Chapter 7
Where did the early Arctic Warming originate?
A. Suggested forcing mechanism
a) An introduction with a lecture given in 1935
On the 30th January 1935, the Royal Scottish Geographical Society honoured the President of the Geographical Society of the Soviet Union, Jules Schokalsky, with the Society's Research Medal. In his address he informed the Society that records provide incontestable evidence of a progressive warming of the Arctic Ocean:
"The branch of the North Atlantic Current which enters it by way of the edge of the continental shelf round Spitsbergen has evidently been increasing in volume, and has introduced a body of warm water so great, that the surface layer of cold water which was 200 metres thick in Nansen's time, has now been reduced to less than 100 metres in thickness." (Schokalsky, 1936)
For this investigation it is now time to ask what might have forced the change in the polar realm. In previous chapters the location and time-period for the sudden Arctic warming 90 years ago has been established, which leads to the question what has or may have triggered the event. Neither Johannessen (Johannessen, 2004)., who recently assumed that the warming in the early part of the 20th century was probably a natural phenomenon, nor Bengtsson (Bengtsson, 2004), who asserted that this climatic anomaly was probably a result of the influx of warmer water into the Barents Sea (see below), can be of much help. Closer to the core issue came Polyakov (Polyakov, 2003), with the conclusion:
· This variability appears to originate in the North Atlantic and is likely to be induced by slow changes in the oceanic thermohaline circulation.
· However, SAT records demonstrate stronger multi-decadal variability in the polar region than at lower latitudes.
· This may suggest that the origin of the variability may lie in the complex interactions between the Arctic and the North Atlantic.
Although all three-research papers come up with a 'conclusion', none of them realises that the results are of little help. As already mentioned in the previous chapter, C.E.P. Brooks (Brooks, 1938) had expressed his disagreement with regard to R. Scherhag's assert on increased atmospheric circulation, as this pushes the problem one stage back because one should still have to account for the change in circulation. Brooks made a thoroughly right diagnosis. All the conclusions which have been previously quoted can be quickly questioned today using Books' comment that he made 70 years ago. What is different from Scherhag's suggestion is the fact that at least two of the quoted opinions make reference to the role that the sea might have played in the warming phenomenon.
b) Slow change in ocean circulation - Oceans interaction
It seems that Polyakov et al. (Polyakov, 2003) have missed the identification of the most interesting points, especially when assuming that the variability might have been induced "by slow changes in oceanic thermohaline circulation". This notion neglects completely the fact that there must have been a very sudden and dramatic change in the oceanic interior. The previous analysis demonstrates this fact beyond any doubt. Obviously, the 'big warming' from the winter of 1918/19 could have been caused only by an extremely rapid change, so quickly that it has never been observed since weather and ocean records have begun to be registered, 200 years ago. The statement sustaining that the "variability appears to originate in the North Atlantic" is not very enlightening either, although the location where the "variability appeared" can be very precisely identified as being the island of Spitsbergen.
It is also difficult to agree with the affirmation sustaining that the "variability may lie in the complex interactions between the Arctic and the North Atlantic".The problem derives particularly from the word "interactions" because the overriding relation between the two oceans is the one-way transport of warm water to the Arctic basin. The West Spitsbergen Current transports warm Atlantic waters to the North, through the Fram Strait into the Arctic Ocean, and, in the opposite direction, the East Greenland Current transports very cold low saline water and sea sice southwards. The features of the two currents are so different that one can consider them, in the widest sense, as very separate entities. While they run in opposite directions, there is inevitable and considerable mixing and interactions going on. But these mixing and interactions cannot be held responsible for the generation of such an extraordinary warming up event. Actually, the higher any interaction at the time period in question, the less significant would have been the warming up of Spitsbergen.
Increased interactions between different currents of the North Atlantic can be excluded. The most prominent currents flowing from South to North (off Norway's coast) and from North to South (off Greenland's coast) are separated by a distance of about 100 to 300 km. There is no claim sustaining that any significant warming, or cooling, or any other relevant change in weather statistics had been observed in the North Atlantic, along the Polar Circle (66o34' N) or in the south of it, in the winter of 1918/19.
c) The wind induced Arctic warming
As it is still asserted nowadays that the early warming "was associated and presumably initiated by a major increase in the westerly and south-westerly wind, north of Norway, this leading to an enhanced atmospheric and ocean heat transport from the warm North Atlantic Current, through the passage between northern Norway and Spitsbergen, into the Barents Sea" (Bengtsson, 2004), this should raise astonishment. Such a statement needs to be challenged for a number of reasons, primarily for ignoring a principle rule already mentioned: The energy that maintains the atmospheric circulation is to a great extent supplied by the ocean (Sverdrup, 1942). Any list of questions should certainly include such as:
· Where did the wind come from to push warm Atlantic water north-eastwards?
· Has the wind over the Norwegian Sea "access" to the warm North Atlantic water?
· How much water could be pushed by wind into the Barents Sea, respectively how much wind must be available, to increase the flow of water from West to East throughout the Barents Sea?
· How can wind influence the flow in the Barents Sea over the time period in question when the sea is at least partly covered by sea ice?
· If the wind pushed water into the Barents Sea between Norway and Spitsbergen, should there not a simultaneous high rise in temperature at the North Cape as there was at Spitsbergen?
(continues)