Driving a high-resolution dynamic ice-sheet model with GCM climate: ice-sheet initiation at 116 000 BP

AbstractMost dynamic ice-sheet studies currently use either empirically based parameterizations or simple energy-balance climate models for the surface mass-balance forcing. If three-dimensional global climate models (GCMs) could be used instead, they would greatly improve the potential realism of coupled climate ice-sheet simulations. However, there are two serious problems in simulating realistic mass balances on ice sheets from GCM simulations: (i) dynamic ice-sheet models and the underlying bedrock topography need horizontal resolution of 50–100 km or less, but the finest practical resolution of atmospheric GCMs is currently ˜250 km, and (ii) GCM surface physics usually neglects the local refreezing of meltwater on ice sheets.Two techniques are described that address these problems: an elevation correction applied to the atmospheric GCM fields interpolated to the ice-sheet grid, and a refreezing correction involving the annual totals of snowfall, rainfall and local melt at each grid-point. As an example of their use, we have used the GENESIS version 2 GCM at 3.75° × 3.75° resolution to simulate the climate at the end of the last interglaciation at ˜116 000 years ago. The atmospheric climate is then used to drive a standard two-dimensional dynamic ice-sheet model for 10 000 years on a 0.5° × 0.5° grid spanning northern North America. The model successfully predicts ice-sheet initiation over the Baffin Island highlands and the Canadian Archipelago, but at a slower rate than observed. A large ice sheet nucleates and grows rapidly over the northwestern Rockies, in conflict with geologic evidence. Possible reasons for these discrepancies are discussed.

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Update on GRACE/GRACE-FO continuity in mass loss of the glaciers and big ice sheets.

10.5194/gstm2020-71 ◽

2020 ◽

Author(s):

Isabella Velicogna ◽

Mohajerani Yara ◽

Enrico Ciraci ◽

Felix Landerer ◽

David Wiese

Keyword(s):

Mass Balance ◽

Climate Models ◽

Global Climate ◽

Ice Sheets ◽

Reanalysis Data ◽

Global Climate Models ◽

Steady Increase ◽

Atlantic Sector ◽

Surface Mass ◽

Ice Caps

<p>The GRACE missions have changed the way that we measure mass changes of ice sheets, glaciers and ice caps, with quantied uncertainties that factor processing errors, atmospheric and oceanic corrections, and removal of glacial isostatic adjustment (GIA). We present GRACE/GRACE-FO estimates of mass balance over the Greenland and Antarctic Ice Sheets and the World&#8217;s glaciers and ice caps (GIC). The data gap between missions is filled with GRACE-calibrated results from the input-output method for ice sheets and surface mass balance (SMB) reconstructions from regional atmospheric climate models and MERRA-2 reanalysis data for the glaciers and ice caps. Over Greenland, we report low losses during the cold years of 2017-2018 followed by record melt in 2019 and an onset of rapid melt for 2020. As warm air and ocean masses get blocked over Greenland more frequently because of interactions between the wobbling jet stream and topography, we observe more high melt events in this decade than recorded in prior centuries. In Antarctica, the ongoing rapid loss in West Antarctica dominates the mass balance, but we observe a steady increase in snowfall in the Atlantic sector of East Antarctica. The exercise provides a mass balance record that can be continuously improved with better corrections and improved processing, with reduced errors, so that we can provide better constraints for ice sheet models in charge of sea level projections and improve the validation of various Earth system models and global climate models.</p>

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Sensitivity of a Greenland ice sheet model to atmospheric forcing fields

The Cryosphere ◽

10.5194/tc-6-999-2012 ◽

2012 ◽

Vol 6 (5) ◽

pp. 999-1018 ◽

Cited By ~ 33

Author(s):

A. Quiquet ◽

H. J. Punge ◽

C. Ritz ◽

X. Fettweis ◽

H. Gallée ◽

...

Keyword(s):

General Circulation ◽

Climate Models ◽

Global Climate ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Global Climate Models ◽

Near Surface ◽

Temperature And Precipitation ◽

The Impact

Abstract. Predicting the climate for the future and how it will impact ice sheet evolution requires coupling ice sheet models with climate models. However, before we attempt to develop a realistic coupled setup, we propose, in this study, to first analyse the impact of a model simulated climate on an ice sheet. We undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary conditions to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyrs of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed one, there are considerable deviations among the ice sheets on regional scales. These deviations can be explained by biases in temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations between the climate models are also due to the differences in the atmospheric general circulation. To account for these differences in the context of coupling ice sheet models with climate models, we conclude that appropriate downscaling methods will be needed. In some cases, systematic corrections of the climatic variables at the interface may be required to obtain realistic results for the Greenland ice sheet (GIS).

