Satellites show arctic sea ice loss leading to a darker Earth

The retreat of Arctic Ocean sea ice is diminishing Earth's reflectivity by an amount considerably larger than previously estimated, NASA says. As the sea ice melts, its white reflective surface is replaced by a relatively dark ocean surface, reducing the amount of sunlight being reflected back to space, causing Earth to absorb an increasing amount of solar energy and become warmer, the space agency said Tuesday. Researchers at Scripps Institution of Oceanography at the University of California, San Diego, analyzed data from instruments aboard several NASA satellites to gauge the sea ice loss and its effect. The Arctic has warmed by 3.6 degrees Fahrenheit since the 1970s as the summer minimum Arctic sea ice extent decreased by 40 percent during the same time period. That has decreased overall reflectivity, also known as albedo, of the arctic region from 52 percent to 48 percent between 1979 and 2011, the researches calculate. "It's fairly intuitive to expect that replacing white, reflective sea ice with a dark ocean surface would increase the amount of solar heating," Scripps graduate student Kristina Pistone said. "We used actual satellite measurements of both albedo and sea ice in the region to verify this and to quantify how much extra heat the region has absorbed due to the ice loss."