Physical Oceanography Exam 2

Ocean Currents - Description 

• Objective

3D picture of the movement of ocean water 

Ocean Currents - Description 

• Things to think about 

• Timer interval 

• What can we measure directly? 

Ocean Currents - Description 

• Problems

• Constantly change 

• Limited number of test instruments and personnel

• Cannot get simultaneous image of entire ocean 

Measuring Currents 

• Lagrangian

Move with current 

Measuring Currents

• Eulerian

Stationary

Examples of Lagrangian devices 

• Displacement of a ship 

• Drift bottles (some are tracked, some aren’t)

• ARGO (measures temp and salinity, 4,162 floats)

• Tracking spills (Oil spills, dye studies, cargo spills, natural disasters, garbage patch, wrecks)

• Research submarine (1969 - Ben Franklin

Disadvantages of Lagrangian devices

• Ship/satellite time may be required 

• Wind a factor 

• Long-term studies

• Monitoring and recovery 

• If not monitored - don’t know what it did between deployment and recovery 

Eulerian devices

• Measurment at a single depth (current meter)

• Measurment at multiple depths - ADCP (Acoustic Doppler Current Profiler)

Describing Currents

• Direction 

• Wind direction - Call it the direction it comes from (North wind coming from North)

• Current Direction - Call it the direction it is moving (North current going North)

Describing Currents

• Discharge 

• Rate or volume of water per unit time 

• Sverdrup = 1,000,000 cubic meters per second 

Describing Currents

• Speed

• Can use many different measurements 

• Knots (old measurement to measure ship _____) 

Features of all surface currents

• Horizontal 

• Driven by wind

• Slow - current is 3% of the wind speed

• Shallow 

Role of currents in heat budget

• Warm water goes from equator to the poles

• Cold water from the poles goes to the equator 

• Winds 2/3, currents 1/3 of head distribution 

Noth Atlantic surface currents 

1. N. Equator current 

2. N. Atlantic current

3. Gulf stream (western boundary)

4. Canary current (easter boundary)

5. Equatorial counter current

6. Norway current

7. Labrador current

South Atlantic surface currents

1. S. Equatorial current

2. Westwind drift

3. Brazil current (western boundary)

4. Benguela current (eastern current)

5. Equatorial counter current

Western

• Warm 

• Narrow

• Fast 

• Deep

Easter

• Cold

• Wide

• Slow

• Shallow

Conditions in center of North Atlantic Gyre

• Climate

• Salinity

• Water temperature

• Nutrient content

• Dissolved oxygen

Sargasso Sea

• No shoreline

• Biological “desert”

• Sargassum

• Water color

• North Atlantic Garbage Patch

Importance of Gulf Stream

• Earth’s heat budget

• Climate on land

• Weather - hurricanes

• Sailors

• Power generation

Dead Zones

• Natural dead zones'

• Made dead zones

• Dead zones getting bigger

• Dead Zone: A place with little to no oxygen

• Seasonal issue

Gulf of Mexico hypoxic zone

• Huge portion of the US drains into the Gulf of Mexico

• Drains from the Mississippi river

• Happens in the spring

• Buffer zones decrease nutrient drainage and yield better crops  

Pacific Ocean

1. N. equatorial current 

2. N. Pacific current

3. Kuroshio current “black tide” 

4. California current 

5. Alaska current 

6. Oyashio current 

7. Equatorial counter current 

8. S. equatorial current 

9. West wind drift 

10. East Australian current 

11. Humbold current / Peru current (collapses when El Nino occurs) 

Indian Ocean

1. N Equatorial current

2. Equatorial counter current 

3. S. Equatorial current 

4. West wind drift 

5. Agulahs current

6. W. Australian current 

Around the South Pole

• Ross G

• Weddell G 

• Un-named G 

• Polar current 

Currents around the Arttic Ocean

• 3 Beufort Gyre

• 6 North Atlantic Current

• (cooked)

Currents in Seas

• Type 1

Going in and out of marginal sea

Currents in Seas

• Type 2 

Surface flow in, deep water coming out 

Currents in Seas

• Type 3

Surface flow out only, well circulated

Currents in Seas

• Type 4

Surface flow out only, stagnant 

Features of all deep-water currents 

• Formed by vertical movement of water downwards

• General pattern of flow 

• Slow speed 

• Coriolis effect 

• Earth’s heat budget (5,100 yrs to get from pole to pole) 

Measurment devices for deep-sea currents

• Drogues (flow with weight) 

• Ben Franklin (submarine)

• Man made material (-H³ - Tritium) 

• Transient Tracers in the Ocean (TTO) 

• Swallow Floats - ARGO

• ADCP 

Thermohaline circulation

• Broecker (coined the term global warming)

• North Atlantic Deep-water (NADW) 

• Circumpolar Deep-water (CDW) 

• Antarctic Bottom water (AVBW) 

• Temp. constant - no sunlight 

• Salinity constant - no precipitation, evaporation, or land runoff 

• Movement driven by bottom topography 

Atlantic Ocean (DEEP)

• Surface waters - North Atlantic Central Water, South Atlantic Central Water. 

• Intermediate waters - Antarctic Intermediate Water, Mediterranean Intermediate Water 

• Deep waters - North Atlantic Deep Water, Antarctic Bottom Water 

Cromwell Current

• Pacific at equator

• 30,000,000 cm³ per second - 1.5 m per second

• 13,000 km long, 300 km wide

View photo

Nonrenewable

Energy from material that takes a long period of time to replace

Renewable

Energy from material that can be replaced in a short period of time

General principles (energy)

• Need it to be dependable and of enough energy to get net energy

• Fan-like turbine

• Need to anchor to the bottom

• Need to be well below the surface

Advantages

• Continuous source of energy

• Inexpensive to run

• Doesn’t use valuable coastal land

• Not an eye sore

• Should be pollution free

• Portable

Disadvantages

• Navigational hazard for submarines

• Interaction with marine life

• Storm damage

• Corrosion of metal parts '

• Mooring

• Cost

• Environmental degradation

Steps in considering

• High energy current

• Energy input vs output 

• Consistency of energy 

• Impacts on organisms 

• Impacts on water quality 

• Cost of Maintenace