubrication and ocean warming-induced discharge increase at the marine margins. For a suite of 10 atmosphere and ocean general circulation models and four representative concentration pathway scenarios, the projected sea-level rise between 2000 and 2100 lies in the range of +1.4 to +16.6 cm. For two low emission scenarios, the projections are conducted up to 2300. Ice loss rates are found to abate for the most favourable scenario where the warming peaks in this century, allowing the ice sheet to maintain a geometry close to the present-day state. For the other moderate scenario, loss rates remain at a constant level over 300 years. In any scenario, volume loss is predominantly caused by increased surface melting as the contribution from enhanced ice discharge decreases over time and is self-limited by thinning and retreat of the marine margin, reducing the ice–ocean contact area. As confirmed by other studies, we find that the effect of enhanced basal lubrication on the volume evolution is negligible on centennial timescales. Our projections show that the observed rates of volume change over the last decades cannot simply be extrapolated over the 21st century on account of a different balance of processes causing ice loss over time. Our results also indicate that the largest source of uncertainty arises from the surface mass balance and the underlying climate change projections, not from ice dynamics.

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Greenland ice sheet contribution to sea level rise during the last interglacial period: a modelling study driven and constrained by ice core data

Climate of the Past ◽

10.5194/cp-9-353-2013 ◽

2013 ◽

Vol 9 (1) ◽

pp. 353-366 ◽

Cited By ~ 42

Author(s):

A. Quiquet ◽

C. Ritz ◽

H. J. Punge ◽

D. Salas y Mélia

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Core ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Interglacial Period ◽

Last Interglacial ◽

Intergovernmental Panel ◽

Orbital Configuration ◽

Global Sea Level

Abstract. As pointed out by the forth assessment report of the Intergovernmental Panel on Climate Change, IPCC-AR4 (Meehl et al., 2007), the contribution of the two major ice sheets, Antarctica and Greenland, to global sea level rise, is a subject of key importance for the scientific community. By the end of the next century, a 3–5 °C warming is expected in Greenland. Similar temperatures in this region were reached during the last interglacial (LIG) period, 130–115 ka BP, due to a change in orbital configuration rather than to an anthropogenic forcing. Ice core evidence suggests that the Greenland ice sheet (GIS) survived this warm period, but great uncertainties remain about the total Greenland ice reduction during the LIG. Here we perform long-term simulations of the GIS using an improved ice sheet model. Both the methodologies chosen to reconstruct palaeoclimate and to calibrate the model are strongly based on proxy data. We suggest a relatively low contribution to LIG sea level rise from Greenland melting, ranging from 0.7 to 1.5 m of sea level equivalent, contrasting with previous studies. Our results suggest an important contribution of the Antarctic ice sheet to the LIG highstand.

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Surface melting over the Greenland ice sheet from enhanced resolution passive microwave brightness temperatures (1979–2019)

10.5194/tc-2020-250 ◽

2020 ◽

Author(s):

Paolo Colosio ◽

Marco Tedesco ◽

Xavier Fettweis ◽

Roberto Ranzi

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Spatial Resolution ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Melting ◽

Passive Microwave ◽

High Temporal Resolution ◽

Ice Dynamics ◽

Enhanced Resolution

Abstract. Surface melting is a major component of the Greenland ice sheet (GrIS) surface mass balance, affecting sea level rise through direct runoff and the modulation on ice dynamics and hydrological processes, supraglacially, englacially and subglacially. Passive microwave (PMW) brightness temperature observations are of paramount importance in studying the spatial and temporal evolution of surface melting in view of their long temporal coverage (1979–to date) and high temporal resolution (daily). However, a major limitation of PMW datasets has been the relatively coarse spatial resolution, being historically of the order of tens of kilometres. Here, we use a newly released passive microwave dataset (37 GHz, horizontal polarization) made available through the NASA MeASUREs program to study the spatiotemporal evolution of surface melting over the GrIS at an enhanced spatial resolution of 3.125 Km. We assess the outputs of different detection algorithms through data collected by Automatic Weather Stations (AWS) and the outputs of the MAR regional climate model. We found that surface melting is well captured using a dynamic algorithm based on the outputs of MEMLS model, capable to detect sporadic and persistent melting. Our results indicate that, during the reference period 1979–2019 (1988–2019), surface melting over the GrIS increased in terms of both duration, up to ~4.5 (2.9) days per decade, and extension, up to 6.9 % (3.6 %) of the GrIS surface extent per decade, according to the MEMLS algorithm. Furthermore, the melting season has started up to ~4 (2.5) days earlier and ended ~7 (3.9) days later per decade. We also explored the information content of the enhanced resolution dataset with respect to the one at 25 km and MAR outputs through a semi-variogram approach. We found that the enhanced product is more sensitive to local scale processes, hence confirming the potential interest of this new enhanced product for studying surface melting over Greenland at a higher spatial resolution than the historical products and monitor its impact on sea level rise. This offers the opportunity to improve our understanding of the processes driving melting, to validate modelled melt extent at high resolution and potentially to assimilate this data in climate models.

