The physical and chemical oceanography of the waters bathing the continental slope of the Celtic Sea

Abstract

Knowledge of the hydrography of the English Channel and Celtic Sea is needed as a background for the life histories of the mackerel, pilchard and herring and, indeed, of every organism living within range of the Plymouth Laboratory. Such knowledge can never be fully attained until we know more of the exchanges with the deep Atlantic Ocean which take place 200–300 miles to the south-west and west over the continental slope. Moreover, at the slope we shall need to know not only what waters move in and out but what move up and down. Long ago Storrow (1925), and no doubt others, saw clearly some of the problems here to be discussed, but they were unable to bring factual evidence to bear. A critical reconstruction of the considerable but fragmentary observations in the neighbourhood of the continental slope of the Celtic Sea will be presented here and supplemented by observations made in 1950 with the generous co-operation of the vessels of the National Institute of Oceanography (Discovery Committee) and in 1948 by H.M. Surveying Ship Dalrymple. Though many of the conclusions remain tentative, it should now be easier to design observational work at sea to test specific hypotheses at the right time and place by the methods of experimental oceanography. The numerical results in 1950 will be published by the Conseil International pour l'Exploration de la Mer.

The water flow into the English Channel from the south-west

“…3, 14) along the parallel 48°20' N. in May was the cold core below 50 m at station 2654 (Table 2). The mean Celtic Sea latitude temperature for 48°20' N. (Cooper, 1960) for 3 weeks earlier was I I '05°C. There is no question but that this water was cold for the place and date.…”

“…Cooper, 1960). Under these conditions recruitment of water into the Channel from the west should be from north of 49°N.…”

On the behaviour of barnacles III. Further observations on the influence of temperature and age on cirral activity

“…The bottom-water temperatures at all localities at which the species has been found, or at nearby stations of similar depth, vary from 7°to 9° (Hoek, 1883;Rouch, 1948;Cooper, 1952) and the annual variation is probably less than 1°(Dr L. H. N. Cooper, personal communications). As far as cirral extension is concerned, the specimens of Hexelasma examined were thus living very close to the upper limit of their optimum range.…”

Comparison between Recent benthic foraminiferal faunas of the Porcupine Seabight and Western Approaches Continental Slope

“…These factors can, and do, vary seasonally, and this means that Mediterranean Water is exceedingly variable in terms of its physical properties (Herman, 1981). Cooper (1952) gives an indication of this variability for the area west of the Celtic Sea shelf (see Fig. 2).…”

“…9"C), and minimum oxygen concentrations (approx. 4 ml/l) at around 1OOOm (Cooper, 1952). The properties of the Mediterranean Water are dependent upon the formation of dense, saline water in the eastern basins of the Mediterranean Sea and upon the amount of mixing this water undergoes as it enters the Atlantic Ocean through the Strait of Gibraltar.…”