The Arctic continues to get warmer and greener, even though this summer was cooler than the last, the National Oceanic and Atmospheric Administration said Thursday with the release of its Arctic Report Card 2013.

Cooler temperatures in the summer helped curb the Arctic region's sea ice loss and extensive melting along the surface of the Greenland ice sheet, but there were still regional weather extremes such as record low May snowfall in Eurasia and record high summer temperatures in Alaska.

"The Arctic caught a bit of a break in 2013 from the recent string of record-breaking warmth and ice melt of the last decade," David M. Kennedy, NOAA's deputy under secretary for operations, said in a statement. "But the relatively cool year in some parts of the Arctic does little to offset the long-term trend of the last 30 years: the Arctic is warming rapidly, becoming greener and experiencing a variety of changes, affecting people, the physical environment, and marine and land ecosystems."

Nearly 150 authors from 14 countries contributed to the research in the Arctic Report Card, a document that has been released annually since 2006.

"The Arctic Report Card presents strong evidence of widespread, sustained changes that are driving the Arctic environmental system into a new state and we can expect to see continued widespread and sustained change in the Arctic," said Martin Jeffries, principal editor of the 2013 Report Card. "But we risk not seeing those changes if we don't sustain and add to our current long-term observing capabilities. Observations are fundamental to Arctic environmental awareness, government and private sector operations, scientific research, and the science-informed decision-making required by the U.S. National Strategy for the Arctic."

Among the report card's key observations were that as much as 44 percent of the surface of the Greenland ice sheet experienced melting and that the region is showing a trend toward greening as vegetation responds to a longer growing season.

Caribou and reindeer herds continue to have unusually low numbers, the report said, while muskox numbers have been increasing. In the Arctic waters there is an increased presence of some fish, including the Atlantic mackerel and Atlantic cod.