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Extraordinary runoff from the Greenland ice sheet in 2012 amplified by hypsometry and depleted firn retention

The Cryosphere ◽

10.5194/tc-10-1147-2016 ◽

2016 ◽

Vol 10 (3) ◽

pp. 1147-1159 ◽

Cited By ~ 23

Author(s):

Andreas Bech Mikkelsen ◽

Alun Hubbard ◽

Mike MacFerrin ◽

Jason Eric Box ◽

Sam H. Doyle ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Equilibrium Line ◽

Aerial Photographs ◽

Discharge Data ◽

Impermeable Barrier ◽

Global Sea Level ◽

Percolation Zone

Abstract. It has been argued that the infiltration and retention of meltwater within firn across the percolation zone of the Greenland ice sheet has the potential to buffer up to ∼  3.6 mm of global sea-level rise (Harper et al., 2012). Despite evidence confirming active refreezing processes above the equilibrium line, their impact on runoff and proglacial discharge has yet to be assessed. Here, we compare meteorological, melt, firn stratigraphy and discharge data from the extreme 2010 and 2012 summers to determine the relationship between atmospheric forcing and melt runoff at the land-terminating Kangerlussuaq sector of the Greenland ice sheet, which drains into the Watson River. The 6.8 km3 bulk discharge in 2012 exceeded that in 2010 by 28 %, despite only a 3 % difference in net incoming melt energy between the two years. This large disparity can be explained by a 10 % contribution of runoff originating from above the long-term equilibrium line in 2012 caused by diminished firn retention. The amplified 2012 response was compounded by catchment hypsometry; the disproportionate increase in area contributing to runoff as the melt-level rose high into the accumulation area.Satellite imagery and aerial photographs reveal an extensive supraglacial network extending 140 km from the ice margin that confirms active meltwater runoff originating well above the equilibrium line. This runoff culminated in three days with record discharge of 3100 m3 s−1 (0.27 Gt d−1) that peaked on 11 July and washed out the Watson River Bridge. Our findings corroborate melt infiltration processes in the percolation zone, though the resulting patterns of refreezing are complex and can lead to spatially extensive, perched superimposed ice layers within the firn. In 2012, such layers extended to an elevation of at least 1840 m and provided a semi-impermeable barrier to further meltwater storage, thereby promoting widespread runoff from the accumulation area of the Greenland ice sheet that contributed directly to proglacial discharge and global sea-level rise.

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Assessment of the Greenland ice sheet–atmosphere feedbacks for the next century with a regional atmospheric model coupled to an ice sheet model

The Cryosphere ◽

10.5194/tc-13-373-2019 ◽

2019 ◽

Vol 13 (1) ◽

pp. 373-395 ◽

Cited By ~ 16

Author(s):

Sébastien Le clec'h ◽

Sylvie Charbit ◽

Aurélien Quiquet ◽

Xavier Fettweis ◽

Christophe Dumas ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Atmospheric Model ◽

