NSIDC - 9/27 - Still Too Early To Say If Arctic Sea Ice Has Hit Minimum

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Overview of current sea ice conditions

Sea ice extent has remained fairly steady over the past week. For more details, see below. Sea ice data are obtained from satellites; see Frequently Asked Questions for more about data sources.



Current sea ice conditions: September 26, 2006

Figure 1 shows the updated image of sea ice extent. Most notably, the polynya in the Beaufort Sea has become smaller because of new ice formation along its edges. The polynya will probably completely freeze over in the next few weeks, if not sooner.

Past updates (see below) speculated on possible mechanisms to explain the formation of the polynya, which at its maximum extent in early September was roughly the size of Indiana. We speculated that anomalous winds may have forced divergence of the ice cover, causing the opening to form.

We recently discussed this idea with two of our colleagues, David Douglas at the United States Geological Survey’s Alaska Science Center in Juneau, and Ignatius Rigor at the University of Washington in Seattle. An alternative scenario that emerged from our discussions is that winds and ocean currents may have transported unusually thin ice into the Beaufort Sea over the past winter; this summer, the thin ice melted out to form the polynya. A slant on this hypothesis is that the thin ice, being relatively weak, would also have been especially susceptible to breakup by winds.

Given the interest in this unusual polynya, a more formal study is warranted.

White indicates areas where sea ice is present. Areas in blue are open ocean, while gray indicates land masses. The pink line shows the average ice extent for September, the end of the summer melt season. The September average is calculated from 1979 through 2000.



Current sea ice conditions in context

It is still too early to state conclusively whether we have reached the sea ice minimum extent. As is evident in Figure 2, showing the updated time series, sea ice extent for the past week or so has stayed fairly constant, with perhaps a slight increase in the past few days. Formation of new ice in some areas, such as around the Beaufort Sea polynya, is apparently being offset by continued melt, or perhaps ice convergence, in other areas.

The latest date that a minimum has occurred over the satellite record was on September 22. Given this historical perspective, we are probably past this year's minimum; however, we will make a final determination next week, when we have the complete data for September.

Surface air temperatures for September 1 through 24, have been above average, breaking the pattern of relatively cool conditions that characterized August, and keeping 2006 on track to be another very warm year in the Arctic.

While low atmospheric pressure has still dominated the Arctic in September, the center of the action has shifted to the central Siberian coast. Offshore winds on the south side of the low appear to be pumping warm air into the Arctic, keeping temperatures fairly high.

EDIT

http://nsidc.org/news/press/2006_seaiceminimum/20060816_arcticseaicenews.html