The Arctic continued to shift to a warmer, greener state in 2013, according to the latest annual Arctic Report Card from the National Oceanic and Atmospheric Administration (NOAA) and NASA.
Scientists are tracking a variety of environmental indicators, including air temperature, snow cover, sea ice extent, ocean temperature, vegetation growth and wildlife behavior. Compared with 2012, most indicators this year were closer to their long-term averages, but signs of change (fueled by long-term warming) were still present.
For instance, most surface waters within the Arctic Circle were warmer than average in summer 2013. Warm waters in the eastern Arctic were probably related to an earlier-than-normal retreat of sea ice from the area and possibly an inflow of warmer water from the North Atlantic. Retreating sea ice would have left the Kara and Barents Seas exposed to warm summer sunlight.
Meanwhile, on the western side of the Arctic, sea ice retreat was later and less extensive than normal, contributing to cooler-than-average surface temperatures in the Chukchi and East Siberian Seas.