A 20-year study of melt processes over Larsen C Ice Shelf using a high-resolution regional atmospheric model: Part 1, Model configuration and validation

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

doi:10.1002/essoar.10506250.1

Cited by 5 publications

(22 citation statements)

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“…While no trends in foehn frequency are evident over the hindcast period, this is likely because we only have 20 years of data and there is considerable interannual variability (cf. Gilbert et al., 2022).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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Quantifying the relative importance of the atmospheric drivers of surface melting on the Larsen C ice shelf is critical in the context of recent and future climate change. Here, we present analysis of a new multidecadal, high‐resolution model hindcast using the Met Office Unified Model, described in Part 1 of this study. We evaluate the contribution of various atmospheric conditions in order to identify and rank, for the first time, the most significant causes of melting over the recent past. We find the primary driver of surface melting on Larsen C is solar radiation. Foehn events are the second most important contributor to surface melting, especially in nonsummer seasons when less solar radiation is received at the surface of the ice shelf. Third, cloud influences surface melting via its impact on the surface energy balance (SEB); when the surface temperature is warm enough, cloud can initiate or prolong periods of melting. Lastly, large‐scale circulation patterns such as the Southern Annular Mode (SAM), El Niño Southern Oscillation, and Amundsen Sea Low control surface melting on Larsen C by influencing the local meteorological conditions and SEB. These drivers of melting interact and overlap, e.g., the SAM influences the frequency of foehn, commonly associated with leeside cloud clearances and sunnier conditions. Ultimately, these drivers matter because sustained surface melting on Larsen C could destabilize the ice shelf via hydrofracturing, which would have consequences for the fate of the ice shelf and sea levels worldwide.

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Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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“…Another likely contributor to the model error in near‐surface temperature is the representation of cloud microphysics (King et al ., 2015; Gilbert et al ., 2020; 2021). Figure 10 compares the simulated low‐level cloud fraction at 1200 UTC on 27 January with cloud data from MODIS at 1309 UTC.…”

Section: Discussionmentioning

confidence: 99%

“…The cloud microphysics is a single‐moment scheme (Wilson and Ballard, 1999), but the version used here has extensive modifications described by Gilbert et al . (2020; 2021) to improve the representation of cloud phase over the LCIS. These modifications considerably improved the simulation of downwelling short‐wave and long‐wave radiation at the surface, and therefore the surface energy budget.…”

Section: Models Observations and Methodsmentioning

confidence: 99%

“…A grid spacing of around 5 km is employed for longer (multi‐year) simulations due to the lower computational cost (e.g. Datta et al ., 2019; Kirchgaessner et al ., 2019; Turton et al ., 2020; Gilbert et al ., 2021). However, there is evidence that the model results/performance can be sensitive to resolution in the 5 to 1.5 km range, raising concerns that a grid spacing of 5 km is not adequate (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The occurrence of foehn winds descending the lee (eastern) side of the Antarctic Peninsula is relatively common (Turton et al ., 2018; Wiesenekker et al ., 2018; Elvidge et al ., 2020) and is crucial in determining the atmospheric conditions over the Larsen C Ice Shelf (LCIS), which is the largest ice shelf on the Antarctic Peninsula and situated on its eastern side. The warm foehn winds can cause near‐surface air temperatures to rise above the melting point for sustained periods and thus drive surface melting over the western parts of the LCIS (Grosvenor et al ., 2014; Luckman et al ., 2014; Elvidge et al ., 2015; 2016; 2020; Kuipers Munneke et al ., 2018; Wiesenekker et al ., 2018; Datta et al ., 2019; Kirchgaessner et al ., 2019; Turton et al ., 2020; Gilbert et al ., 2021). This is most common during the summer months when the near‐surface air temperature is already around the freezing point due to high insolation and results in a distinct west–east gradient in surface melt intensity (Luckman et al ., 2014; Bevan et al ., 2018; Gilbert et al ., 2021).…”

Section: Introductionmentioning

confidence: 99%

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Comparison of kilometre and sub‐kilometre scale simulations of a foehn wind event over the Larsen C Ice Shelf, Antarctic Peninsula using the Met Office Unified Model (MetUM)

Orr

Kirchgaessner

King

et al. 2021

Quart J Royal Meteoro Soc

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A foehn event on 27 January 2011 over the Larsen C Ice Shelf (LCIS), Antarctic Peninsula and its interaction with an exisiting ground-based cold-air pool is simulated using the MetUM atmospheric model at kilometre and sub-kilometre scale grid spacing. Atmospheric model simulations at kilometre grid scales are an important tool for understanding the detailed circulation and temperature structure over the LCIS, especially the occurrence of foehn-induced surface melting, erosion of cold-air pools, and low-level wind jets (so-called foehn jets).But whether there is an improvement/convergence in the model representation of these features at sub-kilometre grid scales has yet to be established. The foehn event was simulated at grid spacings of 4, 1.5 and 0.5 km, with the results compared to automatic weather station and radiosonde measurements. The features commonly associated with foehn, such as a leeside hydraulic jump and enhanced leeside warming, were comparatively insensitive to resolution in the 4 to 0.5 km range, although the 0.5 km simulation shows a slightly sharper and larger hydraulic jump. By contrast, during the event the simulation of fine-scale foehn jets above the cold-air pool showed considerable dependence on grid spacing, although no evidence of convergence at higher resolution. During the foehn event, the MetUM model is characterised by a nocturnal cold bias of around 8 • C and an underestimate of the near-surface stability of the cold-air pool, neither of which improved with increased resolution. This finding identifies a key model limitation, at both kilometre and sub-kilometre scales, to realistically capture the vertical mixing in the boundary layer and its impact on thermodynamics, through either daytime heating from below or the downward penetration of foehn jet winds from above. Detailed model-resolved foehn jet dynamics thusThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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A 20-year study of melt processes over Larsen C Ice Shelf using a high-resolution regional atmospheric model: Part 2, Drivers of surface melting

Gilbert

Orr

Renfrew

et al. 2021

Preprint

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Atmospheric drivers of surface melting were implicated in the collapse of the Larsen A and B ice shelves that previously neighbored Larsen C-the largest remaining ice shelf on the eastern side of the Antarctic Peninsula and which extends north of the Antarctic circle-by increasing firn densification, meltwater ponding, and ultimately hydrofracturing and disintegration (Bell et al., 2018;Scambos et al., 2000). In particular, the large-scale circumpolar westerly circulation is known to have an important role in the Antarctic Peninsula region by influencing local atmospheric conditions via its effect on foehn winds. Foehn winds cause leeside warming and associated melting over these ice shelves (

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A 20-year study of melt processes over Larsen C Ice Shelf using a high-resolution regional atmospheric model: Part 1, Model configuration and validation

Cited by 5 publications

References 53 publications

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

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

Comparison of kilometre and sub‐kilometre scale simulations of a foehn wind event over the Larsen C Ice Shelf, Antarctic Peninsula using the Met Office Unified Model (MetUM)

A 20-year study of melt processes over Larsen C Ice Shelf using a high-resolution regional atmospheric model: Part 2, Drivers of surface melting

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