Refreezing on the Greenland ice sheet: a comparison of parameterizations

Abstract. Retention and refreezing of meltwater are acknowledged to be important processes for the mass budget of polar glaciers and ice sheets. Several parameterizations of these processes exist for use in energy and mass balance models. Due to a lack of direct observations, validation of these parameterizations is difficult. In this study we compare a set of 6 refreezing parameterizations against output of the Regional Atmospheric Climate Model (RACMO2), applied to the Greenland ice sheet. In RACMO2, refreezing is explicitly calculated in a snow model that calculates vertical profiles of temperature, density and liquid water content. For consistency, the parameterizations are forced with output (surface temperature, precipitation and melt) of RACMO2. For the ice sheet-integrated amount of refreezing and its inter-annual variations, all parameterizations give similar results, especially after some tuning. However, the spatial distributions differ significantly. Results are especially sensitive to the choice of the depth of the thermally active layer, which determines the cold content of the snow in most parameterizations.

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Refreezing on the Greenland ice sheet: a comparison of parameterizations

The Cryosphere ◽

10.5194/tc-6-743-2012 ◽

2012 ◽

Vol 6 (4) ◽

pp. 743-762 ◽

Cited By ~ 51

Author(s):

C. H. Reijmer ◽

M. R. van den Broeke ◽

X. Fettweis ◽

J. Ettema ◽

L. B. Stap

Keyword(s):

Climate Models ◽

Climate Model ◽

Regional Climate ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Regional Climate Models ◽

Liquid Water Content ◽

Annual Variations ◽

Output Surface ◽

Snow Model

Abstract. Retention and refreezing of meltwater are acknowledged to be important processes for the mass budget of polar glaciers and ice sheets. Several parameterizations of these processes exist for use in energy and mass balance models. Due to a lack of direct observations, validation of these parameterizations is difficult. In this study we compare a set of 6 refreezing parameterizations against output of two Regional Climate Models (RCMs) coupled to an energy balance snow model, the Regional Atmospheric Climate Model (RACMO2) and the Modèle Atmosphérique Régional (MAR), applied to the Greenland ice sheet. In both RCMs, refreezing is explicitly calculated in a snow model that calculates vertical profiles of temperature, density and liquid water content. Between RACMO2 and MAR, the ice sheet-integrated amount of refreezing differs by only 4.9 mm w.e yr−1 (4.5 %), and the temporal and spatial variability are very similar. For consistency, the parameterizations are forced with output (surface temperature, precipitation and melt) of the RCMs. For the ice sheet-integrated amount of refreezing and its inter-annual variations, all parameterizations give similar results, especially after some tuning. However, the spatial distributions differ significantly and the spatial correspondence between the RCMs is better than with any of the parameterizations. Results are especially sensitive to the choice of the depth of the thermally active layer, which determines the cold content of the snow in most parameterizations. These results are independent of which RCM is used to force the parameterizations.

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Drifting snow measurements on the Greenland Ice Sheet and their application for model evaluation

The Cryosphere ◽

10.5194/tc-8-801-2014 ◽

2014 ◽

Vol 8 (2) ◽

pp. 801-814 ◽

Cited By ~ 10

Author(s):

J. T. M. Lenaerts ◽

C. J. P. P. Smeets ◽

K. Nishimura ◽

M. Eijkelboom ◽

W. Boot ◽

...

Keyword(s):

High Frequency ◽

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Size Distributions ◽

Near Surface ◽

Drifting Snow ◽

Surface Climate ◽

Meteorological Observations ◽

Regional Atmospheric Climate Model

Abstract. This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency snow particle counter (SPC) observations at ~ 1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the horizontal snow transport at this level, which can be related to an overestimation of saltation and the typical size of drifting snow particles.

