[Fig. 13]

Fig. 13. —­ Temperatures at one of the “Fram’s” and one of the “Challenger’s” Stations, to the South of the South Equatorial Current were about the same as those of 1876, when the Challenger was on her way back to England.

We can now make similar comparisons as regards the South Atlantic.  In 1876 the Challenger took a number of stations in about the same region as was investigated by the Fram.  The Challenger’s Station 339 at the end of March, 1876, lies near the point where the Fram’s Station 44 was taken at the beginning of August, 1911.  Both these stations lay in about lat. 17.5deg.  S., approximately half-way between Africa and South America —­ that is, in the region where a relatively slack current runs westward, to the south of the South Equatorial Current.  We can note the difference in Fig. 13, which shows the distribution of temperature at the two stations.  The Challenger’s station was taken during the autumn and the Fram’s during the winter.  It was therefore over 3deg.  C. warmer at the surface in March, 1876, than in August, 1911.  The curve for the Challenger station shows the usual distribution of temperature immediately below the surface in summer; the temperature falls constantly from the surface downward.  At the Fram’s station we see the typical winter conditions; we there find the same temperature from the surface to a depth of 100 metres, on account of cooling and vertical circulation.  In summer, at the beginning of the year 1911, the temperature curve for the Fram’s station would have taken about the same form as the other curve; but it would have shown higher temperatures, as it does in the deeper zones, from 100 metres down to about 500 metres.  For we see that in these zones it was throughout 1deg.  C. or so warmer in 1911 than in 1876; that is to say, there was a much greater store of warmth in this part of the ocean in 1911 than in 1876.  May not the result of this have been that the air in this region, and also in the east of South America and the west of Africa, was warmer during the winter of 1911 than during that of 1876?  We have not sufficient data to be able to say with certainty whether this difference in the amount of warmth in the two years applied generally to the whole ocean, or only to that part which surrounds the position of the station; but if it was general, we ought probably to be able to find a corresponding difference in the climate of the neighbouring regions.  Between 500 and 800 metres (272 and 486 fathoms) the temperatures were exactly the same in both years, and at 900 and 1,000 metres (490 and 545 fathoms) there was only a difference of two or three tenths of a degree.  In these deeper parts of the ocean the conditions are probably very similar; we have there no variations worth mentioning, because the warming of the surface and sub-surface waters by the sun has no effect there, unless, indeed, the currents at these depths may vary so

[Fig. 14]