Arctic Sea Ice Melt Season Officially Over; ice up over 9% from last year

Watts Up With That?
Wednesday, Sept 17, 2008

The Arctic sea ice cover appears to have reached its minimum extent for the year, the second-lowest extent recorded since the dawn of the satellite era. While above the record minimum set on September 16, 2007, this year further reinforces the strong negative trend in summertime ice extent observed over the past thirty years. With the minimum behind us, we will continue to analyze ice conditions as we head into the crucial period of the ice growth season during the months to come.

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Despite overall cooler summer temperatures, the 2008 minimum extent is only 390,000 square kilometers (150,000 square miles), or 9.4%, more than the record-setting 2007 minimum. The 2008 minimum extent is 15.0% less than the next-lowest minimum extent set in 2005 and 33.1% less than the average minimum extent from 1979 to 2000.

Overlay of 2007 and 2008 at September minimum

The spatial pattern of the 2008 minimum extent was different than that of 2007. This year did not have the substantial ice loss in the central Arctic, north of the Chukchi and East Siberian Seas. However, 2008 showed greater loss in the Beaufort, Laptev, and Greenland Seas.

Unlike last year, this year saw the opening of the Northern Sea Route, the passage through the Arctic Ocean along the coast of Siberia. However, while the shallow Amundsen’s Northwest Passage opened in both years, the deeper Parry’s Channel of the Northwest Passage did not quite open in 2008.

A word of caution on calling the minimu

Determining with certainty when the minimum has occurred is difficult until the melt season has decisively ended. For example, in 2005, the time series began to level out in early September, prompting speculation that we had reached the minimum. However, the sea ice contracted later in the season, again reducing sea ice extent and causing a further drop in the absolute minimum.

We mention this now because the natural variability of the climate system has frequently been known to trick human efforts at forecasting the future. It is still possible that ice extent could fall again, slightly, because of either further melting or a contraction in the area of the pack due to the motion of the ice. However, we have now seen five days of gains in extent. Because of the variability of sea ice at this time of year, the National Snow and Ice Data Center determines the minimum using a five-day running mean value.

Ongoing analysis continues

We will continue to post analysis of sea ice conditions throughout the year, with frequency determined by sea ice conditions. Near-real-time images at upper right will continue to be updated every day.

In addition, NSIDC will issue a formal press release at the beginning of October with full analysis of the possible causes behind this year’s low ice conditions, particularly interesting aspects of the melt season, the set-up going into the important winter growth season ahead, and graphics comparing this year to the long-term record. At that time, we will also know what the monthly average September sea ice extent was in 2008—the measure scientists most often rely on for accurate analysis and comparison over the long-term.

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7 Responses to “Arctic Sea Ice Melt Season Officially Over; ice up over 9% from last year”

1. Libertyguy123 Says:
   September 17th, 2008 at 5:52 am

   Anyone remember the 70’s climate threat, global cooling? Without a huge increase in nuclear generated electricity we will all freeze in the dark, REMEMBER that folks? That lie was put forth to help insure the continuation of the civilian nuclear industry which was pushed on us by the lie that nuclear generated electricity would be “too cheap to meter”! Our parents and grandparents bought that one hook, line and sinker and I see we are no smarter now and have learned very little from the past lies we have been told. Global warming is a hoax to con us into accepting a new tax. The sun is responsible for the tiny warming we have seen.

2. cap'n dino Says:
   September 17th, 2008 at 2:25 pm

   I read the same news on Yahoo a day or two ago, however it was worded different. It went like this more or less: Arctic ice cap continues to melt because of global warming, although this years melt did not surpass last years record. They then cited the above mentioned numbers. As soon as i read it, I said to myself: then the ice cap has increased. A net gain over last year. The news spinners are very clever in how they deceive the public. I read the other day that the AGW alarmists are blaming the current 10 year cooling trend as a side effect of global warming. How stupid do they think we are? Libertyguy has it right.

3. RayB Says:
   September 17th, 2008 at 2:43 pm

   I am quite confident that by September 2010 the arctic sea ice extent will be back to or above that of 2005 mark. It’s cooling Stupid!

4. Vierotchka Says:
   September 17th, 2008 at 2:56 pm

   The big difference is that it is much thinner than usual. It may have a larger surface, but it has a far smaller volume.

5. RayB Says:
   September 17th, 2008 at 4:02 pm

   Don’t worry Vierotchka, it will get thicker because… winter is coming!

6. Ken Hall Says:
   September 18th, 2008 at 2:41 am

   Well using the natural warming deniers argument against them, when the north ice cap shrunk to last years smallest level for ONLY 30 years, they were saying that the reduced ice would lead to increased warming because the sea reflects less heat back into space than ice does.

   OK so (A) what happened to stop that?
   and (B) does this mean that more ice this year means less heat so even more ice next year? At this rate the whole world will be covered in ice….

   OK so you natural warming deniers, that IS how stupid your arguments were last year.

   the Northern ice caps have melted away before… How else could submarines have surfaced at the North Pole?

7. RayB Says:
   September 18th, 2008 at 9:29 am

   This thin ice argument is so lame. The fact that there is now ice where there was none last year shows that it was colder this year than at the same time last year. Ice is ice and it takes sub-zero temperature to make it. If there is more that mean it was less warm.