Deep Ocean CurrentsDeep Ocean Currents

90% of the ocean’s water!90% of the ocean’s water!

Depend onDepend on

• Density which is affected by Density which is affected by – temperature temperature

•Colder water is more denseColder water is more dense

– salinity (how much salt is in the water)salinity (how much salt is in the water)•Saltier water is more denseSaltier water is more dense

Thermohaline circulationThermohaline circulation

• Refers to deep currents driven by Refers to deep currents driven by differences in water temperature and differences in water temperature and salinity that arise from salinity that arise from – 1. 1. heating/coolingheating/cooling at the sea surface at the sea surface– 2. Adding or losing 2. Adding or losing surfacesurface freshwater freshwater

(evaporation and sea ice formation (evaporation and sea ice formation increase salinity; precipitation, runoff and increase salinity; precipitation, runoff and ice-melt decrease salinity) ice-melt decrease salinity)

How does thermohaline How does thermohaline circulation work?circulation work?

• Transports huge volumes of cold, Transports huge volumes of cold, salty water from the North Atlantic to salty water from the North Atlantic to the Northern Pacific and brings the Northern Pacific and brings warmer, fresher water in return. warmer, fresher water in return.

Thermohaline Thermohaline circulation :circulation :Called the “Great Called the “Great Ocean Conveyer”Ocean Conveyer”

Oceans and the Oceans and the atmosphere interact to atmosphere interact to

affect climateaffect climate

The ITCZ: The Inter-tropical The ITCZ: The Inter-tropical Convergence ZoneConvergence Zone

Evaporation,Precipitation Evaporation,Precipitation and Oceansand Oceans

• Trade winds carry evaporated water Trade winds carry evaporated water vapor to the Inter-Tropical vapor to the Inter-Tropical Convergence Zone where it Convergence Zone where it condenses as rain. condenses as rain.

What happens at the ITC What happens at the ITC Zone?Zone?

Intense equatorial sun + warm ocean Intense equatorial sun + warm ocean = heat + humidity= heat + humidity

As this air rises, it cools, and the As this air rises, it cools, and the water comes down in frequent water comes down in frequent thunderstorms thunderstorms

Coastal Climates and Coastal Climates and OceansOceans

• 1. Lands that get 1. Lands that get sideswipedsideswiped by by warm currents tend to have a lot of warm currents tend to have a lot of rain in addition to a fairly warm rain in addition to a fairly warm climate. climate.

• 2. Lands hit by cold currents tend to 2. Lands hit by cold currents tend to receive very little precipitation in receive very little precipitation in addition to a comparatively cool addition to a comparatively cool climate. climate.

Coastal climates and oceansCoastal climates and oceans

• 3. Water warms up and cools off much 3. Water warms up and cools off much more slowly than land or air. more slowly than land or air.

• 4. So coastal areas are insulated by 4. So coastal areas are insulated by nearby water and experience narrower nearby water and experience narrower temperature ranges. temperature ranges.

• 5. These Temperate climates have 5. These Temperate climates have narrower narrower temperature ranges and no ranges and no extremes of extremes of precipitation..

EX: Maritime Temperate EX: Maritime Temperate Climate Zone: Britain Climate Zone: Britain

*Has cool summers and mild winters, *Has cool summers and mild winters, smaller annual temperature range. smaller annual temperature range.

*Strongly influenced by the ocean, which *Strongly influenced by the ocean, which maintains fairly steady temperatures maintains fairly steady temperatures across the seasons. across the seasons.

Ocean as COOcean as CO22 sink sink

• Oceans are the largest active carbon Oceans are the largest active carbon sink on Earth.sink on Earth.

• Increased COIncreased CO22 from human activities from human activities is warming the oceans causing ocean is warming the oceans causing ocean acidification and less mixing of acidification and less mixing of nutrients nutrients

• Major ocean currents could be Major ocean currents could be affectedaffected