The sea level response to ice sheet freshwater forcing in the Community Earth System Model

Abstract The Glimmer Community Ice Sheet Model (Glimmer-CISM) has been implemented in the Community Earth System Model (CESM). Glimmer-CISM is forced by a surface mass balance (SMB) computed in multiple elevation classes in the CESM land model and downscaled to the ice sheet grid. Ice sheet evolution is governed by the shallow-ice approximation with thermomechanical coupling and basal sliding. This paper describes and evaluates the initial model implementation for the Greenland Ice Sheet (GIS). The ice sheet model was spun up using the SMB from a coupled CESM simulation with preindustrial forcing. The model's sensitivity to three key ice sheet parameters was explored by running an ensemble of 100 GIS simulations to quasi equilibrium and ranking each simulation based on multiple diagnostics. With reasonable parameter choices, the steady-state GIS geometry is broadly consistent with observations. The simulated ice sheet is too thick and extensive, however, in some marginal regions where the SMB is anomalously positive. The top-ranking simulations were continued using surface forcing from CESM simulations of the twentieth century (1850–2005) and twenty-first century (2005–2100, with RCP8.5 forcing). In these simulations the GIS loses mass, with a resulting global-mean sea level rise of 16 mm during 1850–2005 and 60 mm during 2005–2100. This mass loss is caused mainly by increased ablation near the ice sheet margin, offset by reduced ice discharge to the ocean. Projected sea level rise is sensitive to the initial geometry, showing the importance of realistic geometry in the spun-up ice sheet.

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Forced Patterns of Sea Level Rise in the Community Earth System Model Large Ensemble From 1920 to 2100

Journal of Geophysical Research Oceans ◽

10.1029/2019jc016030 ◽

2020 ◽

Vol 125 (6) ◽

Author(s):

John T. Fasullo ◽

Peter R. Gent ◽

R. S. Nerem

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Large Ensemble ◽

Community Earth System Model

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Greenland Surface Mass Balance as Simulated by the Community Earth System Model. Part II: Twenty-First-Century Changes

Journal of Climate ◽

10.1175/jcli-d-12-00588.1 ◽

2014 ◽

Vol 27 (1) ◽

pp. 215-226 ◽

Cited By ~ 29

Author(s):

Miren Vizcaíno ◽

William H. Lipscomb ◽

William J. Sacks ◽

Michiel van den Broeke

Keyword(s):

Mass Balance ◽

Ice Sheet ◽

Earth System Model ◽

First Century ◽

System Model ◽

Surface Mass Balance ◽

Earth System ◽

Surface Mass ◽

Community Earth System Model ◽

Twenty First Century

Abstract This study presents the first twenty-first-century projections of surface mass balance (SMB) changes for the Greenland Ice Sheet (GIS) with the Community Earth System Model (CESM), which includes a new ice sheet component. For glaciated surfaces, CESM includes a sophisticated calculation of energy fluxes, surface albedo, and snowpack hydrology (melt, percolation, refreezing, etc.). To efficiently resolve the high SMB gradients at the ice sheet margins and provide surface forcing at the scale needed by ice sheet models, the SMB is calculated at multiple elevations and interpolated to a finer 5-km ice sheet grid. During a twenty-first-century simulation driven by representative concentration pathway 8.5 (RCP8.5) forcing, the SMB decreases from 372 ± 100 Gt yr−1 in 1980–99 to −78 ± 143 Gt yr−1 in 2080–99. The 2080–99 near-surface temperatures over the GIS increase by 4.7 K (annual mean) with respect to 1980–99, only 1.3 times the global increase (+3.7 K). Snowfall increases by 18%, while surface melt doubles. The ablation area increases from 9% of the GIS in 1980–99 to 28% in 2080–99. Over the ablation areas, summer downward longwave radiation and turbulent fluxes increase, while incoming shortwave radiation decreases owing to increased cloud cover. The reduction in GIS-averaged July albedo from 0.78 in 1980–99 to 0.75 in 2080–99 increases the absorbed solar radiation in this month by 12%. Summer warming is strongest in the north and east of Greenland owing to reduced sea ice cover. In the ablation area, summer temperature increases are smaller due to frequent periods of surface melt.

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Simulation of LGM ice sheets with the Community Earth System Model version 2

10.5194/egusphere-egu21-15463 ◽

2021 ◽

Author(s):

Sarah L Bradley ◽

Michele Petrini ◽

Raymond Sellevold ◽

Miren Vizcaino ◽

William H. Lipscomb ◽

...

