The Oceans (OCEA ≠ 01)

Winter, 2003

Lecture on Seawater

Slide # 1 Atomic structure (Fig 5-1)

Atoms are the building blocks of all matter

Slide # 2 The Table of ≥Elemental Personality≤

The GOAL: To Attain a Full shell:

Contentment, Nirvana

≥Nobility≤, (Unreactive)

Slide # 3 Water - dipolar molecule (Fig 5-2)
Has electrical POLARITY

Covalent bonds between atoms are due to sharing electrons

Slide # 4 Polarity allows for Hydrogen bonds (Fig 5-3)

Slide #5 Hydrogen bonds cause:

Surface tension, Capillary action, Cohesion (beading)

Slide #6 Polarity results in Dissolving Power!! (Fig 5-4)

Ion = charged atom or molecule

Cation = pos. charged ion

Anion = neg. charged ion

Slide #7 Hydration - water molecules surround ions

Slide #8 Thermal Properties of Water

Heat = total kinetic (moving) energy of molecules

Calorie : amount of heat required to raise 1 gram of water by 1 öC

Temperature = direct measure of kinetic energy of molecules

Degrees Fahrenheit (öF) or Degrees Centigrade (öC)

Slide #9 Water has high heat capacity

Takes a lot of energy to get water to change its temperature.

Water can åholdπ a lot of energy

It slowly heats up or cools down

It keeps åsystemsπ from dramatically changing.

Slide #10 Example of ocean influence on seasonal temperature range (Fig 5-6)

Slide #11 Water in the 3 states or phases (Fig5-5)

Temperature at which ice melts= melting point

Temperature at which ice freezes = freezing point

Temperature at which water boils = boiling point

Temperature at which vapor forms water = condensation point

Slide #12 Phase changes require large amounts of heat (Fig 5-8)

Latent (hidden) heat = energy that is either absorbed or released as water changes state

Melting: latent heat required to break intermolecular bonds in ice

Evaporation: latent heat required to break hydrogen bonds to form gas

Condensation: latent heat is released when gas condenses

Freezing: latent heat is released when water freezes

Slide #13 Latent heat used for phase changes, not for temperature changes (Fig 5-7)

Slide #14 Principles of heat transfer (Fig 5-10)

Slide #15 Evaporation occurs at low latitudes (lots of energy from the sun)
Water transported in atmosphere to higher latitudes (Fig 5-9)

Slide #16 Water Content of Atmosphere reflect where evaporated water is advected by atmospheric circulation

Slide #17 Temperature effect on Density (Fig 5-11)

As water cools to 4∞C: Molecules slow, Water contracts, Density increases

Below 4∞C: Water becomes highly structured and expands, density decreases

As water freezes: Expands by 9%

Slide #18 Salinity = the total amount of solid material and gases dissolved in water (Fig 5-13)

Slide #19 Salinity is the ocean åsaltsπ, many different compounds (Fig 5-14)

Slide #20 Salts come from weathering (via rivers), volcanoes, atmosphere, hydrothermal vents (Fig 5-16)

Slide #21 Seawater salinity

Typically about 3.5% - (3.5% of the weight of seawater is from salts, 96.5% is pure water)

Expressed as parts per thousand (î or ppt). Remember that % is parts per hundred.

35 î means 35 grams of salt are dissolved in 1000 grams of water (1 liter).

Slide #22 Processes affecting seawater salinity

Processes that add fresh water to surface ocean and decrease salinity:

Precipitation

Runoff

Icebergs melting

Sea ice melting

Processes that remove fresh water from the surface ocean and increase salinity:

Evaporation

Sea ice forming

Slide #23 Surface salinity variation (Fig 5-20)

Low in High latitudes

High precipitation and runoff

Low evaporation

High in Tropics and sub-tropics (0 -35ö latitude)

High evaporation

Low precipitation

Dip at Equator

High precipitation partially offsets high evaporation

Slide #24 Salinity of Worldπs Oceans (Fig 5-21) Reflects balance between precipitation and evaporation

Slide #25 Salinity variation with depth (Fig 5-22)

Curves for high and low latitudes begin at different surface salinities

Halocline = layer of rapidly changing salinity

At depth, salinity is uniform

Slide #26 Seawater density

Factors affecting seawater density:

Temperature increase = > Density decrease (inverse relationship)

Salinity increase => Density increase

Pressure increase => Density increase

Temperature has the greatest influence on surface seawater density

Slide #27 Oceans are well stratified (Fig 5-24)

Pycnocline = layer of rapidly changing density

Thermocline = layer of rapidly changing temperature

Not well developed in high latitudes

Barrier to vertical mixing of water and migration of marine life

Slide #28 Ocean layering based on density

Mixed surface layer (surface to 300 meters)

Low density; well mixed by waves, currents, tides

Upper water (300 to 1000 meters)

Intermediate density water containing thermocline, pycnocline, and halocline (if present)

Deep water (below 1000 meters)

Cold, high density water involved in deep current movement