In:
Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 91, No. C12 ( 1986-12-15), p. 14261-14268
Abstract:
Three years of current data from the offshore branch of the Labrador Current are examined. The meters were at least 400 m deep (to avoid being struck by icebergs) and positioned over the 1000‐m isobath on the eastern flank of Hamilton Bank. The currents are predominantly directed along isobath. At periods of 1–8 days the motion is bottom‐intensified; at longer periods (10–40 days) it is essentially independent of depth. One of the objectives of this paper is to determine whether or not the 10‐ to 40‐day fluctuations, which are O (5 cm s −1 ), can be explained by large‐scale wind forcing over the North Atlantic. Monthly variations in the transport of the North Atlantic are calculated by means of the topographic Sverdrup relationship. The Sverdrup return flow along the coast of Labrador, −〈ψ w 〉, is found to have a well‐defined seasonal cycle with a range of 6 Sv. The maximum southward transport generally occurs in February, which is also the month when the standard deviation of (ψ w ) is a maximum (9 Sv). If we assume that the monthly changes of the return flow are barotropic and confined to a boundary current of (say) 100 km width and 1 km depth (the mooring depth), then 1 Sv corresponds to a speed of 1 cm s −1 . We would then expect the large‐scale wind over the North Atlantic to cause the flow along the Labrador coast to vary with a seasonal range of 6 cm s −1 and exhibit monthly variations in winter of ∼9 cm s −1 . However, a comparison of the (ψ w ) and current records shows no similarity. We therefore speculate, with some corroborative evidence from an analysis of Nain sea level, that these energetic variations in the (topographic) Sverdrup return flow along the Labrador Coast probably occur in deeper water, offshore of the current meter mooring. The cause of the barotropic current variations remains unclear. It is possible that they do not reflect genuine transport changes but are due to a meandering of the Labrador Current. Further analysis, and perhaps measurements of bottom pressure, are required to explore this possibility.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/JC091iC12p14261
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
1986
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