Sea ice hit record lows in November
Unusually high air temperatures and a warm ocean have led to a record low Arctic sea ice extent for November, according to scientists at the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder. In the Southern Hemisphere, Antarctic sea ice extent also hit a record low for the month, caused by moderately warm temperatures and a rapid shift in circumpolar winds.
|Iceberg in Paradise Harbour Antarctica [Credit: WikiCommons]|
Arctic sea ice extent averaged 9.08 million square kilometers (3.51 million square miles) for November, 1.95 million square kilometers (753,000 square miles) below the 1981 to 2010 long-term average for the month. Although the rate of Arctic ice growth was slightly faster than average, total extent actually decreased for a brief period in the middle of the month. The decrease in extent measured 50,000 square kilometers (19,300 square miles) and was observed mostly in the Barents Sea, an area of the Arctic Ocean north of Norway, Finland, and Eastern Russia.
NSIDC scientists said the decrease in extent is almost unprecedented for November in the satellite record; a less pronounced and brief retreat of 14,000 square kilometers (5,400 square miles) happened in 2013. November 2016 is now the seventh month this year to have hit a record low extent in the 38-year satellite monitoring period. The November extent was 3.2 standard deviations below the long-term average, a larger departure than observed in September 2012 when the Arctic summer minimum extent hit a record low.
|The Arctic sea ice extent: November 2016 [Credit: National Snow and Ice Data Center |
(NASA Earth Observatory)]
NSIDC scientists said unusually high temperatures over the Arctic Ocean, persistent winds from the south, and a warm ocean worked together to drive the record low Arctic extent. Extending from northeast of Greenland towards Svalbard and Severnaya Zemlya, air temperatures at the 925 hPa level (about 2,500 feet above sea level) were up to 10 degrees Celsius (18 degrees Fahrenheit) above the 1981 to 2010 long-term average for the month. Sea surface temperatures in the Barents and Kara Seas remained unusually high, up to 4 degrees Celsius (7 degrees Fahrenheit) above average around Novaya Zemlya and Svalbard, preventing ice formation. These high temperatures reflected a pattern of winds from the south, which also helped to push the ice northward and reduce the ice extent.
|The Antarctic sea ice extent: November 2016 [Credit: National Snow and Ice Data Center |
(NASA Earth Observatory)]
In the Southern Hemisphere, sea ice surrounding the continent of Antarctica declined very quickly early in the month and set a record low. The average extent for November was 14.54 million square kilometers (5.61 million square miles), 1.81 million square kilometers (699,000 square miles) below the 1981 to 2010 average. This was more than twice the previous record departure from average set in November 1986 and was 5.7 standard deviations below the long-term average.
NSIDC scientists said that higher-than-average temperatures and a rapid shift in Antarctic circumpolar winds appear to have caused the rapid decline in Antarctic sea ice.
|Average monthly Antarctic sea ice extent November 1978 - 2016 |
[Credit: National Snow and Ice Data Center]
"Antarctic sea ice really went down the rabbit hole this time," said NSIDC lead scientist Ted Scambos. "There are a few things we can say about what happened, but we need to look deeper."
NASA scientist and NSIDC affiliate scientist Walt Meier said, "The Arctic has typically been where the most interest lies, but this month, the Antarctic has flipped the script and it is southern sea ice that is surprising us."
Source: University of Colorado at Boulder [December 06, 2016]