208 



KNOWLEDGE 



[September, 1902. 



Ciii>e Ohi'lviiskiii, the most northerly point of Asia, on Sep- 

 tenibor 1 1th, ami (.'iiteri'd the ice north of the New Siberian 

 Islands on September 22ud, in 78 '50' N. From this time 

 she drifted with the ice, being about 79" N., 138' E. on 

 1st January, 1894, in 83^° N., 102^^ E. on 1st January, 

 1S!I">, in almost 80° N.. G7° E. (her farthest north) on 

 15th November, in 85J " N., 47° E. on 1st January, 1896, 

 and in the middle of July she broke out of the ice in 

 84^ N., 15° E., to the north of Spitsbergen. Along the 

 whole of this extensive route, which was traversed by the 

 " Fi-am " in many devious looi)S, observations were made at 

 frequent intervals by lowering thermometers and water- 

 bottles through openings broken in the ice. At least nine 

 observations were made at depths of lUOO fathoms or 

 more, and were it not for the risk of breaking the only 

 available sounding-line, which was wearing thin with use, 

 many others would have been obtained. 



In discussing the instruments and observations, Dr. 

 Nansen has much to say as to their corrections and the 

 probable errors of observation, and if he errs in this matter 

 it is by the perhaps unnecessary refinement of some 

 corrections. These corrections also were in many cases 

 suggested by laboratory work subsequent to the return of 

 the expedition, and if they had been thought of when the 

 observations were made, some little advantage might have 

 resulted. They will, however, bear good fruit in subsequent 

 expeditions. As they stand. Dr. Nansen's observations 

 are at least as accurate and trustworthy as the best work 

 of his predecessors ; but there is no doubt that in the 

 conditions of the polar seas, with a very small range of 

 temperature, and with solid ice to work from, far greater 

 refinements in observational methods are possible than in 

 the open ocean. 



The primary object of investigating the temi^erature 

 and salinity of the water was to throw light on the 

 circulation of that part of the ocean. The observed facts 

 were that a layer of cold and comparatively fresh water, 

 probably due to the great rivers of Northern Asia, covered 

 the surface of the Polar Basin to a depth of about 100 

 fathoms. Beneath this a distinctly warmer and much 

 Salter body of water was found, its high salinity being 

 maintained to the bottom, while its temperature came to a 

 maximum at a depth of about 200 fathoms, from which 

 plane it falls gradually to a minimum near the bottom, 

 but never becomes so cold as the surface layer. This 

 appears to be Atlantic water in course of cooling down, 

 and the very slight rise of temperature observed in it at 

 the bottom is attributed to the influence of the internal 

 heat of the earth. 



The curves of temperature, salinity, density in situ, and 

 the isosteres, or lines of specific volume calculated according 

 to Bjerknes' method, afford a basis for estimating the 

 forces tending to produce circulation in the water, and 

 taking all these into account Dr. Nansen comes to the 

 following conclusion. 



There are at least four systems of currents in a vertical 

 section along the route of the "Fram." (1) A surface 

 current of low salinity {29 to 32 per mille) about 20 metres 

 deep running towards the north-west and west. (2) An 

 underlying slow current of high salinity and very low 

 temperature running in a different direction and consisting 

 of surface water from other parts of the Arctic Sea. (3) 

 A current of relatively warm water of high salinity (351 

 to 35"3 per mille) coming from the Gulf Stream, west of 

 Spitsbergen, and running towards the east at depths 

 below 250 metres. (4) An extremely slow current of colder 

 water filling the deepest part of the basin (below 1000 

 metres), forming the densest part of the preceding current 

 which bas been cooled down and sunk. In the mass of 

 this very slow-moving current which may not renew the 



water in the Polar Basin once in several centuries, Ur. 

 Nansen believes that the internal heat of the earth may 

 give rise to a system of vertical circulation. 



The whole of this difficult subject is discussed at great 

 length, but we cannot say that the difficulties which 

 present themselves to our mind are removed. Of these 

 the chief is why warm Atlantic water penetrating the 

 Polar Basin beneath a sheet of very cold water of h>w 

 salinity should cool more rapidly downward than upward. 

 There must, we should think, be a systc^m of oblique 

 circulation to produce this effect, such as might be 

 produced by the wind. 



In dealing with the surface current, the demonstration 

 of the existence of which gave Dr. Nansen confidence in 

 his plan of a drift-voyage, we are on surer ground. The 

 fact that the " Fram " followed the route which she was 

 expected to traverse of course proved the main fact that 

 there was a drift of ice from the Siberian towards the 

 Grreenland side of the basin. It did not, however, prove 

 whether the ice was simply drifted over by the wind, or 

 carried along by a definite ocean current irrespective of 

 the wind. Wind-drift was, of course, a very powerful 

 factor, as the curious tangled track of the " Fram " clearly 

 proves, but when the influence of the wind was eliminated 

 by considerable periods during which the wind resultant 

 was zero, a residual drift due to a permanent current was 

 plainly visible. This permanent current had an average 

 velocity of 073 nautical mile in 24 hours. That the 

 permanent current was in the main independent of wind- 

 drift appears from the fact that the mean rate of the 

 wind-drift was only 52 nautical mile in 24 hours, 

 and its direction was substantially different. The primary 

 cause of the permanent surface current is cousidere<l 

 to be the volume of fresh water poured in by the Siberian 

 rivers. 



In his discussion of the circulation of water in the 

 Polar Basin, Dr. Nansen makes very large use of the 

 deviation due to the rotation of the earth, as it affects 

 vertical as well as horizontal movements. He employs 

 this hypothesis in constructing a scheme of the probable 

 circulation of the unknown parts of the North Polar area, 

 but points out the uncertainty arising from our ignorance 

 of the configuration of the American margin of the basin, 

 which must have a great influence on the movement of 

 the waters. 



Some remarkable relation shijjs are brought out by a 

 comparison of the oceanograpliical conditions of the North 

 Polar Basin and of the Norwegian Sea. Contradictory as 

 it may appear to our natural opinion, the bottom water in 

 the North Polar Basin is warmer and Salter than that in 

 the Norwegian Sea at the same depth. Thus, between 

 Norway and Iceland, bottom temperatures of — 1°1 C. or 

 lower are obtained, while the coldest bottom water met 

 with by the " Fram " was only — 0°87 C. Hence it is 

 necessai'y to assume that the basins of the two seas are 

 separated l\v a sub-oceanic ridge extending from Spitsbergen 

 to Greenland. The cold and comparatively fresh East 

 Greenland and East Iceland jiolar currents are, in Dr. 

 Nansen's opinion, simply the outflow of the sui'face water 

 of the Arctic Sea, consisting of Atlantic water freshened 

 by the Siberian rivers, and containing a quite insignificant 

 proportion of fresh water due to melting ice. 



Much work must still be done in the northern seas 

 before all the pi-oblems are satisfactorily solved, but the 

 outcome of the " Fram's" researchesis togive a certain basis 

 of fact from which a multitude of fresh ideas will spring, 

 each demanding new and exact observations before it can be 

 settled. Wt> would much like to see the drift of the " Fram " 

 repeated, say from Bering Strait, in a vessel fully equipped 

 for oceauographical work, and we would venture to urge 



