A system of conservative regridding for ice–atmosphere coupling  in a General Circulation Model (GCM)

Abstract. The method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields for use in one-way studies coupling atmospheres and ice flow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded and five transformations between those grids required by a typical coupled atmosphere–ice flow model. This paper develops a theoretical framework for the problem and shows how each of these transformations may be achieved in a consistent, conservative manner. These transformations are implemented in Glint2, a library used to couple atmosphere models with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

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A system of conservative regridding for ice/atmosphere coupling in a GCM

Geoscientific Model Development Discussions ◽

10.5194/gmdd-6-6493-2013 ◽

2013 ◽

Vol 6 (4) ◽

pp. 6493-6568 ◽

Cited By ~ 4

Author(s):

R. Fischer ◽

S. Nowicki ◽

M. Kelley ◽

G. A. Schmidt

Keyword(s):

Finite Element ◽

General Circulation ◽

Flow Model ◽

Source Code ◽

Circulation Model ◽

Surface Mass Balance ◽

Ice Flow ◽

Surface Mass ◽

Flow Models ◽

Ice Model

Abstract. The method of elevation classes has proven to be a useful way for a low-resolution general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields, for use in one-way studies coupling GCMs and ice flow models. Past uses of elevation classes have been a cause of non-conservation of mass and energy, caused by inconsistency in regridding schemes chosen to regrid to the atmosphere vs. downscaling to the ice model. This causes problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded, and five transformations between those grids required by a typical coupled GCM–ice flow model. This paper shows how each of those transformations may be achieved in a consistent, conservative manner. These transformations are implemented in GLINT2, a library used to couple GCMs with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

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On the discretization of the ice thickness distribution in the NEMO3.6-LIM3 global ocean–sea ice model

Geoscientific Model Development ◽

10.5194/gmd-12-3745-2019 ◽

2019 ◽

Vol 12 (8) ◽

pp. 3745-3758 ◽

Cited By ~ 2

Author(s):

François Massonnet ◽

Antoine Barthélemy ◽

Koffi Worou ◽

Thierry Fichefet ◽

Martin Vancoppenolle ◽

...

Keyword(s):

Sea Ice ◽

General Circulation ◽

Large Scale ◽

Thickness Distribution ◽

Circulation Model ◽

Grid Cell ◽

The Arctic ◽

Global Ocean ◽

Ice Thickness ◽

Ice Model

Abstract. The ice thickness distribution (ITD) is one of the core constituents of modern sea ice models. The ITD accounts for the unresolved spatial variability of sea ice thickness within each model grid cell. While there is a general consensus on the added physical realism brought by the ITD, how to discretize it remains an open question. Here, we use the ocean–sea ice general circulation model, Nucleus for European Modelling of the Ocean (NEMO) version 3.6 and Louvain-la-Neuve sea Ice Model (LIM) version 3 (NEMO3.6-LIM3), forced by atmospheric reanalyses to test how the ITD discretization (number of ice thickness categories, positions of the category boundaries) impacts the simulated mean Arctic and Antarctic sea ice states. We find that winter ice volumes in both hemispheres increase with the number of categories and attribute that increase to a net enhancement of basal ice growth rates. The range of simulated mean winter volumes in the various experiments amounts to ∼30 % and ∼10 % of the reference values (run with five categories) in the Arctic and Antarctic, respectively. This suggests that the way the ITD is discretized has a significant influence on the model mean state, all other things being equal. We also find that the existence of a thick category with lower bounds at ∼4 and ∼2 m for the Arctic and Antarctic, respectively, is a prerequisite for allowing the storage of deformed ice and therefore for fostering thermodynamic growth in thinner categories. Our analysis finally suggests that increasing the resolution of the ITD without changing the lower limit of the upper category results in small but not negligible variations of ice volume and extent. Our study proposes for the first time a bi-polar process-based explanation of the origin of mean sea ice state changes when the ITD discretization is modified. The sensitivity experiments conducted in this study, based on one model, emphasize that the choice of category positions, especially of thickest categories, has a primary influence on the simulated mean sea ice states while the number of categories and resolution have only a secondary influence. It is also found that the current default discretization of the NEMO3.6-LIM3 model is sufficient for large-scale present-day climate applications. In all cases, the role of the ITD discretization on the simulated mean sea ice state has to be appreciated relative to other influences (parameter uncertainty, forcing uncertainty, internal climate variability).

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Restoring mass conservation to shallow ice flow models over complex terrain

The Cryosphere ◽

10.5194/tc-7-229-2013 ◽

2013 ◽

Vol 7 (1) ◽

pp. 229-240 ◽

Cited By ~ 21

Author(s):

A. H. Jarosch ◽

C. G. Schoof ◽

F. S. Anslow

Keyword(s):

Complex Terrain ◽

Model Performance ◽

Grid Cell ◽

Mass Conservation ◽

Ice Flow ◽

Flow Models ◽

Mountainous Regions ◽

Steep Terrain ◽

Flux Limiting ◽

Ice Model

Abstract. Numerical simulation of glacier dynamics in mountainous regions using zero-order, shallow ice models is desirable for computational efficiency so as to allow broad coverage. However, these models present several difficulties when applied to complex terrain. One such problem arises where steep terrain can spuriously lead to large ice fluxes that remove more mass from a grid cell than it originally contains, leading to mass conservation being violated. This paper describes a vertically integrated, shallow ice model using a second-order flux-limiting spatial discretization scheme that enforces mass conservation. An exact solution to ice flow over a bedrock step is derived for a given mass balance forcing as a benchmark to evaluate the model performance in such a difficult setting. This benchmark should serve as a useful test for modellers interested in simulating glaciers over complex terrain.