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Evaluation of a new snow albedo scheme for the Greenland ice sheet in the Regional Atmospheric Climate Model (RACMO2)

The Cryosphere ◽

10.5194/tc-14-3645-2020 ◽

2020 ◽

Vol 14 (11) ◽

pp. 3645-3662

Author(s):

Christiaan T. van Dalum ◽

Willem Jan van de Berg ◽

Stef Lhermitte ◽

Michiel R. van den Broeke

Keyword(s):

Climate Models ◽

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Atmospheric Conditions ◽

Snow Albedo ◽

In Situ Data ◽

Moderate Resolution Imaging Spectroradiometer ◽

Regional Atmospheric Climate Model ◽

Snow And Ice

Abstract. Snow and ice albedo schemes in present-day climate models often lack a sophisticated radiation penetration scheme and do not explicitly include spectral albedo variations. In this study, we evaluate a new snow albedo scheme in the Regional Atmospheric Climate Model (RACMO2) for the Greenland ice sheet, version 2.3p3, that includes these processes. The new albedo scheme uses the Two-streAm Radiative TransfEr in Snow (TARTES) model and the Spectral-to-NarrOWBand ALbedo (SNOWBAL) module, version 1.2. Additionally, the bare-ice albedo parameterization has been updated. The snow and ice broadband and narrowband albedo output of the updated version of RACMO2 is evaluated using the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) and Kangerlussuaq transect (K-transect) in situ data and Moderate Resolution Imaging Spectroradiometer (MODIS) remote-sensing observations. Generally, the modeled narrowband and broadband albedo is in very good agreement with satellite observations, leading to a negligible domain-averaged broadband albedo bias for the interior. Some discrepancies are, however, observed close to the ice margin. Compared to the previous model version, RACMO2.3p2, the broadband albedo is considerably higher in the bare-ice zone during the ablation season, as atmospheric conditions now alter the bare-ice broadband albedo. For most other regions, however, the updated broadband albedo is lower due to spectral effects, radiation penetration or enhanced snow metamorphism.

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Drifting snow measurements on the Greenland Ice Sheet and their application for model evaluation

The Cryosphere Discussions ◽

10.5194/tcd-8-21-2014 ◽

2014 ◽

Vol 8 (1) ◽

pp. 21-53 ◽

Cited By ~ 3

Author(s):

J. T. M. Lenaerts ◽

C. J. P. P. Smeets ◽

K. Nishimura ◽

M. Eijkelboom ◽

W. Boot ◽

...

Keyword(s):

High Frequency ◽

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Size Distributions ◽

Near Surface ◽

Drifting Snow ◽

Surface Climate ◽

Meteorological Observations ◽

Regional Atmospheric Climate Model

Abstract. This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency Snow Particle Counter (SPC) observations at ~1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short-lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the typical size of drifting snow particles, as well as the horizontal snow transport at this level.

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FAMOUS version xotzb (FAMOUS-ice): a GCM capable of energy- and water- conserving coupling to an ice sheet model

10.5194/gmd-2020-207 ◽

2020 ◽

Cited By ~ 1

Author(s):

Robin S. Smith ◽

Steve George ◽

Jonathan M. Gregory

Keyword(s):

Climate Models ◽

Climate Model ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Horizontal Resolution ◽

Polar Climate ◽

Snow Model ◽

Major Factors ◽

Scientific Questions

Abstract. The physical interactions between ice sheets and their surroundings are major factors in determining the state of the climate system, yet many current Earth System models omit them entirely or approximate them in a heavily parameterised manner. In this work we have improved the snow and ice sheet surface physics in the FAMOUS climate model, with the aim of improving the representation of polar climate and implementing a bidirectional coupling to the Glimmer dynamic ice sheet model using the water and energy fluxes calculated by FAMOUS. FAMOUS and Glimmer are both low resolution, computationally affordable models used for multi-millennial simulations. Glaciated surfaces in the new FAMOUS-ice are modelled using a multi-layer snow scheme capable of simulating compaction of firn and the percolation and refreezing of surface melt. The low horizontal resolution of FAMOUS compared to Glimmer is mitigated by implementing this snow model on sub-gridscale tiles that represent different elevations on the ice sheet within each FAMOUS grid-box. We show that with this approach FAMOUS-ice can simulate relevant physical processes on the surface of the modern Greenland ice sheet well compared to higher resolution climate models, and that the ice sheet state in the coupled FAMOUS-ice-Glimmer system does not drift unacceptably. FAMOUS-ice coupled to Glimmer is thus a useful tool for modelling the physics and co-evolution of climate and grounded ice sheets on centennial and millennial timescales, with applications to scientific questions relevant to both paleoclimate and future sea level rise.

