deep ocean circulation “other” kind of ocean currents •deep currents –affect deep water...

Download Deep Ocean Circulation  “Other” kind of Ocean currents •Deep currents –Affect deep water below pycnocline (90% of ocean water!) –Driven by density

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  • Deep Ocean CirculationDeep Ocean Circulation

  • Recall: Recall:

    Surface currentsSurface currents Affect surface water above the main Affect surface water above the main

    thermoclinethermocline (

  • Surface

    Deep

    Recall: Recall:

  • The Other kind of Ocean currentsThe Other kind of Ocean currents

    Deep currentsDeep currents Affect deep water below pycnocline Affect deep water below pycnocline

    (90% of ocean water!)(90% of ocean water!) Driven by density differencesDriven by density differences Larger and Larger and slowerslower (way.. Way slower) (way.. Way slower)

    than surface currentsthan surface currents Critical to overall longCritical to overall long--term circulation term circulation

    of ocean of ocean Balance of HEAT Balance of HEAT

    TRANSPORT..(climate..) TRANSPORT..(climate..)

  • Deep currentsDeep currents

    DensityDensity--driven driven Factors affecting density of water:Factors affecting density of water:

    Temperature (most important factor)Temperature (most important factor) SalinitySalinity

    Thus, THERMOHALINE CirculationThus, THERMOHALINE Circulation

    Two ProcessesTwo Processes Deep water Deep water formation formation (Vertical)(Vertical)

    Surface water becomes dense Surface water becomes dense --> sinks> sinks Deep water Deep water movementmovement (Horizontal)(Horizontal)

    Slow, along constant density strataSlow, along constant density strata

  • Deep ocean circulation:Also called thermo-haline circulation

    Temperature (T) Salinity (S)

    Seawater Density depends on both T and S

  • Annual Mean Precipitation Rate (Kg/m2/day)

    Atlantic -Excess Evaporation

    Indo-Pacific -Excess Rain

  • AnnualSea Surface Temperature

    AnnualSea Surface Salinity

  • So where does ocean deep water actually form?

    How would you predict?

  • KEY: Gulf Stream Current

    Carries Salty and Warm

    water to high latitude North

    Atlantic

    Gulf streamGulf stream

  • *

    ICELAND SEA

    Northern cold water deeps: North Atlantic Deep Water (NADW) formation

    Is the main source of deep water to entire world ocean

    *

    LABRADOR SEA

    NADW

  • One other place..

  • *WEDDELL SEA

    Antarctic Bottom Water Formation

  • ANTARCTIC BOTTOM WATER FORMATIONWEDDELL SEA

    Continental Shelf

    Slope

    0 m

    250 m

    Antarctica

    Shelf water becomes salty and dense

    ABW

    Sea ice forms in winter

    Freshwater used to form sea ice

    Open ocean water is fresher and less dense

  • Atlantic Ocean Cross SectionN S

  • Deep water massesDeep water masses

  • SummarySummary

    Two main sources of Deep WaterTwo main sources of Deep Water North Atlantic Deep WaterNorth Atlantic Deep Water

    Salty surface water cools as it reaches Salty surface water cools as it reaches high latitudeshigh latitudes

    Antarctic Bottom WaterAntarctic Bottom WaterCold water becomes salty as sea ice Cold water becomes salty as sea ice

    forms on continental shelvesforms on continental shelves

    NO SOURCES in North PacificNO SOURCES in North Pacific Too freshToo fresh

  • Main Paradigm: the Global Conveyer Belt

  • Global Ocean Conveyor BeltGlobal Ocean Conveyor Beltrepresents net ocean circulationrepresents net ocean circulation

  • Global Circulation (Net Flow)Global Circulation (Net Flow) NADW forms, and flows southNADW forms, and flows south joins the Antarctic Circumpolar Currentjoins the Antarctic Circumpolar Current flows north into Indian flows north into Indian OcOc. then Pacific . then Pacific

    OcOc.. returns to surface in Upwelling regions returns to surface in Upwelling regions

    (spots all over the globe)(spots all over the globe)

  • Global Circulation (Net Flow)Global Circulation (Net Flow) Surface water flows from Pacific Surface water flows from Pacific

    through Indonesiathrough Indonesia through Indian Oceanthrough Indian Ocean around tip of Africa and up to tropical around tip of Africa and up to tropical

    AtlanticAtlantic Gulf Stream carries water to N Atlantic Gulf Stream carries water to N Atlantic

    to start journey againto start journey again

  • Deep Cold Ocean

    Surface Ocean

    Global Conveyor BeltGlobal Conveyor Belttotal turnover time of ocean ~ 1000 yearstotal turnover time of ocean ~ 1000 years

    Deep Cold Oceanresidence time = 1000 years

    Surface Oceanresidence time = 100 years

    DeepWaterFormation

    Residence time is the average amount of time a substance (in this case water) spends in a reservoir

    Upwelling

  • How we know this?How we know this?

  • Slight Slight SequeSeque

  • How old is deep water? How old is deep water?

  • EXTREME deep sea water! EXTREME deep sea water!

  • Natural Energy Laboratory near Kona Natural Energy Laboratory near Kona Hawaii Hawaii

    Pipelines 10 to 600 and 1000 meters, in central N Pacific ocean gyre-

  • What does old water even What does old water even mean? mean?

  • But how would you know But how would you know How old is water? How old is water?

    Deepwater formed at surfaceDeepwater formed at surface NADW and AABWNADW and AABW

    In equilibrium w/atm at surfaceIn equilibrium w/atm at surface

    Background fact:Background fact: CO2 atm >> oceanCO2 atm >> ocean

    CO2 most soluble gas in water CO2 most soluble gas in water

    Once deepwater sinks, isolatedOnce deepwater sinks, isolated CO2 is isolated too!CO2 is isolated too!

  • How old is deep water? How old is deep water?

  • Hows it done?Hows it done?

    Isolate CO2 from seawaterIsolate CO2 from seawater Some chemistry:Some chemistry:

    Inorganic carbon in the oceanInorganic carbon in the oceanHH22O + COO + CO22 > H> H22COCO33 HCO HCO33-- + H+ H++ CO CO33== + H+ H++

    Acidify

  • Hows it done?Hows it done?

    Carbon (awesome atom)Carbon (awesome atom) 1212C major isotopeC major isotope 1313C stable isotopeC stable isotope

    ~1% of all C~1% of all C 1414C radioisotopeC radioisotope

    0.0000000001% (part per trillion)0.0000000001% (part per trillion)Undergoes constant radioactive decayUndergoes constant radioactive decay

    HalfHalf--life of 5730 yrslife of 5730 yrs

  • Hows it done?Hows it done?

    Measure radiocarbon at startMeasure radiocarbon at start Measure radiocarbon at endMeasure radiocarbon at end

    Difference due to decay (gives time)Difference due to decay (gives time) Calculate how long it tookCalculate how long it took

  • Into the labInto the lab

    Isolate COIsolate CO22 (and anything else of interest)(and anything else of interest)

    Bring to your neighborhood Bring to your neighborhood Linear Accelerator Mass SpectrometerLinear Accelerator Mass Spectrometer

  • 1414CC-- (Radiocarbon): (Radiocarbon): CompoundCompound--Specific measurementsSpecific measurements--

    Lawrence Livermore, CAMS

  • Start (Youngest)

    EndEnd(Oldest)(Oldest)

    RESULTRESULT

  • Sound like fun?Sound like fun?

  • ENDEND

    THE CLIMATE LINK

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