scholarly journals Simulation of the future sea level contribution of Greenland with a new glacial system model

2018 ◽  
Vol 12 (10) ◽  
pp. 3097-3121 ◽  
Author(s):  
Reinhard Calov ◽  
Sebastian Beyer ◽  
Ralf Greve ◽  
Johanna Beckmann ◽  
Matteo Willeit ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Surface Temperature ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
System Model ◽  
Surface Mass Balance ◽  
Surface Mass

Abstract. We introduce the coupled model of the Greenland glacial system IGLOO 1.0, including the polythermal ice sheet model SICOPOLIS (version 3.3) with hybrid dynamics, the model of basal hydrology HYDRO and a parameterization of submarine melt for marine-terminated outlet glaciers. The aim of this glacial system model is to gain a better understanding of the processes important for the future contribution of the Greenland ice sheet to sea level rise under future climate change scenarios. The ice sheet is initialized via a relaxation towards observed surface elevation, imposing the palaeo-surface temperature over the last glacial cycle. As a present-day reference, we use the 1961–1990 standard climatology derived from simulations of the regional atmosphere model MAR with ERA reanalysis boundary conditions. For the palaeo-part of the spin-up, we add the temperature anomaly derived from the GRIP ice core to the years 1961–1990 average surface temperature field. For our projections, we apply surface temperature and surface mass balance anomalies derived from RCP 4.5 and RCP 8.5 scenarios created by MAR with boundary conditions from simulations with three CMIP5 models. The hybrid ice sheet model is fully coupled with the model of basal hydrology. With this model and the MAR scenarios, we perform simulations to estimate the contribution of the Greenland ice sheet to future sea level rise until the end of the 21st and 23rd centuries. Further on, the impact of elevation–surface mass balance feedback, introduced via the MAR data, on future sea level rise is inspected. In our projections, we found the Greenland ice sheet to contribute between 1.9 and 13.0 cm to global sea level rise until the year 2100 and between 3.5 and 76.4 cm until the year 2300, including our simulated additional sea level rise due to elevation–surface mass balance feedback. Translated into additional sea level rise, the strength of this feedback in the year 2100 varies from 0.4 to 1.7 cm, and in the year 2300 it ranges from 1.7 to 21.8 cm. Additionally, taking the Helheim and Store glaciers as examples, we investigate the role of ocean warming and surface runoff change for the melting of outlet glaciers. It shows that ocean temperature and subglacial discharge are about equally important for the melting of the examined outlet glaciers.

scholarly journals Simulation of the future sea level contribution of Greenland with a new glacial system model

2018 ◽  
Author(s):  
Reinhard Calov ◽  
Sebastian Beyer ◽  
Ralf Greve ◽  
Johanna Beckmann ◽  
Matteo Willeit ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Surface Temperature ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
System Model ◽  
Surface Mass Balance ◽  
Surface Mass

Abstract. We introduce the coupled model of the Greenland glacial system IGLOO 1.0, including the polythermal ice sheet model SICOPOLIS (version 3.3) with hybrid dynamics, the model of basal hydrology HYDRO and a parameterization of submarine melt for marine-terminated outlet glaciers. Aim of this glacial system model is to gain a better understanding of the processes important for the future contribution of the Greenland ice sheet to sea level rise under future climate change scenarios. The ice sheet is initialized via a relaxation towards observed surface elevation, imposing the palaeo-surface temperature over the last glacial cycle. As a present-day reference, we use the 1961-1990 standard climatology derived from simulations of the regional atmosphere model MAR with ERA reanalysis boundary conditions. For the palaeo-part of the spin-up, we add the temperature anomaly derived from the GRIP ice core to the years 1961–1990 average surface temperature field. For our projections, we apply surface temperature and surface mass balance anomalies derived from RCP 4.5 and RCP 8.5 scenarios created by MAR with boundary conditions from simulations with three CMIP5 models. The hybrid ice sheet model is fully coupled with the model of basal hydrology. With this model and the MAR scenarios, we perform simulations to estimate the contribution of the Greenland ice sheet to future sea level rise until the end of the 21st and 23rd centuries. Further on, the impact of elevation-surface mass balance feedback, introduced via the MAR data, on future sea level rise is inspected. In our projections, we found the Greenland ice sheet to contribute to global sea level rise between 1.9 and 13.0 cm until the year 2100 and between 3.5 and 76.4 cm until the year 2300, including our simulated additional sea level rise due to elevation-surface mass balance feedback. Translated into additional sea level rise, the strength of this feedback in the year 2100 varies from 0.4 to 1.7 cm, and in the year 2300 it ranges from 1.7 to 21.8 cm. Additionally, taking Helheim and Store Glaciers as examples, we investigate the role of ocean warming and surface runoff change for the melting of outlet glaciers. It shows that ocean temperature and subglacial discharge are about equally important for the melting of the examined outlet glaciers.

