1. Chemical and Physical Features of Seawater and the World Ocean
“If there is magic on this planet, it is contained in water.”
Loren Eiseley
“Well, me don’t swim too tough so me don’t go in the water too deep.”
Bob Marley

2. What is Water ? Introduction – the stuff covers 70% of the Earth
Brainstorming activity
Chemical & Physical Properties of Water
Categorization activity
Defend your categories
If time permits… why the answer to life is 104.5º

3. Chemical & Physical Properties
Physical property – properties that describe a substance without changing the identity of the substance.
Physical change – change that does not result in the production of a new substance, only the appearance of the substance
Chemical property – properties that describe how a substance changes into a completely different substance
Chemical change – change that results in the production of another substance

4. Common Properties of Water
Physical Properties
Chemical Properties
Cohesion/Surface tension
Found in all three states on the earth
Universal Solvent – dissolves more substances than any other common liquid
Conduction of heat – highest of all liquids (except for mercury)
pH – water dissociates into anions (OH-) and cations (H+)
Latent heat of vaporization – highest of all common substances
Polarity – water has positive and negative ‘ends’
Latent heat of fusion – high for a molecule of its size (melting/freezing)
Hydrophobic effect
Heat capacity – highest of all common solids & liquids
Density – max at 4ºC for pure water
Viscosity –relatively low for a liquid
Latent heat of fusion – change of state from solid to liquid (melting/freezing)
Latent heat of vaporization – energy required to change substance into gas (boiling/evaporation)

5. References Castellano, A. (2006) “Victoria Beach”
Castro, P. & M.E. Huber (2005) Marine Biology, 5th ed. McGraw-Hill Higher Education, Boston, MA.
“Chemical Properties of Water” PlanetWater.au.com Retrieved on Feb 3, 2007 from
“floating water 5” (2006) wester
Lower, S. (2007) “H2O a gentle introduction to the structure of water.” Retrieved on Feb 3, 2007 from
Nybakken, J.W. & M.D. Bertness (2005) Marine Biology, An Ecological Approach, 6th ed. Pearson Education, Inc., San Francisco.
Perlman, H. (2006) “Water properties” Water Science for Schools. USGS. Retrieved on Feb 3, 2007 from
Petrucci, R.H. (1982) General Chemistry Principles and Modern Applications, Macmillan Publishing Co. Inc., New York.

6. The Water Molecule Two hydrogen atoms, one oxygen atom
H atoms form 105º angle
This angle produces an asymmetrical dipole. Slight (+) charge on the H atoms and slight (-) charge on the O atoms. O H
105º

7. O H
The Water Molecule
These slight charges cause the (+) H atoms of one water molecule to attract the (-) O atoms of other water molecules.
These weak bonds are called hydrogen bonds.
Water can hydrogen bond with other substances aside from itself. O H O H

8. Why does ice float? Density-Temperature Relationship
Background
Temperature is a measure of kinetic energy (KE). As KE decreases, hydrogen bonds stay formed and break less. Water molecules stay closer together until…
Explanation
As the temperature approaches 4ºC, less dense ice clusters begin to form in the liquid.
At 0ºC when all water molecules become locked in the rigid ice lattice, the hydrogen bonds actually hold molecules farther apart than at 4ºC. This creates spaces making the water less dense.

9. Why does ice float? Density-Temperature Relationship Graph

10. How can water bugs “stride” across water without breaking the surface
How can water bugs “stride” across water without breaking the surface? Surface tension and cohesion
The cohesion or mutual attraction of water molecules creates a flexible barrier on the surface of water.
This helps support aquatic insects such as water striders (Halobates sp.)

11. Why do fish not get electrocuted when lightning strikes the ocean
Why do fish not get electrocuted when lightning strikes the ocean? Conductivity
Explanation
Conductivity is a property that measures the ability of a substance to transmit heat, electricity, or sound.
Pure water is not a good conductor of electricity. Its conductivity is about 20 dS/m.
(Compare with silver – the highest conductivity with 63 x 106 S/m)
In addition, the electrical charge of lightning usually spreads instantaneously along the surface of the water from the location of the strike and to a lesser degree below the surface at the strike site. Fish in other areas are not affected.

