This is the next in an occasional series of diaries on the state of Northern Hemisphere Arctic sea ice (and other topics as warranted), written in memory of Johnny Rook, who passed away in early 2009. He was the author of the Climaticide Chronicles.
Loss of sea ice has slowed sharply in the last week, from 80-120 km2 per day to 30-70 km2 per day (numbers approximate and from the joint International Arctic Research Center -- Japan Aeronautical Exploration Agency Information System (IJIS). The recent rate of sea ice extent loss is below the long term 1979-2000 average as you will see in the chart below from the National Snow and Ice Data Center (NSIDC).
A Reversal of Pressure Anomalies
In the last week, the high pressure anomalies over the Arctic basin reversed to low pressure anomalies, and vice versa over parts of Siberia. This can be seen by comparing the two graphics below.
Sea Level Pressure Anomaly: 3-9 July 2010
Sea Level Pressure Anomaly: 24 June - 1 July 2010
What is the impact of this change in pressure anomalies on the temperature patterns in the Arctic? See the following two graphics for approximately the same two periods below.
925-hPa Temperature Anomalies: 2-8 July 2010
925-hPa Temperature Anomalies: 24 June - 1 July 2010
Note the temperature reversal to cooler than normal over the central Arctic basin. Warmth increased in north-central Siberia and adjacent Arctic Ocean waters. The Canadian Archipelago, while not quite so warm as the previous period, was still above normal, which should contribute to ice melt over the straits between the island, and may help open up the Northwest Passage in the next month or so.
Changes in Sea Ice Extent Over the Last Week
The two sea level pressure graphics are not quite mirror images of each other, but the impact apparently has been significant, as can be seen in the slowdown of loss of sea ice extent below, including data through 9 July 2010.
Time Series of Arctic Sea Ice Extent, 1 April through 31 August, from National Snow and Ice Data Center NSIDC
The reduction in rate of sea ice loss is annotated. We now have more sea ice than the same date in 2007. And today's graphic including 10 July shows the sea ice extent essentially going horizontal. I don't expect that will last, and is likely the result of the encountering of thicker multiyear sea ice that is more prevalent this year than in previous years (see the June 2010 diary from last week for details). But I think it's less likely now that we'll hit a record minimum sea ice extent this September also as a result.
Current Conditions
The North Pole web cams launched by NOAA have been taking photos for the season. Camera #2's picture is shown below.
NOAA Web Cam 2: 7:35 UTC 10 July 2010
Note it's cloudy; direct solar radiation helps greatly in the melting of the ice. Cool, cloudy weather is not favorable for this process, obviously.
Weather conditions over the Arctic, courtesy of the University of Cologne, Germany are shown below.
Weather Conditions from 12 UTC 10 July 2010
There appears to be (though data is pretty sparse) a region of the Arctic basin below freezing at this time, on the North American/Siberian side.
Summary
Arctic sea ice extent decreased much more slowly this week than the prior week, and during the month of June. This seems to be a consequence of changes in weather regime and the age and thickness of the existing ice near the coast of Alaska, northwest Canada, and Siberia. The next few weeks will tell us a great deal whether we'll reach a new record low sea ice minimum; I'm "betting" against it.
Stay tuned.