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A new world natural vegetation map for global change studies

Anais da Academia Brasileira de Ciências ◽

10.1590/s0001-37652008000200017 ◽

2008 ◽

Vol 80 (2) ◽

pp. 397-408 ◽

Cited By ~ 31

Author(s):

David M. Lapola ◽

Marcos D. Oyama ◽

Carlos A. Nobre ◽

Gilvan Sampaio

Keyword(s):

Large Scale ◽

New World ◽

Climate Models ◽

Global Climate ◽

Horizontal Resolution ◽

Vegetation Classification ◽

Natural Vegetation ◽

Global Climate Models ◽

Vegetation Map ◽

Vegetation Maps

We developed a new world natural vegetation map at 1 degree horizontal resolution for use in global climate models. We used the Dorman and Sellers vegetation classification with inclusion of a new biome: tropical seasonal forest, which refers to both deciduous and semi-deciduous tropical forests. SSiB biogeophysical parameters values for this new biome type are presented. Under this new vegetation classification we obtained a consensus map between two global natural vegetation maps widely used in climate studies. We found that these two maps assign different biomes in ca. 1/3 of the continental grid points. To obtain a new global natural vegetation map, non-consensus areas were filled according to regional consensus based on more than 100 regional maps available on the internet. To minimize the risk of using poor quality information, the regional maps were obtained from reliable internet sources, and the filling procedure was based on the consensus among several regional maps obtained from independent sources. The new map was designed to reproduce accurately both the large-scale distribution of the main vegetation types (as it builds on two reliable global natural vegetation maps) and the regional details (as it is based on the consensus of regional maps).

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IMPROVING THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) PRECIPITATION FORECASTS AT SEASONAL SCALE OVER THE HIMALAYAN REGION USING MACHINE LEARNING

International Journal of Big Data Mining for Global Warming ◽

10.1142/s263053482150008x ◽

2021 ◽

Author(s):

SOURABH SHRIVASTAVA ◽

RAM AVTAR ◽

PRASANTA KUMAR BAL

Keyword(s):

Machine Learning ◽

North American ◽

Climate Models ◽

Global Climate ◽

Horizontal Resolution ◽

Summer Monsoon Rainfall ◽

Global Climate Models ◽

Himalayan Region ◽

Model Ensemble ◽

The North

The coarse horizontal resolution global climate models (GCMs) have limitations in producing large biases over the mountainous region. Also, single model output or simple multi-model ensemble (SMME) outputs are associated with large biases. While predicting the rainfall extreme events, this study attempts to use an alternative modeling approach by using five different machine learning (ML) algorithms to improve the skill of North American Multi-Model Ensemble (NMME) GCMs during Indian summer monsoon rainfall from 1982 to 2009 by reducing the model biases. Random forest (RF), AdaBoost (Ada), gradient (Grad) boosting, bagging (Bag) and extra (Extra) trees regression models are used and the results from each models are compared against the observations. In simple MME (SMME), a wet bias of 20[Formula: see text]mm/day and an RMSE up to 15[Formula: see text]mm/day are found over the Himalayan region. However, all the ML models can bring down the mean bias up to [Formula: see text][Formula: see text]mm/day and RMSE up to 2[Formula: see text]mm/day. The interannual variability in ML outputs is closer to observation than the SMME. Also, a high correlation from 0.5 to 0.8 is found between in all ML models and then in SMME. Moreover, representation of RF and Grad is found to be best out of all five ML models that represent a high correlation over the Himalayan region. In conclusion, by taking full advantage of different models, the proposed ML-based multi-model ensemble method is shown to be accurate and effective.

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CMIP5 model selection for ISMIP6 ice sheet model forcing: Greenland and Antarctica

The Cryosphere ◽

10.5194/tc-14-855-2020 ◽

2020 ◽

Vol 14 (3) ◽

pp. 855-879 ◽

Cited By ~ 10

Author(s):

Alice Barthel ◽

Cécile Agosta ◽

Christopher M. Little ◽

Tore Hattermann ◽

Nicolas C. Jourdain ◽

...

