On the Surface Temperature of the North Sea and of the North Atlantic (Classic Reprint)

Book excerpt: Excerpt from On the Surface Temperature of the North Sea and of the North Atlantic When we have defined, in regard to the main temperature wave, the mean-value and the half-range, we get, by addition or subtraction of this latter value from the former, to what we may call the Mean Maximum and the Mean Minimum temperatures. They are not strictly the mean maxima or mean minima of the year, for to determine these we should have to take into our calculations the in uence of the half-yearly and other higher oscillations of temper ature. But as a rule even the half-yearly uctuation is of no great magnitude, and the higher oscillations are very small indeed, so small that we can scarcely say whether they are real phenomena or (as is much more probable) are mere appearances due to our imperfect data. In any case, the approximate Mean Maxima and Minima, as we have defined them, - the maxima and minima, that is to say, of the fundamental sine-wave, - are features of considerable interest, whose local variations are often well worth studying. Let us now begin, after this short introduction, to consider the main results of our temperature investigations. Our object is to understand the temperature phenomena of the North Sea, and of the waters which surround the other coasts of our own islands. But all our coastal waters are but a part of the great system of waters of the Atlantic Ocean, and we cannot properly understand any of our local phenomena without some preliminary knowledge of the ocean temperatures of the whole North Atlantic basin. The temperature phenomena of the ocean are closely inter connected with the system of ocean currents; and these in turn are correlated with the system of prevailing winds, and are greatly affected by the form itself of the ocean-basin. Were the whole globe covered by a shoreless ocean, the distribu tion of temperature therein would be comparatively simple; and in the absence of wind it would be very simple indeed. For the main phenomenon would be that of a steady cooling of the surface of the sea from the Equator towards the poles, the temperature varying from a maximum at the one to a minimum at the other, as a simple function of the cosine of the latitude, At the same time, the waters of the ocean would not be stationary; for the waters cooled in the neighbourhood of the pole would be rendered heavier thereby, and would tend to sink, while the warmer and lighter waters farther south would always tend to oat over the colder and heavier layers. There would, in short, be a steady drift to the northward of warm surface waters from the Equator, while the cold waters of the pole would form a steady return-current at the bottom. The obvious effect as regards the surface temperatures would be that at any point14 Fishery Board for Scotland. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."