Y1,S2 - Oceanography Flashcards
Name 3 types of Remote sensing?
-Ship-borne sonar and seismic surveys
-Passive satellite imagery
-Active satellite microwave altimetry and scattrerometry
What is ship-borne sonar and seismic surveys?
-‘Radar’ images using sound waves
-3 dimensonal picture of water density and ocean bottom rock structure
What is passive satellite imagery?
-Pictures formed from microwave and different coloured optical emissions
-Intensity of infra-red (heat) gives surface water temperature green colour of chlorophyll gives phytoplankton concentration
What is active satellite microwave altimetry and scatterometry?
-Satellite transmits microwaves pulse and recieves it reflected from the sea
-Pulse shape defines surface roughness so can deduce wave height and hence wind speed
-Detailed sea surface shape determines both ocean current speed and sea bottom topography
What are bathymetric profiles?
Depth profiles
What is a hypsographic curve?
A cumulative frequency curve showing the percentages of the Earth surfcae that le above, below or between any given levels
What is Ocean bathometry classifed by?
The slope and depth of the sea floor
What is the depth of the Abyssal plane?
~4.5km deep
What is the water depth of the MOR?
1.5-2.5km deep
How deep is the trench?
6-11Km deep
What is the height of the MOR?
2.5Km
What can be used as a proxy for ocean bathymetry?
Satellite altimetry
submarine canyons may appear on…
Continental shelves
What is Isostasy?
The proposition that at some depth under the ocean, the combined weight of overlying mantle, ocean crust and water is the same as the combines weight of mantle and continetla crust the sme depth under the continental crust the same depth under the continents.
What does an isostaic balance between oceanic and cotinental crust produce?
A 5km step at the Ocean basin edge
What would happen if the heat generated bynatural radioactivity in the Earths deep interior was not brought to the surface?
The mantle would melt
How is heat generated by natural radioactivity in the Earth transported?
By convection, which involves the flow of the transport of the underlying. mobile asthenosphere as well as transport of the overlying lithosphere
What forms at the axial ridge of a mid-ocean spreading centre when the asthenosphere cools?
The lithospheric plate
What continuosly replaces existing lithospheric plates?
New asthenosphere rising and cooling at the ridge axis; i then thickens as it moves away and cools.
How does the lithosphere change as it approaches he MOR axis?
The lithosphere is progressively younger, warmer and less dense. Its lower density makes it more elevated
What is Ocean crust generated by?
Partial melting of the upper mantle
What is the thickness of the ocean crust determined by?
The amount of melt, which in turn is determined by the temperature of the upper mantle
What is the normal upper mantle temperature?
1385C
What oceanic crust thickness does the normal upper mantle temperature produce?
Crustal thickness of 7km
What is necessary to allow convection to carry away heat generated by the decay of natural radioactivity within the Earth?
Internal mobility i.e. the asthenosphere
What is the purpose of a breach in the lithosphere?
Necessary to allow this heat to escape because the lithosphere acts as an insulating blanket. Conduction is much less efficient and convection is impossible within the lithosphere, so heat would build up at its base and general melting of the mantle would still take place.
Where is the lithospheric breach?
The breach is at the centre of mid-ocean ridges. It is the central point of symmetry for sea-floor spreading which creates new lithosphere by the cooling of rising asthenosphere. The two lithospheric plates seperate and recede at a few cm/y, keeping open the breach.
What happens as the lithospheric plates recede?
The lithospheric plates cool by conduction of heat to sea water. As it cools, the lithosphere contracts and so becomes of higher density. Also as it cools, the lithosphere contracts and so becomes of higher density. Also as it cools, the depth of the critical ~800C isotherm and so the lithosphere thickens
Is asthenospheric mantle warmer than lithospheric mantle?
Asthenospheric mantle is warmer than lithospheric mantle and so is more expanded and less dense
What is also an important mechansim of heat loss?
Hydrothermal circulation
What is hydrothermal circulation?
Near ridges-precolation of sea-water through cracks
Where does a plate lose heat from when it cools?
By loosing heat from its top surface ONLY
How does a plate cooling affect the depth to the critical isotherm?
When a plate cools, the depth to the critical isotherm increases like the square root of time. When a pplied to the ocean lit5hosphere, this simple formula explains the observed shape of mid-ocean ridges up to about 80 million years old.
What is the formula that explains the observed shape of mid-ocean ridges?
d=200 + 350t^1/2
where t= age in million years,
and d=water depth in metres
What mineral are sea-floor basalts rich in?
