Characteristics of surface “melt potential” over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19

Orr, Andrew ORCID: https://orcid.org/0000-0001-5111-8402; Deb, Pranab; Clem, Kyle R.; Gilbert, Ella ORCID: https://orcid.org/0000-0001-5272-8894; Bromwich, David H.; Boberg, Fredrik; Colwell, Steve; Hansen, Nicolaj; Lazzara, Matthew A.; Mooney, Priscilla A.; Mottram, Ruth; Niwano, Masashi; Phillips, Tony ORCID: https://orcid.org/0000-0002-3058-9157; Pishniak, Denys; Reijmer, Carleen H.; van de Berg, Willem Jan; Webster, Stuart; Zou, Xun. 2023 Characteristics of surface “melt potential” over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19. Journal of Climate, 36 (10). 3357-3383. 10.1175/JCLI-D-22-0386.1

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Abstract/Summary

We calculate a regional surface “melt potential” index (MPI) over Antarctic ice shelves that describes the frequency (MPI-freq, %) and intensity (MPI-int, K) of daily maximum summer temperatures exceeding a melt threshold of 273.15 K. This is used to determine which ice shelves are vulnerable to melt-induced hydrofracture and is calculated using near-surface temperature output for each summer from 1979/80 to 2018/19 from two high-resolution regional atmospheric model hindcasts (using the MetUM and HIRHAM5). MPI is highest for Antarctic Peninsula ice shelves (MPI-freq 23-35%, MPI-int 1.2-2.1 K), lowest (2-3%, < 0 K) for Ronne-Filchner and Ross ice shelves, and around 10-24% and 0.6-1.7 K for the other West and East Antarctic ice shelves. Hotspots of MPI are apparent over many ice shelves, and they also show a decreasing trend in MPI-freq. The regional circulation patterns associated with high MPI values over West and East Antarctic ice shelves are remarkably consistent for their respective region but tied to different large-scale climate forcings. The West Antarctic circulation resembles the central Pacific El Niño pattern with a stationary Rossby wave and a strong anticyclone over the high-latitude South Pacific. By contrast, the East Antarctic circulation comprises a zonally symmetric negative Southern Annular Mode pattern with a strong regional anticyclone on the plateau and enhanced coastal easterlies/weakened Southern Ocean westerlies. Values of MPI are 3-4 times larger for a lower temperature/melt threshold of 271.15 K used in a sensitivity test, as melting can occur at temperatures lower than 273.15 K depending on snowpack properties.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JCLI-D-22-0386.1
ISSN:	0894-8755
Additional Keywords:	Extreme events; Antarctica; Ice shelves; El Nino; Snowmelt/icemelt; Climate models
Date made live:	07 Mar 2023 13:16 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/534182

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