Oceanography Prelim 1

Big Bang happened roughly ____________ years ago
15 billion
At the time of the big bang, there was only ________ and _______ in the universe
hydrogen, helium
Gravity pulls these two things together to form _______ elements through ________ ________
heavier, thermonuclear reaction
These heavier elements are
carbon, nitrogen, phosphorous
Larger stars exploding formed
gold, copper, etc
our own sun is thought to be a _______ ________ ______
third generation star
Roughly, there are _____ _______ galaxies with ______ _______ stars
100 billion, 100 billion
temperatures in the core of large masses increase due to _____________ ______________
compressional heating
Core temperatures at 10 million degrees kelvin cause ________ ___________ of H –> He
nuclear fusion
nuclear fusion of H –> He
-thermonuclear fusion reaction
forms heat and visible light
All _______, __________, and __________ atoms making up my current physical body were at one point sitting in the center of a boiling hot star
carbon, nitrogen, phosphorous
Terrestrial planets build up by
multiple collisions and accretion of planetesimals
giant outer planets grew by ______ ____________
gas accretion
inner planets are:
-terrestrial
-relatively small
-contain the heavier elements (Fe, Si, O)
-rocky shell over a metallic core
-4.6 billion years old
outer planets are:
-gaseous
-mostly volatile gases (H, He)
-same composition as the sun
planetesimals
asteroids and comets. essentially, compositions of grain, matter
__________ years ago, rock-forming elements condensed into small solid grains as _______ cooled
4.6 billion; nebula
______ formed when Earth was hit by a Mars sized object (__________ years after Earth accreted)
Moon; 100 million
______ ______ _______ makes 23 degree angle with _______ ______
earth spin axis; orbital plane
early earth :
-atmosphere consisted of hydrogen and helium
-most of the gases lost to space
modern Earth:
-out-gassing from volcanoes releases — water, carbon dioxide, sulfur dioxide. N2, H2, Cl2
-water vapor condensed and precipitated to form oceans –> anaerobic life develops
-photosynthetic life evolves and this produces a modern oxygen rich atmosphere
5 oceans
pacific, atlantic, indian, arctic, southern
average depth of oceans
4 km
_______ % of earth is water
70
scale earth down to size of
beach ball
in scaled down earth,
ocean thickness would be _____
atmospheric thickness would be ____
1.5 mm
4.5 mm
______ _______ of the atmosphere’s mass is within _____ ____ of the planetary surface
three quarters; 12 km
Earth and sun are middle aged, both have about ____ ________ years of life left
4 billion
Latitude runs ______ to _____, it is a measure of degrees from ________ and _______ _______ to a certain point.
East; West
Equator; global center
*equator is 0
Longitude runs _______ to ______, it is a measure of degrees from ________ ________ and _______ ________ to a certain point
North, South
Prime Meridian; global center
*prime meridian is 0 (greenwich, england)
Marine Geology
Bathymetry
bottom depth
single-bean sonar
creates a track line of bottom depth as the ship moves forward
multi-beam sonar
creates a swath of bottom depth as the ship moves forward
towed multi-beam sonar
creates a high resolution swath of bottom depth as the ship moves forward
theory of continental drift
alfred wegener 1915
developed the idea of plate tectonics; not well accepted at the time despite overwhelming evidence.
