« AnteriorContinuar »
DEEP SEA SOUNDINGS.
happy undisturbed repose, but when roused by cruel treatment they are ever ready to exert all their maternal instinct in defence of their offspring. It is during these seven days we devote ourselves to a scientific examination of deep-sea temperatures in the Arctic seas. An account of our operations is deserving of a chapter on that special subject.
“ Where the North Pole in moody solitude Spreads her huge tracts and frozen waters round.”
In the following remarks there are points respecting the temperature of the Arctic Sea, to which access is obtained through the broadest gateway to the North, i.e., that between Greenland and Norway, the portal of which is guarded by Spitzbergen. In the western portion, along the coast of Greenland, it is more or less blocked with ice, and the water is cold. In the eastern part, in the vicinity of Spitzbergen, there is warm water and an open sea at certain seasons of the year as far north as 81°, and in some years one or two degrees further. Nearly all the discoveries in these regions have been made by persons engaged in commercial enterprise ; so that, even when favourable opportunities offered, their interests restrained them from taking advantage of the same.
In 1871 Mr. B. Leigh Smith made a cruise in his
schooner yacht Samson, and reached 81° 24' N., with an open sea before him, comparatively free from ice. The pack-ice was drifting southwards, and the water at the surface was 33° F., while at 300 fathoms it was 42° F. This fact was observed by Captain Scoresby in lat. 78° N., 0ʻ:10 W., surface 32° F., and at a depth of 760 fathoms 38° F. In 1872 the cruise in which we had the pleasure of assisting, gave the following results. On this occasion the sea was crowded with ice, and, as we have said, the ship was beset.
The ice had evidently required more than one year for its formation ; its surface was covered with opaque snow, and was generally flat, and in no case rose higher than the gangway of the little schooner.
Owing to the floes presenting a comparatively smooth surface, with a total absence of icebergs, we were led to form the opinion that no land can exist in the vicinity immediately north of Spitzbergen, as the southerly drift would be sure to bring down floating bergs, which are always formed in the valleys of northern land.
On this occasion observation with the Miller-Casella thermometer confirmed the result of the previous year, viz. gradual increase of temperature at great depth. On July 12th, when in 80° 17' N., and when the vessel was fixed in the ice, the temperature gradually
increased to 64° F. at a depth of 600 fathoms. These facts indicate the southward flow of a vast body of warm water. It cannot be said that the heat is derived from the Gulf Stream, because nowhere in its course, even in such latitudes as 50° or 60°, does it acquire so high a temperature, even at the surface ; and it is highly improbable that the general warmth of the ocean along the west coasts of North Europe, on the shores of Norway, could possibly be supplied by the limited body of warm water which leaves the Gulf of Florida. If the whole of the Gulf Stream water were spread over the warm-water area in the north, its depth, even allowing the most liberal estimate for its volume, would not exceed ten fathoms; whereas warm water of 42° F. occurs to the depth of 400 fathoms in this region, and north of Spitzbergen it is found as high as 64° F. at 600 fathoms. If it be said that this temperature is due to the northward drifting of the Atlantic from warmer localities, we are met by two difficulties, of which one is, that the soundings obtained by Carpenter and others gave temperatures much below 64°, and the other is, that the waters flow south, not north. Volcanic action, or a warm mineral spring rising from the ocean-bottom, may by some be imagined to be the cause of the temperature of 64°; but there is no evidence of either of
SOUTHERLY DRIFT OF ICE.
these agencies, and it is quite reasonable to suppose any other feasible cause. Passing over the discovery of 64° F. at this depth, we still have to account for the water of 42° F. flowing southwards, as evidenced by the increase of its temperature as we proceeded northwards.
It is clear that this question of temperature requires further investigation ; and it is also clear that whatever the result may be, it will materially affect all the prevailing theories respecting oceanic currents. It is not improbable that this warm water flows from the circumpolar region ; and if so it would indicate a circumpolar sea.
Many facts are known which are consistent with this view. Every year the edge of the pack-ice, and the ice-fields themselves, break up and drift south, at a rate sometimes equal to thirteen miles a day, as found by Captain Parry. This does not occur when the northern ocean is wholly covered with ice, in the winter season. The drifting of the ice (as also currents) implies a sea free of ice somewhere in the north, occupying an area at least as extensive as the drift-ice. As has been seen, some of the ice is the result of more than one year's growth ; and as the ice travels southerly, say, from four to thirteen miles or more per diem, a similar area of open sea must be simultaneously forming round the pole, the ice-holes