Although Arctic sea ice extent did not set a low record this year, it’s still clear that there is less sea ice than there used to be. Scientists are keeping a close eye not only on the dwindling ice, but also on the ripple effect its loss might have on the rest of the Arctic environment. A big question involves the exchange of heat between ocean and air—and the weather patterns that result. What does current research say about how floating ice—or the lack of it—might be changing the Arctic atmosphere? Continue reading
Polar scientists are celebrating an anniversary of sorts. Thirty-five years ago, sea ice research took a great leap forward. On October 26, 1978, the Scanning Multichannel Microwave Radiometer (SMMR) beamed its first data records back down to Earth. The instrument, pronounced simmer, was capable of mapping global sea ice concentration and extent, giving scientists a more comprehensive look at Arctic and Antarctic sea ice. Thanks to SMMR and its successor remote sensing instruments, scientists now have a long and detailed record of sea ice that helps them understand how sea ice works, and how it is changing.
Fine-tuning the view
Researchers had employed remote sensing to monitor sea ice since the mid 1960s. Microwave radiometers can see through clouds, providing an uninterrupted view of ocean, land, and ice below the overcast conditions that often prevail at the poles. So scientists hoped that the instruments would be able to accurately distinguish between ice and water. But they soon discovered that SMMR, launched aboard the Nimbus-7 satellite, could distinguish between first-year ice and multiyear ice. This distinction is particularly important in the Arctic, which maintains a portion of its sea ice pack from year to year, unlike Antarctica.
In contrast to previous instruments, SMMR was multichannel, which allowed it to better resolve ambiguities in the data. For instance, features that might look similar in one channel may look different in another channel. These distinctions allowed researchers to fine tune their knowledge of the sea ice pack. They could also begin pairing this time series with other observations to see how other phenomena affected both first-year and multiyear ice.
Tracking the time series
Satellite observations have given scientists a direct and consistent source of data year-round from even the most inhospitable polar regions. The Nimbus-7 SMMR operated for only nine years, but it set the pattern for a series of multichannel satellite instruments that continue to capture a record of conditions from decade to decade. Scientists can now monitor concentration and extent, observe when ice forms and melts each year, discern how young or old ice is, and see where winds and ocean currents push it. While there may be no cake or ice cream to celebrate, SMMR’s birthday reminds us how much knowledge we now have about Earth’s polar climates.
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SMMR data at NSIDC
After a cool Arctic summer, sea ice at the North Pole has recovered somewhat from last year’s record low extent. While this is a welcome pause in the downward trend of sea ice extent, some are taking it a step further and hailing this rebound as evidence that the Arctic is no longer warming. But does the recent uptick mean that we have entered a period of global cooling? NSIDC scientists point out why we shouldn’t be reading too much into one summer of less sea ice decline. Continue reading
Guest post by Walt Meier, NSIDC Scientist
Arctic sea ice set a record minimum extent in September 2012, far below the previous record low in 2007. Summer extents have been far lower than average for the last decade, with several record or near-record years. Looking at the numbers, one is tempted to think that the Arctic Ocean may reach nearly sea ice-free conditions within just a few years. But most expert analyses indicate that we’re likely at least a couple decades away from seeing a blue Arctic Ocean during the summer.
NSIDC recently switched the baseline against which we analyze Arctic sea ice extent. Previously, we relied on a baseline that coincided with the beginning of the satellite period and stretched 20 years, from 1979 to 2000. The new baseline runs from 1981 to 2010, covering 30 years. Why did we make such a change?
Switching to a 30-year baseline allows us to be consistent with other climate monitoring agencies, which commonly use a 30-year time period for conducting analyses. This new baseline also helps account for the wider variations observed in Arctic sea ice extent. Continue reading