5.6 Paleoceanography
a
-
CLOSURE OF '
1 INDONESIAN SEAWAY
2 EAST MEDITERRANEAN GATEWAY
3 STRAITS OF GIBRALl'AR
4 PANAMA STRAITS
b
CLOSING OF OLDER
AND OPENING OF NEW
OCEANIC GATEWAVS
Fig. 5.27. a Exchange of warm surface and colder
deep water along the conveyer belt of the modem
oceans. (Modified and simplified from Broecker
1998). b Eocene oceans and post-Eocene closure or
Pacific flows as surface current via the Indonesian passage
to the Indian Ocean, around South Africa, and then northward into the Caribbean Sea and, as Gulf Stream, into the
North Atlantic. On its way through warm low-Iatitude reOPENING OF
5 DRAKE PASSAGE
6 TASMANIAN PASSGE
7 NORTH ATLANTIC
GATEWAYS
243
opening of oceanic gateways which led to a drastic
reorganization of thermohaline circulation. (Modified
from Seibold and Berger 1996)
gions, the salinity of the surface water increases. After
cooling in the subpolar regions of the North Atlantic, the
relatively dense water masses sink and flow as deep-water
current again southward to the South Atlantic, where they