Keyword(s):

Ice Sheets ◽

Ice Sheet ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Last Deglaciation ◽

Model Version ◽

Starting Point ◽

Community Earth System Model ◽

The Last Deglaciation

The last deglaciation provides as unique a framework to investigate the processes of ice sheet and climate interaction during periods of mass loss as in the current climate. Here we simulate the Last Glacial Maximum (LGM) northern hemisphere ice sheets climate, surface mass balance (SMB), and dynamics with the Community Earth System Model version 2 (CESM2, Danabasoglu et al., 2020)) and the Community Ice Sheet Model version 2 (CISM2, Lipscomb et al., 2019). This LGM simulation will be later used as starting point for coupled CESM2-CISM2 simulations of the last deglaciation.&#160;CESM2 is run at the nominal resolution used for IPCC-type projections (approx. 1 degree for all components). The model includes an advanced snow/firn and SMB calculation (van Kampenhout et al, 2019; Sellevold et al, 2019) the land component (CLM, cite) that has been evaluated and applied to the simulation of the future Greenland melt (van Kampenhout et al, 2020, Muntjewerf et al., 2020a,b, Sellevold & Vizcaino, 2020).&#160;Our analysis examines how the global, Arctic, and North Atlantic climate result in the simulated radiative and turbulent heat fluxes over the ice sheets, and the mass fluxes from precipitation, refreezing, runoff, and sublimation. We also examine the simulated ice streams in CISM2, which is run at 8 km under a higher-order approximation for ice flow.

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Surface Mass Balance of the Greenland Ice Sheet in the Energy Exascale Earth System Model

10.5194/egusphere-egu21-14017 ◽

2021 ◽

Author(s):

Adam Schneider ◽

Stephen Price ◽

Jonathan Wolfe ◽

Charles Zender

Keyword(s):

Sea Level ◽

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Earth System Model ◽

System Model ◽

Surface Mass Balance ◽

Earth System ◽

Surface Mass ◽

Global Sea Level

Since 1993, nearly 10 percent of the observed rise in global mean sea level can be attributed to the coincident increase in surface mass loss from the Greenland Ice Sheet (GrIS) (Meredith et al., 2019; WCRP, 2018). To determine the GrIS surface mass balance (SMB), defined as the ice sheet&#8217;s annual net (surface) mass increase due to snow accumulation minus ablation, a climate model can be coupled to a snowpack model, which enables simulating relevant hydrologic processes including precipitation, phase changes, and runoff. Recent developments within the Energy Exascale Earth System Model (E3SM) include an active ice sheet component. To explore GrIS snowpack conditions relevant to present-day climate, we conduct simulations demonstrating the evolution of SMB and accumulation of snowpack depth, first in E3SM&#8217;s land component (ELM). After forcing ELM&#8217;s surface condition using 20th century atmospheric reanalysis, we couple ELM to E3SM&#8217;s atmosphere component (EAM) and simulate both atmospheric and snowpack conditions over a fixed GrIS geometry. Finally, we activate the MPAS-Albany Land Ice model (MALI), which enables prognostic SMB calculations including elevation-change feedbacks. We find broad agreement in the spatial patterns of GrIS SMB compared to regional climate model (RACMO) and Community Earth System Model (CESM) simulations. We provide insights regarding the use of a statistical downscaling method, which involves using multiple elevation classes with time-varying areal coverages within ELM grid-cells. Within this dynamic system, we can begin investigating elevation feedbacks, where the atmospheric temperature lapse rate allows the SMB to accelerate both positively and negatively in a rapidly changing climate.References<ul><li>Meredith, M., M. Sommerkorn, S. Cassotta, C. Derksen, A. Ekaykin, A. Hollowed, G. Kofinas, A. Mackintosh, J. Melbourne-Thomas, M.M.C. Muelbert, G. Ottersen, H. Pritchard, and E.A.G. Schuur, 2019: Polar Regions. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Po&#776;rtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegri&#769;a, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.</li> <li>WCRP Global Sea Level Budget Group: Global sea-level budget 1993&#8211;present, Earth Syst. Sci. Data, 10, 1551&#8211;1590, https://doi.org/10.5194/essd-10-1551-2018, 2018.</li> </ul>

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Greenland Surface Mass Balance as Simulated by the Community Earth System Model. Part I: Model Evaluation and 1850–2005 Results

Journal of Climate ◽

10.1175/jcli-d-12-00615.1 ◽

2013 ◽

Vol 26 (20) ◽

pp. 7793-7812 ◽

Cited By ~ 39

Author(s):

Miren Vizcaíno ◽

William H. Lipscomb ◽

William J. Sacks ◽

Jan H. van Angelen ◽

Bert Wouters ◽

...

