Geology Reference
In-Depth Information
Figure 5 A schematic diagram of the thermohaline circulation of the world ocean, also
know as the great ocean conveyor belt, highlighting polar regions of deepwater
formation, deepwater circulation eastward from the poles and the returning
westward surface water flow
(Adapted from IPCC, 2001.
5
)
is formed in the Norwegian Sea and off the southern coast of Greenland.
The flow of the NADW can be traced southwards through the Atlantic
Ocean to Antarctica, where it is diverted eastward into the Southern
Indian Ocean and South Pacific. There it heads northwards and either
enters the North Pacific or becomes mixed upward into the surface layer in
the equatorial region. The transit time is on the order of 1000 years. As
noted previously, the thermocline acts as an effective barrier against
mixing of dissolved components in the ocean. Consequently, this deepwa-
ter formation process in high latitudes is important because it facilitates
the relatively rapid transport of material from the surface of the ocean
down to great depths. The deep advection of atmospherically derived CO
2
is a pertinent example. The formation of NADW could diminish with
climatechangebecausesurfacewaterswouldbewarmerandlessdensedue
to enhanced melting of ice in the Arctic region.
Diverse processes can form intermediate waters within the water
column. In the southern South Atlantic, the NADW overrides the
denser ABW. Antarctic Intermediate Water results from water sinking
along the Antarctic Convergence (
B
501S). Relatively warm, saline