Wegner had the wrong forcing mechanism of movement
plate tectonic theory
was accepted after sea floor spreading and sea floor subduction were discovered in post WW2 exploration
Earths’s composition
-rigid outer crust (thin and rigid, floats on mantle)
-plastic upper mantle
-outer core (molten)
-inner core (solid)
theory of plate tectonics:
steady accumulation of evidence leading to the birth of a new theory
Alfred Wegener noticed apparent ____ _____ of continents as well as the ________________________
good fit;
distribution of fossil and mineral belts
________ ___________ in ocean crust provided strong evidence of seafloor spreading
magnetic anomaly
_______ __________ are a proxy measurement of geologic time–each __________________
magnetic anomalies;
anomaly can be assigned a specific geologic date
Discover of deep sea trenches and associated seismic activity helped to explain:
the eventual loss of ocean crust that was initially formed at mid ocean ridges
driving mechanism of plate tectonics:
convection in the mantle and slab pull
oceanic crust
-thin: 5km
-relatively higher density
– consists of mostly basalt
-average density 3g/cm cubed
-thinner and only slightly less dense so they float lower in the mantle
continental crust
-thick: 70 km
-has a relatively lower density
-consists mostly of granite
-average density – 2.7 g/cm cubed
-thicker and less dense so they float higher on the mantle
________ ________ is created by divergent boudnaries
mid-ocean ridge
convergent boundaries
oceanic and continental
oceanic and oceanic
continental and continental
convergent boundaries: oceanic and continental
-deep ocean trenches
-explosive volcanoes
-subduction related volcanoes are particularly explosive and dangerous
-mount st helens
convergent boundaries: oceanic and oceanic
-older plate goes under
-deep ocean trench
-chain of volcanoes = island arc
convergent boundaries: continental and continental
mountains are formed
everest
transform boundaries
plates slide laterally relative to one another
sediment thickness is high near coast due to:
river runoff of terrigenous sediment and high productivity that leads to high rain rate of biological material
red clays found in open ocean:
slow rain of continental dust
________ or ___________ sediments found in high biological productivity regions
calcareous, siliceous
rate of accumulation is very slow; 10 meter sediment core can =
millions of years
proxy measurements of past ocean conditions:
-surface water conditions
-biological productivity
most oxygen has mass of
16
some oxygen has mass of 18
proxy measure for temperature measurement is to use:
isotope ratio of oxygen preserved in shells of calcite fossils
O18 is preferentially __________ from the water and incorporated into ______ _______ during growth
removed; calcite shells
All things equal, calcite in shells grown in ______ _______ will have more O18 than calcite grown in _______ _______
colder temperatures; warmer temperatures
we are currently experiencing a _______ mass extinction
6th
Waves and Tides
wavelength
crest to crest distance
wave speed
distance a wave crest travels per unit time
wave period
time it takes a wave crest to travel one wavelength
wave frequency
number of crests passing a fixed location per unit of time
waves propagate ______ but not ______
energy; mass
Determinants of wave speed:
-wavelength
-bottom depth
waves with longer wavelength travel _______ than waves with shorter wavelength
faster
waves traveling in deeper water travel ________ than waves traveling in shallower water
faster
under certain exceptional circumstances, __________________________ will be the primary determinant of wave speed
only wavelength or only bottom depth
in very deep water, _________ determines wave speed
wavelength
in very shallow water, ___________ determines wave speed
bottom depth
deep water waves
-bottom depth is deeper that 1/2 the wavelength
-speed is a function of wavelength only
-more wavelength = more fast
shallow water waves
-bottom depth is shallower than 1/20 the wavelength
-speed is a function of depth
-more shallow = more slow
intermediate waves
speed is a function of both wavelength and bottom depth
wave dispersion
self sorting of deep water waves leaving a storm region based on wavelength
wave refraction
the bending of shallow water wave fronts due to change in bottom depth
(focusing and defocusing of wave energy on headlands and bays respectively)
______ _______ is different in different seasons
sand movement
summer (constructive waves)
gentle waves push offshore sandbar shoreward to create wide and gently sloping sandy summer beach
winter (deconstructive waves)
storm waves drag sand off the beach to be stored in offshore sandbar, resulting in rocky winter beach
-steep beach
rip currents
-initiated when large waves push water onto an elevated beach face
-seldom wider than about 10 meters
-can pull a person hundreds of meters offshore
wave height determinants
wind speed, wind duration, wind fetch
wave height determinants: wind speed
sets the upper possible limit on wave height for a fully developed sea
wave height determinants: wind duration
modulates the upper possible limit on wave height
wave height determinants: wind fetch
the distance over which wind can blow without obstruction
modulates the upper possible limit on wave height
higher wind speed =
higher wave height