scholarly journals The effect of overshooting 1.5 °C global warming on the mass loss of the Greenland ice sheet

2018 ◽  
Vol 9 (4) ◽  
pp. 1169-1189 ◽  
Author(s):  
Martin Rückamp ◽  
Ulrike Falk ◽  
Katja Frieler ◽  
Stefan Lange ◽  
Angelika Humbert
Keyword(s):  
Global Warming ◽  
Mass Loss ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
21St Century ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Surface Mass

Abstract. Sea-level rise associated with changing climate is expected to pose a major challenge for societies. Based on the efforts of COP21 to limit global warming to 2.0 ∘C or even 1.5 ∘C by the end of the 21st century (Paris Agreement), we simulate the future contribution of the Greenland ice sheet (GrIS) to sea-level change under the low emission Representative Concentration Pathway (RCP) 2.6 scenario. The Ice Sheet System Model (ISSM) with higher-order approximation is used and initialized with a hybrid approach of spin-up and data assimilation. For three general circulation models (GCMs: HadGEM2-ES, IPSL-CM5A-LR, MIROC5) the projections are conducted up to 2300 with forcing fields for surface mass balance (SMB) and ice surface temperature (Ts) computed by the surface energy balance model of intermediate complexity (SEMIC). The projected sea-level rise ranges between 21–38 mm by 2100 and 36–85 mm by 2300. According to the three GCMs used, global warming will exceed 1.5 ∘C early in the 21st century. The RCP2.6 peak and decline scenario is therefore manually adjusted in another set of experiments to suppress the 1.5 ∘C overshooting effect. These scenarios show a sea-level contribution that is on average about 38 % and 31 % less by 2100 and 2300, respectively. For some experiments, the rate of mass loss in the 23rd century does not exclude a stable ice sheet in the future. This is due to a spatially integrated SMB that remains positive and reaches values similar to the present day in the latter half of the simulation period. Although the mean SMB is reduced in the warmer climate, a future steady-state ice sheet with lower surface elevation and hence volume might be possible. Our results indicate that uncertainties in the projections stem from the underlying GCM climate data used to calculate the surface mass balance. However, the RCP2.6 scenario will lead to significant changes in the GrIS, including elevation changes of up to 100 m. The sea-level contribution estimated in this study may serve as a lower bound for the RCP2.6 scenario, as the currently observed sea-level rise is not reached in any of the experiments; this is attributed to processes (e.g. ocean forcing) not yet represented by the model, but proven to play a major role in GrIS mass loss.

scholarly journals Estimating the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional atmospheric climate model MAR

2013 ◽  
Vol 7 (2) ◽  
pp. 469-489 ◽  
Author(s):  
X. Fettweis ◽  
B. Franco ◽  
M. Tedesco ◽  
J. H. van Angelen ◽  
J. T. M. Lenaerts ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Near Surface ◽  
Surface Mass

Abstract. To estimate the sea level rise (SLR) originating from changes in surface mass balance (SMB) of the Greenland ice sheet (GrIS), we present 21st century climate projections obtained with the regional climate model MAR (Modèle Atmosphérique Régional), forced by output of three CMIP5 (Coupled Model Intercomparison Project Phase 5) general circulation models (GCMs). Our results indicate that in a warmer climate, mass gain from increased winter snowfall over the GrIS does not compensate mass loss through increased meltwater run-off in summer. Despite the large spread in the projected near-surface warming, all the MAR projections show similar non-linear increase of GrIS surface melt volume because no change is projected in the general atmospheric circulation over Greenland. By coarsely estimating the GrIS SMB changes from GCM output, we show that the uncertainty from the GCM-based forcing represents about half of the projected SMB changes. In 2100, the CMIP5 ensemble mean projects a GrIS SMB decrease equivalent to a mean SLR of +4 ± 2 cm and +9 ± 4 cm for the RCP (Representative Concentration Pathways) 4.5 and RCP 8.5 scenarios respectively. These estimates do not consider the positive melt–elevation feedback, although sensitivity experiments using perturbed ice sheet topographies consistent with the projected SMB changes demonstrate that this is a significant feedback, and highlight the importance of coupling regional climate models to an ice sheet model. Such a coupling will allow the assessment of future response of both surface processes and ice-dynamic changes to rising temperatures, as well as their mutual feedbacks.

