New research suggests that glaciers in part of the Antarctic ice shelf may be melting at an unprecedented rate, raising concerns about rising sea levels.
The findings of the research by the University of Bristol, UK, were published in the journal Science. The scientists focused their research on a 750km long stretch of the coastline in the southwest of the continent where many glaciers are sliding down the mountainous terrain into the Bellingshausen Sea.
The team analysed more than 10 years of satellite data, including that from the European Space Agency’s Cryosat-2. This satellite can measure the elevation of the underlying ice surface to a very high degree of accuracy.
For much of the first decade of the new millennium, satellite data indicated that glaciers were gaining snow and ice at the same rate they were slipping into the sea. But it appears that from around 2009/10, the surface of the ice began to reduce at an alarming rate – up to four metres per year in some locations. The loss of ice is estimated to be around 60 cubic kilometres per year.
Antarctic ice and snow melt is estimated to contribute just 0.5mm to global sea rise each year. These findings raise the possibility of a rapid increase in this figure.
According to lead author Dr Bert Wouters the cause of this rapid melt is probably the warming of the waters surrounding Antarctica.
“… winds have become much stronger, they are pushing more water from the deep ocean on to the continental shelf of Antarctica. This water is relatively warm. It’s not warm like in Majorca, for example, but it has a temperature of one to two degrees centigrade, which is above the freezing temperature of ice, so it carries enough heat to melt the glaciers and their ice shelves from below” said Dr Wouters.
The region has certainly seen some very warm conditions in recent months. The Esperanza Base at the northern tip of Graham Land recorded a record-breaking temperature of 17.5C on March 24.
The Bristol team also used data from NASA’s Grace satellites which measure the Earth’s gravity field and can indirectly calculate the loss of ice mass.
Despite this, other scientists have challenged the team’s findings. According to a director at the Centre for Polar Observation and Modelling at the University of Leeds, Andy Shepherd, their calculations might have overlooked shifts in snowfall.
“I think the new estimates of ice loss computed [from the thinning of the ice] are far too high, because the glaciers in this sector just haven’t speeded up that much,” he said.
The Intergovernmental Panel on Climate Change suggests that global sea level rises are expected to accelerate, from 20cm in the last century, to almost one metre by 2100.