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?