Page 13 - Carbonate Sedimentology and Sequence Stratigraphy

4 WOLFGANG SCHLAGER

A) atmosphere B) atmosphere
ocean surface (gyres)

polar front
subarctic
westerlies

horse latitudes N subtropical

trade winds
N equatorial
doldrums
S equatorial

Fig. 1.3.— Weyl’s (1970) model of surface circulation in the ocean. A) The atmosphere has three circulation cells per hemisphere. In
the northern hemisphere of a non-rotating Earth, these cells would induce winds at the surface of the northern hemisphere that blew
northward between equator and horse latitudes, southward between horse latitudes and polar front, and northward again in the polar
region. The Coriolis force deflects these winds to the right, thus creating the wind fields we currently observe. B) The wind fields depicted
in Fig. A shear over the surface layer of the ocean and induce currents there. The surface currents deviate to the right of the wind vector
in the northern hemisphere because of Ekman transport caused by the Coriolis force. The results are west-flowing currents under the
trade winds, east-flowing currents under the westerlies, and west-flowing currents in the polar regions. In modern ocean basins, N-S
running coasts block most of these currents and deflect them to form large closed circulation loops called gyres.

60°

30°

0°

30°

60°

Fig. 1.4.— Surface circulation in the modern oceans. After Strahler (1971), modified. The principal features of Weyl’s model are
present, albeit with some distortions due to the shape of the ocean basins. In the south, around Antarctica, the gyre-circulation is
replaced by the globe-circling Antarctic Current.