Keyword(s):

Model Selection ◽

Climate Models ◽

Climate Modeling ◽

Global Climate ◽

Ice Sheet ◽

Global Climate Models ◽

Historical Period ◽

Climate Projections ◽

Subsurface Ocean ◽

Spatial Domains

Abstract. The ice sheet model intercomparison project for CMIP6 (ISMIP6) effort brings together the ice sheet and climate modeling communities to gain understanding of the ice sheet contribution to sea level rise. ISMIP6 conducts stand-alone ice sheet experiments that use space- and time-varying forcing derived from atmosphere–ocean coupled global climate models (AOGCMs) to reflect plausible trajectories for climate projections. The goal of this study is to recommend a subset of CMIP5 AOGCMs (three core and three targeted) to produce forcing for ISMIP6 stand-alone ice sheet simulations, based on (i) their representation of current climate near Antarctica and Greenland relative to observations and (ii) their ability to sample a diversity of projected atmosphere and ocean changes over the 21st century. The selection is performed separately for Greenland and Antarctica. Model evaluation over the historical period focuses on variables used to generate ice sheet forcing. For stage (i), we combine metrics of atmosphere and surface ocean state (annual- and seasonal-mean variables over large spatial domains) with metrics of time-mean subsurface ocean temperature biases averaged over sectors of the continental shelf. For stage (ii), we maximize the diversity of climate projections among the best-performing models. Model selection is also constrained by technical limitations, such as availability of required data from RCP2.6 and RCP8.5 projections. The selected top three CMIP5 climate models are CCSM4, MIROC-ESM-CHEM, and NorESM1-M for Antarctica and HadGEM2-ES, MIROC5, and NorESM1-M for Greenland. This model selection was designed specifically for ISMIP6 but can be adapted for other applications.

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Climate, the Antarctic ice sheet and ground heat flux

Annals of Glaciology ◽

10.3189/s0260305500015731 ◽

1995 ◽

Vol 21 ◽

pp. 144-148

Author(s):

Garth W. Paltridge ◽

Christopher M. Zweck

Keyword(s):

Heat Flux ◽

Steady State ◽

Climate Models ◽

Global Climate ◽

Ice Sheet ◽

Global Climate Models ◽

Balance Model ◽

Antarctic Ice Sheet ◽

Ground Heat Flux ◽

The Antarctic

A simple steady-state energy and mass-balance model of the Antarctic ice sheet is developed. Basically it is a set of two equations with two unknowns of steady-state height h and potential basal temperature Tb. Tb determines whether, and to what extent, there is liquid water at the base of the ice which in turn affects the values of h and Tb. Simultaneous changes of sea-level temperature and precipitation (changes related to each other as might be expected from global climate models) indicate a maximum in the field of possible steady-state ice volumes which may not be far from the presently observed conditions. The possibility of cyclical variation in ground heat flux associated with convection of water and heat in the continental crust is discussed. The mechanism might be capable of generating cycles of ice-sheet volume with relatively short periods similar to those of Milankovitch forcing.

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Impact of ocean forcing on the Aurora Basin in the 21st and 22nd centuries

Annals of Glaciology ◽

10.1017/aog.2016.27 ◽

2016 ◽

Vol 57 (73) ◽

pp. 79-86 ◽

Cited By ~ 7

Author(s):

S. Sun ◽

S. L. Cornford ◽

D. E. Gwyther ◽

R. M. Gladstone ◽

B. K. Galton-Fenzi ◽

...

Keyword(s):

Climate Models ◽

Global Climate ◽

Ice Sheet ◽

Adaptive Mesh ◽

Global Climate Models ◽

Ice Shelf ◽

Amundsen Sea ◽

Ice Shelves ◽

Future Warming ◽

East West

ABSTRACTThe grounded ice in the Totten and Dalton glaciers is an essential component of the buttressing for the marine-based Aurora basin, and hence their stability is important to the future rate of mass loss from East Antarctica. Totten and Vanderford glaciers are joined by a deep east-west running subglacial trench between the continental ice sheet and Law Dome, while a shallower trench links the Totten and Dalton glaciers. All three glaciers flow into the ocean close to the Antarctic circle and experience ocean-driven ice shelf melt rates comparable with the Amundsen Sea Embayment. We investigate this combination of trenches and ice shelves with the BISICLES adaptive mesh ice-sheet model and ocean-forcing melt rates derived from two global climate models. We find that ice shelf ablation at a rate comparable with the present day is sufficient to cause widespread grounding line retreat in an east-west direction across Totten and Dalton glaciers, with projected future warming causing faster retreat. Meanwhile, southward retreat is limited by the shallower ocean facing slopes between the coast and the bulk of the Aurora sub-glacial trench. However the two climate models produce completely different future ice shelf basal melt rates in this region: HadCM3 drives increasing sub-ice shelf melting to ~2150, while ECHAM5 shows little or no increase in sub-ice shelf melting under the two greenhouse gas forcing scenarios.

