Cryosphere Journal Entry
Cryosphere Journal Entry
Arctic Melt Season Getting Longer (March 15, 2010)
The Arctic's melt season is getting longer. In areas shown in dark red, the season is up to 40 days longer per decade than in the past. NASA.
With all the news about global warming, it comes as no surprise that the melt season in the Arctic is growing. Every year, some of the sea ice melts in summer and refreezes in winter. A new NASA study shows the melt season is both starting earlier and lasting longer. The study tracked seasonal changes in the ice cap in the Arctic between 1979 and 2007. Data is from satellite measurements of energy radiated by the ice.
The melt season begins on the day in the spring when ice stops freezing and melting is continuous. The season ends when the ice begins to freeze again. Data shows the melt season increased, on average, more than six days per decade. The change was most dramatic along ice pack edges and at lower latitudes, where the melt season is as much as 40 days longer per decade.
Changes in the melt season are accelerating because of a positive feedback loop, a process in which a change in one factor triggers more of the same. In other words, melting itself leads to more melting. That's because dark ocean water absorbs more solar energy than mirror-like ice. An earlier melt season allows ocean water to soak up heat for a longer time. The extra heat delays refreezing.
Other studies show the area covered by sea ice is shrinking from rising temperatures in the Arctic. This rise is blamed on increased greenhouse gas levels in the atmosphere.