Keyword(s):

Mass Balance ◽

Climate Models ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Earth System Model ◽

System Model ◽

Surface Mass Balance ◽

Earth System ◽

Surface Mass ◽

Community Earth System Model

Abstract The modeling of the surface mass balance (SMB) of the Greenland Ice Sheet (GIS) requires high-resolution models in order to capture the observed large gradients in the steep marginal areas. Until now, global climate models have not been considered suitable to model ice sheet SMB owing to model biases and insufficient resolution. This study analyzes the GIS SMB simulated for the period 1850–2005 by the Community Earth System Model (CESM), which includes a new ice sheet component with multiple elevation classes for SMB calculations. The model is evaluated against observational data and output from the regional model Regional Atmospheric Climate Model version 2 (RACMO2). Because of a lack of major climate biases, a sophisticated calculation of snow processes (including surface albedo evolution) and an adequate downscaling technique, CESM is able to realistically simulate GIS surface climate and SMB. CESM SMB agrees reasonably well with in situ data from 475 locations (r = 0.80) and output from RACMO2 (r = 0.79). The simulated mean SMB for 1960–2005 is 359 ± 120 Gt yr−1 in the range of estimates from regional climate models. The simulated seasonal mass variability is comparable with mass observations from the Gravity Recovery and Climate Experiment (GRACE), with synchronous annual maximum (May) and minimum (August–September) and similar amplitudes of the seasonal cycle. CESM is able to simulate the bands of precipitation maxima along the southeast and northwest margins, but absolute precipitation rates are underestimated along the southeastern margin and overestimated in the high interior. The model correctly simulates the major ablation areas. Total refreezing represents 35% of the available liquid water (the sum of rain and melt).

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Present-day and future Greenland Ice Sheet precipitation frequency from CloudSat observations and the Community Earth System Model

The Cryosphere ◽

10.5194/tc-14-2253-2020 ◽

2020 ◽

Vol 14 (7) ◽

pp. 2253-2265

Author(s):

Jan T. M. Lenaerts ◽

M. Drew Camron ◽

Christopher R. Wyburn-Powell ◽

Jennifer E. Kay

Keyword(s):

Climate Models ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Precipitation Frequency ◽

Worst Case ◽

Rainfall Frequency ◽

Community Earth System Model

Abstract. The dominant mass input component of the Greenland Ice Sheet (GrIS) is precipitation, whose amounts and phase are poorly constrained by observations. Here we use spaceborne radar observations from CloudSat to map the precipitation frequency and phase on the GrIS, and we use those observations, in combination with a satellite simulator to enable direct comparison between observations and model, to evaluate present-day precipitation frequency in the Community Earth System Model (CESM). The observations show that substantial variability of snowfall frequency over the GrIS exists, that snowfall occurs throughout the year, and that snowfall frequency peaks in spring and fall. Rainfall is rare over the GrIS and only occurs in regions under 2000 m elevation and in the peak summer season. Although CESM overestimates the rainfall frequency, it reproduces the spatial and seasonal variability of precipitation frequency reasonably well. Driven by the high-emission, worst-case Representative Concentration Pathway (RCP) 8.5 scenario, CESM indicates that rainfall frequency will increase considerably across the GrIS, and will occur at higher elevations, potentially exposing a much larger GrIS area to rain and associated meltwater refreezing, firn warming, and reduced storage capacity. This technique can be applied to evaluate precipitation frequency in other climate models and can aid in planning future satellite campaigns.

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Description and demonstration of the coupled Community Earth System Model v2 ‐ Community Ice Sheet Model v2 (CESM2‐CISM2)

Journal of Advances in Modeling Earth Systems ◽

10.1029/2020ms002356 ◽

2021 ◽

Author(s):

Laura Muntjewerf ◽

William J. Sacks ◽

Marcus Lofverstrom ◽

Jeremy Fyke ◽

William H. Lipscomb ◽

...

Keyword(s):

Ice Sheet ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Community Earth System Model

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Altimeter-era emergence of the patterns of forced sea-level rise in climate models and implications for the future

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1813233115 ◽

2018 ◽

Vol 115 (51) ◽

pp. 12944-12949 ◽

Cited By ~ 15

Author(s):

John T. Fasullo ◽

R. Steven Nerem

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Climate Models ◽

Internal Variability ◽

Forced Response ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Community Earth System Model

The satellite altimeter record has provided an unprecedented database for understanding sea-level rise and has recently reached a major milestone at 25 years in length. A challenge now exists in understanding its broader significance and its consequences for sea-level rise in the coming decades and beyond. A key question is whether the pattern of altimeter-era change is representative of longer-term trends driven by anthropogenic forcing. In this work, two multimember climate ensembles, the Community Earth System Model (CESM) and the Earth System Model Version 2M (ESM2M), are used to estimate patterns of forced change [also known as the forced response (FR)] and their magnitudes relative to internal variability. It is found that the spatial patterns of 1993–2018 trends in the ensembles correlate significantly with the contemporaneous FRs (0.55 ± 0.10 in the CESM and 0.61 ± 0.09 in the ESM2M) and the 1950–2100 FRs (0.43 ± 0.10 in the CESM and 0.51 ± 0.11 in the ESM2M). Unforced runs for each model show such correlations to be extremely unlikely to have arisen by chance, indicating an emergence of both the altimeter-era and long-term FRs and suggesting a similar emergence in nature. Projected patterns of the FR over the coming decades resemble those simulated during the altimeter era, suggesting a continuation of the forced pattern of change in nature in the coming decades. Notably, elevated rates of rise are projected to continue in regions that are susceptible to tropical cyclones, exacerbating associated impacts in a warming climate.

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