scholarly journals Greenland ice sheet contribution to sea-level rise from a new-generation ice-sheet model

2012 ◽  
Vol 6 (6) ◽  
pp. 1561-1576 ◽  
Author(s):  
F. Gillet-Chaulet ◽  
O. Gagliardini ◽  
H. Seddik ◽  
M. Nodet ◽  
G. Durand ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass ◽  
Continental Scale ◽  
New Generation

Abstract. Over the last two decades, the Greenland ice sheet (GrIS) has been losing mass at an increasing rate, enhancing its contribution to sea-level rise (SLR). The recent increases in ice loss appear to be due to changes in both the surface mass balance of the ice sheet and ice discharge (ice flux to the ocean). Rapid ice flow directly affects the discharge, but also alters ice-sheet geometry and so affects climate and surface mass balance. Present-day ice-sheet models only represent rapid ice flow in an approximate fashion and, as a consequence, have never explicitly addressed the role of ice discharge on the total GrIS mass balance, especially at the scale of individual outlet glaciers. Here, we present a new-generation prognostic ice-sheet model which reproduces the current patterns of rapid ice flow. This requires three essential developments: the complete solution of the full system of equations governing ice deformation; a variable resolution unstructured mesh to resolve outlet glaciers and the use of inverse methods to better constrain poorly known parameters using observations. The modelled ice discharge is in good agreement with observations on the continental scale and for individual outlets. From this initial state, we investigate possible bounds for the next century ice-sheet mass loss. We run sensitivity experiments of the GrIS dynamical response to perturbations in climate and basal lubrication, assuming a fixed position of the marine termini. We find that increasing ablation tends to reduce outflow and thus decreases the ice-sheet imbalance. In our experiments, the GrIS initial mass (im)balance is preserved throughout the whole century in the absence of reinforced forcing, allowing us to estimate a lower bound of 75 mm for the GrIS contribution to SLR by 2100. In one experiment, we show that the current increase in the rate of ice loss can be reproduced and maintained throughout the whole century. However, this requires a very unlikely perturbation of basal lubrication. From this result we are able to estimate an upper bound of 140 mm from dynamics only for the GrIS contribution to SLR by 2100.

scholarly journals Greenland Ice Sheet contribution to sea-level rise from a new-generation ice-sheet model

2012 ◽  
Vol 6 (4) ◽  
pp. 2789-2826 ◽  
Author(s):  
F. Gillet-Chaulet ◽  
O. Gagliardini ◽  
H. Seddik ◽  
M. Nodet ◽  
G. Durand ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass ◽  
Continental Scale ◽  
New Generation

Abstract. Over the last two decades, the Greenland Ice Sheet (GrIS) has been losing mass at an increasing rate, enhancing its contribution to sea-level rise. The recent increases in ice loss appear to be due to changes in both the surface mass balance of the ice sheet and ice discharge (ice flux to the ocean). Rapid ice flow directly affects the discharge, but also alters ice-sheet geometry and so affects climate and surface mass balance. The most usual ice-sheet models only represent rapid ice flow in an approximate fashion and, as a consequence, have never explicitly addressed the role of ice discharge on the total GrIS mass balance, especially at the scale of individual outlet glaciers. Here, we present a new-generation prognostic ice-sheet model which reproduces the current patterns of rapid ice flow. This requires three essential developments: the complete solution of the full system of equations governing ice deformation; an unstructured mesh to usefully resolve outlet glaciers and the use of inverse methods to better constrain poorly known parameters using observations. The modelled ice discharge is in good agreement with observations on the continental scale and for individual outlets. By conducting perturbation experiments, we investigate how current ice loss will endure over the next century. Although we find that increasing ablation tends to reduce outflow and on its own has a stabilising effect, if destabilisation processes maintain themselves over time, current increases in the rate of ice loss are likely to continue.

How will the Greenland Ice Sheet develop under Extreme Melt Events?