Iron
Sea-floor basalts can be…
Magnetised
How does temperature affect the ability for sea-floor basalt to magnetise?
When heated above a characteristic temperature (called the Curie Temperature and typically about 300-500C), they, like all magnetic materials, lose their ability to be magnetised but gain again on coolingn
What remnant magnetisation do volcanic rocks cooling through their curie temperature aquire?
A remnant magnetisation in the direction of the Earths magnetic field at that time.
Describe the timescale of the Earths cycle of a reversing magnetic field?
The legnth of these normal and revered periods averages about 1 million years but is characteristically irregular, making a unique pattern which can be used for dating.
Why is there a characteristically irregular pattern in tree rings?
Due to the irregular pattern of severe winters or dry summers
What acts as a magnetic tape recorder of the reversal sequence of the Earths magnetic field?
Spreading sea floor, formed of cooling basaltic lavas
What confirms the model of sea floor spreading?
Measuring the pattern of stronger magnetisation (recorded when the field was normal) and weaker magnetisation (the recorded feild is opposite to the present one). The pattern is symmetrical about the mid-ocean ridge axis
How do we know the crustal ages?
1.Magnetic anomoly stripes
2.Simulated hot-spot plume
Describe the formation of ocean crust…
1.At shallower depths, the pressure is less. A decrease i pressure lowers the melting point of mantle rocks
2.The thinner lithosphere at a mid-ocean ridges causes the asthenospheric isotherms to be shallower and domed up there
3.Under normal temperature conditions (a temp at the top of the freely convecting zones of about 1280C), about 13% of partial meltial melting occurs becasue of uplifted isotherms. The mineral components of the mantle which melt first rise to the surface where they cool to form the basaltic ocean crust
4. 13% of melt results in an ocean crust which is 7km thick.
What happens if the temperature of the undisturbed mantle happens to be higher andd name an example?
There is a grerater proportion of partial melting, producing a thicker oceanic crust. Iceland is a place where the spreading centre straddles a ‘hot spot’ and crust up to 25km thick has been produced here
Why do older plates sink?
-Because the mantle component of oceanic lithosphere is cooler (and hence more contracted and more dense) than the underlying asthenospheric mantle
-A more dense material DOESN’T FLOAT on a less dense material
-The higher density mantle component inreases in thickness with age and eventually offsets the buoyancy of the crust welded to it after about 150-200 mn years of cooling:it is then unstable and sinks
What does the mantle component of the oceanic lithosphere thicken with?
Age- after about 100mys, it’s about 80km thick. But there is always a fixed thickness of ocean crust welded on it.
Where does oceanic lithosphere subduct (sink)?
At ocean trenches, causing a characteristic dipping zones of EQs ( a Benioff Zone)
Describe the nature of EQs found in Benioff zones?
-Can ONLY occure in the lithosphere
-Tend to normally be found in the to 20km where the lithosphere is particularly brittle
What creates an island arc volcano?
Any water combined with basalt during hydrothermal circulationnear ridges, together with any sediment accumulated on the volanic floor of the ocean which is not physically scraped off as the pate descends, boils off or melts at the higher temperatures found at a depth- a subduction zone generates a characteristic type of island arc volcano
Describe the depth of EQs found near trenches?
Found at depths up to 700km
What temperature would the Earths surface be without greenhouse gases?
~-18 degrees C
Where does the Earth itersect less solar radiation?
Earth intersects less solar radiation at high latitudes.
Incoming flux is proportional to cosine(latitude)
True or False:
All attitudes on the Earth radiate similar heat back into space…
True
What is thermal radiation?
A function of the temperature of the object (absolute temperature)
What is absolute temperature?
C + 273
Does incoming heat create net surplus/ loss of radiation at the equator?
Net surplus
Does incoming heat create net surplus/ loss of radiation at higher lattitudes ?
Net loss
What should heat input from the sun be balanced with?
Heat loss by the atmosphere, ocean and land
In what mediums is heat transferred between the equator and the poles?
In the atmosphere and ocean
Is the Earths surface or atmosphere hotter?
The Earths surface is hotter than atmosphere above, thus heat moves form hot to cold and so is transferred upwards.
At what rate does the troposphere temperature typically decrease?
typically decreases upwards at a rate of 6.5/km
Adding or taking ways heat from water can…
- Increase or decrease the temperature of liquid water
2.Keep the temperature of the water the same but make it evaporate or freeze
What is the heat capacity of water?
