oceanography Flashcards
origin/meaning of oceanography
okeanos - Oceanus
graphia - recording/ describing
why oceanography isn’t really a correct term
oceanology = study of oceans
oceanography as a pure science
not. it is a compilation of biology, chemistry, physics, geology.
3 broad stages of ocean exploration
1,2 Early investigations
3. Modern investigations
Early investigations focused on
exploring oceans
exploring landmasses
early scientific investigation of ocean
Early oceanography, the explorers
James Cook
Robert Fitzroy
Wyville Thomson
Fridtjof Nansen
Early oceanography, the time
1700-1900 CE
James Cook
1768-1779
3 major voyages
mapped NZ and Aust
data: geo, bio, currents, tides, temps
Robert Fitzroy and Charles Darwin
1831-1836
HMS Beagle
South America, Galapagos
Came out of the HMS Beagles expedition
Two major ecological theories
- Atoll formation
- Natural selection
Wyville Thomson
1872-1876
Circled globe
Explore abyss
data: water chem, temp, currents, biota, sedimentary
Major Thomson discoveries
Refuted abiotic abyss theory
Recorded 7000+ species down to 9km
First sea-bottom topography charts
Abiotic abyss theory
Forbes
no species in abyss
Nansen
1893-1896
circulation of Arctic ocean
Drifted in boat (Fram) for three years locked in sea ice off Siberia, about 2km/yr
Nansen discoveries
no polar continent
water depths along path
water-mass structure
circulation patterns
Modern Oceanography
1900+ CE
Marine institutes
German scientists
Collaborations
Marine institutes
beginning of educating people in oceanography
Scripps, 1903, California
Woods Hole, 1930, Mass.
German scientists
1925-1927
Survey S Atlantic
Echo sounding
Vertical profiles
Major collaborations
International geophysical year, 1957-1958
International Indian ocean expedition, 1959-1965
Deep sea drilling project, 1968-1975
Major discoveries of deep sea drilling project
seafloor spreading
plate tectonics
Current/ future research
- International efforts (cost)
- Technology
Oceanography technology
Submersibles (Alvin)
ROV (Jason)
Computers (Modelling)
Satellites (GPS)
Earths interior, sections
Crust
Mantle
Outer core
Inner core
Earth’s crust
solid
35-50km, 0.4%
Al, Si, O
Earth’s Mantle
Solid / plastic
2900 km, 68%
Mg, Fe, Si, O
Outer core
Molten
2200km thick
inner core
Solid
1300km
Fe, Ni
Earths divisions based on physical characteristics
Lithosphere Asthenosphere Mesosphere Outer core Inner core
Lithosphere
Rigid and brittle
Crust + upper mantle
Asthenosphere
Plastic
intermediate mantle
T>P
Mesosphere
rigid
lower mantle
P>T
Outer core physical state
molten Fe-Ni alloys
T>P
Inner core physical state
solid Fe-Ni alloys
P>T
Earths spheres
Hydrosphere
Atmosphere
Biosphere
Hydrosphere
all ‘free’ water
97% in ocean
10% of total water
Atmosphere
gases
N 79%, O 16%
Remaining 90% of water, not in hydrosphere
locked in rocks
Biosphere
living and non-living
thin but dynamic
organic - C, H, O
Measurement of seafloor topography based on depth
bathymetry
greatly improved after WWII
physiographic provinces
Continental margins
deep ocean basins
midocean ridges
Parts of continental margin
continental shelf
continental slope
continental rise
Continental shelf
up to 1000km wide
0.5 deg slope
ends at 130-200m depth
continental slope
2-3km deep
4 deg slope
steep, v-shape canyons
continental rise
up to 500km wide
1 deg slope
base up to 4km deep
Deep ocean basin
beyond margin
several bathymetric features
bathymetric features
Abyssal plains
abyssal hills
seamounts
deep-sea trenches
Abyssal plain
3-5km deep
100-1000m thick
<0.5 deg slope
Abyssal hill
domes
<1000m tall
100km wide
volcanic rock
Seamount
> 1000m tall
Extinct or active volcano
flat-topped seamount
guyot
deep-sea trench
3-5km deeper than surrounding
against contin. margin
partially sed. filled
steep-sided
Midocean ridges
Connected, >60,000km cover 1/3 of ocean floor mountain ranges rift valley geologically active volcanoes, earthquakes transform faults
max ocean depth
11km
earthquake epicentres
midocean ridges
transform faults
deep sea trenches
earthquake types
shallow and weak
shallow-to-deep and strong
band of earthquakes in subduction zone
benioff zone
benioff zone
45 degrees into earth
subducting plate and melting
after subducting plate melts
molten portion lower density, rises to surface, volcanic arc
Predominant subduction zones
Pacific (ring of fire)
15-45 cm/yr subduction
ocean-ocean convergence produces
andesite
density btw basalt and granite
lithosphere contains
brittle outer shell
crust
upper mantle
3 types of plate boundaries
tension
compression
sliding
sliding plate boundaries
transform faults
tension plate boundaries
divergent zones
driving force of plate tectonics
thermal convection
thermal convection
heat transfer by fluid motion
heat - lower density - rise - convect
currents- draging of plates
cold edge of subducting
slab-pull
subducting plate pulls plate down
water molecule
dipole
bent
105 deg between H
covalent bonds
covalent bonds
share electrons
H2O residual charge
+ at H end
- at O end
most common elements dissolved in seawater
Na+
Cl-
water clusters
irregular grouping of molecules
size decreases w/ increased T
H bonded
Ice density
8% less than water
Ice
open hexagonal crystals
angle btw H expands to 109.5
chemical bonding
water density
max at 3.98 deg C
solutes in seawater
salt ions nutrients gases dissolved metals org compounds
salt ions
major constituents
85.6% Na and Cl
99% w/ sulfate, Mg, Ca, K
particles that don’t change concentration over large areas on average
conservative
salinity
g/ kg seawater
ppt
principle of constant proportion
relative proportions of major constituents are constant
use of principle of constant proportion
can determine S by measuring only one ion
measuring salinity
conventionally measure Cl- and use principle of constant proportion
chlorinity /salinity relation
S = 1.80566 x cholorinity
why measure Cl -
halogen
less reactive
sw freezing pt
-1.91 @ 35 ppt
sw density
greater than fw
adding solutes increases atomic mass
sw vapor pressure
lower than fw
salinity lowers vp
fw evaporates at higher rate
why does salinity lower vp
more molecular bonds
isotherms
parallel to latitudes
vary seasonally
characteristic of tropical, temperate oceans
thermocline
thermocline depths
200-1000m
temperate ocean thermocline
~ inexistent in March
grows during spr-summ
weakens in winter
global salinity
highest btw 20-30 deg
decreases twd poles, equator
surface salinity
- dependent on evaporation and precipitation
- closely follow evap-precip line
polar SST
low
evap and precip both minimal
temperate SST
low
evap moderate
precip max
haloclines occur
40 deg N - 40 deg S