Ice Dynamics ◽

Surface Slopes ◽

Regional Atmospheric Model ◽

Basin Scale ◽

Coupling Strategies

Abstract. In the context of global warming, growing attention is paid to the evolution of the Greenland ice sheet (GrIS) and its contribution to sea-level rise at the centennial timescale. Atmosphere–GrIS interactions, such as the temperature–elevation and the albedo feedbacks, have the potential to modify the surface energy balance and thus to impact the GrIS surface mass balance (SMB). In turn, changes in the geometrical features of the ice sheet may alter both the climate and the ice dynamics governing the ice sheet evolution. However, changes in ice sheet geometry are generally not explicitly accounted for when simulating atmospheric changes over the Greenland ice sheet in the future. To account for ice sheet–climate interactions, we developed the first two-way synchronously coupled model between a regional atmospheric model (MAR) and a 3-D ice sheet model (GRISLI). Using this novel model, we simulate the ice sheet evolution from 2000 to 2150 under a prolonged representative concentration pathway scenario, RCP8.5. Changes in surface elevation and ice sheet extent simulated by GRISLI have a direct impact on the climate simulated by MAR. They are fed to MAR from 2020 onwards, i.e. when changes in SMB produce significant topography changes in GRISLI. We further assess the importance of the atmosphere–ice sheet feedbacks through the comparison of the two-way coupled experiment with two other simulations based on simpler coupling strategies: (i) a one-way coupling with no consideration of any change in ice sheet geometry; (ii) an alternative one-way coupling in which the elevation change feedbacks are parameterized in the ice sheet model (from 2020 onwards) without taking into account the changes in ice sheet topography in the atmospheric model. The two-way coupled experiment simulates an important increase in surface melt below 2000 m of elevation, resulting in an important SMB reduction in 2150 and a shift of the equilibrium line towards elevations as high as 2500 m, despite a slight increase in SMB over the central plateau due to enhanced snowfall. In relation with these SMB changes, modifications of ice sheet geometry favour ice flux convergence towards the margins, with an increase in ice velocities in the GrIS interior due to increased surface slopes and a decrease in ice velocities at the margins due to decreasing ice thickness. This convergence counteracts the SMB signal in these areas. In the two-way coupling, the SMB is also influenced by changes in fine-scale atmospheric dynamical processes, such as the increase in katabatic winds from central to marginal regions induced by increased surface slopes. Altogether, the GrIS contribution to sea-level rise, inferred from variations in ice volume above floatation, is equal to 20.4 cm in 2150. The comparison between the coupled and the two uncoupled experiments suggests that the effect of the different feedbacks is amplified over time with the most important feedbacks being the SMB–elevation feedbacks. As a result, the experiment with parameterized SMB–elevation feedback provides a sea-level contribution from GrIS in 2150 only 2.5 % lower than the two-way coupled experiment, while the experiment with no feedback is 9.3 % lower. The change in the ablation area in the two-way coupled experiment is much larger than those provided by the two simplest methods, with an underestimation of 11.7 % (14 %) with parameterized feedbacks (no feedback). In addition, we quantify that computing the GrIS contribution to sea-level rise from SMB changes only over a fixed ice sheet mask leads to an overestimation of ice loss of at least 6 % compared to the use of a time variable ice sheet mask. Finally, our results suggest that ice-loss estimations diverge when using the different coupling strategies, with differences from the two-way method becoming significant at the end of the 21st century. In particular, even if averaged over the whole GrIS the climatic and ice sheet fields are relatively similar; at the local and regional scale there are important differences, highlighting the importance of correctly representing the interactions when interested in basin scale changes.

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The trough-system algorithm and its application to spatial modeling of Greenland subglacial topography

Annals of Glaciology ◽

10.3189/2014aog67a001 ◽

2014 ◽

Vol 55 (67) ◽

pp. 115-126 ◽

Cited By ~ 2

Author(s):

Ute C. Herzfeld ◽

Brian W. McDonald ◽

Bruce F. Wallin ◽

Phillip A. Chen ◽

Helmut Mayer ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Algebraic Topology ◽

Dynamic Models ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Dynamics ◽

Subglacial Topography ◽

Radar Measurements ◽

Elevation Model

AbstractDynamic ice-sheet models are used to assess the contribution of mass loss from the Greenland ice sheet to sea-level rise. Mass transfer from ice sheet to ocean is in a large part through outlet glaciers. Bed topography plays an important role in ice dynamics, since the acceleration from the slow-moving inland ice to an ice stream is in many cases caused by the existence of a subglacial trough or trough system. Problems are that most subglacial troughs are features of a scale not resolved in most ice-sheet models and that radar measurements of subglacial topography do not always reach the bottoms of narrow troughs. The trough-system algorithm introduced here employs mathematical morphology and algebraic topology to correctly represent subscale features in a topographic generalization, so the effects of troughs on ice flow are retained in ice-dynamic models. The algorithm is applied to derive a spatial elevation model of Greenland subglacial topography, integrating recently collected radar measurements (CReSIS data) of the Jakobshavn Isbræ, Helheim, Kangerdlussuaq and Petermann glacier regions. The resultant JakHelKanPet digital elevation model has been applied in dynamic ice-sheet modeling and sea-level-rise assessment.

