scholarly journals Dynamic modelling of future glacier changes: mass-balance/elevation feedback in projections for the Vestfonna ice cap, Nordaustlandet, Svalbard

2015 ◽  
Vol 61 (230) ◽  
pp. 1121-1136 ◽  
Author(s):  
M. Schäfer ◽  
M. Möller ◽  
T. Zwinger ◽  
J.C. Moore
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Dynamic Modelling ◽  
Coupled Model ◽  
Climate Change Scenarios ◽  
Ice Flow ◽  
Ice Cap ◽  
Mass Balance Models

AbstractFuture projections of the evolution of ice caps as well as ice sheets and consequent sea-level rise face several methodological challenges, one being the two-way coupling between ice flow and mass-balance models. Full two-way coupling between mass-balance models – or, in a wider scope, climate models – and ice flow models has rarely been implemented due to substantial technical challenges. Here we examine some coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analysing the impacts of different coupling intervals on mass-balance and sea-level rise projections. By comparing coupled to traditionally deployed uncoupled strategies, we prove that neglecting the topographic feedbacks in the coupling leads to underestimations of 10–20% in sea-level rise projections on century timescales in our model. As imposed climate scenarios increasingly change mass balance, uncertainties in the unknown evolution of the fast-flowing outlet glaciers decrease in importance due to their deceleration and reduced mass flux as they thin and retreat from the coast. Parameterizing mass-balance adjustment for changes in topography using lapse rates as a cost-effective alternative to full coupling produces satisfactory results for modest climate change scenarios. We introduce a method to estimate the error of the presented partially coupled model with respect to as yet unperformed two-way fully coupled results.

scholarly journals Changes in beach shoreline due to sea level rise and waves under climate change scenarios: application to the Balearic Islands (Western Mediterranean)

2016 ◽  
Author(s):  
Alejandra R. Enríquez ◽  
Marta Marcos ◽  
Amaya Álvarez-Ellacuría ◽  
Alejandro Orfila ◽  
Damià Gomis
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Regional Climate ◽  
Wave Climate ◽  
Sandy Beaches ◽  
Western Mediterranean ◽  
Climate Change Scenarios ◽  
Swash Zone ◽  
Climate Scenarios

Abstract. In this work we assess the impacts in reshaping coastlines as a result of sea level rise and changes in wave climate. The methodology proposed combines the SWAN and SWASH wave models to resolve the wave processes from deep waters up to the swash zone in two micro-tidal sandy beaches in Mallorca Island, Western Mediterranean. In a first step, the modelling approach is validated with observations from wave gauges and from the shoreline inferred from video monitoring stations, showing a good agreement between them. Afterwards, the modelling setup is applied to the 21st century sea level and wave projections under two different climate scenarios, RCP45 and RCP85. Sea level projections were retrieved from state of the art regional estimates, while wave projections were obtained from regional climate models. Changes in the coastline are explored under mean and extreme wave conditions. Our results indicate that the studied beaches would suffer a coastal retreat between 7 and up to 50 m, equivalent to half of the present-day aerial beach surface, under the climate scenarios considered.

scholarly journals Regional Greenland accumulation variability from Operation IceBridge airborne accumulation radar

2017 ◽  
Vol 11 (2) ◽  
pp. 773-788 ◽  
Author(s):  
Gabriel Lewis ◽  
Erich Osterberg ◽  
Robert Hawley ◽  
Brian Whitmore ◽  
Hans Peter Marshall ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Drainage Basin ◽  
Function Analysis ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Accumulation Rates ◽  
Surface Mass

Abstract. The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge accumulation radar flights totaling  >  17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100–300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a−1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GrIS surface mass balance estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.

A regional atmospheric warming threshold for irreversible Greenland ice sheet mass loss

2020 ◽  
Author(s):  
Michiel van den Broeke ◽  
Brice Noël ◽  
Leo van Kampenhout ◽  
Willem-Jan van de Berg
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Global Climate Models ◽  
The Future

<p>The mass balance of the Greenland ice sheet (GrIS, units Gt per year) equals the surface mass balance (SMB) minus solid ice discharge across the grounding line. As the latter is definite positive, an important threshold for irreversible GrIS mass loss occurs when long-term average SMB becomes negative. For this to happen, runoff (mainly meltwater, some rain) must exceed mass accumulation (mainly snowfall minus sublimation). Even for a single year, this threshold has not been passed since at least 1958, the first year with reliable estimates of SMB components, although recent years with warm summers (e.g. 2012 and 2019) came close. Simply extrapolating the recent (1991-present) negative SMB trend into the future suggests that the SMB = 0 threshold could be reached before ~2040, but such predictions are extremely uncertain given the very large interannual SMB variability, the relative brevity of the time series and the uncertainty in future warming. In this study we use a cascade of models, extensively evaluated with in-situ and remotely sensed (GRACE) SMB observations, to better constrain the future regional warming threshold for the 5-year average GrIS SMB to become negative. To this end, a 1950-2100 climate change run with the global model CESM2 (app. 100 km resolution) was dynamically downscaled using the regional climate model RACMO2 (app. 11 km), which in turn was statistically downscaled to 1 km resolution. The result is a threshold regional Greenland warming of close to 4 degrees. We then use a range of CMIP5 and CMIP6 global climate models to translate the regional value into a global warming threshold for various warming scenarios, including its timing this century. We find substantial differences, ranging from stabilization before the threshold is reached in the RCP/SSP2.6 scenarios with a limited but still significant sea-level rise contribution (< 5 cm by 2100) to an imminent crossing of the warming threshold for the RCP/SSP8.5 scenarios with substantial and ever-growing contributions to sea level rise (> 10 cm by 2100). These results stress the need for strong mitigation to avoid irreversible GrIS mass loss. We finish by discussing the caveats and uncertainties of our approach.</p>

scholarly journals Changes in beach shoreline due to sea level rise and waves under climate change scenarios: application to the Balearic Islands (western Mediterranean)

