One day every September, sea ice in the Arctic Ocean stops stops melting as the warmth of summer fades. The next day there is slightly more ice than the day before. The annual Arctic Sea Ice minimum has been reached. Ice coverage now builds again as the colder winds of fall and winter return.
On Sept. 16, Arctic Sea ice reached its annual minimum. It is the 6th lowest ice level on record in the 35 years that satellites have been tracking Arctic Sea ice. This summer, an area of ice the size of the northeast U.S. from Tennessee to Maine melted in the Arctic.
The record Arctic Sea ice melt of 2012 caught everyone’s attention. It’s been fingerprinted for changing jet stream patterns that may have lead to more extreme weather in the past year, including the highly unusual path of Hurricane Sandy last October.
So researchers have been keeping a keen eye on the extent of melt in the Arctic this summer. Would a thinner ice sheet be more vulnerable to melt in 2013?
The National Snow and Ice Data Center keeps track of all things frozen in our world. It’s called the cryosphere. It turns out the summer of 2013 was cooler and cloudier in the Arctic than last year. There were fewer storms with high winds to break up the ice sheet.
The result as you might expect was less Arctic Sea ice melt than the record level of 2012.
Still, at 1.97 million square miles this summer’s ice coverage was the 6th lowest on record in the past 35 years. It is also 432,000 square miles below the 30 year average for ice melt from 1981-2010.
The overall trends show this summer continues the longer term trend of extensive ice melt in the Arctic. Some interesting perspective from science writer Andrew Freedman at Climate Central.
This year’s melt represents a significant gain in sea ice extent from last year — when the ice cover plummeted to a record low — but scientists cautioned that long-term trends are what is most important, with most projections still showing a seasonally ice free Arctic Ocean by the middle of the century, if not sooner.
In addition, measurements of sea ice volume are at near-record low levels, indicating that the ice cover is unusually thin and vulnerable.
The long-term decline in sea ice, both in terms of the extent of sea ice cover as well as its thickness, is largely due to warming caused by human activities and natural variability, as the Arctic is warming at nearly twice the rate of the rest of the globe.
As has been the case in recent years, the sea ice at the end of the 2013 melt season is unusually thin, which makes it more susceptible to the influence of weather systems. This year, weather patterns in the Arctic were more favorable for maintaining more of the ice cover than during the past few summers, sea ice experts said.
But the thinness of the sea ice also indicates that it won’t take much to reach another record low in future melt seasons.
“Basically this summer was a bit colder than we’ve seen the last several years,” said Julienne Stroeve, a scientist at the NSIDC said in an email interview. “Even though the ice was likely thinner this winter than last winter according to estimates from CryoSat, the relatively cooler summer was able to keep more of that thin ice around.”
It will be interesting to see how Arctic ice reacts in the next few years. Will the thinner ice be more vulnerable to warmer Arctic summers? Will we see any recovery in ice coverage and thickness, or will we see new record ice minimums ahead? How will the jet stream react to changes in the Arctic?