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Simulations of the Greenland ice sheet 100 years into the future with the full Stokes model Elmer/Ice

Journal of Glaciology ◽

10.3189/2012jog11j177 ◽

2012 ◽

Vol 58 (209) ◽

pp. 427-440 ◽

Cited By ~ 91

Author(s):

Hakime Seddik ◽

Ralf Greve ◽

Thomas Zwinger ◽

Fabien Gillet-Chaulet ◽

Olivier Gagliardini

Keyword(s):

Global Warming ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Streams ◽

Simulation Code ◽

Dynamic Scenario ◽

The Future ◽

Basal Sliding

AbstractIt is likely that climate change will have a significant impact on the mass balance of the Greenland ice sheet, contributing to future sea-level rise. Here we present the implementation of the full Stokes model Elmer/Ice for the Greenland ice sheet, which includes a mesh refinement technique in order to resolve fast-flowing ice streams and outlet glaciers. We discuss simulations 100 years into the future, forced by scenarios defined by the SeaRISE (Sea-level Response to Ice Sheet Evolution) community effort. For comparison, the same experiments are also run with the shallow-ice model SICOPOLIS (SImulation COde for POLythermal Ice Sheets). We find that Elmer/Ice is ~43% more sensitive (exhibits a larger loss of ice-sheet volume relative to the control run) than SICOPOLIS for the ice-dynamic scenario (doubled basal sliding), but ~61 % less sensitive for the direct global warming scenario (based on the A1 B moderate-emission scenario for greenhouse gases). The scenario with combined A1B global warming and doubled basal sliding forcing produces a Greenland contribution to sea-level rise of ~15cm for Elmer/Ice and ~12cm for SICOPOLIS over the next 100 years.

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Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1512482112 ◽

2015 ◽

Vol 112 (46) ◽

pp. 14191-14196 ◽

Cited By ~ 62

Author(s):

Johannes Feldmann ◽

Anders Levermann

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Horizontal Resolution ◽

West Antarctica ◽

Amundsen Sea ◽

Ice Dynamics ◽

Antarctic Ice Sheet ◽

Topographic Features ◽

Global Sea Level

The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades’ enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner–Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia.

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Semi-equilibrated global sea-level change projections for the next 10 000 years

Earth System Dynamics ◽

10.5194/esd-11-953-2020 ◽

2020 ◽

Vol 11 (4) ◽

pp. 953-976

Author(s):

Jonas Van Breedam ◽

Heiko Goelzer ◽

Philippe Huybrechts

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Sea Level Change ◽

Strong Increase ◽

Antarctic Ice Sheet ◽

Level Change ◽

Global Sea Level ◽

The Antarctic

Abstract. The emphasis for informing policy makers on future sea-level rise has been on projections by the end of the 21st century. However, due to the long lifetime of atmospheric CO2, the thermal inertia of the climate system and the slow equilibration of the ice sheets, global sea level will continue to rise on a multi-millennial timescale even when anthropogenic CO2 emissions cease completely during the coming decades to centuries. Here we present global sea-level change projections due to the melting of land ice combined with steric sea effects during the next 10 000 years calculated in a fully interactive way with the Earth system model of intermediate complexity LOVECLIMv1.3. The greenhouse forcing is based on the Extended Concentration Pathways defined until 2300 CE with no carbon dioxide emissions thereafter, equivalent to a cumulative CO2 release of between 460 and 5300 GtC. We performed one additional experiment for the highest-forcing scenario with the inclusion of a methane emission feedback where methane is slowly released due to a strong increase in surface and oceanic temperatures. After 10 000 years, the sea-level change rate drops below 0.05 m per century and a semi-equilibrated state is reached. The Greenland ice sheet is found to nearly disappear for all forcing scenarios. The Antarctic ice sheet contributes only about 1.6 m to sea level for the lowest forcing scenario with a limited retreat of the grounding line in West Antarctica. For the higher-forcing scenarios, the marine basins of the East Antarctic Ice Sheet also become ice free, resulting in a sea-level rise of up to 27 m. The global mean sea-level change after 10 000 years ranges from 9.2 to more than 37 m. For the highest-forcing scenario, the model uncertainty does not exclude the complete melting of the Antarctic ice sheet during the next 10 000 years.

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