Abstract
Abstract. Measurements of the slope current at two locations north-west of Ireland have been made between April and December 1994, 40 m above the seabed in a water depth of 660 m. A persistent poleward along-slope current was observed at both locations, with measured means of 10 and 21cms–1 respectively. A CTD transect across the slope near one mooring indicated the presence of a light, warm, saline core of water at the shelf edge. Peak currents were O(50)cms–1, with strongest mean flow at the location with steeper slope. Variability at sub-tidal periods, principally 2–5 and 11–12 days, was apparent. The shorter-period variability was well correlated with coastal sea-level variations measured at a land point near to one of the moorings. The variability in the slope current at this period appeared to be a result of the warm current core movement up/down slope, probably as a result of interaction with higher-mode shelf waves. Some suggestion of a bottom-trapped diurnal wave was also found at one location.
Highlights
A polewards- ̄owing current is known to exist along most, if not all, of the North-east Atlantic margin, extending northwards from the Iberian margin to the Norwegian Sea (Pingree and LeCann, 1989, 1990; Huthnance and Gould, 1989)
The observation of mean currents between 10 and 20 cm sÀ1 measured in the slope region south of the Malin Shelf falls between the lower values found to the south, e.g. 6 cm sÀ1 at 500-m depth at the Goban Spur (Pingree and LeCann, 1989), 8±9 cm sÀ1 between 500 and 780 m on the Porcupine Bank slope (James, 1982), and the generally higher values found along the Hebrides slope, of y 15±30 cm sÀ1 between 58 and 59 N during CONSLEX (Huthnance, 1986)
The measured current a warm saline core of water was located at the shelf edge, similar to that previously measured along the Malin and Hebrides slopes
Summary
A polewards- ̄owing current is known to exist along most, if not all, of the North-east Atlantic margin, extending northwards from the Iberian margin to the Norwegian Sea (Pingree and LeCann, 1989, 1990; Huthnance and Gould, 1989) This shelf-edge current (SEC) plays an important role in physical exchange processes at the shelf break and cross-shelfuxes (Huthnance, 1995). The SEC is relatively warm and saline, as shown by CTD measurements across the Malin and Hebrides Shelf (Hill and Mitchelson-Jacob, 1993) These observations indicated that between 56±59N the depth of the current core decreased by about 100 m per 200 km of northward transport. Mean speeds and low-frequency variability are discussed, together with a comparison with previous observations along the slope These are the ®rst reported measurements of sub-surface currents in this particular shelf-edge region
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