NSIDC Report For 12 September - Unsure If We've Reached Ice Minimum

[hatrack]

12 September 2006

Overview of current sea ice conditions

Current sea ice conditions are still well below the long-term average, but, as of yesterday, sea ice extent showed a modest increase; whether we have reached the seasonal minimum or may see further reductions is still unclear. For more details, see below. Sea ice data are obtained from satellites; see Frequently Asked Questions for more about data sources.

Figure 1 shows current sea ice extent. The most notable feature of this image is that the polynya in the Beaufort Sea has grown still larger. Closer inspection of satellite images shows that ice concentrations just south of the polynya are quite low. If this ice melts, the polynya may open up to the sea very soon and we may see further reductions in the overall sea ice extent.

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.




Figure 2 shows an updated time series. As of yesterday, ice extent is not currently declining. The most recent data actually show a small rise. We may have already reached the September sea ice minimum extent. The relatively cool and stormy conditions that characterized August (see reports below) may have averted a repeat of the extreme ice losses of 2005. If we have reached the minimum, this year would be the fifth lowest in the satellite record.



That said, we are not at all certain that we have reached the minimum; given the precariously low ice concentrations bounding the southern edge of the Beaufort Sea polynya discussed above, ice extent may start declining again.

No matter what happens from here on, September 2006 continues the pattern of strongly below-average sea ice extent.

Our colleague, Sheldon Drobot at the University of Colorado, has developed a statistical forecasting system aimed at predicting average sea ice extent for the entire month of September (not the absolute minimum discussed above). The forecast is based on spatial patterns of multiyear sea-ice concentration from the preceding spring, as well as spatial patterns of total sea-ice concentration and surface air temperature. The methodology is discussed in a recent paper by his group; for more information visit http://ccar.colorado.edu/arifs.

Based on August data, Drobot's group is forecasting a September average of 6.11 million square kilometers (2.4 million square miles), which would rank as the fourth lowest on record. The prediction system indicates only a 3% chance of a record minimum this year. Based on July data, they had forecasted 5.94 million square kilometers (2.3 million square miles), the second lowest on record. The difference between the forecasts is further evidence that cooler conditions in August may have helped “save” the sea ice cover.





EDIT

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