Ocean circulation 1

Ocean currents

Flowing masses of ocean water/wind-driven (providing energy) currents, or surface currents, move water horizontally

Vertically and horizontally

Deep ocean currents, move .... they are density driven currents

Direct methods

Something interacting with the current (floating drifter, current meter)

Indirect methods

Nothing interacts with the current. (pressure gradiant, radar altimeters, doppler flow meter)

noisy

The sea surface is very...

Chemical tracers (human caused)

Tritium (Radioactive water ) and chlorofluorocarbons

- Tritium (Radioactive water ) and chlorofluorocarbons

- Characteristic temperature + salinity

- Argo

Scientists measures this in deep currents

Argo

Global array of free-drifting profiling floats. Floating device tracked through time

buoyancy

The floating device can control its...

surface currents

Affect only 10% of ocean water on earth

ocean surface

surface currents is friction between wind and ...

2%

... of wind energy transferred to ocean surface

speed

Surface currents has a slower ... than corresponding winds

pycnocline

A layer of water in which there is a rapid change of density with depth. Surface currents occur above it.

salinity and temperature

Determines density

Fridtjok Nansen

Floating ice doesn't move the same direction as the wind

right

The floating ice moves at a 20-40 degree angle to the ... of the wind

V. Walfrid Ekman

Developed circulation model in 1905

Circulation model

Explains balance between friction + Coriolis effect and describes direction and flow o waters at different depths near surface of the ocean

Ekman transport (net transport)

Average movement of surface waters

north

90 degrees to right of wind in ... hemisphere

south

90 degrees to left of wind in .... hemisphere

Wind belts

Set water in motion

flow

Distribution of continents disrupts...

- friction

- gravity

- coriolis effect

What is flow influenced by?

high

Everywhere around the equator, the pressure is low bc of the....temperature of the oceans near it. (Air rises)

low

Everywhere around the poles, the pressure is high because of the ..... temperature of the oceans near it (Air sinks)

trade winds

Create ocean surface currents that move water from east to west

Prevailing westerlies

Move water in the opposite direction, creating a giant loop of water

Ocean surface currents

Will closely match the major wind belts of the world if there is no continents

Subtropical gyres

Large, circular loops of moving water

30 degrees latitude

5 of the subtropical gyres are centered around ....

4

They are bounded by ... currents depending on the hemisphere they are in

- Northern/Southern boundary currents

- Eastern boundary current

- Equatorial current

- Western boundary current

What are the 4 currents?

Piling up of water in middle of gyre

Coriolis effect causes convergence:

pulls

Gravity "..." water downhill

Forces

... nearly balance creating rotational flow

Ideal

Path around the hill of water in equilibrium

Actual

Slightly downslope due to friction

poles

Coriolis effect increases toward the ....

strongly

Eastward-flowing high latitude water turns toward the equator more ...

Western boundary

Fast, narrow, deep, large transport volume, move warm water from equator toward poles, gulf stream, kuroshio current, east australian current, brazil current, agulhas current (warm water)

Eastern boundary

Slow, wide, shallow, small transport volume, move cold water from poles toward equator, canary current, benguela current, california current, humboldt current, west australian current (cool water)

2/3

Wind belts transfer .... heat from tropics to the poles

1/3

Ocean currents transfer ... heat from tropics to the poles

temperature and humidity

Affect ... levels on land