The salinity and temperature of the Irish Channel and the waters south of Ireland / by Donald J. Matthews.

  • Matthews, Donald John, 1873-1956.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The salinity and temperature of the Irish Channel and the waters south of Ireland / by Donald J. Matthews. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    On the General Circulation of the Water in the Irish Area. A complete account of the circulation in the Irish area would require a more detailed knowledge of the changes in the surface drift in the open ocean to the south and west of Ireland than we yet possess. At present the only information available for every month in the year is derived from the analysis of surface samples collected continuously for several years on liners sailing between the English Channel and New York. These samples were taken for the Marine Biological Association in connection with the International Fishery Investigations and analysed by the present writer. The mean salinities have been calculated for every month and plotted on charts, and at the same time curves have been drawn for certain selected areas where the observations are sufficiently numerous. One of these areas lies in 50° N. Lat. between 11° W. Long, and 20° W. Long, and has a breadth of about ten miles in a north and south direction. It is therefore in the path of the surface drift current which flows approximately northwards to the west of Ireland. The curve shows a maximum of about 35-59 per thousand in February, falling regularly to 35-54 per thousand in May, rising again slightly in June, falling in July to about 35-50 per thousand, which value remains almost unaltered to September, and reaching a sharp minimum in October with 35-43 per thousand. After this there is a sudden rise to a secondary maximum towards the end of November, a slight fall in December and January, and then again the maximum in February. Shortly, there is a well defined and sharp minimum in October, and immediately following this a rise to a high and somewhat long drawn out maximum beginning in November and culminating in February. The Plymouth observations across the entrance to the English Channel show very similar results. The maximum is in January and February, and the minimum in the late summer, though it is somewhat irregular. The charts published in this report show that the saltest water enters the Irish area between Land’s End and the Scilly Islands, and detailed observations made along this line on several cruises at intervals of from half a mile to one mile on the Marine Biological Association’s steamers have shown that the axis of highest salinity lies midway between the Longships Rock and the Seven Stones Lightship, that is, at a distance of only a few miles off Land’s End. This current of salt warm water is derived from a current which has already entered the English, Channel from a south-westerly direction, and has in part turned northwards and north-westwards to escape into the Irish Channel. It is practically certain that this water has come from the mouth of the English Channel and not directly from the open sea because further westwards a great area of lower surface salinity stretches southwards across the fairway