Bering Strait: Cryosphere Today vs Real World

Thanks to NASA’s Earth Observatory site, a (rare?) opportunity to compare Arctic sea ice extension as shown on Cryosphere Today with the real world (as seen by the Terra satellite).

DISCLAIMER: The following should in no way be interpreted as suggesting anything untoward is being done at Cryosphere Today

The Earth Observatory’s “Image of the Day” for Jan 16, 2010 shows “Ice and Clouds in the Bering Strait“.

Ice and Clouds in the Bering Strait
Fig. 1 - Ice and Clouds in the Bering Strait

What are we looking at? The shapes of the islands clearly indicate it’s the sea between the Russian and Alaska coasts just to the South of St Lawrence Island.

St Lawrence Island
Fig. 2 - St Lawrence Island
Part of the Bering Strait (from Google Maps)
Fig. 3 - Part of the Bering Strait (from Google Maps)
Part of the Bering Strait (from Google Maps)
Fig. 4 - Part of the Bering Strait (from Google Maps)

Let’s take now the sea ice extent image from Cryosphere Today, for Jan 16, 2010, and zoom in to the area described above:

Cryosphere Today, Jan 16, 2010
Fig. 5 -Cryosphere Today, Jan 16, 2010
Detail from Cryosphere Today, Jan 16, 2010
Fig. 6 - Detail from Cryosphere Today, Jan 16, 2010
Detail from Cryosphere Today, Jan 16, 2010
Fig. 7 - Detail from Cryosphere Today, Jan 16, 2010

We can finally compare Fig. 7 with Fig. 1.

Ice and Clouds in the Bering Strait
Fig. 1 - Ice and Clouds in the Bering Strait

What is evident is that the Cryosphere Today processing eliminates the kind of ice that can be found right at the edge of the pack (visible as “dendrils” after a suitable magnification). The neat sea ice – open water distinction is a computational illusion.

"wavy tendrils—newly formed, thin sea ice"
Fig. 8 - "wavy tendrils—newly formed, thin sea ice"

Other evidence of missing sea ice from the Cryosphere Today image is along the Alaskan coast, for example in the black, apparently ice-free “shadow” of Nunivak island

Nunivak Island
Fig. 9 - Nunivak Island
Cryosphere Today, around Nunivak Island
Fig. 10 - Cryosphere Today, around Nunivak Island
Nunivak Island, Jan 16, 2010
Fig. 11 - Nunivak Island, Jan 16, 2010

Seemingly, the ice around the island is “broken up” by its presence, and for some reason disappears in a restricted area in the Cryosphere Today image.

So the question is…how much of this “marginal” ice is lost in Cryosphere Today compared to the real world?

Mystery In The Sea Of Okhotsk

sea of Okhotsk
sea of Okhotsk

Whatever happened in the sea of Okhotsk, the area most conspicuously “free” now from polar ice when compared to 30 years ago?

Of the 400,000-odd sq km missing from the average, 300,000 concern the sea of Okhotsk, and 100,000 the sea of Barents.

In any case, anomalies are overrated as a tool to understand what happens at the Poles. For example the Arctic Basin anomaly is zero, simply because there is only so much ice cover possible for it. If the average is 100%, even the coldest year will never show a positive anomaly…

Arctic Sea Ice: Animation of Thirty Years

Among the general boredom of reading about the latest awfully hollow “demonstration” that humans are at fault by way of exclusion (and in the process, finding the fingerprint of human-induced rise in temperature in places such as Antarctica where temperature has not risen…unless it’s the Peninsula they are referring to), here some animations of how arctic sea ice has appeared between 1979 and 2008, around October 28, according to Cryosphere Today (note: some years are missing, and for other years I had to take the nearest available image)

Animated Arctic Sea Ice - around Oct 28
Animated Arctic Sea Ice - around Oct 28

You may have to click on the images above to be able to properly see the animated GIFs.

One could be forgiven to think the following:

  • there isn’t much of a polar ice cover “shrinking trend”, but rather a lot of expansions and contractions, plus a freakish small configuration in 2007
  • the 2008 cover is very simiar to 2000’s, apart from an ice-free area East of Novaya Zemlja
  • one can almost sea the warm water flowing in through the Bering Strait, sometimes reaching East as far as Banks Island (1987, 1998)
  • the “losses” in sea ice in the Baltic and northwestern Siberia may or may not relate to a change in data processing between 2003 and 2005

Note how different the last 3 years look, as they include the snow cover exactly when, say, the ice in the White Sea suddenly goes.

Something Odd About Regional Arctic Sea Ice

There is something strange about the Arctic sea ice data posted at Cryosphere Today.

If I sum up each individual sea’s contribution (plots at the bottom of this post), the totals do no agree with the overall Northern Hemisphere values.

This is a list of anomaly and absolute values in millions sq km, region by region for Sep 10, 2007; March 01, 2008 and Sep 09, 2008:

(Approximated values obtained with Plot Digitizer. I have asked Chapman for the actual figures…if I get them, I’ll change the post accordingly)

Region,Anomaly Sep 07,Anomaly Mar 08,Anomaly Sep 08,Absolute Sep 07,Absolute Mar 08,Absolute Sep 08,Mean Sep 07,Mean Mar 08,Mean Sep 08
Arctic Basin,-0.97,0.07,-0.75,2.37,4.2,2.59,3.34,4.13,3.34
Hudson Bay,-0.02,-0.05,-0.02,0,1.22,0,0.02,1.27,0.02
St Lawrence,0,0,0,0,0.19,0,0,0.19,0
East Siberian,-0.31,0.01,-0.31,0.01,0.9,0.01,0.32,0.89,0.32
Canadian Archipelago,-0.13,0,-0.1,0.11,0.6,0.14,0.24,0.6,0.24

Northern Hemisphere,-2.05,-0.48,-1.92,2.94,13.85,3.17,4.99,14.33,5.09


(The “Mean” columns reconstruct the 1979-2000 mean by subtracting the anomaly from the absolute measured ice cover)

You can see that my digitization appears to consistently underestimate the anomalies, and overestimate the absolute measured ice cover. The result is that there is for example a huge 720,000sq km difference between the total of all 1979-2000 March means, and the value reported for the Northern Hemisphere on Cryosphere Today.

It would be nice to know if anybody else has attempted this, and/or has the actual values rather than the graphs.

NOTE ADDED 11 SEP: Unfortunately the graphs below do not use the same scale, so visual inspection can be misleading