Models of the North Atlantic circulation

Atkins, Nigel (1984) Models of the North Atlantic circulation. (PhD thesis), Kingston Polytechnic,


Homogeneous models of the central and western North Atlantic circulations are investigated. A topographic interior model is analysed to determine its behaviour under certain conditions of wind stress and basin geometry. This leads to the recognition of the need for transport layers along the continental margins forming the western limits of the sea. The steeply inclined slope regions are found significant in this respect, provided that their widths are not less than O(E[sup]1/4) in magnitude, since if these become more narrow, the zones are not capable of transporting sufficient water volumes, without violating matching conditions demanded?y underlying lower Ekman layers. Steady models of the continental shelves off the eastern North American seaboard, with meridional coastlines, are considered. One of these permits the dominant alongshore velocity to equal a specified function of latitude along any chosen isoline of f/H. Another assumes that this current decays to zero on leaving the shelf region. This particular model is extended to remove the restriction of having a straight, north-south coast. In all cases, the direction in which information is transmitted has the coast to its right. Good qualitative agreement with observed current data from the area is noted. An O(E[sup]1/3)-wide, mildly topographic, abyssal depth layer located on the continental rise of the western Atlantic is analysed. This is found sufficient for completing the oceanic transport balance, and its proximity to the east of relatively narrow slopes off southern North America, makes it an attractive. model for the off-shelf behaviour of the Gulf Stream. The eastern North American coastline is approximated by an arc of a circle, with oceanic diameter, and a time-dependent model over its shelf zone is examined. This is capable of propagating low frequency continental shelf waves from the same, right-bounded direction as the aforementioned steady models.

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