Surface Currents and Deep Currents

Currents

Current: A horizontal movement of water in a well-defined pattern.

In the ocean, there are surface currents and deep currents.

Surface Currents

What do you think causes surface currents?

Answer: WIND.

What do you think affects the direction surface currents flow?

Answer: Controlled by 3 factors: Air currents (such as major wind belts), Earth’s rotation (Coriolis Effect), and the location of the continents (deflect and divide currents).

World Surface CurrentsNorth Atlantic Gyre

North Pacific Gyre

Heat transfer by surface currents

What do you notice about how surface currents transfer heat?

Answer: Warm water is brought from equator towards poles. Cold water from poles to the equator.

What causes England to be fairly warm even though it is the same latitude as Canada?

Answer: Warm water from Gulf Stream.

Deep Currents

Unlike surface currents, deep currents are not caused or controlled by winds.

Deep Currents: A stream-like movement of ocean water deep below the surface.

Any ideas on how deep currents form?

Answer: Density differences due to changing salinity and temperature (Thermohaline Circulation).

Ocean Conveyer Belt of Deep Currents

Deep Currents

How does the conveyer belt work?

At poles, water freezes. As freshwater is locked up in ice, saltier water is left in the ocean.

Saltier water is more dense and it sinks.

As surface water is pulled in to replace sinking water, a deep current is formed.

This process drives the global conveyer belt.

Climate Change

How could a warming global climate affect earth’s conveyer belt?

Answer: Warming could cause increased rainfall in the North Atlantic, and the melting of glaciers and sea ice. This fresh water could disrupt the sinking of cold, salty water. This sequence of events could slow or even stop the conveyor belt, which could result in potentially drastic temperature changes in Europe and elsewhere.