'Ice Arches' Promoted 2007 Arctic Ice Loss

In 2007, a large volume of old ices separated from the Arctic sheet, and was pushed into the ocean, where it naturally melted. Now, experts at the NASA Jet Propulsion Laboratory (JPL), in Pasadena, California, believe they know why this happened. Using data from satellite study as support, they suggest that the phenomenon was triggered by the fact that “ice arches” no longer formed between separate land points, which thus remained open. This subjected two ice sheets behind them to influences from water currents and strong winds, thus promoting their disintegration.

The ice spreads in the Arctic reached a record-low in 2007, and climatologists were completely puzzled by the vast amount of ice that was lost to the oceans. In addition to negatively influencing the global climate, melting ice can also raise the level of the world's oceans, endangering hundreds of million of people living in low-lying, coastal areas. Experts explain that, in the case of the Arctic, each autumn sees the expansion of ice sheets until they are confined by surrounding continents. This means that the only possible way for ice to escape is through a small number of passages that remain opened, including the Fram Strait and the Nares Strait.

“There are a couple of ways to lose Arctic ice: when it flows out and when it melts. We are trying to quantify how much we're losing by outflow versus melt,” explains JPL expert Ron Kwok, who was also the leader of the new study. When peering through the satellite data, the team determined that the 40-kilometer-wide Nares Strait had lost its ice arches during the 2007 season, which in turn allowed ice it should have kept back to escape through it. Two years ago, more ice existed through Nares than thought possible.

“Until recently, we didn't think the small straits were important for ice loss,” Kwok reveals. “One of our most important goals is developing predictive models of Arctic sea ice cover. Such models are important not only to understanding changes in the Arctic, but also changes in global and North American climate. Figuring out how ice is lost through the Fram and Nares straits is critical to developing those models,” says NASA Headquarters cryosphere program manager Tom Wagner. Details of the new work are published in the February issue of Geophysical Research Letters.