Three glaciers in the Northeast region of Greenland are melting away faster than expected, threatening a precipitous rise in sea levels, according to a study published on March 16 in Nature Climate Change. Although the increase in the melting rate of glaciers worldwide is well-known among scientists, the Greenland glaciers in the northeast have long been considered among the most stable. But now scientists believe they are melting at a rate faster than anticipated.
Northeast Greenland is one of the coldest and driest regions on the planet and the stability of the area has been routinely taken for granted. Previous studies of rising sea levels hadn’t even looked at the area. The glaciers there restrain a vast, 370 mile long ice stream with deeper connections into the interior of the ice mass than any of the other glaciers on the island. This stream alone makes up 16 percent of that mass. Regional stability is vital because a precipitous melting in that region could accelerate that of the entire sheet.
Greenland’s ice sheet is the second largest in the world, after Antarctica’s, covering 680, 000 square miles, or 80 percent, of the island. The ice rises to a mean altitude of over 7000 feet, reaching almost two miles at its thickest point. Scientists say the entire sheet will melt to nothing in the next 2000 years, raising sea levels by up to 24 feet. Other, smaller glaciers and ice caps lie around the periphery of the island, covering an additional 35,000 square miles.
The stability of Greenland and parts of Antarctica are the two largest considerations when it comes to projecting rising sea levels, and the melting of the northeast glaciers are occurring at a faster rate than previously expected. Researchers from Denmark, the Netherlands, the U.S., and China used data from aircraft, satellites, and digital photos, sequenced from 1976 to the present, to take thickness measurements. The results showed that the Northeast glaciers were retreating at a rate similar to a glacier in the southwest known as the Jakobshavn glacier, now known as the fastest in Greenland or Antarctica. In the summer of 2012 the recorded speed of that glacier reached 46 meters a day, four times what is was in 1990.
The topography of Greenland slopes upwards toward the center and radially downward toward the peripheral coasts, This means that the ice streams and masses that coastal glaciers hold back have the potential to fall into the sea in progressively larger sections spurred on by the force of gravity, further accelerating the rise in sea levels. The bases of these coastal glaciers, then, with their bases extending down into the sea bed, serve as brakes this potential force.
Sea levels have risen 8 inches since 1900 and are expected to rise another three feet by 2100. Greenland alone accounts for six percent of this activity. Since the 1960s air temperatures across the arctic rose 3.6 Fahrenheit, twice that of areas further toward the equator. This has warmed arctic sea water temperatures in which the bases of coastal glaciers rest. And the Northeast glaciers of Greenland, once seen as a stronghold, are now melting; and quickly.
By Robert Wisnewski