Perhaps I was a little quick in my previous post, or at least on polarporal.dk I found two maps that do not show the same area. This time I will take the English versions of the pages and then after that there will be sea ice maps from Norway, Canada, the US, and more details from the seas above Russia. Along the way I will comment on the differences:
First there is
Sea Ice Extent: Polar Portal map I posted previously, and pay special attention to the area from the North pole along 160 degrees east, remember the ice cover and compare with map nr two:
The new map I found on
Sea Ice Thickness and Volume: Polar Portal Notice the extend of the ice is greater than on the previous map, especially along the 160 degree mark between the two Russian Islands
Apparently the first map from Polar Portal made by OSI-SAF showing sea ice extend neglects ice covers in the low end, say 10-20 %, but then again this is not ice free conditions. Moreover it seems more inaccurate when it comes to the seas north of Russia, where even spots of dense ice cover are neglected. OSI SAF has a website
OSI SAF | Observing oceans from space from where Polar Portal gets their maps. About the accuracy they say on
Global Sea Ice Concentration (AMSR-2) | OSI SAF
| Thresold accuracy | 20 % |
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| Target accuracy | 10 % for NH-product. 15 % for SH-product |
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| Optimal accuracy | 10 % |
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| Verification/validation method | Comparison with high resolution manual ice charts |
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10-20% accuracy would of course count for a lot and it seems they prefer to err on the side of reporting too little ice.
And again the Russian map from
Charts of ice conditions which is responsible for the northern sea route navigation. Green is 1/10-6/10 red is 7/10-10/10 coverage:
In an attempt to solve the doubts about the quality of the data on the above maps, I found the page of the Norwegian Ice Service on
Ice Information Portal It is surprisingly detailed.
Compared with the Russian map they are close, but perhaps the Russian map is slightly more conservative, I have gone back and forth many times comparing the perspective, but this seems to be the case. I assume any ship moving in this area would use the Norwegian maps.
The Canadian ice service also offers maps at
Canadian sea ice concentration map - Canada.ca Comparing with the Russian map it appears similar, the coding is slightly different, but it does not change much. Both the Norwegian and the Canadian maps are very limited in the area they cover.
Then I visited the U.S. National Ice Center, Naval Ice Center at
U.S. NIC Products and then went to their library of maps:
U.S. NIC where todays maps of the Arctic Ice shows a picture where the projection appears to be pretty close to having the North Pole in the center although the perspective is different from the Russian map.
When I compare this last American map with the first sea ice extend map from OSI-SAF it almost appears as if they have removed the yellow areas on the US map and with a broad brush smoothed out the edges around the red areas and called that the extent of Arctic ice cover. Now they have their own satellites, but this is the impression. When I compare the US map with the sea ice thickness map on Polar Portal there is more correspondence.
If we go back to the the Russian page, they have four areas for which they offer more detailed maps if ice is present:
Kara Sea
Laptev Sea
East-Siberian Sea
Chukchi Sea is ice free
For the Kara Sea there is this map:
And to the east of the above map there is the Laptev sea:
The above two maps clearly indicate that one has to sail close the shore and watch out for the ice bergs that still appears to be floating around.
For the East-Siberian Sea there is this map, which gives details that the big maps can only cover with approximation:
The above area looks safe at the present if one sails close to the shore. At the end of the day, it appears that if there is a choice between relying on data only based on satellite images like the OSI DAF and Polar Portal estimates of sea ice thickness and then those made by people responsible for sea navigation, I would rather rely on the latter, as they, besides satellite data, are likely to take the conditions observed in the areas where ice is present into greater consideration, and probably receive surface feedback all the time, but since some areas are not accessible, one has to study both kinds of information.
I almost can't believe this small excercise got this complicated, but doubts have been put to rest, and if anyone dares to pull out the OSI-SAF maps posted on Polar Portal to prove there is hardly any ice left in the Arctic, then there is some good data available from many sources to show those maps are a bit misleading.
Ascou @ax3domaines 1450m only #ariege#pyrenees