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July Sea Ice: Antarctic High Vs Trend Decline In Arctic

07.08.2014
07.08.2014 09:23 Age: 3 yrs

NSIDC reports near record Antarctic sea ice extent in July and Arctic sea ice extent in line with the long term trend decline while robustly defending its measurements of Antarctic sea ice growth.

Click to enlarge. Figure 1. Arctic sea ice extent for July 2014 was 8.25 million square kilometers (3.19 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Credit: National Snow and Ice Data Center

Click to enlarge. Figure 2. The graph above shows Arctic sea ice extent as of August 4, 2014, along with daily ice extent data for four previous years. 2014 is shown in blue, 2013 in green, 2012 in orange, 2011 in brown, and 2010 in purple. The 1981 to 2010 average is in dark gray. Credit: National Snow and Ice Data Center

Click to enlarge. Figure 3. Monthly July ice extent for 1979 to 2014 shows a decline of 7.4% per decade relative to the 1981 to 2010 average. Credit: National Snow and Ice Data Center

Click to enlarge. Figure 4a. Antarctic sea ice extent for July 2014 was 17.40 million square kilometers (6.72 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole. Credit: National Snow and Ice Data Center

Click to enlarge. Figure 4b. The graph above shows Antarctic sea ice extent as of August 4, 2014, along with daily ice extent data for four previous years. 2014 is shown in blue, 2013 in green, 2012 in orange, 2011 in brown, and 2010 in purple. The 1981 to 2010 average is in dark gray. Credit: National Snow and Ice Data Center

Click to enlarge. Figure 5. This graph shows the differences in Antarctic sea ice extent between Version 2 and Version 1 of the Bootstrap algorithm. Blue indicates when Version 2 derived values were lower than Version 1; red indicates when Version 2 derived values were higher than Version 1. The vertical dashed lines indicate satellite sensor changes. Credit: I. Eisenman et al., The Cryosphere

Here is the text of the latest NSIDC report released on 6 August 2014

Overview of conditions

Arctic sea ice extent declined at a fairly rapid rate through the first three weeks of July, but the loss rate then slowed due to a shift in weather patterns. In Antarctica, the advance of sea ice nearly halted for about a week in early July, and then resumed. At the end of the month, Antarctic extent was at or near a record high for this time of year.

July 2014 average ice extent was 8.25 million square kilometers (3.19 million square miles). This is 1.85 million square kilometers (714,000 square miles) below the 1981 to 2010 average for the month.

Ice extent is below average in nearly all sectors of the Arctic. Open water continued to grow in the Laptev and Beaufort Seas, reaching well north of 80oN in the Laptev Sea. By the end of the month, the Alaskan Coast was essentially free of ice except for small patches of very diffuse ice off Barrow. The Barents Sea, Hudson Bay, and Baffin Bay/Davis Strait are now essentially ice free. Large areas of low concentration ice in the central Beaufort Sea are likely to melt out in coming weeks. The Northwest Passage through the channels of the Canadian Arctic Archipelago remains choked with ice. Parts of the Northern Sea Route are still difficult to traverse because of high-concentration, near-shore ice between the Laptev and East Siberian seas and also north of the Taymyr Peninsula.

Conditions in context

For July 2014 as a whole, ice extent declined at an average rate of 86,900 square kilometers (33,600 square miles) per day, close to the 1981 to 2010 average July rate of 86,500 square kilometers (33,400 square miles) per day. However, this averages together a fairly fast rate of decline over the first three weeks of the month with a slower rate of decline over the remainder of the month.

The slower ice loss later in the month reflects a shift in weather patterns. For much of the month, high pressure at sea level dominated the central Arctic Ocean and the Barents Sea. However, this pattern broke down and was replaced by lower-than-average pressure over the central Arctic Ocean. A low pressure pattern tends to bring cool conditions and the counterclockwise winds associated with this pattern also tend to spread the ice out.

July 2014 compared to previous years

July 2014 is the 4th lowest Arctic sea ice extent in the satellite record, 340,000 square kilometers (131,000 square miles) above the previous record lows in July 2011, 2012, and 2007. The monthly linear rate of decline for July is 7.4% per decade.

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Source

See NSIDC here.