2017 ◽  
Vol 17 (7) ◽  
pp. 1075-1089 ◽  
Author(s):  
Alejandra R. Enríquez ◽  
Marta Marcos ◽  
Amaya Álvarez-Ellacuría ◽  
Alejandro Orfila ◽  
Damià Gomis
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Regional Climate ◽  
Wave Climate ◽  
Sandy Beaches ◽  
Western Mediterranean ◽  
Climate Change Scenarios ◽  
Swash Zone ◽  
Climate Scenarios

Abstract. This work assesses the impacts in reshaping coastlines as a result of sea level rise and changes in wave climate. The methodology proposed combines the SWAN and SWASH wave models to resolve the wave processes from deep waters up to the swash zone in two micro-tidal sandy beaches in Mallorca island, western Mediterranean. In a first step, the modelling approach has been validated with observations from wave gauges and from the shoreline inferred from video monitoring stations, showing a good agreement between them. Afterwards, the modelling set-up has been applied to the 21st century sea level and wave projections under two different climate scenarios, representative concentration pathways RCP45 and RCP85. Sea level projections have been retrieved from state-of-the-art regional estimates, while wave projections were obtained from regional climate models. Changes in the shoreline position have been explored under mean and extreme wave conditions. Our results indicate that the studied beaches would suffer a coastal retreat between 7 and up to 50 m, equivalent to half of the present-day aerial beach surface, under the climate scenarios considered.

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 Regional Greenland Accumulation Variability from Operation IceBridge Airborne Accumulation Radar

2016 ◽  
Author(s):  
Gabriel Lewis ◽  
Erich Osterberg ◽  
Robert Hawley ◽  
Brian Whitmore ◽  
Hans Peter Marshall
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Climate Model ◽  
Function Analysis ◽  
Greenland Ice Sheet ◽  
Northern Region ◽  
Snow Accumulation ◽  
Accumulation Rates

Abstract. The mass balance of the Greenland Ice Sheet (GIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge Accumulation Radar flights totaling > 17 700 km from 2013–2014 to determine snow accumulation in the GIS dry snow and percolation zones over the past 100–300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.037 ± 0.022 and 0.064 ± 0.033 m w.e. a−1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the central northern region, for example, the Regional Atmospheric Climate MOdel (RACMO2) underestimates by 26.9 ± 4.5 %, while in the southeast region the Modèle Atmosphérique Régional (MAR) overestimates by as much as 35.5 ± 6.8 %. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GIS surface mass balance estimates. Empirical orthogonality function analysis suggests that the first two principal components account for 33 % and 18 % of the variance and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. From 1976–2014 accumulation increased over most of the ice sheet's interior, consistent with the response to a positive AMO trend over this period. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.

scholarly journals Global mean thermosteric sea level projections by 2100 in CMIP6 climate models

2021 ◽  
Author(s):  
Svetlana Jevrejeva ◽  
Hindumathi Palanisamy ◽  
Luke Jackson
Keyword(s):  
Thermal Expansion ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Coupled Model ◽  
Rate Of Change ◽  
Historical Period ◽  
Coastal Zones ◽  
Ensemble Mean ◽  
Global Mean

<p>Most of the excess energy stored in the climate system is taken up by the oceans leading to thermal expansion and sea level rise. Future sea level projections allow decision-makers to assess coastal risk, develop climate resilient communities and plan vital infrastructure in low- elevation coastal zones. Confidence in these projections depends on the ability of climate models to simulate the various components of future sea level rise. In this study we estimate the contribution from thermal expansion to sea level rise using the simulations of global mean thermosteric sea level from 15 available models in the Coupled Model Intercomparison Project Phase (CMIP) 6. We calculate a global mean thermosteric sea level rise of 18.8 cm [12.8 - 23.6 cm, 90% range] and 26.8 cm [18.6 - 34.6 cm, 90% range] for the period 2081–2100, relative to 1995-2014 for SSP245 and SSP585 scenarios respectively. In a comparison with a 20 model ensemble from CMIP5, the CMIP6 ensemble mean of future global mean thermosteric sea level rise (2014-2100) is higher for both scenarios and shows a larger variance. By contrast, for the period 1901-1990, global mean thermosteric sea level from CMIP6 has half the variance of that from CMIP5. Over the period 1940-2005, the rate of CMIP6 ensemble mean of global mean thermosteric sea level rise is 0.2 ± 0.1 mm yr<sup>-1</sup>, which is less than half of the observed rate (0.5 ± 0.02 mm yr<sup>-1</sup>). At a multi-decadal timescale, there is an offset of ~10 cm per century between observed/modelled thermosteric sea level over the historical period and modelled thermosteric sea level over this century for the same rate of change of global temperature. We further discuss the difference in global mean thermosteric sea level sensitivity to the changes in global surface temperature over the historical and future periods.</p><p> </p>

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.

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.

GLOBAL IMPACT AND UNCERTAINTY ASSESSMENT OF SEA LEVEL RISE BASED ON MULTIPLE CLIMATE MODELS

2018 ◽  
Vol 74 (5) ◽  
pp. I_167-I_174 ◽  
Author(s):  
Koujiro TSUCHIDA ◽  
Makoto TAMURA ◽  
Naoko KUMANO ◽  
Eiji MASUNAGA ◽  
Hiromune YOKOKI
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Uncertainty Assessment ◽  
Global Impact
Sign in / Sign up

Export Citation Format

Share Document