The Oceanic Conveyor Belt
Study Guide

Updated 08.22.09


The Oceanic Conveyor Belt or Thermohaline Circulation (THC)
is the global density-driven deep circulation of the deep ocean.

It is connected to the wind-driven or surface circulation
through vertical motions.

The most dense water on Earth forms off Antarctica.
The Antarctic Bottom Water (AABW) sinks to the ocean floor,
it is then guided by sea-floor topography
as it flows into the Atlantic, Pacific and Indian Ocean basins.

AABW is forced to rise. It is then warmed and eventually re-circulates.

AABW may be out of contact with the atmosphere
for thousands of years before re-surfacing.

The Arctic Ocean is isolated from the Pacific, except for the small Bering Strait.
The only cold dense water that can be part of the
conveyor belt circulation forms in the North Atlantic.

North Atlantic Deep Water (NADW) is not as dense as AABW so stays on top of it.
AS AABW rises, NADW sinks to replace it.

If less NADW forms because of global warming and less ice formation
the conveyor belt will slow and global climate will be affected.

Click Here for a NASA article on this topic.

Click Here for a NASA visulaization of the THC

Click Here for an article on the THC

Arctic Ocean Near Greenland
A Case for Global Warming

In the basin between Greenland and Baffin Island
dense, saline water sinks to the bottom and is trapped
by a rise that forms a sill.

Each winter as sea ice forms, because of the enhanced salinity
of the water it is more dense and sinks.
See cross section below

Dr. Ruth Curry at the Woods Hole Oceanographic Institute
has documented the steady DECREASE in salinity in the basin
since the 1970's

This is caused by either less sea ice froming, increased melting of the Greenland Ice Cap
or a combination of both. All possibilities indicate global warming.

Typical Arctic Ocean Winter Sea Ice

Average Annual Sea Ice Cycle

Thinning Arctic Sea Ice

Blue indicates thinner ice, % shown on scale.