A 20‐Year Study of Melt Processes Over Larsen C Ice Shelf Using a High‐Resolution Regional Atmospheric Model: 2. Drivers of Surface Melting

Gilbert, Ella; Renfrew, Ian A.; King, John C.; Lachlan-Cope, Tom

doi:10.1029/2021jd036012

Cited by 3 publications

(2 citation statements)

References 58 publications

(176 reference statements)

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“…4a). A deeper ASL typically brings relatively warm, northerly air flows down the western side of the AP 41 , enhancing surface air temperature and the likelihood of melting 42 .…”

Section: Links With Antarctic Climatementioning

confidence: 99%

“…5b), suggesting that local variability in surface meteorological conditions and extreme weather events are more important. Localised melt rates on the AP are strongly influenced by variations in weather conditions including solar radiation 42,43 , foehn winds 43,44 and low cloudcover 45 . Although strongly linked to broader climatic patterns, the interaction and timing of these local drivers appear key to controlling the most extreme meltwater ponding events, and are likely responsible for the overall increasing trend in AP meltwater area.…”

Section: Links With Antarctic Climatementioning

confidence: 99%

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Continent-scale mapping reveals a rise in East Antarctic surface meltwater

Tuckett

Ely

Sole

et al. 2022

Preprint

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The future sea-level contribution from the Antarctic ice sheets is highly uncertain. Ice dynamic, hydrofracture, and radiative processes related to surface meltwater are predicted to become increasingly important for Antarctic mass-loss as atmospheric temperatures rise. Our understanding of Antarctic surface meltwater, however, remains limited, with previous studies restricted in spatial or temporal scope. Here, we leverage cloud computing to overcome these limitations and produce the first Antarctic-wide, monthly dataset of surface meltwater spanning 2006 to 2021. Surface meltwater covered 3732 km2 across Antarctica on average during each melt season, with 30% on grounded ice. High interannual variability in meltwater coverage across the Antarctic Peninsula and in East Antarctica correlates with large-scale modes of climate variability, but this control is absent where meltwater coverage is comparatively low in West Antarctica. In East Antarctica, we find a significant increasing trend in meltwater area of 66 km2 per year (197% total change) which, in the absence of a clear climatic trend, we attribute to ice sheet surfaces becoming more favourable to ponding. Future increases in melt rate could therefore cause proportionally larger increases in meltwater coverage with implications for the resilience of ice shelves, and increased surface-to-bed hydraulic connections on grounded ice.

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“…4a). A deeper ASL typically brings relatively warm, northerly air flows down the western side of the AP 41 , enhancing surface air temperature and the likelihood of melting 42 .…”

Section: Links With Antarctic Climatementioning

confidence: 99%

Section: Links With Antarctic Climatementioning

confidence: 99%

Continent-scale mapping reveals a rise in East Antarctic surface meltwater

Tuckett

Ely

Sole

et al. 2022

Preprint

View full text Add to dashboard Cite

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Evaluating the impact of enhanced horizontal resolution over the Antarctic domain using a variable-resolution Earth system model

Datta,

Herrington,

Lenaerts

et al. 2023

The Cryosphere

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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.

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The importance of cloud properties when assessing surface melting in an offline-coupled firn model over Ross Ice shelf, West Antarctica

Hansen,

Orr,

Zou

et al. 2024

The Cryosphere

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Abstract. The Ross Ice Shelf, West Antarctica, experienced an extensive melt event in January 2016. We examine the representation of this event by the HIRHAM5 and MetUM high-resolution regional atmospheric models, as well as a sophisticated offline-coupled firn model forced with their outputs. The model results are compared with satellite-based estimates of melt days. The firn model estimates of the number of melt days are in good agreement with the observations over the eastern and central sectors of the ice shelf, while the HIRHAM5 and MetUM estimates based on their own surface schemes are considerably underestimated, possibly due to deficiencies in these schemes and an absence of spin-up. However, the firn model simulates sustained melting over the western sector of the ice shelf, in disagreement with the observations that show this region as being a melt-free area. This is attributed to deficiencies in the HIRHAM5 and MetUM output and particularly a likely overestimation of night-time net surface radiative flux. This occurs in response to an increase in night-time downwelling longwave flux from around 180–200 to 280 W m−2 over the course of a few days, leading to an excessive amount of energy at the surface available for melt. Satellite-based observations show that this change coincides with a transition from clear-sky to cloudy conditions, with clouds containing both liquid water and ice water. The models capture the initial clear-sky conditions but seemingly struggle to correctly represent cloud properties associated with the cloudy conditions, which we suggest is responsible for the radiative flux errors.

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A 20‐Year Study of Melt Processes Over Larsen C Ice Shelf Using a High‐Resolution Regional Atmospheric Model: 2. Drivers of Surface Melting

Cited by 3 publications

References 58 publications

Continent-scale mapping reveals a rise in East Antarctic surface meltwater

Continent-scale mapping reveals a rise in East Antarctic surface meltwater

Evaluating the impact of enhanced horizontal resolution over the Antarctic domain using a variable-resolution Earth system model

The importance of cloud properties when assessing surface melting in an offline-coupled firn model over Ross Ice shelf, West Antarctica

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