Cache of historical Arctic sea ice maps discovered

Bill Tuttle says:
May 2, 2012 at 10:32 am

The convoys were trying for speed — hugging the edge of the ice rather than making a direct run would not only have prolonged their agony, but simplified the U-boats’ search for them. Most aerial attacks on the Murmansk convoys were by He-111s, Bf-110s, and FW-200s (based at Stavanger), which had the range to pick up the convoys a day after they passed Iceland and follow them to Tromso, where they’d get picked up by the Ju-87s and get hit all the way to Murmansk.

Well clearly the convoys could not have sailed north of the sea ice, so their courses do establish the maximum possible southern extent of the ice. In Churchill’s excellent 6 volume history of the war he details multiple attempts to enlist US participation in the recapture of Norway (probably in ’43). Among the reasons he gave are the elimination of German naval and air bases, which would allow a more southerly route for the Murmask/Archangel convoys. This would reduce loses, reduce round-trip time, and thereby increase total tonnage delivered.
If I recall correctly, Churchill asserted the convoys had to detour 200 or more miles north to avoid the worst of the U-boat and air attacks.
Clearly not as accurate as an actual survey map, but I still think there is some value in the convoy routes as an indicator of sea ice, if you have nothing else to go on.

Willis Eschenbach says:
May 2, 2012 at 11:49 am

Generally, I find myself surprised by the abilities of the map-makers of previous days. Dig out some of the charts from Captain Cooks voyages (mostly drawn by the infamous Captain Bligh of the Bounty mutiny fame), and you will be amazed by their accuracy.

Extremely accurate cartography had been developed well before 1900. Starting in 1800 William Lambton began the great trigonometric survey to map the Indian subcontinent. Completed nearly 50 years later by George Everest after Lambton’s death in 1823 it was a monumental achievement. From the description on Amazon ( here ):

The Great Arc
The Dramatic Tale Of How India Was Mapped And Everest Was Named
The Great Indian Arc of the Meridian, begun in 1800, was the longest measurement of the earth’s surface ever to have been attempted. Its 1,600 miles of inch-perfect survey took nearly fifty years, cost more lives than most contemporary wars, and involved equations more complex than any in the precomputer age.
Rightly hailed as “one of the most stupendous works in the history of science,” it was also one of the most perilous. Through hill and jungle, flood and fever, an intrepid band of surveyors carried the Arc from the southern tip of the Indian subcontinent up into the frozen wastes of the Himalayas. William Lambton, an impossible martinet, completed it. Both found the technical difficulties horrendous. With instruments weighing a half-ton, their observations often had to be conducted from flimsy platforms ninety feet above the ground or from mountain peaks enveloped in blizzard. Malaria wiped out whole survey parties; tigers and scorpions also took their toll. Yet the results were commensurate. The Great Arc made possible the mapping of the entire Indian sub-continent and teh development of its roads, railways and telegraphs. India as we now know it was defined in the process. The Arc also resulted in the first accurate measurements of the Himalayas, an achievement that was acknowledged by the naming of the world’s highest mountain in honor of Everest. More important still, by producing new values for the curvature of the earth’s surface, the Arc significantly advanced our knowledge of the exact shape of our planet.
This saga of astounding adventure and gigantic personalities is here told in detail for the first time. With an eye for intriguing incident and an ear for the telling phrase, one of the finest writers on India vividly resurrects the nineteenth century’s most ambitious scientific endeavor.

(the book is worth a read, BTW).
So by the time these maps were made, there was an established high standard for cartography.
It is also worth noting that around 1922 the US Geological Survey team (part of the US army) established the distance between Mt. Wilson and Mt. Baldy in California (over 11 miles) to within 0.25 inches, to support Michaelson’s experiments determining the speed of light. They did this packing survey equipment on mules into the scrub hills and canyons between these two mountains.
So to support WIllis’ point, if it was important maps made around 1900 could be very accurate, even without satellites, lasers, and atomic clocks.

Frank Lansner says:
May 2, 2012 at 2:26 am
And CCIS, when we see photos of US navy submarine surfacing near the north pole around 1960, does that really suggest extremely thick ice back then?
According to the commander of the Skate the ice at the N Pole was too thick to surface through in 1958. The following year they were able to break though the ice in frozen leads, at their first attempt they were unable to break through so surfaced faster the next time and broke through. The surfacing at the pole itself was their toughest one which took about two hours to break through, when they surfaced they were surrounded by ten foot hummocks of ice which implies one hundred foot thick ice!

This is quite simply the best historical Arctic ice mapping ever found, DMI have to be given even more respect for this work done in the past. The implications are huge and it’s about time certain groups were more honest with their historic Arctic ice data. The Cryosphere should use these to represent a more accurate picture of past Arctic ice.

RE: CCIS says:
May 2, 2012 at 1:38 am
“…There is a concept called volume…”
Which is poorly understood and very difficult to measure. Your link is to an article where some guy toodles about on an ice-breaker at the edges of the ice, and thinks he has an idea of the total v0lume. It also mentions aircraft buzzing along with a dangling radar. (It does not mention the satalite that bounces radar from way out in space, or the other, now-defunct satallite that measured using a lazer beam.)
You seem totally satified, when this fellow assures you the total volume is less. I am not. First of all, any data gathered today cannot be compared with earlier data, for all the data is recent and no earlier data exists. However I am also disatisfied because the actual data is never made public in a manner that allows the public to digest it.
I have seen no evidence that either radar or lazer are precice enough to pick up the pressure ridges which web the frozen surface of the arctic sea, yet these very narrow ridges, which look like the finest webs in even the most enlarged pictures from outer space, hold a disproportionate amount of the total volume.
Even in the depths of winter, ice can stretch like an accordian when winds diverge. This forms leads of open water even in the pitch dark, and at thirty to fifty below they swiftly freeze over. Then, when winds converge, the ice is like an accordian compressed. This forms pressure ridges where the ice is buckled and crunched and piled up, (and also piled down, for nine-tenths of any iceburg is under water.)
These pressure ridges are high enough to get in the way of brave and foolish people attempting to trudge north in the dead of winter, and therefore such people stick to the flat stretches, which are the frozen-over leads. (When such explorers take measurements with core-samplers, it is upon a nice, flat lead, where ice is newest and thinnest, and not up on the peak of a pressure ridge, which, if it sticks up six feet, also sticks down fifty-four feet.) (Likely this is smart, for it is easier to drill down through six feet of ice than sixty.)
Considering pressure ridges hold so much volume, it is important to determine whether radar and lazar beams can actually pick them up.
Don’t point laymen to numbers and computer-code that they can’t understand, but rather translate that data into an easy-to-digest picture of the surface that the radar or lazer beam actually sees. Does it show the big pressure ridges but not the small ones? Does it show them at all, or does it just show the surface as a flat average?
Until I can see a nice, neat illustration like that, I don’t want to hear talk about “volume.” As far as I can see “volume” is still basically an unknown, and is simply a topic Alarmists bring up when they are looking bad, in terms of “extent” and “area.”