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FAMOUS version xotzt (FAMOUS-ice): a general circulation model (GCM) capable of energy- and water-conserving coupling to an ice sheet model

Geoscientific Model Development ◽

10.5194/gmd-14-5769-2021 ◽

2021 ◽

Vol 14 (9) ◽

pp. 5769-5787

Author(s):

Robin S. Smith ◽

Steve George ◽

Jonathan M. Gregory

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Circulation Model ◽

Horizontal Resolution ◽

Snow Model ◽

Major Factors

Abstract. The physical interactions between ice sheets and their surroundings are major factors in determining the state of the climate system, yet many current Earth system models omit them entirely or approximate them in a heavily parameterised manner. In this work we have improved the snow and ice sheet surface physics in the FAMOUS climate model, with the aim of improving the representation of polar climate and implementing a bidirectional coupling to the Glimmer dynamic ice sheet model using the water and energy fluxes calculated by FAMOUS. FAMOUS and Glimmer are both low-resolution, computationally affordable models used for multi-millennial simulations. Glaciated surfaces in the new FAMOUS-ice are modelled using a multi-layer snow scheme capable of simulating compaction of firn and the percolation and refreezing of surface melt. The low horizontal resolution of FAMOUS compared to Glimmer is mitigated by implementing this snow model on sub-grid-scale tiles that represent different elevations on the ice sheet within each FAMOUS grid box. We show that with this approach FAMOUS-ice can simulate relevant physical processes on the surface of the modern Greenland ice sheet well compared to higher-resolution climate models and that the ice sheet state in the coupled FAMOUS-ice–Glimmer system does not drift unacceptably. FAMOUS-ice coupled to Glimmer is thus a useful tool for modelling the physics and co-evolution of climate and grounded ice sheets on centennial and millennial timescales, with applications to scientific questions relevant to both paleoclimate and future sea level rise.

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A realistic Greenland ice sheet and surrounding glaciers and ice caps melting in a coupled climate model

Climate Dynamics ◽

10.1007/s00382-021-05816-7 ◽

2021 ◽

Author(s):

Marion Devilliers ◽

Didier Swingedouw ◽

Juliette Mignot ◽

Julie Deshayes ◽

Gilles Garric ◽

...

Keyword(s):

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Coupled Climate Model ◽

Ice Caps

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Seasonal mass variations show timing and magnitude of meltwater storage in the Greenland Ice Sheet

The Cryosphere ◽

10.5194/tc-12-2981-2018 ◽

2018 ◽

Vol 12 (9) ◽

pp. 2981-2999 ◽

Cited By ~ 6

Author(s):

Jiangjun Ran ◽

Miren Vizcaino ◽

Pavel Ditmar ◽

Michiel R. van den Broeke ◽

Twila Moon ◽

...

Keyword(s):

Mass Balance ◽

Climate Model ◽

Spatial Scales ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Mass Balance ◽

High Accumulation ◽

Outlet Glacier ◽

Surface Mass ◽

Meltwater Runoff

Abstract. The Greenland Ice Sheet (GrIS) is currently losing ice mass. In order to accurately predict future sea level rise, the mechanisms driving the observed mass loss must be better understood. Here, we combine data from the satellite gravimetry mission Gravity Recovery and Climate Experiment (GRACE), surface mass balance (SMB) output of the Regional Atmospheric Climate Model v. 2 (RACMO2), and ice discharge estimates to analyze the mass budget of Greenland at various temporal and spatial scales. We find that the mean rate of mass variations in Greenland observed by GRACE was between −277 and −269 Gt yr−1 in 2003–2012. This estimate is consistent with the sum (i.e., -304±126 Gt yr−1) of individual contributions – surface mass balance (SMB, 216±122 Gt yr−1) and ice discharge (520±31 Gt yr−1) – and with previous studies. We further identify a seasonal mass anomaly throughout the GRACE record that peaks in July at 80–120 Gt and which we interpret to be due to a combination of englacial and subglacial water storage generated by summer surface melting. The robustness of this estimate is demonstrated by using both different GRACE-based solutions and different meltwater runoff estimates (namely, RACMO2.3, SNOWPACK, and MAR3.9). Meltwater storage in the ice sheet occurs primarily due to storage in the high-accumulation regions of the southeast and northwest parts of Greenland. Analysis of seasonal variations in outlet glacier discharge shows that the contribution of ice discharge to the observed signal is minor (at the level of only a few gigatonnes) and does not explain the seasonal differences between the total mass and SMB signals. With the improved quantification of meltwater storage at the seasonal scale, we highlight its importance for understanding glacio-hydrological processes and their contributions to the ice sheet mass variability.

