Recent increase in surface melting of West Antarctic ice shelves linked to Interdecadal Pacific Oscillation

Since the late 1990s, summer surface melt across ice shelves in the Ross-Amundsen Sea sector of West Antarctica increased significantly, as demonstrated by satellite measurements and MetUM simulations. This contrasts with the period from 1979 to the late 1990s, which witnessed a decreasing summer melt trend driven by the positive trend in Southern Annular Mode. The increase in summer melt since the late 1990s is linked to an increase in geopotential height and intensified anticyclonic blocking along coastal West Antarctica, which strengthened northerly winds over the Ross-Amundsen Sea sector, leading to enhanced advection of warm, marine air. Our analysis reveals a strong connection between summer melt indices and sea surface temperatures in the South Pacific Convergence Zone during this period. Moreover, increased summer precipitation in South Pacific Convergence Zone since the late 1990s strengthened the Rossby wave teleconnection toward West Antarctica, contributing to enhanced blocking along the coastal region. This is consistent with the transition of the Interdecadal Pacific Oscillation to its negative phase.

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