Exam Flashcards
Three main components of early atmosphere
H2O, CO2, N2
Source of early atmosphere
Volcanic
What happened to the oxygen produced by photolysis?
Consumed by oxidation of reducing materials
Proto-ocean formed…
4 billion years ago
4 records of photosynthesis
stable isotopic record of oxygen, banded iron formations, red bed sediments and stromatolites
Has shelf, slope and rise
Continental margin
Flattest place on Earth
Abyssal plains
How are guyots formed?
Erosion of seamount tops
Age of oldest oceanic crust
180 million years old
Average spreading subduction rate
10-100mm/a
Why do some smaller sediments have slower settling velocities?
They have a higher surface area so ‘stick’ together
Where do 60% of riverine lithogenic sediments come from?
The Tropics
How fast do ferromanganese nodules grow?
1-4mm/Ma
Coccolithophores, foraminifera and pteropods are …. biogenic sediments
calcerous
Diatoms and radiolarians are … biogenic sediments
siliceous
Distribution of volcanic sediments
globally
Most insignificant marine sediment
Cosmogenic
Lysocline is where
calcite starts to dissolve
CCD depth
4-5km
Two types of bulk emplacements
slumps and turbidity currents
… of rain falls over ocean
78%
Steady states have
inputs=outputs
size/(input/output)
Residence time
… of radiation emitted by surface reabsorbed by water in atmosphere as long-wave radiation
90%
Surrounds ions to dissolve them due to dipole-ion interactions
Hydration sheath
Average sea water salinity (0/00)
35
Total Dissolved Solids in seawater
3500 mg l-1
Most abundant ions in seawater
Sodium and bicarbonate
What adds bicarbonate to rivers as there is little in rain?
Dissolution of rocks such as limestone
Why is there little silica in seawater?
It’s used by marine organisms such as radiolaria
What is salinity?
The concentration of all dissolved substances in seawater expressed in ppt as a dimensionless ratio
Why is salinity fairly uniform?
Mixing from ocean currents as long residence times
Where is the highest salinity
20-30 degrees N/S
How is salinity measured?
Measuring electrical conductivity using a salinometer
K, Na, Ca, Mg and Si provided to seawater from where?
Weathering of crustal rocks
Volcanism provides what elements?
Cl and S
What can be a salinity sink and source?
Hydrothermal vents
Evaporate formation, aerosol formation, adsorption and, sedimentation and burial are what?
Salinity sinks
How many tonnes of salt do rivers carry to oceans each year?
4 billion
Example of secondary minerals formed by weathering
orthoclase to kaolinite and dissolved silica
Seawater pH is…
8.3-8.5
Dissolved seawater constituents…
contribute to salinity
Particulate seawater constituents…
accumulate as sediments and break down on the seafloor
Dissolved salts, ions, nutrients, minerals, trace elements, DOM (e.g. DOC) and dissolved gases…
Pass the 0.45 micrometre filter (dissolved constituents)
Sediments, dust, ash, exoskeletons, living and dead organic matter…
Retained by 0.45 micrometre filter (particulate constituents)
Has the shortest element residence time
Al 2+
Major constituents are conservative so…
they remain unchanged by chemical or biological reactions
Zooplankton package phytoplankton waste into faecal pellets to be consumed by bacteria called
Marine snow (macroscopic aggregation)
Total incoming insolation
340 wm-2
Trade winds are
easterlies
Wind driven currents move from
friction and pressure gradients
At right angles to wind from Coriolis force
Ekman transport
Geostrophic flow when what 2 forces in balance?
Pressure gradient and Coriolis force
Anticyclonic in N. Hemisphere
Clockwise circulation
Why does Western Boundary intensification occurs?
Coriolis stronger in higher latitudes so affects westerlies more than Trade winds so higher pressure gradient when pushing water west
In unstable layering density…
decreases with depth
Lower latitudes have what type of layering?
Stable
Thermohaline circulation driven by…
density differences
75% of clean water has what temperature and salinity
0-5 degrees C and 34-35 0/00
Deep and bottom layers over…
2km
A water mass is a …
large body from common source region with little changes in salinity and temperature and slow mixing between water masses
In MOC after water down wells where does it flow?
Along Western boundaries
MOC draws…
warm water northward
Why does upwelling occur at the Southern Ocean?
Westerlies around the Antarctic so Ekman transport directed left. Water moves northwards and this must be replenished from depth
Why is the Southern Ocean important?
Sole place on Earth where all water masses involved in MOC come together, mix and transform
El Nino/La Nina temperature anomaly of +/- 0.5 degrees is a standard measure known as what?
Oceanic Nino Index
What is the Southern Oscillation Index?
Tahiti-Darwin monthly mean sea level pressure anomalies hPa
Reversed winds in El Nino mean what for Peru Current?
