What do we know about the Arctic sea ice?

Arctic sea ice reflects sunlight, keeping the polar regions cool and moderating global climate. According to scientific measurements, Arctic sea ice has declined dramatically over at least the past thirty years, with the most extreme decline seen in the summer melt season.

Read timely scientific analysis year-round below. We provide an update during the first week of each month, or more frequently as conditions warrant.

Arctic sea ice begins autumn freeze-up

Arctic sea ice extent, after reaching its seasonal minimum last week, has begun its annual cyclical increase in response to the setting sun. A cooler melt season, retention of first-year ice, and dispersive ice motion set the 2008 melt season apart from 2007.

Overview of conditions

Arctic sea ice extent on September 23, 2008, was 4.59 million square kilometers (1.77 million square miles), an increase of 77,000 square kilometers (30,000 square miles) above the minimum extent of 4.52 million square kilometers (1.74 million square miles) measured last week.

Conditions in context

Arctic sea ice extent, after reaching its seasonal minimum last week, has begun its annual cyclical increase in response to autumn cooling. The ice will grow over the cold, dark winter months and reach its maximum annual extent sometime next March.

During the intervening time, NSIDC will continue to provide updates on conditions. Also, note that as the season of ice growth progresses, NSIDC will slide the x-axis in Figure 2 to focus on the five-month window around the most current month. In our January entry, we will include a calendar-based full-year timeseries showing January 2008 through December 2008 extent compared to 2007 and to the 1979 to 2000 average.

High retention of first-year ice

Perhaps the most interesting aspect of the 2008 melt season was the higher-than-average retention of first-year sea ice (see earlier entries, including April 7). Relatively thin first-year ice is more prone to melting out completely than older, thicker ice. However, more of this year’s first-year ice survived the melt season than is typical. Sea ice age maps from Sheldon Drobot, our colleague at the University of Colorado at Boulder, show that much more first-year ice survived in 2008 than in 2007. This is one of the reasons that 2008 did not break last year's record-low minimum.

One cause of the high first-year ice survival rate was that this summer was cooler than in 2007. Lower temperatures slowed the melt rate in the early part of the season. While conditions in August favored rapid ice loss, they were not enough to make up for this early-season "cushion." Furthermore, much of this year's first-year ice was located at higher latitudes than in 2007, covering even the geographic North Pole. Regions that are far north have lower melt rates because they receive less solar energy than more southerly regions.

Dispersive sea ice motion

Sea ice motion also helps determine how the ice will fare each melt season. In 2007, a strong northward sea ice motion at the end of the melt season pushed ice floes together, compacting the ice. The tightly packed ice and high temperatures worked together to create a record-low extent.

This year, the wind patterns were different, leading to a less compacted ice cover. This, paired with slower summer melt, helped keep the overall extent larger.

I would suggest additional reading as well.

"Researchers at the Japan Aerospace Exploration Agency found at their latest study that ice sheets in the Arctic Ocean could shrink this summer to the smallest area on record since satellite observation of the sheets began in 1978. This shrinking is happening gradually year by year due to the global warming and increased average temperatures.

Many different studies agree that if current global warming trend continues, Arctic would be ice free by the summer of 2040."

Below are additional links

As with global warming, it's not an 'A or B' situation. The Artic is sensitive to these oscillations, and it's also the most sensitive area on the planet to global warming. One revealing fact is that even though we had a strong La Nina cycle this year (and low solar output), we had a record melt in terms of Arctic sea ice volume.

That the most of the science people on the AGW side still do not know how to phrase the questions to the computers. They are asking questions that require several thousand documented variables to be stated and they are providing one or two. Skeptics know they do not have all the answers or a solution to the worlds problems, but they also know the believers know less about the problems than they do or they would not resort to alarmist tactics like spoiled two year olds to get their way.

http://wattsupwiththat.com/2007/10/07/california-c...

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