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Reconstructing the distribution of surface mass balance over East Antarctica (DML) from 1850 to present day

10.5194/egusphere-egu2020-13959 ◽

2020 ◽

Author(s):

Nicolas Ghilain ◽

Stéphane Vannitsem ◽

Quentin Dalaiden ◽

Hugues Goosse

Keyword(s):

Spatial Distribution ◽

Mass Balance ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Ice Cores ◽

Global Climate Models ◽

East Antarctica ◽

Surface Mass Balance ◽

Surface Mass

<p>Over recent decades, the Antarctic Ice Sheet has witnessed large spatial variations at its surface through the surface mass balance (SMB). Since the complex Antarctic topography, working at high resolution is crucial to represent accurately the dynamics of SMB. While ice cores provide a mean to infer the SMB over centuries, the view is very spatially constrained. Global Climate models estimate the spatial distribution of SMB over centuries, but with a too coarse resolution with regards to the large variations due to local orographic effects. We have therefore explored a methodology to statistically downscale the SMB components from the climate model historical simulations (1850-present day). An analogue method is set up over a period of 30 years with the ERA-Interim reanalysis (1979-2010 AD) and associated with SMB components from the Regional Atmospheric Climate Model (RACMO) at 5 km spatial resolution over Dronning Maud in East Antarctica. The same method is then applied to the period from 1850 to present days using an ensemble of 10 simulations from the CESM2 model. This method enables to derive a spatial distribution of SMB. In addition, the changes in precipitation delivery mechanisms can be unveiled.</p>

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An Analysis of Convectively Coupled Kelvin Waves in 20 WCRP CMIP3 Global Coupled Climate Models

Journal of Climate ◽

10.1175/2009jcli3422.1 ◽

2010 ◽

Vol 23 (11) ◽

pp. 3031-3056 ◽

Cited By ~ 48

Author(s):

Katherine H. Straub ◽

Patrick T. Haertel ◽

George N. Kiladis

Keyword(s):

Climate Models ◽

Global Climate ◽

Three Dimensional ◽

Kelvin Waves ◽

Global Climate Models ◽

Specific Humidity ◽

Tropospheric Temperature ◽

Wave Band ◽

Kelvin Wave ◽

Shallow Convection

Abstract Output from 20 coupled global climate models is analyzed to determine whether convectively coupled Kelvin waves exist in the models, and, if so, how their horizontal and vertical structures compare to observations. Model data are obtained from the World Climate Research Program’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel dataset. Ten of the 20 models contain spectral peaks in precipitation in the Kelvin wave band, and, of these 10, only 5 contain wave activity distributions and three-dimensional wave structures that resemble the observations. Thus, the majority (75%) of the global climate models surveyed do not accurately represent convectively coupled Kelvin waves, one of the primary sources of submonthly zonally propagating variability in the tropics. The primary feature common to the five successful models is the convective parameterization. Three of the five models use the Tiedtke–Nordeng convective scheme, while the other two utilize the Pan and Randall scheme. The 15 models with less success at generating Kelvin waves predominantly contain convective schemes that are based on the concept of convective adjustment, although it appears that those schemes can be improved by the addition of convective “trigger” functions. Three-dimensional Kelvin wave structures in the five successful models resemble observations to a large degree, with vertically tilted temperature, specific humidity, and zonal wind anomalies. However, no model completely captures the observed signal, with most of the models being deficient in lower-tropospheric temperature and humidity signals near the location of maximum precipitation. These results suggest the need for improvements in the representations of shallow convection and convective downdrafts in global models.

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Influence of albedo parameterization on surface mass balance in the perspective of Greenland ice sheet modelling in EC-Earth

10.5194/tc-2016-281 ◽

2016 ◽

Author(s):

Michiel Helsen ◽

Roderik Van de Wal ◽

Thomas Reerink ◽

Richard Bintanja ◽

Marianne Sloth Madsen ◽

...

Keyword(s):

Mass Balance ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Mass Balance ◽

Surface Mass

Abstract. The albedo of the surface of ice sheets changes as a function of time, due to the effects of deposition of new snow, ageing of dry snow, melting and runoff. Currently, the calculation of the albedo of ice sheets is highly parameterized within the Earth System Model EC-Earth, by taking a constant value for areas with thick perennial snow cover. This is one of the reasons that the surface mass balance (SMB) of the Greenland ice sheet (GrIS) is poorly resolved in the model. To improve this, eight snow albedo schemes are evaluated here. The resulting SMB is downscaled from the lower resolution global climate model topography to the higher resolution ice sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice sheet model simulations. This results in an optimised albedo parameterization that can be used in future EC-Earth simulations with an interactive ice sheet component.

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