12. Why do coastal areas have slower temperature changes than inland areas
Why do coastal areas have slower temperature changes than inland areas? Heat capacity
Background
Heat – energy of molecular motion
Water can absorb or give up heat by conduction (molecular exchange of heat) or convection (mixing)
Explanation
Water can hold heat longer and release heat more slowly than land.
Temperature differential between land and ocean will cause uneven heating of air masses which drive winds and moderate any drastic temperature changes.
Off-shore breeze
On-shore breeze

13. Why don’t fats and oils dissolve in water? Polarity
Fats and oils are nonpolar molecules.
These compounds do not have slight regions of charge like water does.
Therefore water molecules are not attracted to nonpolar molecules and actually can be repelled by them.
Basis for cell membranes and the water repellency of marine mammals and birds.

14. Why does water dissolve more substances than any other common liquid
Why does water dissolve more substances than any other common liquid? The Universal Solvent
Because water is polar, it dissolves most substances, especially other polar molecules and compounds composed of ions, atoms or molecules that carry an electrical charge.
These ionic compounds are often called salts.
NaCl (salt) most common dissolved salt in ocean. There are many others.
Seawater is a solution of these salts.
Salt crystal

15. Seawater Seawater is 96.5% water 3.5% dissolved compounds
Sources of salts and dissolved solids:
Erosion of rocks and soil
Solutes released from rivers
Breakdown of organisms
Condensation of rain from the atmosphere
Releases from hydrothermal vents
Seawater is
96.5% water
3.5% dissolved compounds

16. Salinity Total amount of dissolved salts in seawater.
Measured in parts per thousand (ppt)
Grams of salt left behind when 1000g of water evaporate
Average value 35 ppt or 35‰
Range from 0‰ near river mouths to 40% in the dead sea.
Globally, seawater salinity remains constant. Rule of constant proportions states that the percentage of various ions in seawater remains constant.

17. Surface Salinities of the Oceans

18. Dissolved compounds in seawater
Inorganic substances (salts, nutrients)
Dissolved gases
Organic compounds (fats, oils, vitamins, amino acids, proteins)
Nitrates and phosphates (usually in excess as pollution)
Pollution (DDT, PCBs, chlorinated hydrocarbons that are synthetic)

19. Dissolved Gases Primarily nitrogen, carbon dioxide, oxygen
N2 biologically inert.
CO2 needed for photosynthesis and pH buffering.
O2 required for respiration.
                                              
stories/s htm

20. Factors that Affect Salinity
Salinity increases due to…
freezing of seawater.
evaporation.
Salinity decreases due to…
melting of icebergs and sea ice.
precipitation.
run-off from rivers.

21. pH The amount of hydrogen ions in a substance is referred to as pH.
pH = (pondus hydrogeni or “power of hydrogen”
pH = -log10 [H+]
Scales ranges from 0 to 14.
Therefore, a pH of 14 means that the water is very alkaline (basic) while pH 1 means it is acidic. A pH of 7 is neutral.

22. Seawater pH
The carbonic acid – bicarbonate – carbonate system keeps seawater at a pH value between 7.5 and 8.4.
The oceans are an enormous “sink” for atmosphere CO2

24. The Carbon Buffering System
Seawater has an unusually large capacity to absorb CO2.
CO H2O  H2CO3 (carbonic acid)
H2CO3  H HCO3 – (bicarbonate ion)
HCO3 –  H CO32- (carbonate ion)

25. Ocean Acidification

27. Work Cited
Kreger, Chris. "Acid Mine Drainage: Alkalinity." Exploring the Environment: Water Quality Wheeling Jesuit University. 2 Oct 2008 < Lower, Stephen. "A gentle introduction to water and its structure." H2O Oct 2008 < "October 2006 Archives." [Weblog The Marine Electronics Weblog] Oct Panbo . 1 Oct 2008 < Water Conductivity Lenntech Water Treatment & Purification B.V.. 1 Oct 2008 < Woodruff, Steve W.. "Water & Weather." Los Angeles Pierce College Weather Station. 1 Oct 2008 <

