Arctic sea ice
Read the report at http://nsidc.org/arcticseaicenews/
The maximum extent of this year's Arctic sea ice was the fifth lowest annual maximum on record, according to a report by Boulder's National Snow and Ice Data Center last week.
Record-keeping of the ice in the planet's northernmost waters began in 1978. The lowest annual maximum was recorded in March 2011.
"It is yet one more indication that the sea ice is in trouble," said NSIDC director Mark Serreze.
Over the past 10 years, sea ice maximums and minimums "have been much lower than anything we've seen," said NSIDC senior research scientist Ted Scambos.
The annual report also noted that temperatures in the north have been rising: The average temperature this year in the Arctic was several degrees warmer than the 1981-2010 average.
Every fall in the Arctic, the sea ice begins to refreeze and spread out. The ice reaches its maximum extent on March 9, on average, though the date varies "considerably" from year to year, according to the report. After the March maximum, the melt begins again.
Arctic sea ice reached its annual maximum extent on March 21 in 2014 — relatively late in the season. The report notes a late surge in ice growth due to weather events, but it's unclear whether it's a trend.
"The last few years we've seen these late ends to sea ice extent," Scambos said. "We just don't know for sure if this is significant, if it's a warming thing or what."
NSIDC researchers also took a look at multi-year ice — ice that survived an Arctic summer and becomes part of the next winter's ice pack. During the summer of 2013, a larger portion of first-year ice survived, compared to recent years, and became second-year ice this past winter.
Serreze said the biggest changes in sea ice have taken place in the summer minimums. The lowest minimum on record was September of 2012. The small increase in 2013 was due to natural variability, he said.
"The real questions out there are, what is going to happen during the summer?" Serreze said. "Where we'll be in the record books this September, who knows. That is because of the natural variability sitting on top of this overall trend" of shrinking sea ice, he said.
As for next winter and beyond, Serreze said he thinks the downward trend with sea ice will continue. "I still believe that we could see no sea ice as early as 30 years from now."