The Greenland ice sheet is shrinking
Satellite readings show Greenland is losing large quantities of ice. The enormous ice cap constituting the inland ice is melting at an ever-increasing rate, and there is every indication that the inland ice is contributing to the rise in sea level of the oceans.
An enormous net loss
Scientists are monitoring developments using satellites, light aircraft and observations on the ice, and most agree that global warming is the cause of this melting.
At the heart of the problem is the fact that ice formation occurring on the inland ice as a result of winter snowfalls cannot compensate for the melting. In other words, there is a net loss of ice. Calculations by a Dano–US team of scientists show an annual volume loss of about 257 km³.
The average net loss of ice in 2080 will have reached 465 km³ – a loss of ice 80% greater than today, estimate research scientists of the International Arctic Research Center, Fairbanks, Alaska, state to Ritzau.
The melting is accelerating
In the period from 2000 to 2008, the melting of the Greenlandic ice shed accelerated drastically, and new research from the summer of 2009 shows that the Greenlandic ice shed is much more sensitive to variations in temperature than hitherto expected. The amount of melting water from the Greenlandic ice shed varies by up to 25 percent from year to year. In 2007, which was a warm year in Greenland, twice as much ice melted as in 2004. In 2008, however, the amount of melted ice had fallen by 25 percent compared to the year before. Earlier, researchers of climate change had not been aware of the large variations in the mounts of melt water. This means that the effects of global warming are actually bigger than IPCC, The UN Panel on Climate Change, estimated in their latest rapport in 2007.
Glaciers are calving sooner
Readings show that the periphery of the inland ice is accelerating outwards. Therefore, the glaciers are calving sooner and more violently than before, and enormous icebergs are forming.
At the same time, the fronts of the largest glaciers are receding. This is due to a rise in summer temperatures. Only very little additional heat would be required for the snow covering large areas to disappear. A temperature increase of 1 °C distributed evenly across the large ice cap is enough to melt a vertical metre of ice each year. In other words, this would require one additional metre of ice to form from winter snowfalls in order to prevent the glacier from receding.
Measuring the ice
In the past, it was incredibly expensive and difficult to collect accurate information on the melting of the inland ice. In recent years, however, advanced satellites have made it possible to gather very accurate data, and a GPS network, GNET, positioned along the edge of the inland ice will provide data for use in calculations. GNET, which will be completed in 2010, is being established as a collaborative venture involving research scientists from the US, Luxembourg and Denmark.
GEUS is leading an ongoing monitoring programme (Programme for Monitoring of the Greenland Ice Sheet (PROMICE)that combines readings from GPS stations with data from aircraft and satellites to equip scientists to calculate the combined mass loss of the inland ice on an annual basis.
Meltwater in the sea
The inland ice is releasing increasing amounts of fresh water into the North Atlantic, which has a major impact on global ocean currents. This could have inherent consequences for the global climate, but no one knows exactly how or to what extent.
Professor Dorte Dahl-Jensen of the Niels Bohr Institute at the University of Copenhagen believes sea levels may rise by almost 1 m by the year 2100. In the rapport of 2007 IPCC, UN Intergovernmental Panel on Climate Change, estimated that the maximum rise in sea level this century would be around 59 cm. Since then the IPCC has recognized that the rise in the sea level will probably be much higher. The reason for this is that the IPCC report only calculated the effect caused by melting sea ice and did not, due to uncertainties and lacking knowledge, include melt water coming from the Greenlandic ice sheet and glaciers around the world.
According to Dorte Dahl-Jensen, it is reasonable to expect a 30 cm rise in sea level coming from the melting of the ice on Greenland and another 30 cm from melting of ice in Antarctica. The rest will come from small glaciers, and from water in the sea expanding as it gets warmer in the sea expanding as it warms.
If all the inland ice were to melt
If all of Greenland's inland ice were to melt, sea levels around the Earth would rise by six to seven metres, because the volume of the ice corresponds to approximately 8% of global fresh water.