28. The Salinity-Temperature-Depth Relationship in the World Oceans
Part One – Depth Profiles

29. Seawater – General Trends
Temperature and salinity determine the density of seawater.
Colder water is more dense; therefore, it sinks.
Saltier water is more dense; therefore, it sinks.
Which is more variable on the earth? Temperature or salinity?
Which would have a greater effect on the density of seawater? Temperature or salinity?

30. Global Sea Surface Temperature
This image shows the temperature of the ocean water at the surface. Measurements were taken from August 6-11, The temperature scale is in Celsius. Cold temperatures are shown in pink to purple, moderate temperatures in aqua to green and warm temperatures in yellow to red.
This particular data set was taken by the NOAA-16 satellite. NOAA-16 is part of the TIROS series of polar-orbiting, environmental satellites. Image courtesy of The National Oceanic and Atmospheric Administration (NOAA)

31. Surface Salinities of the Oceans

32. Biogeographical Zones
Based on sea surface temperature, four major biogeographical zones emerge:
Polar
Cold temperate
Warm temperate (subtropical)
Tropical (equatorial)

33. Global Sea Surface Salinity
Where are salinities the greatest? The least?
Why might salinities be lower around Scandanavia and the Arctic Circle?
Are there any trends in the global sea surface salinity?

34. Depth Profiles
Increasing variable 
Graph that shows a specific ocean variable plotted against depth.
Usually drawn “upside down” with increasing depth on the Y-axis and the variable across a top X-axis so that the graph represents an “ocean profile.”
For any specific location, a depth profile can be understood as a vertical ‘snapshot’ of a column of water or water column.
 Increasing depth (m)

35. Depth Profiles Which one represents temperature? salinity?
Why these patterns? What contributes to them?
© National Oceanic and Atmospheric Association (NOAA)

36. Depth Profiles How do temperature and salinity contribute to density?
© National Oceanic and Atmospheric Association (NOAA)

37. Salinity-Temperature-Depth Profile
Thermocline – the depth zone of the most rapid temperature decline
Halocline – the depth zone of the most rapid salinity change
Pycnocline – the depth zone of rapid density change
What contributes to the increasing density of water at depth? Pressures increase thus causing an increase density.
© Lamont-Doherty Earth Observatory

38. Other Profiles
What might the depth profile look like for the following variables?
Dissolved oxygen
Transparency of light
Pressure

39. Light Transparency
As light enters our atmosphere it is scattered. Only 65% reaches the Earth.
The sea surface reflects more light into space.
As light penetrates, seawater absorbs red, orange and purple light.
Blue and green light penetrate deeper. 10% of blue light makes it to 100m, 1% of green light.
This diagram offers a basic illustration of the depth at which different colors of light penetrate ocean waters. Water absorbs warm colors like reds and oranges (known as long wavelength light) and scatters the cooler colors (known as short wavelength light). Image courtesy of Kyle Carothers, NOAA-OE

40. Light Transparency
Sunlight is composed of colors with different wavelengths
ROY G BIV
Longer wavelengths (red/orange) have lower energy than shorter wavelengths (violet/indigo)
E = hc/λ
where E = energy, h = Planck’s constant, c = speed of light, and λ = wavelength

41. Light Transparency General trends:
Longer wavelengths are absorbed at the surface. Shorter wavelengths can penetrate to depths of approximately 1000m in clearest waters.
Extent of light attenuation defines photic zone
Euphotic zone – surface to approx. 200m max. – sufficient sunlight for photosynthesis
Disphotic zone – variable m, usually m – insufficient sunlight for photosynthesis (less than 1% of sunlight penetrates)
Aphotic zone – below disphotic zone – no light
Pattern can vary with suspended/dissolved substances.
More suspended/dissolved substances 
less light penetration