4.2 kilo-Joules raise 1kg of water by 1degC
True or false:
Evaporation and ice melting (changes of state) require more heat energy than just raising the temperature of liquid water?
True
What is the latent heat of fusion of water?
355 kilo-Joules melt 1kg of ice
What is the latent heat of evaporation of water?
2257 kilo-Joules evaporate 1kg of water
Water stores about ___ times as much heat as rock?
8 times
What is adiabatic expansion?
Expansion when things cool
What is the drop in temperature due to adiabatic expansion of dry air?
~10/km
What is temperature?
A measure of the amount of internal energy per unit volume
What is the effect of adiabatic expansion of dry air when rising in the atmosphere?
Becomes coolwe than the surrounding air and so contracts more, becomes more dense and sink. Thus dry air will not rise far in the atmosphere.
Why might adiabatic decrease in temperature with height for air containing a lot of water apour may be much less than 10/km?
Because as it cools some water condenses as rain drops and the latent heat of vapourisation is released. Hense when moist air rises, it becomes less dense than the surrounding air and can accelerate upwards till the adiabatic temp. gradient becomes more than 6.5/km
When does air in the atmosphere lose heat?
When it stops rising, it will lose heat slowly by radiation out into space and it will gradually sink.
What direction are the winds in the Northern Hemisphere deflected?
Right
What direction are the winds in the Southern Hemisphere deflected?
Left
What are the Hadley cells driven by?
Driven by thermal convection of air that must be both warm and moist; precipitation within thunder clouds is a necessary part of the system. Thus they control the geographic distrubution of both evaporation and precipitation.
What is Aphelion?
Distant path position to the sun
What is Perihelion?
Close path position to the sun
What causes seasonality?
Land as rocks heat up and cool down at a much faster speed than water
Why is there a larger evaporation rate in the sub-tropics than the tropics?
Because drier trade winds blow towards the equator and smaller evaporation i the tropical belt as the air becomes moister.
What are the asssossications woth sea surface salinity?
Higher salinity - sub tropical evaporation
Lower salinity - Due to equatorial rainfall
what drives ocean circulation?
-Force balance
-Surface wind stress
-Buoyancy
What are these forces, Force balance, Surface wind stress, Buoyancy modified by?
-Friction
-Coriolis force
-Tidal forces
What does force cause?
Acceleration
What is the ‘steady state’ principle?
The sum of all forces acting at any instant must add up to zero
What drives the surface-current ocean circulation?
Wind driven
What does the density of sea water depend on?
Salinity and temperature
What drives deep ocean circulation?
-Thermo-haline driven
Describe Buoyancy?
-More dense sea water sinks
-Density increased by lower temperature and higher salinity
-Jointly they determine where and when water sinks to greater depth
What is the typical range for temperature of seawater?
-2 to 30 deg C
What is the salinity range for sea water?
25-40 %, tough typically 34-35%
What is the density of pure water at 4 deg C?
1000 kg/m3
What is the typical density of sea water?
1027 kg/m3
Define friction:
A force which only operates one motion, has started laminar flow viscosity not important turbulent flow and eddy viscosity causing mixing
Define Coriolis force:
A force which only only operates once motion and has started deflecting currents t the right in the northern hemisphere and to the left in the southern hemisphere
What causes tidal forces?
Caused by the gravitational pull of the sun and moon
Mixing can take place very slowly by a process called…
Diffusion or more rapidly by advection
Define diffusion:
Transport of heat or salinity through the water without the water moving - Very inefficient
Define advection:
Properties (eg heat and salinity) carried with water as it moves.
Mixing only occurs faster than diffusion if the motion is turbulent rather than laminar.
What are water masses?
Large bodies of water that do not mix significantly in periods of decades or centuries
Why are boundary layers significant?
Because this is where most active processes take places, at the surface, at coasts or on the ocean bottom
What happens to salinity and temperature when mixing takes place?
The amount of heat and salinity in the water remains the same as heat and salinity are conserved
How are different water masses identified?
Different water masses usually have a characteristic signature in terms of their salinity and temperature. These properties are used to identify different water masses.
What happens when two water masses are mixed in different proportions?
The total amount of pure water, heat and salt must stay the same in the mixture as in the sum of the components
What is used for sampling sea water?
-Nansen bottle (with reversing thermometer)
-CTD (conductivity -salt, temperature, depth-pressure) with rosette water sampler
What causes variation in water pressure?
Temperature, salinity and pressure
How do winds pass energy to the sea?
