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Climate Matters

NEW YORK CITY

* SPECIAL REPORT *

The National Academy of Sciences is having a public briefing Friday, March 11 at 10 a.m. ET to discuss the new report, Attribution of Extreme Weather Events in the Context of Climate Change.

The report explores the advances in attribution of extreme weather events to global warming. More information on the briefing is available on the National Academy's site.



Story Highlights

  • The annual maximum Arctic sea ice extent is threatening to set a record low this year.

  • Maximum ice cover on the Great Lakes is way down this year and on a long term downward trend.

  • Decreasing ice can have effects on the environment, economy, and even national security.
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MELT AWAY

The annual maximum sea ice extent in the Arctic Ocean usually occurs in middle to late March. But last year that maximum came in late February, and there are signs the peak may come early again this year, suggesting a shorter winter in a warming Arctic. Given the planet just had its hottest calendar year on record, followed by one of the Arctic’s hottest winters on record, it’s no surprise that this year’s sea ice maximum is challenging its record low. Remember, this is a different measurement from the one taken in September, when the annual minimum sea ice extent is measured.

The area of ice in February averaged 5.48 million square miles, which is the lowest February extent since the satellite era began in 1979. This is 77,000 square miles — an area about the size of South Dakota — less than the previous February record set in 2005. The phenomenal warmth in the Arctic in February played a role, with air temperatures 11-14°F above the 1981-2010 average over the central Arctic Ocean. In the long term, this puts the rate of February decline in Arctic ice extent at 3 percent per decade since 1979.

The decrease in ice provides new shortcut shipping lanes through the Arctic and poses new national security concerns, as less ice allows easier access to competitive oil and natural gas resources in the Arctic. Decreasing ice also increases the amount of solar energy absorbed by the Arctic Ocean, further enhancing planetary warming.

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LAKE EFFECT

On the Great Lakes, the maximum ice cover this year is down substantially from 2014 and 2015, which were the 2nd and 4th highest percentages on record, respectively. Despite its large season-to-season variability, the maximum winter ice cover has been trending downward in recent decades. In addition to curtailing recreational activities such as ice fishing, less ice can alter the lake-effect snow season. Our recent report highlighted how more open water may be responsible for the recent increase in the amount of lake-effect snow. But as the atmosphere continues to warm, the longer term outlook is for a snow season that will eventually be shorter and start later.

Less ice cover also has environmental impacts on the lakes. According to the Environmental Protection Agency, plankton, an important link in the food web, are better protected beneath the ice. Similarly, ice also shelters the eggs for some types of native fish. That’s bad news for local fish like lake trout and whitefish. Less ice also means warmer surface water, which tends to not mix as well with the colder water below. This leads to a concentration of pollutants such as nitrogen and phosphorus and lower levels of oxygen in the upper part of the water column. Those conditions can lead to more widespread algae blooms, which present a threat to drinking water and native species that call the lakes home.

WXshift.com

See the decline in Arctic sea ice and the warming feedback it causes >>

Supporting Multimedia from the Archive

Lake Effect Snow Trends

grab from the archive >>

Fall’s Arctic Sea Ice Minimum

grab from the archive >>

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