Melting Ice & Rising Seas

According to a new study released by NASA’s Jet Propulsion Laboratory (JPL), the Greenland Ice Sheet has lost more than 300 billion tons of ice every year since 2004, and the loss is increasing at the rate of 31 billion tons of ice per year as the planet keeps getting warmer.

Almost as big as Alaska, the Greenland Ice Sheet spans 600,000 square miles (1.7 million square kilometers). It is 2 miles (3km) thick and is losing more ice in the summer than it gains back in winter. The Ice Sheet’s summer melt season now lasts 70 days longer than it did in the 1970s. The Greenland Ice Sheet has the ultimate potential to raise the world’s oceans by more than 20 ft. (6m).

At the bottom of the world, the Antarctic Ice Sheet covers 5.4 million square miles (14 million square km), an area larger than China and India combined, and 9 times larger than the Greenland Ice Sheet. It contains enough ice to raise the world’s ocean levels by about 190 ft. (58m).

The Transantarctic Mountains divide Antarctica into West Antarctica and the much larger East Antarctica. The ice shelves in East Antarctica appear to be fairly stable at this point, but the ice shelves in West Antarctica are collapsing. In 2002, a 1,250 square mile (3,240 square km) chunk of the Larsen B Ice Shelf in West Antarctica broke off and floated away. In the years since then, the remainder of Larsen B and the glaciers it had been holding in place have been gradually sliding into the sea. Scientists studying the problem believe the collapse of the entire West Antarctica Ice Shelf is underway. One study predicted that in the next 200 to 1,000 years, the West Antarctica Ice Sheet will disappear, adding up to 12 ft. (4m) of sea level rise.

The reason for the more rapid melting of West Antarctica appears to be a layer of warm ocean water eating away at the bottom of the ice shelf.

Although East and West Antarctica hold far more ice than Greenland, the Antarctica melt rate is much slower. At the moment, Antarctica is losing 118 billion tons of ice a year, compared to Greenland’s more than 303 billion tons. Together, they account for about two thirds of annual sea level rise. The remaining third is due to ocean water expanding as it gets warmer. The world’s oceans have risen 8 in. (2.9cm) since 1900. But the rate of rise is speeding up. We’ve had a nearly 3 in. (7.4cm) increase in just the past 20 years.

How much and how fast will the oceans rise in our future? The UN’s Intergovernmental Panel on Climate Change projects up to a 38 in. (97cm) rise by 2100, depending on the melt rate of the ice sheets and how quickly we can control the burning of fossil fuels and the warming of our planet. If you live in a coastal community, it will probably be a good idea to start thinking about remedial action against a rising sea. Or get ready to pull on your rubber boots.