The Oceanography of the Celtic Sea I. Wind Drift

Abstract

The dependence of prevailing wind drift in the Celtic sea upon prevailing winds is discussed and a proposal made to use wind records for the Scilly Meteorological Observatory for assessing drift currents for use in biological investigations.If there is no seasonal change in the direction of the prevailing winds, nevertheless, the wind drift in summer will be more northerly than in winter.The terms ‘current’, ‘residual water movement’ and ‘drift’, as used in this series of papers, are denned. The Ekman–Thorade equation for computing wind drift from wind is discussed and applied to the drift of the biological indicator Muggiaea atlantica in 1938. The two approaches agree to suggest that either method may be applied in biological distribution studies.Some effects of drift, due to variable winds, on plankton distribution are outlined.

The influence of physical stability on spring, summer and autumn phytoplankton blooms in the Celtic Sea

“…Matthews (1914) and Harvey (1925Harvey ( ,1929 considered there was a northward flow between Lands End and the Scilly Isles whilst Carruthers (1934) (and Carruthers, Lawford & Veley (1951)) considered the flow was directed towards the English Channel. The dichotomy was examined by Lee (i960) and independently by Cooper (1960Cooper ( , 1967, who considered that all the evidence could be assimilated if one accepts that a narrow well-mixed corner current flows intermittently around Land's End from the south to the north coasts of Cornwall. However, although the discrete measurements of temperature, salinity and phosphate were shown to be similar, continuity between south and north Cornwall was not clearly established.…”

“…The Celtic Sea extends from the south of Ireland and the St Georges Channel across the continental shelf, with the Bristol and English Channels as its eastern limits ( Fig. 1) (Cooper, 1967). Although various investigations of the physical oceanography (Matthews, 1914;Cooper, 1967) and zooplankton (Russell, 1934(Russell, , a, b, 1936Corbin, 1947; and more recently Southward, 1962;Bary, 1963) of this area have been carried out, there is little or no information on seasonal changes in levels of chlorophyll ' a ' and inorganic nutrients, and on the importance of tidal mixing in determining these distributions.…”

“…1) (Cooper, 1967). Although various investigations of the physical oceanography (Matthews, 1914;Cooper, 1967) and zooplankton (Russell, 1934(Russell, , a, b, 1936Corbin, 1947; and more recently Southward, 1962;Bary, 1963) of this area have been carried out, there is little or no information on seasonal changes in levels of chlorophyll ' a ' and inorganic nutrients, and on the importance of tidal mixing in determining these distributions. Since the speeds of the tidal streams range from weak (~ 0-5 knot) in the northern part of the Celtic Sea to strong (~ 3 knots) around the Scilly Isles and Ushant (Fig.…”

Seasonal Variations in Inorganic Phytoplankton Nutrients in the Inshore Waters of Cardigan Bay

“…The increase in phosphate concentration during the autumn is thus unlikely to be due to increased turbulence and the lowering of the thermocline through vertical mixing. Cooper (1967) stated that in autumn mixing in the Celtic Sea proceeds from west to east, so that by December mixing is complete and wind drift may move the whole water column towards the Irish Sea and the Bristol and English Channels. Hence nutrientrich water, brought to the surface in the Celtic Sea, may enter Cardigan Bay and partially account for the autumnal phosphate increase.…”

“…(Fig. 1) is bounded on the west by the southern Irish Sea and St George's Channel, and to the southwest by the northern limits of the Celtic Sea as defined by Cooper (1967). All other boundaries are terrestrial, the Lleyn Peninsula to the north, the west coast of Wales to the east and the rocky promontory of Pembrokeshire in the south.…”