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has been di scussed. As poi nted out by Ei ttrei m and others<br />

(1969) and Eittreim and Ewing (1972), the nepheloid layer<br />

188<br />

north of Cape Hatteras is deep and intense, while it is more<br />

di ffuse and spans a broader depth range to the south. In<br />

their detailed discussion of light-scattering observations<br />

in the western North Atlantic, Eittreim and Ewing point out<br />

that, among the several sediment inputs to the nepheloid<br />

1 ayer north of Cape Hatteras (Western Boundary Undercurrent<br />

'Iload" from north, hemipelagic, pelagic, atmospheric, sea-<br />

floor erosion, and turbidity currents), turbidity currents<br />

are probably most important. Small, epi sodi c turbi di ty<br />

cu rren ts ori g i nati n gin the nume rous s ubma ri ne canyons no rth<br />

of Cape 'Hatteras would maintain the intense light-scattering<br />

observed in the nepheloid layer there, while the layer would<br />

be considerably weaker to the south, where there are few<br />

submarine canyons to contribute sediment. This effect is<br />

illustrated in Figure 7.3 where several of Eittreim's<br />

profiles are related to the transporting water mass by<br />

plotting light scattering against potential temperature.<br />

The extent of mi xi ng of NADW and AABW has al so been<br />

discussed previously (Chapter VI). However, since the water<br />

masses 1 i e along the same e/S curve, whi ch is very nearly a<br />

straight line below 2.0oe, one cannot use the classical<br />

methods to determine the degree of mixing. One indication<br />

that mixing is not ~trong is that the coldest water returning<br />

from the north along the Caicos Outer Ridge (Section 6,<br />

\ Ii<br />

ì<br />

~

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