Water Chemistry Ocean Currents Wind Gyres Upwelling/Downwelling Waves Tides
Has semi-charged nature Good solvent Combines with other ions (Na +, Cl -, Ca +2, Mg -2, H +, HCO 3 -, CO 3 -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 Evaporation Ice formation Rain fall F.W. input from rivers (etc)
Ionic Composition of major ionic components of seawater is nearly constant: Cl - SO 4 - Na + Marcet’s Principle Mg -2 Ca +2 etc. Average time a constituent stays in sea water (residence time) is very high relative 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 C Open Ocean: -1.9 – 27 o C Deep (>1000 m) tropical oceans : 2-4 o C Coryphaenoides acrolepisCoryphaenoides acrolepis, Rattail fish; Monterey Canyon, CA
pH Open water average approx. 8
Relevant Chemistry CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - HCO 3 - H + + CO 3 -2 Ca +2 + CO 3 -2 CaCO 3 Carbon dioxide & Water Carbonic acid Bicarbonate ion Carbonate ion Calcification Calcium carbonate; foundation of Limestone; corals etc. Calcium (recall photosynthesis & cellular respiration)
Levinton 1982 (23-25 o C for coral REEFS) Calcification w/r/t temperature http://www.springerlink.com/content/l634 21782p60jh88/http://www.springerlink.com/content/l634 21782p60jh88/ (15-19 o C is threshold) Optimum rate of calcification in warm water
Ocean Currents Coriolis Effect: Turntable visualization Equator rotates at about 1700 km/hr 30 o N, 30 o S Latitude rotates at about1500 km/hr 60 o N, 60 o S Latitude rotates at about 800 km/hr Coriolis EffectSine (latitude) CE 0 0.0 30 0.5 60 0.86 90 1.0
Wind Wind 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/oce an-in-motion.htm
Gyres Caused by Coriolis Effect: Pushes water to center of gyre. Sea surface can be 2m higher 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 NorthSouth LowHIghHigh Warm moist air rising ITCZ Subtropical High Northeast Trade Winds Southeast Trade Winds DoldrumsHorse latitudes Hadley Cell Tropical Rainforests Deserts Cold dry air descending
ITCZ Tropic of Cancer 23.5 o N latitude Trade winds Westerlies
North Pole South Pole Intertropical Convergence Zone – low pressure Subtropical High Pressure Polar Front – low 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 oneλto pass a point (sec/crest) H= height H
Frequency (f)= crests/sec Period = 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” from ocean 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/eart hsunmoon.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 basin shape (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 High High High High High 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?