It’s weaker so less upwelling
What’s displaced by El Nino/La Nina?
Walker circulation
When North Atlantic Oscillation is in positive mode pressure differences are…
higher, so stronger storms
What wave type has the wave height?
Swell
The four factors involved in wind generated waves are…
Wind velocity, wind duration, fetch and original sea structure
What is significant wave height?
The mean wave height of the highest 1/3 of waves?
What moves across the sea surface?
Wave energy (not particles)
Two motions in progressive waves are…
forward and orbital
When does circulation not reach sea floor?
if water depth is equal to or greater than 1/2 the wavelength
When wave depth is equal to or less 1/20 of wavelength, what happens?
Wave motion is flatter and reaches the seafloor
What’s the celerity?
Speed at which crests (peaks) propagate
What changes happens when waves approach the coast?
They slow down (become dependent on water depth for speed), refract to coastline shape and collapse as a shore breaker
What remains constant in a wave?
The periods
Why do waves refract?
Slow down due to changes in water depth. A an angle different parts of same crest have different speeds so waves end up reorientating themselves
What are the three types of shore breakers?
Spilling, plunging and surging
What wave type carries the most energy?
Tides
Why are tides shallow water waves, despite their long wavelengths?
Their wavelengths dwarf water depths
Why do different latitudes experience different tide types?
The declination of the Earth (28.5 degrees) means some areas will enter a bulge once and some twice a day
What is the position of celestial bodies during neap tides?
Sun and Moon and 90 degrees to each other relative to the Earth
What direction does the rotary tide wave move in the Northern Hemisphere?
Anti-clockwise
Cotidal lines…
connect points where high tide (crest of rotary wave) occur at the same time each day
Corange lines…
link parts of rotary wave with same tidal range
What three factors contribute to tidal bores?
Large tidal ranges (>5m), tapering basin geometry and water depths decreasing systematically
Beaches are…
active zones of sediment transportation between an erosional area above sea level and depositional below water level
Nearshore contains what 3 zones?
swash, surf and breaker
Swash zone is…
covered and uncovered by water with each surge
A beam is…
a prominent flat topped wave deposit
Backshore zone
land adjoining nearshore
Offshore zone
open water
Beach profiles can be…
swell (growth) or storm (erosion)
Wave setup leads to?
Rip currents (after piling of water)
Why do longshore currents occur?
As there is no room for orbital motion, water is transported on shore and this needs to evacuated and this arises from a water pressure gradient. They diverge at zones of maximum setup and converge at zones of minimum setups
Three controls on deltas are…
river, wave and tidal
Three ways an estuary can be formed?
glaciation, drowned rivers and tectonic activity
How do concentrations of conservative elements change?
Addition or removal of seawater
Three minor elements in seawater?
N,P and S
What is the removal process of components in seawater?
Removes substances from the dissolved phase and adds them to the particulate phase which can be removed from the water column via sedimentation
What is the removal process of adsorption?
When metal ions are attracted to the residual surface charges on particles
What happens to the elements in algae derived detritus that were taken up aa biological uptake in primary production?
They are released during bacterial breakdown and released at depth to be recycled
Mean solar irradiance in Tropics and high latitudes are…
9000 and 500 WM-1 respectively
What are the three factors that control angle of incidence?
Latitude, season and time of day
When there is low solar elevation, there is a…
high angle of incidence and high reflectance loss
Light attenuation controls light underwater and is the combined effects of…
absorption and scattering
Light attenuation is described by…
Beer-Lambert Law
Light intensity (I)…
decreases exponentially with depth
K is usually what?
0.02-0.2m-1
What zone is between euphotic and aphotic?
disphotic
What are the three optically active components of seawater?
Particulate matter, dissolved matter and water itself
Thee euphotic zone depth (Ze) is equal to what?
3Zs (3 x Secchi depth)
What does the euphotic zone depth represent?
The deepest depth primary producers can sustain themselves
Why is the part of the ocean south of Greenland cooling?
Freshwater inputs mean less dense water formation, destabilising MOC so less heat transported to N. Atlantic
How much as the deep ocean warmed?
1.4 x 10^23
Three types of plastic degradation?
Physical, mineralisation and biofouling/defouling
Compensation point (GPP=Respiration and NPP=0) represents what?
Euphotic zone depth
What does primary production depend on?
Mixing and stratification?
Why, for primary production, are tropical regions nutrient limited?
Strong permanent thermocline due to high solar irradiance all year acts as a mixing barrier?
Warm core rings are…
anticyclonic
Three types of tidal power generation
Barrages, fences and turbines
Three types of wave power generation
oscillating water column, float system and overtopping system
Advantage of current power
Stable and predictable as constant direction
