Ocean CurrentsOcean Currents

The Reality of Sending a The Reality of Sending a Message in a BottleMessage in a Bottle

Ocean Current LayersOcean Current Layers

Surface Currents – upper 10% of the Surface Currents – upper 10% of the ocean; upper 400 mocean; upper 400 m

Pycnocline – the layer between Pycnocline – the layer between surface and deep waters; where a surface and deep waters; where a rapid change in temperature, salinity rapid change in temperature, salinity and density occurand density occur

Deep Current – lower 90% of the Deep Current – lower 90% of the oceanocean

Ocean Water PropertiesOcean Water Properties

How they impact ocean currentsHow they impact ocean currents•Temperature – remember heat Temperature – remember heat

rises!rises!•Salinity – remember salty water Salinity – remember salty water

sinks!sinks!•Density – a function of Density – a function of

temperature and salinitytemperature and salinity

Ocean Surface TemperaturesOcean Surface Temperatures

http://www.bigelow.org/shipmates/sstemp_lg.gifhttp://www.bigelow.org/shipmates/sstemp_lg.gif

Temperature vs. CurrentsTemperature vs. Currents

http://earth.usc.edu/~stott/Catalina/Oceans.html

Ocean Surface SalinitiesOcean Surface Salinities

http://www.bigelow.org/shipmates/salinity_lg.gifhttp://www.bigelow.org/shipmates/salinity_lg.gif

Ocean DensityOcean Density

http://www.windows.ucar.edu/tour/link=/earth/Water/density.html&edu=highhttp://www.windows.ucar.edu/tour/link=/earth/Water/density.html&edu=high

Primary Current ForcesPrimary Current Forces

These Start the Water MOVING:These Start the Water MOVING:•Solar HeatingSolar Heating•WindsWinds•GravityGravity•Coriolis Force/EffectCoriolis Force/Effect

Current Forces ExplainedCurrent Forces Explained

Sun/solar heatingSun/solar heating - - causes water to causes water to expand and moveexpand and move

WindsWinds - - push the water; winds push the water; winds blowing for 10 hrs across ocean will blowing for 10 hrs across ocean will cause the surface water to flow @ cause the surface water to flow @ ~2% wind speed; wind has the ~2% wind speed; wind has the greatest effect on surface currentsgreatest effect on surface currents

GravityGravity - pull water downhill or pile - pull water downhill or pile against the pressure gradient against the pressure gradient (high/low); influences tides(high/low); influences tides

WindsWinds

http://www-earth.usc.edu/~stott/Catalina/Oceans.htmlhttp://www-earth.usc.edu/~stott/Catalina/Oceans.html

Wind Driven Ocean CurrentsWind Driven Ocean Currents

http://www.bigelow.org/shipmates/hc_currents_lg.gifhttp://www.bigelow.org/shipmates/hc_currents_lg.gif

Current Influences (cont’d)Current Influences (cont’d) Coriolis effect/forceCoriolis effect/force - Force due to - Force due to

the Earth's rotation, capable of the Earth's rotation, capable of generating currents. It causes generating currents. It causes moving bodies to be deflected to the moving bodies to be deflected to the right in the Northern Hemisphere and right in the Northern Hemisphere and to the left in the Southern to the left in the Southern Hemisphere. The "force" is Hemisphere. The "force" is proportional to the speed and proportional to the speed and latitude of the moving object. It is latitude of the moving object. It is zero at the equator and maximum at zero at the equator and maximum at the polesthe poles

http://www.csc.noaa.gov/text/glossary.htmlhttp://www.csc.noaa.gov/text/glossary.html

causes the water to move around the mound of causes the water to move around the mound of waterwater

Surface CurrentsSurface Currents Surface current – with surface circulation Surface current – with surface circulation

is less dense and influenced by windsis less dense and influenced by winds1.1. Warm surface currents: wind and Earth’s Warm surface currents: wind and Earth’s

rotationrotation2.2. Cold surface currents: flow towards the Cold surface currents: flow towards the

equatorequator3.3. Upwelling current: cold, nutrient rich; result Upwelling current: cold, nutrient rich; result

of windof wind4.4. Western Boundary currents: warm & fastWestern Boundary currents: warm & fast5.5. Eastern Boundary currents: broad, slow, cool Eastern Boundary currents: broad, slow, cool

& shallow, associated with upwelling& shallow, associated with upwelling Ex: Ex: Gulf StreamGulf Stream = surface current that is = surface current that is

the upper 20% of the ocean, western the upper 20% of the ocean, western boundary currentboundary current

Deep CurrentsDeep Currents Deep water – cold, dense, salty; move by density Deep water – cold, dense, salty; move by density

forces and gravity; move slower than layers aboveforces and gravity; move slower than layers above• Thermohaline Circulation: is global ocean circulation. It is Thermohaline Circulation: is global ocean circulation. It is

driven by differences in the density of the sea water which is driven by differences in the density of the sea water which is controlled by temperature (thermal) and salinity (haline). In controlled by temperature (thermal) and salinity (haline). In the North Atlantic it transports warm and salty water to the the North Atlantic it transports warm and salty water to the North. There the water is cooled and sinks into the deep North. There the water is cooled and sinks into the deep ocean. This newly formed deep water is subsequently ocean. This newly formed deep water is subsequently exported southward. This slow (~0.1 m/s), but giant exported southward. This slow (~0.1 m/s), but giant circulation has a flow equal to about 100 Amazon Rivers. circulation has a flow equal to about 100 Amazon Rivers. Together with the Gulf Stream it contributes to the Together with the Gulf Stream it contributes to the comparatively warm sea surface temperature along the comparatively warm sea surface temperature along the coast of western Europe and to the relative mild European coast of western Europe and to the relative mild European winters. Once the water are in the deep, they remain there winters. Once the water are in the deep, they remain there for up to 1000 years. for up to 1000 years.

http://www.climate.unibe.ch/~christof/div/fact4thc.htmlhttp://www.climate.unibe.ch/~christof/div/fact4thc.html Ex: Ex: Global Conveyer BeltGlobal Conveyer Belt = deep current that is the = deep current that is the

lower 20% of the ocean; takes 1,000 years to lower 20% of the ocean; takes 1,000 years to complete the cyclecomplete the cycle

Global Conveyer BeltGlobal Conveyer Belt

Thermohaline circulation links the Earth's oceans. Cold, dense, salty water from the Thermohaline circulation links the Earth's oceans. Cold, dense, salty water from the North Atlantic sinks into the deep and drives the circulation like a giant plunger. North Atlantic sinks into the deep and drives the circulation like a giant plunger.

http://www.columbia.edu/cu/record/23/11/13.htmlhttp://www.columbia.edu/cu/record/23/11/13.htmlGraphic - Graphic - http://www.grida.no/climate/vital/32.htmhttp://www.grida.no/climate/vital/32.htm

Other CurrentsOther Currents

Gyres – large mounds of water; large Gyres – large mounds of water; large circular currents in the ocean basincircular currents in the ocean basin

Ex: Ex: North Atlantic GyreNorth Atlantic Gyre = consists of = consists of 4 separate currents – N. Equatorial, 4 separate currents – N. Equatorial, Gulf Stream, N. Atlantic Drift and Gulf Stream, N. Atlantic Drift and Canary CurrentsCanary Currents

Ocean Currents & Living ThingsOcean Currents & Living Things

Currents are important to marine life Currents are important to marine life as they help move food and nutrients as they help move food and nutrients making them available for making them available for photosynthesis, metabolic photosynthesis, metabolic requirements and or consumption.requirements and or consumption.