Polar Regions in the Earth System (PolarRES)
Published April 28, 2023 | Version v1
Journal article Open

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

Creators

  • 1. British Antarctic Survey, Cambridge, United Kingdom
  • 2. Indian Institute of Technology, Kharagpur, India
  • 3. Victoria University of Wellington,Wellington, New Zealand
  • 4. Byrd Polar and Climate Research Center, The Ohio State University, Columbus, Ohio
  • 5. DanishMeteorological Institute, Copenhagen, Denmark
  • 6. DanishMeteorological Institute, Copenhagen, Denmark; Geodesy and Earth Observation, DTU-Space, Technical University of Denmark, Lyngby, Denmark
  • 7. University of Wisconsin–Madison, Madison, Wisconsin; Madison Area Technical College, Madison, Wisconsin
  • 8. NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
  • 9. Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan
  • 10. National Antarctic Scientific Center, Kyiv, Ukraine
  • 11. Utrecht University, Utrecht, Netherlands
  • 12. Met Office, Exeter, United Kingdom
  • 13. Byrd Polar and Climate Research Center, The Ohio State University, Columbus, Ohio; Scripps Institution of Oceanography, La Jolla, California

Description

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 the 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.

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Additional details

Funding

PolarRES – Polar Regions in the Earth System 101003590
European Commission