Primarily as waves rather than currents
What is wave base?
Half of the wave length
What is wave dispersion?
When waves formed outside the fetch will sort out each other according to speed.
What waves have a chaotic spectrum?
Waves formed in the fetch area, for example due to a storm passing by.
How does wave size affect wave speed?
Short waves travel slower than long waves
What is wave generation associated with?
Associated with laminar flow NOT wind friction
What is the wavelength spectrum at its source?
-Large range of wavelengths
-Chaotic
Why do wavelength patterns change further away from the source?
Because waves with a longer wavelength travel faster
What is the wavelength spectrum at far field?
-Smaller range of wavelengths
-Predominantly long wavelengths
What affects swells as they move from deep ocean into shallow water?
The wave speed changes from the deep-water to the shallow water condition as speed becomes controlled by water depth NOT by wavelength
How does water depth affect wave speed?
As they approach the shore, the wave speed decreases as the water depth decreases.
What are the consequences of the wave speed decreasing as water depth decreases?
-Amplitude increases
-Direction of travel changes due to refraction
What is Huygens principle?
Every point on a wave-front may be considered a source of secondary spherical wavelets. New wavefront defined by tangential to all surfaces
How does wavelength and wave height change as water shallows?
Shorter wavelength and larger height
How does wave form change as the amplitude of the wave increases?
-The profile changes from the shape of a simple sine wave
-The peak becomes sharper and the trough smoother (This shape is called a trochoid)
-The peak travels faster than the trough so that the front face becomes steeper than the back
-And eventually the peak tumbles over as the wave breaks
What do tides result in?
This results in many different types of land and marine effects but the best known is the rise and fall of the level of the sea with a period of ~half a day
What is a trochoid?
The line traced by a point on the radius of a rolling cylinder. The wave shape is this case up-side-down.
Describe the geometry of the Earth-Moon-Sun system?
-The Moon is a satellite orbiting the Earth
-The Earth and Moon together act like a satellite orbiting the Sun
-Also both the moon revolve around a common centre of mass
What balance of two forces are required to keep the motion of the geometry of the Earth-Moon-Sun system steady?
1.The force of gravity attracting the satellite to the object it orbits
2.The centrifugal force tending to make them fly apart
How does gravity vary with distance?
Gravity decreases when the distance separating the attracting masses increases
How does centrifugal force vary with distance?
Centrifugal force increases when the distance from the spin axis increases
Subtropical gyres are…
Anticyclonic
Describe the three types of tides?
1.Diurnal
2.Semi-Diurnal
3.Long-Period tides
What tides are experienced in one day?
Semi-Diurnal:
1.2 high tides
2.2 low tides
or
Diurnal:
One high and low tide a day
Why are spring tides larger than neap tides?
Because when the effect of the moon and sun act together or oppose each other the net tide varies significantly.
On what time-scale do spring tides take place?
On a fortnightly cycle
What are amphidromic points?
Points of little to zero tidal change
What does a tidal phase show?
How many hours high tide is delayed in relation to the equilibrium tide
For a whole ocean basin, the posotion and size of high tide can be mapped with two co-tidal charts.
What are they?
1.Tidal phase
2.Amplitude
What is the direction of the circulation of high tides around the amphidromic points in the Northern hemisphere?
Anti-clockwise
What is the direction of the circulation of high tides around the amphidromic points in the Southern hemisphere?
Clockwise
What 4 forces control the ocean current?
1.Wind stress (Force proportional to wind speed)
2.Pressure( Horizontal part of the pressure force is proportional to rate of change of pressure in horizontal direction)
3.Friction (Proportional to rate of lateral chang in current velocity)
4.Coriolis force (Proportional to curretn speed and sine of latitude; due to the Earth’s rotation)
What direction is the coriolis force defelcted to in the Northern hemisphere?
Right
What direction is the coriolis force defelcted to in the Southern hemisphere?
Left
What is Ekman transport?
Wind stress balances coriolis force
What forms an ekman spiral?
Because of friction, the detailed behaviour is different:
The current direction changes with depth, being about 45 degrees to wind at surface and forming an Ekman spiral.
What angle is the depth average flow in an ekman spiral?
Remains at 90 deg to the wind
In geostrophic flow what does water move along?
Water moves along isobars
In geostrophic flow where is higher pressure in the Southern and Northern hemisphere?
-Right in the Northern hemisphere
-Left in the Southern hemisphere
Why do winds circulate around anti-cyclones?
