1.
2.
3.
I. Thermohaline circulation
A. Gradients caused by differences in density of
the water masses generate slow currents
-sinking of cold and
dense water produced in the high latitudes
B. Well defined water masses are identifiable in
the water column
C. "Great Ocean Conveyor"
II. ENSO – El Niño/Southern Oscillation
(not in book, so more detail here)
A. Normal conditions
1. trade winds blow from
east to west across Pacific
2. sea surface level
3. sea surface temperature
is 8o C higher in the W. Pacific than in the E.
4. upwelling off the coast
of S. America
a. nutrient rich water
b. high production, diverse ecosystems, major fisheries
B. El Niño conditions
1. originally recognized
and named by fisherman off the coast of South America
2. appearance of unusually
warm water in the Pacific ocean off the coast of S. America; El
Niño
conditions often begin to occur in Dec./Jan.
3. upwelling is stopped
4. fish and bird populations
are disrupted
5.disruption of
ocean-atmosphere system in the tropical Pacific that affects
weather around the globe -- due
to the 'Southern Oscillation' (Gilbert Walker in 1928) -- an
inter-annual
switch in tropical sea level pressure
between W and E Pacific
6. 1957 - large El
Niño;
scientists first realized that El Niño affects not only Peru and
Ecuador on the S. American coast,
but the entire Pacific Ocean and is tied to the Southern Oscillation.
7. El Niño occurs
when there is a large scale weakening of the trade winds -- warming of
the surface layers in the eastern and central equatorial Pacific
Ocean.
Thermocline increases in depth in the eastern Pacific and is closer
to the surface in the West.
8. Rain follows the warm
water eastward, leading to flooding in Peru and drought in Indonesia
and
Australia.
9. El Niños occur
irregularly at intervals of 2-7 years (average 3-4 years) and last
12-18
months (typically)
10. Severe El Niños
have recently resulted in a few thousand deaths worldwide (mudslides,
floods,
droughts-fires), left thousands of
people homeless, and caused billions of $ worth of damage.
11. Changes the distribution
of organisms in the ocean -- anchovy, warm water species
12. Some positives as well
as negatives
rain in Chile and SW US -- may be vital for desert ecosystems
heavy snowfall increased tourism in the West
mild winter in much of N. US and Europe -- saved heating dollars
C. La Niña -- other extreme of the ENSO
cycle
where sea surface temperatures in the tropical Pacific drop below
normal.
Also has
global consequences
(currently developing La Niña)
D. ENSO is illustrative of the major effects of
ocean circulation on ocean systems and global climate
III. Tides
(see
textbook pp. 267-270 for more information)
A. Definition -- predictable rise and fall of sea
level
B. Important for organisms; especially in intertidal
zone
C. Balance of gravitational and centripetal forces
controlled by:
1. positions of moon and
earth
2. earth's tilt (23.5
degrees
from vertical)
3. moon's elliptical orbit
-- sometimes closer to earth than others
4. full tidal cycle is 24
hours and 50 minutes
D. Spring tides versus neap tides
1. spring --
greatest
range (height of tides); moon and sun are directly aligned with earth
2. neap -- minimum
range; moon and sun at right angles relative to earth
E. Semidiurnal, diurnal and mixed tides
1. semidiurnal
2. diurnal
3. mixed
F. Bay of Fundy (Nova Scotia); Cook Inlet (Alaska);
geometry of basin contributes to huge tides
IV. Properties of Water
A. H2O
B. Polar molecule
C. Hydrogen bonds
D. Only substance on earth that naturally occurs
in all three states (solid, liquid, gas)
E. Special properties of water
1. cohesion --
a. water 'sticks to itself'
b. cohesion causes there to be surface tension
i. highest surface tension of all common liquids
ii. specialized organisms live on ocean surface or suspended below it
c. cohesion also influences the viscosity of water
i. viscosity affected by temperature -- increases as it gets colder
ii. viscosity affected by salinity -- increases as it gets more saline
iii. important in sinking rates of organisms
iv. important in movement of organisms -- for very small organisms,
life
in water is like living in Karo Syrup
2. heat of
vaporization/evaporation
3. latent heat of
fusion/melting
4. heat capacity
a. quantity of heat needed to raise the temp. of 1 g of substance 1
degree
C
b. highest of all common solids and liquids
c. temperature buffer for organisms --
5. density-temperature
relationship
- ice
6. Excellent solvent
('universal solvent')
V. Chemical composition of seawater
1. salinity
a. total amount of dissolved
material in water
b. 1,000 g of average
seawater contains ~35 g of dissolved salts (96.5% water;
3.5%
dissolved substances)
c. units - parts per
thousand (o/oo) or practical salinity
units
(psu)
d. away from coastal areas,
salinity varies within a narrow range 34-37 psu
e. near shore salinity can
be more variable
f. salinity is determined
by a balance of precipitation (rain and snow; and river input
from
precipitation on land), evaporation and
freezing
g. salinity strongly affects
what organisms are in seawater
2. what are the dissolved substances?
