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more likely here
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|Arctic sea ice extent near average in
November says NSIDC here
|Rate of melt of Antarctic ice sheet has tripled
Arctic sea ice extent in June was below the long term average as the usual summer melt season continued, according to an analysis released by the US National Snow and Ice Data Center (NSIDC).
June 2014 averaged 11.31 million square kilometers which is 580,000 square kilometers below the average for the month measured through the period from 1981 to 2010. This makes June 2014 the sixth lowest June in the history of satellite observations which stretches back to 1979. Since the end of March, Arctic sea ice extent has remained within two standard deviations of this long term average although the rate of melt accelerated towards the end of the June (see figures 1 and 2).
The NSIDC notes that Arctic air temperatures in June were 1oC-2oC below average. “This is in stark contrast to the unusually warm summers of many recent years, particularly 2012 and 2007 when air temperatures over the Arctic Ocean averaged up to 4 degrees (in 2012) to 6 degrees (in 2007) Celsius (7 degrees Fahrenheit) above average”, the NSIDC states in its report. The cool conditions in June 2013 were attributed to a generally cyclonic pattern of atmospheric circulation, the report says. However, by late June 2014 the more typical pattern of high pressure over the Beaufort Sea had developed, coupled with low pressure over Alaska and Eurasia, adds NSIDC.
These cooler Summer temperatures may be fueling computer model forecasts of above average Arctic sea ice extent later this year. The sea ice extent forecast generated by US agency NOAA's CFS v2 climate model (see figure 7) continues to predict that the anomaly – the deviation from the long term average - for Arctic sea ice will become much less negative during July and turn positive in August, September and October for the first time since the mid-1990s.
Greater than average sea ice extent in August and September may be made possible due to a reported thickening in Arctic sea ice and a build up of multiyear ice detected by the European Space Agency's CryoSAT-2 spacecraft last year. Thicker ice is more likely to survive the summer melt season and so add to the extent of sea ice as it starts to expand again into the autumn and winter.
There is certainly evidence from data collected in March that Arctic sea ice is thicker than last year in some areas. NASA sea ice researcher Nathan Kurtz, who work's on NASA's Operation IceBridge, believes that the data on sea ice thickness for March “does point to some recovery in the multiyear ice pack compared to March 2013”.
The thickness of the ice from the CryoSat-2 map shows it is about 2.5-3 meters thick, which is consistent with typical multiyear thickness values in recent years, according to Kurtz. He said that in the March data there was “considerably more multiyear ice this year than last, much of this consists of second year ice which formed a tongue that extends up toward the East Siberian Sea. This ice is thick enough to survive the summer melt season which could increase Arctic sea ice extent in September, but whether it will survive depends largely on the weather”.
However, it must be noted that the NOAA forecast remains a forecast and that the rate of melt observed in the Arctic sea ice accelerated towards the end of June.
Separately, a record sea ice extent anomaly was reported for Antarctic sea ice at the end of June (see figures 8 and 9). Occasionally, the NSIDC uses its monthly Arctic sea ice analysis to comment on what is happening with Antarctic sea ice but the NSIDC's monthly sea ice analysis for June released on 2 July 2014 contains no analysis on the Antarctic.
Below is the monthly Arctic Sea Ice News and Analysis report for June issued by the NSIDC on 2 July 2014. the figures 1 through 6 on the right were released with this analysis. Figure 7 is from NOAA. Figures 8 and 9 are taken from the Daily Image Update at the top of the Arctic Sea Ice News And Analysis page where the below report is published.
Arctic sea ice extent continues its seasonal decline. Through most of June the pace of decline was near average, but increased towards the end of the month.
June 2014 averaged 11.31 million square kilometers (4.37 million square miles). This is 580,000 square kilometers (224,000 square miles) below the 1981 to 2010 average for the month.
Large areas of open water quickly opened up in the Laptev Sea at the beginning of June and continued to expand through the month. The southern part of the Beaufort Sea has also opened and melt ponds are apparent on the open drift first-year ice and extending into the pack ice (see Figure 5 below). Nevertheless, ice extent in this region continued to be above the levels of recent years through much of the month. Extent was lower than average in the Barents Sea, Hudson Bay, and the East Greenland Sea, but higher than in recent years in the Kara Sea.
