UPDATES: New NSIDC data and a press release from them added below.
While some folks (Joe Romm in particular) are touting the recent University of Bremen press release suggesting a new record low has been met, declaring record minimum Arctic extent was reached on Sept 8 at 4.24 million km2, (See http://iup.physik.uni-bremen.de:8084/amsr/minimum2011-en.pdf) five other sources of sea ice data, NSIDC and JAXA, DMI, Cryosphere Today, and NANSEN don’t agree with that new record claim (at least not yet). While still far from certain, as weather, wind, and ocean currents could still force a turn downwards, the NSIDC graph suggests we may have turned the corner this year.
[UPDATE: This extent graph above (dated 9/12) was updated by NSIDC since posting this story ~ 6AM this morning, and it shows further deviation from 2007, compare to the NSIDC graph of 9/11 below.]
Below, I’ve added a vertical line to show the turning point for the 1979-2000 average (in red) and how it compares to the current NSIDC data.
The JAXA graph, which uses a different satellite sensor (AMSRE vs SSMI) also suggests that we didn’t yet reach a new record low and that we may have turned the corner.
The Danish Meteorological Institute shows much the same:
NANSEN’s Arctic ROOS plot shows a similar turn, and suggest that not only have we not reached a new record low, but the extent has not gotten lower than 2008:
Cryosphere Todayhas an anomaly plot that shows so far, 2011 has not exceeded the 2007 record minimum.
For extent, only the University of Bremen (shown below) shows this year to be lower, and has no turn. It uses the
same SSMI sensor as NANSEN and NSIDC, it uses the same AMSRE sensor as JAXA, which doesn’t show a record low, so the difference must be in processing of the data:
Given that five other sources of sea ice data don’t show a new record low, and suggest that the corner may have been turned, I find it rather odd that the University of Bremen would stick their neck out and declare a new record low before the traditional end of the Arctic melt season.
The wording from their press release hardly seems scientific and more than a bit over the top:
Alerting message from the Arctic: The extent the the Arctic sea ice has reached on Sep. 8 with 4.240 million km2 a new historic minimum (Figure 1). Physicists of the University of Bremen now confirm the apprehension existing since July 2011 that the ice melt in the Arctic could further proceed and even exceed the previous historic minimum of 2007. It seems to be clear that this is a further consequence of the man-made global warming with global consequences. Directly, the livehood of small animals, algae, fishes and mammals like polar bears and seals is more and more reduced.
The answer to why such language might be used, perhaps prematurely in the face of other datasets which presently disagree, may be found in the proximity of the upcoming Climate Reality Project (aka the Gore-a-thon) on September 14-15. Al needs something to hold up as an example of gloom, since sea ice didn’t repeat the 2007 low in 2008, 2009, or 2010, and the Antarctic has not been cooperative with the melt meme at all, remaining boringly “normal” and even above normal last year.
We’ll know the answer when we see if this Bremen missive is included in Al’s upcoming presentation.
As for whether or not Arctic sea ice extent turned the corner this year, note below that in the prime ice areas, surface air temperature is well below freezing. So. it is up to the wind and ocean currents and other vagaries of weather to determine if we have in fact bottomed out, or if there’s still some loss to come.
If it has turned the corner, it will be about a full week earlier than usual. There could still be another downward blip, as happened in 2010 and in 2007, so I’m not ready to call a turn for certain yet, but it does look encouraging.
UPDATE2: NSIDC has posted an update in their Sea Ice News section, which I’m reposting below in entirety for WUWT readers:
Overview of conditions
On September 10, Arctic sea ice extent was 4.34 million square kilometers (1.68 million square miles). This was 110,000 square kilometers (42,500 square miles) above the 2007 value on the same date. The record minimum Arctic sea ice extent, recorded in 2007, was 4.17* million square kilometers (1.61 million square miles).
The rate of decline has flattened considerably the last few days: Arctic sea ice is likely near its minimum value for the year. However, weather patterns could still push the ice extent lower. NSIDC scientists will make an announcement when ice extent has stopped declining and has expanded for several days in a row, indicating that the Arctic sea ice has reached its lowest extent for the year and has begun freezing over. During the first week of October, after data are processed and analyzed for the month of September, NSIDC scientists will issue a more detailed analysis of this year’s melt season and the state of the sea ice.
NSIDC’s sea ice data come from the Special Sensor Microwave Imager/Sounder (SSMIS) sensor on the Defense Meteorological Satellite Program (DMSP) F17 satellite. This data record, using the NASA Team algorithm developed by scientists at NASA Goddard Space Flight Center, is the longest time series of sea ice extent data, extending back to 1979.
Other sea ice data are available from other data providers, using different satellite sensors and sea ice algorithms. For example, data from the University of Bremen indicate that sea ice extent from their algorithm fell below the 2007 minimum. They employ an algorithm that uses high resolution information from the JAXA AMSR-E sensor on the NASA Aqua satellite. This resolution allows small ice and open water features to be detected that are not observed by other products. This year the ice cover is more dispersed than 2007 with many of these small open water areas within the ice pack. While the University of Bremen and other data may show slightly different numbers, all of the data agree that Arctic sea ice is continuing its long-term decline.
For more information about the Arctic sea ice minimum, see the NSIDC Icelights article, Heading Towards the Summer Minimum Ice Extent.
*Near-real-time data initially recorded the 2007 record low as 4.13 million square kilometers 1.59 million square miles). The final data, reprocessed by NASA Goddard Space Flight Center using slightly different processing and quality control procedures, record the number as 4.17 million square kilometers (1.61 million square miles). NSIDC reports daily extent as a 5-day average. For more about the data, see the FAQ, Do your data undergo quality control?