______ in the open ocean is limited by the size of the storm system
fetch
equilibrium model of tides =
highly idealized but instructive
-tide wave treated as a deep water wave in equilibrium
-no interference from continents
diurnal
1 high tide and 1 low tide per day
semidiurnal
2 equal high tides and 2 equal low tides per day
mixed semidiurnal
2 unequal high tides and 2 unequal low tides per day
tidal bulges created by the
pull of the gravity of the moon and centrifugal force
tidal bulges are on ________ sides of the earth and case the _____________ over roughly a _________
opposite;
rise and fall of the tides;
24 hr period
tide rises at
180 degrees
tide falls at
90 degrees
tidal day = 24 hr and 50 min
moon orbit is inclined at ___________ which causes changes in _____________
28 degrees; the daily pattern of tides
spring tides
-occur when the moon pulls along the same line as the sun
-occur on new and full moons
-relatively higher
neap tides
-occur when the moon pulls at 90 degrees to the sun
-occur on first and last quarter moon
daily patterns =
diurnal, semidiurnal, mixed semidiurnal
monthly patterns =
spring, neap
dynamic theory of tides–a more realistic view of tides:
-rotary tidal motion
-larger tidal ranges in coastal vs open ocean regions
-tide wave treated as a forced shallow water wave
-affected by the Coriolis force
-continents interfere with the propagation of the tide wave
all ocean tides are pinched upwards from the ________________ on all the ocean
cumulative lateral pull by the moon
_______ are not large enough to experience this, hence no tides
lakes
tide waves are ______ _____ _____ _____
forced shallow water waves
_________ __________ causes the high tide to occur sometime after the moon appears to pass overhead
frictional drag
_______ ________ has a very significant effect on the direction of tidal propagation
Coriolis Force
Coriolis always acts exactly to the ________ of the direction of motion in the northern hemisphere, and always directly to the ________ of the motion in the southern hemisphere
right; left
Physical Oceanography
Global surface wind patterns
easterlies, westerlies, trades
contained within latitude bands
0-30
30-60
60-90
ocean surface temperatures
-warmest near equator
-coldest near poles
atmospheric convection and precipitation is strongest along ______________
the equator
the weight of a column of air is ______ _________ to the average molecular weight of the mix of all molecules making up the air
directly proportional
vertical distribution of density directly influences the ________________________
vertical movement of water in the ocean
salt concentration and water temperature jointly determine _________ _________
seawater density
surface ocean temp is determined by the ______________
exchange of heat between the ocean surface and the atmosphere
ocean temp is a measure of ____________
the heat energy contained in the ocean
when more energy than leaves the ocean surface, ________________.
converse is also true.
the surface warms
__________ adds heat
sunlight
________ _________ takes away heat
evaporative cooling
all direct solar heating takes place _______________
very near the ocean surface (0-30m)
permanent thermocline:
broad region centered at around 500 m where seawater temp changes from warm to uniformly cold
seasonal thermocline
in some ocean regions, occurs in summer and is erased in winter
seasonal pycnocline
a region of strong change in density with depth…comes and goes with net heat gains in spring and summer and net heat losses in fall and winter
permanent pycnocline
remains in place at around 500 meters and is the result of the long term balance between the downward heating/mixing at the surface and upward mixing of cold water from below
Ekman transport
a slab of surface ocean water (30-60m) moved by wind forcing
-due to wind force, friction force, and coriolis force
-moves at exactly 90 degrees to the direction of the wind forcing
geostrophic currents
currents that move along lines of constant pressure
geostrophic balance
the point at which currents move with steady speed with coriolis and pressure gradient forces in perfect opposition…results in geostrophic current
subtropical gyre development
-westerly and trade winds drive the ekman layer to the center of the gyre to create a mound of surface water
-the push of coriolis turns the fluid until it travels along concentric lines of constant pressure (geostrophic balance)
western boundary currents
-western side of subtropical gyres
-very swift and narrow
-bring warm water from the tropics to high latitudes
eastern boundary currents
-eastern side of subtropical gyres
-broad and slow
-bring cold water from the high latitudes toward the tropics
atlantic ocean temp at depth
-warm thin surface layer
-cold thick deep layer
-thermocline separates the warm and cold layers
atlantic ocean salinity at depth
-high salinity in surface layer in subtropics
-deep ocean salinity more uniform and generally matches the surface salinity at higher latitude-especially northern high latitudes
temp/salinity: NADW (North Atlantic Deep Water)
-labrador sea
-imminger sea
-greenland sea
-norwegian sea
temp/salinity: AABW (antarctic bottom water)
-weddell sea
-rose sea
temp/salinity: AAIW (antarctic intermediate water)
global conveyer belt circulation:
combining the deep circulation and the wind-driven surgace circulation