42. Why do red fish disappear in deep waters?

43. Dissolved Oxygen Oxygen low solubility in seawater
only 5.4 ml/L at 35 ppt
and 20ºC (8 ml/L at 0ºC)
more soluble in colder
water
less soluble in saltier
oxygen minimum zone –
usually 500 to 1000m depth
Oxygen (ml per L)
Depth (m)
Change in dissolved oxygen with depth in eastern tropical Pacific Ocean (red line) and the tropical Atlantic Ocean (orange line). Modified from Oceanography: An Introduction, D.E. Ingmanson & W.J. Wallace, ©1973.

44. Dissolved Oxygen Oxygen Minimum Zone
depth in open ocean waters at which oxygen concentration approaches zero
usually between 200 and 1000m
Why there?
Inputs of O2 to the oceans
wave action, storms, surface mixing, photosynthesis
Depletion of O2 from the oceans
respiration, decomposition
At this depth, consumption of O2 by organisms for respiration consumes all of the oxygen, without suitable replacement by photosynthesis or surface mixing.

45. Pressure
Surface
1 atmosphere of air (1kg/cm3 or 14.7 lbs./in.2 or ≈ 1 bar) pushing down at sea level
With Depth
water more dense than air
each 10m of depth increases pressure by an additional atmosphere
linear relationship
What is significance for marine organisms?
What is significance for marine research and exploration?
Pressure (atm)
Depth (m)

47. References
Castro, Peter, and Michael E. Huber. Marine Biology. 5th. Boston: McGraw Hill Higher Education, 2005.
Davidson, M.A., Abramowitz, M., Olympus America, Inc., and Florida State University, (2003 Aug 1). Optical Microscopy Primer. Retrieved February 21, 2007, from Molecular Expressions Web site:
Enchanted Learning.com, (2007). Twilight Ocean (Disphotic) Zone Animal Printouts. Retrieved February 21, 2007, from Biomes-Habitats Web site:
Naik, Naomi. "Plot the Temperature Profile." Climate Kids Corner. Lamont-Doherty Earth Observatory. 19 Feb 2007
National Oceanic and Atmospheric Association (NOAA) (2007 Feb 12). Deep Light. Retrieved February 21, 2007, from Ocean Explorer Web site:
National Oceanic and Atmospheric Association (NOAA). "NOAA/NESDIS Edge Image Display." Windows to the Universe LUniversity Corporation for Atmospheric Research (UCAR). 19 Feb 2007 <
Nybakken, James W., and Mark D. Bertness. Marine Biology: An Ecological Approach. 6th. San Francisco: Pearson Education, Inc., 2005.
photic zone. (2007). In Encyclopædia Britannica. Retrieved February 20, 2007, from Encyclopædia Britannica Online:

48. Quiz Thursday Salinity-Temperature-Depth Relationships Depth Profiles
Thermocline
Halocline
Pycnocline
Light DO
Pressure
Stratification (three layers)
Stability
Overturn
Global Thermohaline Circulation

49. The Salinity-Temperature-Depth Relationship in the World Oceans
Part Two – The Three-Layered Ocean and the Great Conveyor Belt

50. The oceans are three-dimensional
Horizontally from north to south/ east to west (geographic changes)
Vertically – depth
Which dimension has the biggest influence on living conditions?
DEPTH – this third dimension is controlled by density
What two variables have the greatest effect on density?
TEMPERATURE & SALINITY

51. Stratification
Less dense water (warmer/less salty/or both) floats at the surface
Denser water (colder/saltier/or both) tends to sink
Creates stratification
essentially causes layers to form in the ocean.
imparts vertical stability to the ocean

52. The Three-Layered Ocean
Surface layer
surface to approx. 200m
also called the mixed layer, because it is mixed by wind, waves, currents, & storms
may be the only layer found in shallow coastal waters over the continental shelf
seasonal thermoclines may form here
Intermediate layer
bottom of surface layer to approx. 1,500m
main thermocline can be found here
Deep & bottom layers
below 1,500m
uniformly cold (less than 4ºC)
Deep
& bottom layers
Surface layer
200
Intermediate layer
1500
Depth (m)
5000

