Atmosphere Journal Entry
Arctic Ice Getting Thinner (April 27, 2009)
This summer, sea ice in the Arctic melted to its second lowest level ever recorded. NASA.
New research shows that sea ice in the Arctic is getting thinner. A greater percentage of it is now made up of thinner, seasonal ice and less of it is thicker, longer-lasting ice. As a result, the total mass of the ice cap is shrinking.
Thinner seasonal sea ice melts in the summer and refreezes in the winter. Thicker perennial sea ice lasts two summers or more without melting. In the 1980s and 1990s, seasonal ice made up between 40 and 50 percent of the total. Now it accounts for over 70 percent.
In the winter of 2008–2009, sea ice in the Arctic covered an area of 5.8 million square miles (14.5 million sq. km), the fifth-lowest total ever measured. Compared to the the 1979 to 2000 average winter peak, it represents an ice loss about the size of Texas.
The changes are alarming. The Arctic's ice cap works like a gigantic air conditioner for Earth's climate control system. The glassy ice surface reflects huge amounts of sunlight back into space. As more ice melts, less light is reflected and more solar energy is absorbed by the darker ocean. The extra heat speeds the melting of the ice.
Scientists blame the rise in temperatures on the increase in greenhouse gases like carbon dioxide, mostly from the burning of fossil fuels.