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Use of ISLSCP II data to intercompare and validate the terrestrial net primary production in a land surface model coupled to a general circulation model

Journal of Geophysical Research Atmospheres ◽

10.1029/2006jd007721 ◽

2007 ◽

Vol 112 (D2) ◽

Cited By ~ 17

Author(s):

Li Dan ◽

Jinjun Ji ◽

Yong He

Keyword(s):

Primary Production ◽

General Circulation Model ◽

Land Surface ◽

General Circulation ◽

Net Primary Production ◽

Land Surface Model ◽

Circulation Model ◽

Surface Model

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Effect of Human-Induced Land Disturbance on Subseasonal Predictability of Near-Surface Variables Using an Atmospheric General Circulation Model

Atmosphere ◽

10.3390/atmos10110725 ◽

2019 ◽

Vol 10 (11) ◽

pp. 725

Author(s):

Tomohito J. Yamada ◽

Yadu Pokhrel

Keyword(s):

General Circulation Model ◽

Land Surface ◽

General Circulation ◽

Atmospheric General Circulation Model ◽

Circulation Model ◽

Weather Forecast ◽

Surface Model ◽

Near Surface ◽

Land Disturbance ◽

Atmospheric General Circulation

Irrigation can affect climate and weather patterns from regional to global scales through the alteration of surface water and energy balances. Here, we couple a land-surface model (LSM) that includes various human land-water management activities including irrigation with an atmospheric general circulation model (AGCM) to examine the impacts of irrigation-induced land disturbance on the subseasonal predictability of near-surface variables. Results indicate that the simulated global irrigation and groundwater withdrawals (circa 2000) are ~3600 and ~370 km3/year, respectively, which are in good agreement with previous estimates from country statistics and offline–LSMs. Subseasonal predictions for boreal summers during the 1986–1995 period suggest that the spread among ensemble simulations of air temperature can be substantially reduced by using realistic land initializations considering irrigation-induced changes in soil moisture. Additionally, it is found that the subseasonal forecast skill for near-surface temperature and sea level pressure significantly improves when human-induced land disturbance is accounted for in the AGCM. These results underscore the need to incorporate irrigation into weather forecast models, such as the global forecast system.

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The Antarctic surface mass balance in a stretched grid general circulation model

Annals of Glaciology ◽

10.1017/s0260305500013823 ◽

1997 ◽

Vol 25 ◽

pp. 73-78 ◽

Cited By ~ 7

Author(s):

Gerhard Krinner ◽

Christophe Genthon

Keyword(s):

Mass Balance ◽

General Circulation Model ◽

General Circulation ◽

Circulation Model ◽

Horizontal Resolution ◽

Spatial And Temporal Variability ◽

Surface Mass Balance ◽

Surface Mass ◽

Simulated Surface ◽

The Antarctic

The Laboratoire de Météorologie Dynamique (LMD) variable-grid atmospheric general circulation model (AGCM) was used in this study for a five-year high-resolution simulation of the Antarctic climate. The horizontal resolution is about 100 km over a large part of the ice sheet. This study focuses on the simulated surface mass balance (precipitation-evaporation sublimation-melt) and on the spatial and temporal variability of snowfall in Antarctica. The simulated annual mean surface mass balance for the whole continent is close to the observed value, and the model simulates well the spatial distribution of the surface mass balance. The annual cycle of snowfall exhibits a clear minimum in summer over the high interior plateau as well as for Antarctica as a whole, in agreement with the observations. In the interior of the continent, the model produces a permanent light background snowfall that accounts for about 5% of the total annual precipitation. The bulk of the snowfall is produced irregularly during periods that generally last only two or three days that are caused by cyclones off the coast.

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Evaluation of the Surface Representation of the Greenland Ice Sheet in a General Circulation Model

Journal of Climate ◽

10.1175/jcli-d-13-00635.1 ◽

2014 ◽

Vol 27 (13) ◽

pp. 4835-4856 ◽

Cited By ~ 53

Author(s):

Richard I. Cullather ◽

Sophie M. J. Nowicki ◽

Bin Zhao ◽

Max J. Suarez

Keyword(s):

General Circulation Model ◽

Seasonal Cycle ◽

General Circulation ◽

Climate Models ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Circulation Model ◽

Grid Spacing ◽

Surface Mass ◽

Dominant Feature

Simulated surface conditions of the Goddard Earth Observing System model, version 5 (GEOS-5), atmospheric general circulation model (AGCM) are examined for the contemporary Greenland Ice Sheet (GrIS). A surface parameterization that explicitly models surface processes including snow compaction, meltwater percolation and refreezing, and surface albedo is found to remedy an erroneous deficit in the annual net surface energy flux and provide an adequate representation of surface mass balance (SMB) in an evaluation using simulations at two spatial resolutions. The simulated 1980–2008 GrIS SMB average is 24.7 ± 4.5 cm yr−1 water-equivalent (w.e.) at ½° model grid spacing, and 18.2 ± 3.3 cm yr−1 w.e. for 2° grid spacing. The spatial variability and seasonal cycle of the ½° simulation compare favorably to recent studies using regional climate models, while results from 2° integrations reproduce the primary features of the SMB field. In comparison to historical glaciological observations, the coarser-resolution model overestimates accumulation in the southern areas of the GrIS, while the overall SMB is underestimated. These changes relate to the sensitivity of accumulation and melt to the resolution of topography. The GEOS-5 SMB fields contrast with available corresponding atmospheric models simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is found that only a few of the CMIP5 AGCMs examined provide significant summertime runoff, a dominant feature of the GrIS seasonal cycle. This is a condition that will need to be remedied if potential contributions to future eustatic change from polar ice sheets are to be examined with GCMs.

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