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

• DOI: 10.1175/jcli-d-22-0386.1
• Publication Date: 2022-10-14T20:58:41Z
• Authors: Andrew Orr; Pranab Deb; Kyle R. Clem; Ella Gilbert; David H. Bromwich; Fredrik Boberg; Steve Colwell; Nicolaj Hansen; Matthew A. Lazzara; Priscilla A. Mooney; Ruth Mottram; Masashi Niwano; Tony Phillips; Denys Pishniak; Carleen H. Reijmer; Willem Jan van de...; Stuart Webster; Xun Zou
• Keywords: Westerlies; Atmospheric Circulation; Anticyclone

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