water chemistry ocean currents wind gyres upwelling/ downwelling waves tides

WaterChemistryOcean CurrentsWindGyresUpwelling/DownwellingWavesTides

Has semi-charged natureGood solventCombines with other ions (Na+, Cl-, Ca+2, Mg-2,

H+ , HCO3-, CO3

-2 High specific heat (long time to heat up, long time to cool down)

Sea Water: Salinity related to dissolved salts, not just NaCl. Measured optically (refractometer) refraction salinity

chemically (chlorinity: just Cl- ) electrically (conductivity; more accurate than chlorinity)

Typical units= ppt= parts per thousand=gm dissolved salts /kg sea water Open ocean water ranges from 33-38 0/00

Water

Salinity

EvaporationIce formation

Rain fallF.W. input from rivers (etc)

Ionic Composition of major ionic components of seawater is nearly constant:Cl-

SO4-

Na+ Marcet’s PrincipleMg-2

Ca+2

etc.

Average time a constituent stays in sea water (residence time) is very highrelative to the average time to evenly mix the constituent in the ocean.

This is true for the open ocean, but varies as one gets closer to a coast.

Bahama Bank; 40 ppt

Salinity varies with Latitude

Temperature

Total Range: -1.9 – 40 o COpen Ocean: -1.9 – 27 o C

Deep (>1000 m) tropical oceans : 2-4 oC

Coryphaenoides acrolepis,

Rattail fish; MontereyCanyon, CA

pH Open water average approx. 8

Relevant Chemistry

CO2 + H2O H2CO3

H2CO3H+ + HCO3

-

HCO3- H+ + CO3

-2

Ca+2 + CO3-2 CaCO3

Carbon dioxide & Water Carbonic acid

Bicarbonate ion

Carbonate ion

Calcification

Calcium carbonate; foundation of Limestone; corals etc.

Calcium

(recall photosynthesis & cellular respiration)

Levinton 1982 (23-25oC for coral REEFS)

Calcification w/r/t temperature

http://www.springerlink.com/content/l63421782p60jh88/ (15-19oC is threshold)

Optimum rate of calcification in warm water

Ocean Currents

Coriolis Effect: Turntable visualizationEquator rotates at about 1700 km/hr

30oN, 30oS Latitude rotates at about1500 km/hr

60oN, 60oS Latitude rotates at about 800 km/hr

Coriolis Effect Sine (latitude)

CE

0 0.030 0.560 0.8690 1.0

WindWind drags sheets of water along the surface.

Velocity of the surface is 0.02 Velocity of wind (rule of thumb)

Surface sheet pulls on “sheets” below it, to a lesser and lesser extent

Wind effects can be detected down to 100 m

Stoke’s Drift: the wave-generated movement of a particle suspended in water

Wind

100 m

1. Surface water is deflected 45 deg. from direction of the wind due to Coriolis Effect

2. Surface water drags layer below it in the same direction, but at a slower speed. The slower speed shortens the length of the vector ( ), the Coriolis Effect deflects the direction of the vector.

Surface layer

100-150 m

At depth, water can move in opposite direction to the wind !!!

Wind

This model is known as the Ekman spiral, named for the Swedish physicist V Walfrid Ekman (1874-1954) who first described it mathematically in 1905. Ekman based his model on observations made by the Norwegian explorer Fridtjof Nansen (1861-1930).

http://oceanmotion.org/html/background/ocean-in-motion.htm

Langmuir Circulation

Gyres

Caused by Coriolis Effect: Pushes water to center of gyre. Sea surface can be 2mhigher in center of gyre than on periphery.

2m

Water flows down slope of lens= gravity flow

Geostrophic flow= balance between Coriolis flow to center and gravity flow to periphery

Can concentrate floatable garbage

“Earth”, “Twist; twisted cord”

Where does it rain the most?

Where the sun shines the most!

TropopauseHeight

North South

LowHIgh High

Warm moist air rising

ITCZSubtropical High Subtropical High

Northeast Trade Winds

Southeast Trade Winds

Doldrums Horse latitudesHorse latitudes

Hadley Cell Hadley Cell

Tropical Rainforests Deserts Deserts

Cold dry air descending

ITCZ

Tropic ofCancer

23.5 o

N latitudeTrade winds

Westerlies

North Pole

South Pole

Intertropical Convergence Zone – low pressure

Subtropical High Pressure

Subtropical High Pressure

Polar Front – low pressure

Polar Front – low pressure

Polar High Pressure

Polar High Pressure

Polar easterlies

Surface westerlies

Northeast trade winds

Southeast trade winds

Surface westerlies

Polar easterlies

-

45

60

23.5

0

90

30: Deserts

Upwelling

Density Gradient

Downwelling

Waves

λ

Direction of movement

T= period; time it takes for one λ to pass a point (sec/crest)

H= height

H

Frequency (f)= crests/secPeriod = sec/crest = ( 1/f)

Velocity = M/sec= wavelength/period=λ/T

Substituting: Velocity = λ/1/f or

Velocity = λf

Waves move ashore at V=λf

The waves reach shallower water and the rotating circles of water begin hitting the bottom.The bottom slows down relative to the surface and λ gets smaller. The “frequency push” fromocean remains constant, but there is now resistance from the bottom. …..Leads to Refraction.

Since λ DECLINES and f stays at least the same…….V must decline V=λf

Typical ocean waves can travel at approx 55.8 mph (90 km/hr)Tsunami waves travel at 589 mph (950 km/hr)

Refraction: Change(∆) in direction of a wave at a boundary between two media.

Depth change acts like a media change

Tides

The moon orbits the earth 50 min slower than the earth rotates around it’s axis

View from North

Sun, Earth, Moon

http://library.thinkquest.org/29033/begin/earthsunmoon.htm

Moon rotates around earth every 27.32 days

It orbits between 28.5 N Lat. and 28.5 S Lat.

The moon rises about 50 min. later each day

12 12:50 1:40 2:30

Thursday Wednesday Tuesday

Monday

At midnight

Do student demo

Gravitational Pull

Centrifugal Force

Timing of tide is based on orbital expectations of Sun & Moon

Transit time of tidal bulge is modified by ocean depth and basinshape (morphology)

Shallow, narrow basins SLOW the tide.

Therefore,

Timing can be different compared to expectations.

Eg. Bay of Fundy (NB, NS, Canada, Gulf of California, Bristol Channel (UK)

noon midnight noon noon midnight noon

High High High High High

Low Low Low

Semidiurnal Mixed Diurnal“partial daily” “daily”

http://www.pol.ac.uk/ntslf/pdf/Tortola_2010_+0400.pdf

Tide Predictions found at:

Questions

How do we incorporate this into our research?