Tuesday, 26 June 2012

Confirmed: Antarctic ice shelves NOT melting

Remember all those reports about the fast melting Antarctic ice shelves? A new study - based on real measurements, not computer models - by researchers from the Norwegian Polar Institute published in the journal Geophysical Letters shows that they we wrong: 
“It has been unclear, until now, how much warm deep water rises below the Fimbul Ice shelf, and previous ocean models, focusing on the circulation below the Fimbul Ice Shelf, have predicted temperatures and melt rates that are too high, suggesting a significant mass loss in this region that is actually not taking place as fast as previously thought,” said lead author of the study and PhD student at the Norwegian Polar Institute (NPI), Tore Hattermann.
The Fimbul Ice Shelf – located along eastern Antarctica in the Weddell Sea – is the sixth largest of the forty-three ice shelves that dapple Antarctica’s perimeter. Both its size and proximity to the Eastern Antarctic Ice Sheet – the largest ice sheet on Earth, which if it melted, could lead to extreme changes in sea level – have made the Fimbul Ice Shelf an attractive object of study.
The team is the first to provide direct, observational evidence that the Fimbul Ice Shelf is melting from underneath by three, equally important processes. Their results confirm a 20-year-old theory about how ice shelves melt that, until now, was too complex to be further investigated with models that had no direct observations for comparison. These processes likely apply to other areas of Antarctica, primarily the eastern half because of its similar water and wind circulation patterns, Hattermann said.

It turns out that past studies, which were based on computer models without any direct data for comparison or guidance, overestimate the water temperatures and extent of melting beneath the Fimbul Ice Shelf. This has led to the misconception, Hattermann said, that the ice shelf is losing mass at a faster rate than it is gaining mass, leading to an overall loss of mass. The model results were in contrast to the available data from satellite observations, which are supported by the new measurements.
The team’s results show that water temperatures are far lower than computer models predicted, which means that the Fimbul Ice Shelf is melting at a slower rate. Perhaps indicating that the shelf is neither losing nor gaining mass at the moment because ice buildup from snowfall has kept up with the rate of mass loss, Hattermann said.
“Our data shows what needs to be included in the next generation models, in order to be able to do a good job in predicting future melt rates,” Hattermann said.
Read the entire article here

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