The US space agency, NASA, yesterday released brand
new images showing the pace of ice loss from Earth's two vast ice
sheets, Greenland and Antarctica.
The amount of ice lost from the frozen expanses at the
very north and south of the planet is accelerating, say the
scientists, and together have helped raise global sea level by more
than 7cm since 1992.
The Greenland ice sheet covers approximately 1.7m
square kilometres (660,000 square miles), an area almost as big as
Alaska. At its thickest point, the ice sitting on top of the land
is more than 3km deep.
Since 2004, Greenland has been losing an average
of 303bn tonnes of ice every year, according to
NASA data, with the rate of loss accelerating by 31bn tonnes
per year every year.
In the animation below, red shows areas that have lost
ice, blue shows areas that have gained ice.
Change in the mass of the Greenland Ice Sheet between
January 2004 and June 2014, as measured by the GRACE satellite.
Goddard's Scientific Visualization Studio.
The stunning video images
above come from the Gravity Recovery and Climate Experiment
twin-satellite. The satellites orbit the poles, measuring
changes to the Earth's land and water masses and work out
differences in the planet's gravitational field every 30
Some of the ice lost from Greenland is as result of
the huge glaciers melting. But most of it is down to warming air
overhead directly melting the surface of the ice sheet. A
press release accompanying yesterday's data explains:
"Greenland's summer melt
season now lasts 70 days longer than it did in the early 1970s.
Every summer, warmer air temperatures cause melt over about half of
the surface of the ice sheet - although recently, 2012 saw an
extreme event where 97% of the ice sheet experienced melt at its
Greenland officially reaches the end of the summer
melt season next week, when scientists will be able to say how 2015
has compared with previous years in terms of the speed of ice
Changing ocean currents and temperatures are also
melting the Greenland ice sheet from the bottom up, scientists
say. A new three-year NASA project called Oceans Melting
Greenland (OMG ) aims to
get a better handle on how the rate of ice loss compares to surface
Covering nearly 14m square kilometres (5.4m square
miles), Antarctica is more than eight times the area of
Greenland. The continent is also losing ice, though less
quickly than its northern counterpart. Antarctica has lost, on
average, 118bn tonnes of ice per year since 2004, compared to
Greenland's 303bn tonnes.