Ice extent during June declined by an average of 78,900 square kilometers (30,500 square mile) per day, faster than the 1981 to 2010 average June rate of 57,200 square kilometers (22,100 square miles) per day. Last March’s relatively low maximum extent helped set the stage for June’s low extent. June is a month that has seen large variability in the rate of ice loss in recent years. In 2012, a period of rapid acceleration occurred during the first half of the month, kick-starting the decline towards the eventual record low extent that September. So far, 2014 has failed to match the 2012 loss rates. However, ice extent on June 30th came within 300,000 square kilometers (115,800 square miles) of that in 2012. The 2014 rate of ice decline also accelerated toward the end of June as wide areas of low-concentration ice on the peripherial areas of the Arctic Ocean opened up, especially in the Hudson and Baffin bays. This increased rate of loss is typical of late June and early July, and is visible in the 30-year mean trend for Arctic sea ice (see the ChArctic interactive sea ice chart).
June 2014 is the 6th lowest Arctic sea ice extent in the satellite record, 490,000 square kilometers (189,000 square miles) above the previous record low June 2010. The monthly linear rate of decline for June is 3.6% per decade.
At the 925 mb level (approximately 3000 feet above sea level) average June temperatures over parts of the Arctic Ocean were from 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) below the 1981 to 2010 average, but with a warming trend over the latter half of the month; the last week of June saw temperatures of 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average over the central Arctic Ocean. June 2013 was also slightly cooler than average. This is in stark contrast to the unusually warm summers of many recent years, particularly 2012 and 2007 when air temperatures over the Arctic Ocean averaged up to 4 degrees (in 2012) to 6 degrees (in 2007) Celsius (7 degrees Fahrenheit) above average.
The cool conditions in June 2013 were attributed to a generally cyclonic pattern of atmospheric circulation. However, by late June 2014 had the more typical pattern of high pressure over the Beaufort Sea developed, coupled with low pressure over Alaska and Eurasia.
Landsat 8, launched in February of 2013, has been regularly acquiring images of the world’s daylit land surface since May of that year. The mission recently increased the pace of image acquisition, covering nearly all available daylit areas each day, and expanded coverage of sea ice areas in the Arctic and coastal areas of Greenland (the latter with ascending node, or evening hour, coverage). Coverage for the Arctic Ocean is focused on the far western and far eastern Arctic, that is, the Beaufort, Chukchi, and East Siberian Sea, although substantial coverage of sea ice is included in the acquisition of all Arctic land areas. Ascending (evening) and decending (morning, the typical acquisition time) coverage of coastal Greenland permits better tracking of glacier flow and in particular sea ice break-up and glacier retreat in the fjord areas.
The images, and the historical (somewhat variable) record of Arctic coverage provide information on ice type, surface melting and melt ponds, ice motion, coastal fast ice break-up, lead fraction and shear zones within the ice.
As noted in last month’s post, satellite and airborne sensors are now able to provide good coverage of the Arctic ice thickness. However, as with any remote sensing estimate, the observations come with uncertainty. Direct measurements, even though they do not provide wide-coverage, are important for validation. They can also provide a useful indication of general ice conditions (thickness, temperature) at the beginning of the ice season. Such direct observations, in concert with available satellite and airborne data, can improve seasonal forecasts of sea ice, such as those provided in the recently released Sea Ice Outlook.
In March, the U.S. Navy’s Office of Naval Research (ONR) Marginal Ice Zone project deployed three clusters of mass balance buoys on the sea ice, complementing ongoing similar deployments by the U.S. Army Cold Regions Research and Engineering Laboratory. These mass balance buoys not only provide a simple thickness, but can also provide a time series of the evolution of the ice, both at the top and bottom surface. The ONR buoys additionally include air temperatures sensors, which are useful for monitoring atmospheric conditions, as well as temperatures through and below the ice.
ONR deployed three clusters of buoys in the Beaufort Sea at three different latitudes. Initial ice thickness at the sites was between 1.5 and 2 meters (4 to 7 feet). During April and May, there were brief incursions of above freezing air temperatures leading to some melt, but temperatures mostly remained below freezing until early June. All three clusters show continuous above freezing air temperatures starting by the second week of June. With the higher temperatures, melt has commenced on both the top and bottom surfaces.
The Beaufort Sea has been a region of dramatic summer ice loss in recent years, particularly 2012, with regions dominated by thicker, multi-year ice melting out completely. While vigorous melt has begun, it remains to be seen how the ice cover will evolve over the rest of the melt season.
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