2020 ◽  
Author(s):  
Johanna Beckmann ◽  
Alison Delhasse ◽  
Ricarda Winkelmann
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Potential Effect ◽  
Dynamical Response ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Total Impact

<pre class="moz-quote-pre">In the past years, Greenland has been affected by several extreme melt events, particularly in the years 2010, 2012 and most recently, during this year's spring/summer. With progressing climate change, extreme melt events can be expected to occur more frequently and become more severe/persistent. So far, however, longer-term projections of ice loss from Greenland typically rely on scenarios that only take account of gradual changes in the climate, for instance, based on the Representative Concentration Pathways. Extreme melt events have generally been underestimated and their potential effect on future surface mass balance shows already serve impacts for sea-level rise. <br /> Here we investigate the total impact of future extreme melt events on the Greenland Ice Sheet. We force the thermodynamically coupled parallel ice sheet model PISM with idealized surface-mass-balance scenarios that include extreme melt events. Thereby, we investigate the dynamical response of the ice sheet model to changes in frequency and intensity of extreme melt events and quantify their impacts with respect to sea-level rise. </pre> <p> </p>

scholarly journals Eemian Greenland ice sheet simulated with a higher-order model shows strong sensitivity to surface mass balance forcing

2019 ◽  
Vol 13 (8) ◽  
pp. 2133-2148
Author(s):  
Andreas Plach ◽  
Kerim H. Nisancioglu ◽  
Petra M. Langebroek ◽  
Andreas Born ◽  
Sébastien Le clec'h
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Higher Order ◽  
Interglacial Period ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass

Abstract. The Greenland ice sheet contributes increasingly to global sea level rise. Its history during past warm intervals is a valuable reference for future sea level projections. We present ice sheet simulations for the Eemian interglacial period (∼130 000 to 115 000 years ago), a period with warmer-than-present summer climate over Greenland. The evolution of the Eemian Greenland ice sheet is simulated with a 3-D higher-order ice sheet model, forced with a surface mass balance derived from regional climate simulations. Sensitivity experiments with various surface mass balances, basal friction, and ice flow approximations are discussed. The surface mass balance forcing is identified as the controlling factor setting the minimum in Eemian ice volume, emphasizing the importance of a reliable surface mass balance model. Furthermore, the results indicate that the surface mass balance forcing is more important than the representation of ice flow for simulating the large-scale ice sheet evolution. This implies that modeling of the future contribution of the Greenland ice sheet to sea level rise highly depends on an accurate surface mass balance.

Projections of 21st century sea-level contribution from the retreat of Humboldt Glacier, North Greenland

2021 ◽  
Author(s):  
Trevor Hillebrand ◽  
Matthew Hoffman ◽  
Mauro Perego ◽  
Stephen Price ◽  
Abby Roat ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
21St Century ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Velocity ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Basal Friction

<p>Humboldt Glacier drains ~5% of the Greenland Ice Sheet and has retreated and accelerated since the late 1990s. The northern section of the terminus has retreated towards an overdeepening in the glacier bed that extends tens of kilometers towards the ice sheet interior, raising the possibility of a rapid increase in ice discharge and retreat in the near future. Here we investigate the potential 21st century sea-level contribution from Humboldt Glacier with the MPAS-Albany Land Ice (MALI) ice sheet model. First, we optimize the basal friction field using observations of surface velocity and ice surface elevation to obtain an initial condition for the year 2007. Next, we tune parameters for calving, basal friction, and submarine melt to match the observed retreat rates and surface velocity changes. We then simulate glacier evolution to 2100 under a range of climate forcings from the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), using ocean temperatures from the MIROC5 Earth System Model, with surface mass balance and subglacial discharge from MAR3.9/MIROC5. Our simulations predict ~3.5 mm of sea-level rise from the retreat of Humboldt Glacier by 2100 for RCP8.5, and ~1 mm for RCP2.6. The results are insensitive to the choice of calving parameters for grounded ice, but a low stress threshold for calving from floating ice is necessary to initiate retreat. We find that a highly plastic basal friction law is required to reproduce the observed acceleration, but the choice of basal friction law does not have a large effect on the magnitude of sea-level contribution by 2100 because much of the ice is at present close to floatation in the areas that retreat most significantly. Instead, the majority of ice mass loss comes from increasingly negative surface mass balance. Preliminary results from experiments with a subglacial hydrology model suggest that the simple treatment of subglacial discharge used in our 21st century projections (as used in the ISMIP6-Greenland protocol) underestimates spatial variability of melting at the glacier front but gives a reasonable approximation of total melt. When compared to the recent ISMIP6 estimates of 60–140 mm sea-level rise from the entire Greenland Ice Sheet by 2100, our estimate of 3.5 mm from Humboldt Glacier indicates a significant but far from dominant contribution from this single large outlet.</p>

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