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Sensitivity of Greenland Ice Sheet Projections to Model Formulations

Journal of Glaciology ◽

10.3189/2013jog12j182 ◽

2013 ◽

Vol 59 (216) ◽

pp. 733-749 ◽

Cited By ~ 87

Author(s):

H. Goelzer ◽

P. Huybrechts ◽

J.J. Fürst ◽

F.M. Nick ◽

M.L. Andersen ◽

...

Keyword(s):

Regional Climate Model ◽

Sea Level ◽

Flow Model ◽

Climate Model ◽

Regional Climate ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Flow ◽

Outlet Glacier ◽

Glacier Dynamics

AbstractPhysically based projections of the Greenland ice sheet contribution to future sea-level change are subject to uncertainties of the atmospheric and oceanic climatic forcing and to the formulations within the ice flow model itself. Here a higher-order, three-dimensional thermomechanical ice flow model is used, initialized to the present-day geometry. The forcing comes from a high-resolution regional climate model and from a flowline model applied to four individual marine-terminated glaciers, and results are subsequently extended to the entire ice sheet. The experiments span the next 200 years and consider climate scenario SRES A1B. The surface mass-balance (SMB) scheme is taken either from a regional climate model or from a positive-degree-day (PDD) model using temperature and precipitation anomalies from the underlying climate models. Our model results show that outlet glacier dynamics only account for 6–18% of the sea-level contribution after 200 years, confirming earlier findings that stress the dominant effect of SMB changes. Furthermore, interaction between SMB and ice discharge limits the importance of outlet glacier dynamics with increasing atmospheric forcing. Forcing from the regional climate model produces a 14–31 % higher sea-level contribution compared to a PDD model run with the same parameters as for IPCC AR4.

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Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers

The Cryosphere Discussions ◽

10.5194/tcd-6-593-2012 ◽

2012 ◽

Vol 6 (1) ◽

pp. 593-634 ◽

Cited By ~ 12

Author(s):

J. E. Box ◽

X. Fettweis ◽

J. C. Stroeve ◽

M. Tedesco ◽

D. K. Hall ◽

...

Keyword(s):

Solar Energy ◽

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Dominant Factor ◽

Water Runoff ◽

Albedo Feedback ◽

Ablation Area ◽

Regional Climate Model Output ◽

Surface Melt

Abstract. Greenland ice sheet mass loss has accelerated in the past decade responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. Using satellite observations of albedo and melt extent with calibrated regional climate model output, we determine the spatial dependence and quantitative impact of the ice sheet albedo feedback in twelve summer periods beginning in 2000. We find that while the albedo feedback is negative over 70 % of the ice sheet, concentrated in the accumulation area above 1500 m, positive feedback prevailing over the ablation area accounts for more than half of the overall increase in melting. Over the ablation area, year 2010 and 2011 absorbed solar energy was more than twice as large as in years 2000–2004. Anomalous anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme since 2007 enabled three amplifying mechanisms to maximize the albedo feedback: (1) increased warm (south) air advection along the western ice sheet increased surface sensible heating that in turn enhanced snow grain metamorphic rates, further reducing albedo; (2) increased surface downward solar irradiance, leading to more surface heating and further albedo reduction; and (3) reduced snowfall rates sustained low albedo, maximizing surface solar heating, progressively lowering albedo over multiple years. The summer net radiation for the high elevation accumulation area approached positive values during this period.

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