53. Stability
Stability – likelihood that a water column in the ocean will remain stratified.
High stability
large density difference between deep and shallow water
keeps water column stratified
Low stability
slight density difference between deep and shallow water
relatively easy to mix the two layers

54. Overturn Instability (unstable)
surface layer becomes more dense than deep layer
surface water sinks resulting in downwelling
process known as overturn
What might a depth profile look like when downwelling occurs?
Straight Line Profiles
What climate conditions might cause downwelling?
Occurs in temperate/polar regions in winter when surface water cools
once water sinks, its temperature and salinity do not change since the processes that change them are surface phenomena
becomes a “signature” for the water mass
oceanographers can follow these water masses as they circulate throughout the oceans

55. Global Thermohaline Circulation
Gets its name from fact that it is driven by density differences in water masses which are in turn caused by temperature and salinity differences.
It acts as a giant conveyor belt.
Importance:
Extends throughout ocean depths
Regulates the Earth’s climate
Transports heat and nutrients throughout globe
Chemically mixes the world’s oceans
Brings oxygen-rich surface water to the deep sea

57. Great Ocean Conveyor – A Critical Look
IPCC – Intergovernmental Panel on Climate Change

58. The Great Ocean Conveyor
Water sinks…
Norwegian Sea (North Atlantic Deep Water – NADW)
Forms due to heat loss and high salinity
Labrador Sea
Deep convection
Weddell Sea (Antarctic Bottom Water – ABW) – densest
Forms mostly because of low temperature
…and returns to surface.
Indian Ocean
North Pacific Ocean
Both due to warming by equatorial temperatures and the parting of ocean water by equatorial tradewinds.
An oceanic roundabout. As warm ocean currents in the subpolar gyre gradually cool, they warm Europe and may trigger seesaws in climate (McCartney et al., 1996, Oceanus, 39, 19-23)
Main Currents in the North Atlantic
Moves at 4 in/sec
Takes 1,000 years to complete the circulation

59. The thermohaline circulation "conveyor belt"
The thermohaline circulation "conveyor belt". Purple arrows indicate cold, deep ocean currents. Red arrows show shallow, warm water circulation patterns. Credit: Image courtesy CLIVAR (after W. Broecker, modified by E. Maier-Reimer)

60. Thermohaline Circulation in 3D!

61. Role of THC in Climate Change
Brings warmth from the tropics to higher latitudes
Particularly in the North Atlantic
Has “shut off” in recent geologic past
(12,800 years ago - the Younger Dryas)
Evidence
Oxygen isotope and carbon dioxide isotopes in ice cores
Foraminifera and glacial deposits in sediment cores
Low latitude glaciology
LDEO - Abrupt Climate Change - Younger Dryas Explanation
SATELLITES SEE GULF STREAM WARM WATERS This is a NASA satellite image of the warm waters of the Gulf Stream running up the U.S. eastern seaboard. The Gulf Stream shows up as a winding rope of orange and yellow (indicating warm waters) against the cooler green and blue waters. Credit: MODIS Ocean Group NASA/GSFC SST product by U. Miami

62. References
Castro, Peter, & Michael E. Huber. Marine Biology. 5th. New York: The McGraw-Hill Companies, Inc., Hoffman, Jennifer. Science 101: Ocean Science. Irvington, NY: Harper Collins Publishers, Inc., Kunzig, Robert. "In deep water." Discover Dec 1996: Naik, Naomi. "2: What scientific evidence do we have that abrupt climate change has happened before?." Abrupt Climate Change Lamont Doherty Earth Observatory of Columbia University. 3 Mar 2008 < Russell, Randy. "Transfer and Storage of Heat in the Oceans." Windows to the Universe. 6 June The Regents of the University of Michigan. 3 Mar <