a. inorganic salts
b. organic compounds
(originally
from organisms)
c. dissolved gases
3. source of dissolved solids
a. chemical weathering of
rocks on land, carried to sea by runoff & rivers (e.g., Na, Mg)
b. earth's interior;
released
through hydrothermal vents (e.g., Cl, S)
c. atmosphere (volcanoes,
other sources) -- enter in rain or snow
4. The inorganic salts
a. major ions -- 99.28%
of the solid matter in seawater
ION
% by weight
i. chloride (Cl-)
55.04%
ii. sodium (Na+)
30.61%
iii. sulfate (SO42-)
7.68%
iv. magnesium (Mg2+)
3.69%
v. calcium (Ca2+)
1.16%
vi. potassium (K+)
1.10%
b. minor ions -- bring
total
up to 99.99% of the dissolved substances
bicarbonate (HCO3-), bromide (Br-),
boric acid (H3BO3), strontium (Sr2+),
fluoride (F-)
0.003%
c. ratios among these
salt
ions remains virtually constant -- rule of constant proportions
5. dissolved gases
a. oxygen (O2),
carbon dioxide (CO2) and nitrogen (N2)
b. the lower the
temperature,
the greater the solubility of gases (cold water has more oxygen)
c. much lower solubilities
of gases in water than in air
d. oxygen profiles
i. maximum in the upper 10-20 m
a) photosynthesis by plants releases oxygen
b) diffusion of oxygen from the atmosphere
ii. oxygen declines below this -- used by respiration
iii. oxygen minimum zone -- generally between 200 and 1,000 m
in
the open ocean
iv. below this oxygen increases to some extent -- colder water formed at the poles
e. carbon dioxide
i. increasing concentrations in atmosphere
ii. photosynthesis
and respiration
iii. reacts with seawater to form bicarbonate and carbonate ions
1.
2.
3.
iv.
bicarbonate is one of the minor ions -- is relatively abundant
v.
more CO2 stores in the ocean than in on land -- carbon
doesn’t
generally limit photosynthesis in the ocean
vi. pH; buffering system
vii. seawater slightly alkaline due to the bicarbonate buffering
system
and to sodium, calcium and potassium -- pH typically
7.5-8.4 and fairly constant
VI. Nutrient cycling
B. Phosphorus Cycle
1. Phosphorus rock on land
is the major reservoir
2. Erosion/weathering brings
it to water
3. Plants/phytoplankton
take it up
4. Returned by decomposition
5. Lost when dead organisms
sink to the bottom and are buried
C. Nitrogen Cycle
1. Air is the major
reservoir
2. Only a few organisms
can take up atmospheric N (N fixing bacteria and algae)
3. Useful N is also produced
by volcanoes
4. Taken up by organisms
5. Released by decomposition
6. Some loss to burial in
sediments
VII. Light in Water
A. transparency of water is vital -- photosynthesis
and temperature
B. sunlight contains all of the colors of the
spectrum
(rainbow), but not all colors penetrate equally well
C. open ocean is most transparent to blue light
D. red light penetrates least
E. eventually all light is absorbed by the water
and there is total darkness
F. near the coasts lots of sediment may be brought
in from rivers that reduces the light penetration
G. this suspended material near shore can give the
coastal waters a greenish tint