Evaluating the impact of enhanced horizontal resolution over the Antarctic domain using a variable-resolution Earth system model
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Published:2023-09-06
Issue:9
Volume:17
Page:3847-3866
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Datta Rajashree Tri, Herrington Adam, Lenaerts Jan T. M.ORCID, Schneider David P., Trusel LukeORCID, Yin Ziqi, Dunmire DevonORCID
Abstract
Abstract. Earth system models are essential tools for understanding
the impacts of a warming world, particularly on the contribution of polar
ice sheets to sea level change. However, current models lack full coupling
of the ice sheets to the ocean and are typically run at a coarse resolution
(1∘ grid spacing or coarser). Coarse spatial resolution is
particularly a problem over Antarctica, where sub-grid-scale orography is
well-known to influence precipitation fields, and glacier models require
high-resolution atmospheric inputs. This resolution limitation has been
partially addressed by regional climate models (RCMs), which must be forced
at their lateral and ocean surface boundaries by (usually coarser) global
atmospheric datasets, However, RCMs fail to capture the two-way coupling
between the regional domain and the global climate system. Conversely,
running high-spatial-resolution models globally is computationally
expensive and can produce vast amounts of data. Alternatively, variable-resolution grids can retain the benefits of high
resolution over a specified domain without the computational costs of
running at a high resolution globally. Here we evaluate a historical
simulation of the Community Earth System Model version 2 (CESM2)
implementing the spectral element (SE) numerical dynamical core (VR-CESM2)
with an enhanced-horizontal-resolution (0.25∘) grid over the
Antarctic Ice Sheet and the surrounding Southern Ocean; the rest of the
global domain is on the standard 1∘ grid. We compare it to
1∘ model runs of CESM2 using both the SE dynamical core and the
standard finite-volume (FV) dynamical core, both with identical physics and
forcing, including prescribed sea surface temperatures (SSTs) and sea ice concentrations from
observations. Our evaluation reveals both improvements and degradations in
VR-CESM2 performance relative to the 1∘ CESM2. Surface mass
balance estimates are slightly higher but within 1 standard deviation of
the ensemble mean, except for over the Antarctic Peninsula, which is
impacted by better-resolved surface topography. Temperature and wind
estimates are improved over both the near surface and aloft, although the
overall correction of a cold bias (within the 1∘ CESM2 runs) has
resulted in temperatures which are too high over the interior of the ice
sheet. The major degradations include the enhancement of surface melt as
well as excessive cloud liquid water over the ocean, with resultant impacts
on the surface radiation budget. Despite these changes, VR-CESM2 is a
valuable tool for the analysis of precipitation and surface mass balance
and thus constraining estimates of sea level rise associated with the
Antarctic Ice Sheet.
Funder
National Science Foundation National Aeronautics and Space Administration
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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