Geophys. Res. Lett. 34, L18504 (2007)

Credit: © Punchstock

Antarctic snowmelt is occurring farther inland and at higher altitude than previously observed, according to a new analysis of satellite observations.

A team led by Marco Tedesco at the University of Maryland, US, and NASA mapped the extent and duration of Antarctic melting continent-wide over 20 years using microwave satellite imagery. Unlike other satellite instruments that use visible or infrared data, the sensors can measure the microwave radiation naturally emitted by snow and ice, can see through clouds, and can even detect subsurface melting, day and night.

The data show that from 1987 to 2006, Antarctica, as a whole, cooled, but in some years, coastal areas became warmer. The greatest extent and duration of melting was observed at the Ross Ice Shelf — the continent's largest ice shelf — where the researchers detected episodes of persistent melting lasting three or more days, starting in 1991–1992. In early 2005, the persistent melt reached nearly 900 kilometres from the coast and an altitude of 2 kilometres in the Transantarctic Mountains — farther inland and higher than ever before recorded. Ice shelves slow the flow of glaciers, and a weakened Ross Ice Shelf could allow much greater quantities of inland ice to reach the ocean, potentially resulting in a significant rise in sea level.