Midterm #1 results
posted early next week
see BlackBoard
Answer Keys for both White and Blue exams
will be provided on course website
Scantrons will be returned in labs next week
Physical and Chemical
Structure of the Ocean
Why are the oceans blue?
How is sound transmitted in the ocean?
Why is the ocean “layered” in many locations?
How do you keep your beer cool in the tropics?
Light Absorption in Water
Intensity decreases
rapidly with depth
Blue and green
penetrate deepest,
giving the ocean its
color
Why do objects lose their
color with depth?
The colors other than blue (and
green) are absorbed by the water
molecules in the first few meters -only blue (and green) are reflected
Sound in Sea Water
Sound
is transmitted better in water than
it is in air
Sound velocity in the ocean is about 1500
m/s, or about 4 times its speed in air
Sound velocity increases with pressure
and temperature
SOFAR Sound Channel
Sound is focused into the SOFAR channel
because it is a low velocity region
Sound is transmitted best through this
channel -- good for whales and submarines
(e.g., “Hunt for Red October”)
Heard Island Experiment
Global Warming -- faster velocity??
Go to Sounds
Ocean Temperature
Solar Heating
Uneven heating of
Earth’s surface
Release of heat as
infrared radiation
Requires flow of
heat by oceans and
atmosphere
Surface circulation
Global Heat Budget
 heat at the Earth's
surface (342 W/m2)
is supplied by
absorption of
‘short-wave’ solar
radiation from the
sun.
 heat lost from
Earth is through
long-wave radiation
back to space.
The Greenhouse Effect
The Atmosphere is transparent to
sunlight (ultraviolet [UV] and visible)
Clouds absorb or reflect about half
Sunlight heats the Earth’s surface, which
then radiates energy as longer wavelength
energy (infrared)
This energy is trapped by the
atmospheric gases (CO2, H2O, CH4)
Special Properties of Water
RECALL:
Melting and boiling points are very high
Highest heat capacity of common liquids
High heat of fusion and vaporization
Sea Surface Temperatures
only 0°-30°C world-wide
Land:
50°C to 50°C
Local Annual Heat Budgets
 Amount of solar energy captured at one location
on the Earth varies with season
Local Annual Heat Budgets
Where we live
 Amount of solar energy captured at one location
on the Earth varies with season
Temperature (vertical profile)
Seasonal
changes in
temperature
profile
Temperature (vertical profile)
Thermocline
Cool drinks go
here
Temperatures with Depth
Thermocline -- sharp temperature
change
Evaporation - Precipitation
Over the oceans, evaporation exceeds
precipitation
The balance is restored by rain over
the continents, returning water via
rivers
Evaporation vs Precipitation
Climate Belts
Ocean Surface Salinity
Salinity Variations
Salinity Variations
Surface salinity follows evaporationprecipitation pattern
Atlantic Ocean is generally more salty
than Pacific Ocean, in spite of river input
-- why??
Isthmus of Panama
Net transfer of
fresh water
from Atlantic
to Pacific
Salinity of Rivers and Ocean Water
Can’t just concentrate
river water to get
seawater
How do we explain this
observation?
Rivers
Ocean
Concept of Residence Time
Each element removed
from ocean in different
ways
And at different rates
e.g. Cl- vs. SiO2
Residence Time
Flux has units of mass
per unit time
Reservoir has units of
mass
R/F has units of time
Density of Sea Water
(Where does Oregon’s seawater plot?)
Density of Sea Water
(Where does Oregon’s seawater plot?)
Oregon’s ocean
Bottom Water
Density Rules!
Where does the Ocean’s
Deepest Water Come From?
The densest seawater is COLD and
SALTY
This is formed at high latitudes in the
North and South Atlantic:
North Atlantic Deep Water (NADW)
Antarctic Bottom Water (AABW)
Could dense seawater form in the tropics?
(evaporation!)
Dissolved Gases in the Ocean
Important Gases in the Ocean
Oxygen -- Respiration, Decomposition
CO2 -- Photosynthesis, CaCO3
Nitrogen -- Nutrient for growth (NO3)
Methane -- a product of decomposition
Photosynthesis and Respiration
Biology interacts with the Chemistry
Dissolved Oxygen
Biochemical Recycling
Summary: Biochemical Cycles
Elements enter oceans through rivers
Gases enter oceans thru air-sea boundary
Biology alters distribution of elements
(“nutrients”) and gases
Ocean circulates nutrients to surface, but
only in a few places (called “upwelling”)
Interaction of physics, chemistry and
biology => geological record (sediments)