Due to the balance of atmospheric pressure by the coriolis force
Where is the flow of water geostrophic?
In the ocean interior away from the equator
How does wind stress set up gyres in the ocean?
1.First wind stress causes Ekman transport to pile up water towards the centre of the gyre
2.The pressure gradient then balances the coriolis force with geostrophic currents parallel to the wind
What is a local relative vorticity?
Relative rotation, developed from the ocean, on scales which vary from local eddies to planet wide gyres
About a locally vertical axis, what is the Earths planetary vorticity?
Planetary vorticity is 2 sin
What direction is the Earths planetary vorticity?
positive anticlockwise
What is total vorticity?
The sum pf planetary vorticity and local relative vorticity.
Unless it is made to rotate by external forces the total vorticity of a parcel of water is copnserved as it moves about.
When does planet vorticity increase?
-As the lattitude increases
e.g Water moving northward in the northern hemisphere
-When wind torque increases
Subpolar gyres are…
cyclonic
Where do currents intensify
Westward intensification of all currents- strong currents are all on the western boundary, regardless of hemisphere
What is ekman pumping?
Ekman transport convergence = downwelling
What is Ekman suction?
Ekman transport divergence = upwelling
What makes up Sverdrup transport?
-Ekman pumping provides the squashing and stretching
-The water colums must respond. They do this by changing latitude
Describe the movement of squashing?
Equatorward movement
Describe the movement of stretching?
Poleward movement
What is sverdrup transport?
Meridional flow due to pumping and suction
What compensates for the Sverdrup transport?
The western boundary currents are developed in all ocean basins as a strong and deep poleward flow of water
What produces eddies?
Conservation of vorticity
How does friction alter vorticity?
Friction can create or destroy vorticity by producing a velocity gradient.
Frictional effects are confined to a boundary layer
What is the simplest way to trace the flow of water?
Image its temperature
Describe the formation of rings?
The formation of rings of cold or warm water is an important mechanism that facilitates energy exchange between both surface water masses (i.e cold in the North and warm in the South)
What are anti-cyclonic winds?
Clockwise winds around high atmospheric pressure
Describe the global system of surface currents in relation to the Subtropical Gyre?
Wind pattern driven by warm moist air rising near the Equatorial Anti-cyclonic winds creates a central mound in sea surface topography by Ekman flow. Pressure gradient balances coriolis force to create near surface currents flowing clockwise - subtropical gyre
What are ocean currents dramatically modified by?
-Distrubution of continets and oceans
-Shallow and deep water
What interrupts zonal wind patterns?
The difference in specific heat capacity and humidity between continents and oceans
What do winds tend to circulate around?
Oceans or continent-based centres
Where is the only place where a current can flow around a whole zone of lattitude getting land in the way?
Southern ocean
What makes the sea surface elevated?
The wind driving the sea against the western side of the ocean, making the sea surface elevated and forming a head of pressure pushing forward
What is the effect of wind stress being confined to the surface mixed layer?
The wind stress is confined to the surface mixed layer but there it exceeds the pressure gradient and so drives the westwards equatorial current within the mixed layer.
Where do important zones of deep water coastal upwelling occur?
Along the eastern boundaries of oceans, particularly associated with subtropical gyres
Name the 2 vertical component/divisons of the Ocean?
Photic and Aphotic
What does benthic mean?
-within the water column between the surface ocean and deep ocean
-Associated with the seafloor;at the lowest levels of the ocean
-In, on and close to the seafloor
-From ocean surface to greatest depths
What makes up the Photic zone?
Epipelagic
What is the depth range for the Epipelagic zone?
0-200m
What makes up the Aphotic zone?
-Mesoplagic
-Bathypelagic
-Abyssalpelagic
-Hadalpelagic
What is the average depth and temperature range for the Mesopelagic zone?
200-700/1000m
>10 deg C
What is the average depth and temperature range for the Bathpelagic zone?
700/1000-2000/4000m
10-4 deg C
What is the average depth and temperature range for the Abyssalpelagic zone?
2000/4000-6000m
<4 deg C
What is the average depth and temperature range for the Hadalpelagic zone?
6000-10,000m
<4 deg C
What are the three classifications of Marine biota according to lifestyle?
-Planktonic
-Nektonic
-Benthic
There IS possibility of overlap between these classifications.
Describe the lifestyle of Planktonic biota?
They have no individual movement hence, they drift with the current.
Some swim weakly-nektoplankton
Describe the types of Planktonic biota?
Animals, plants, bacteria and archaea
E.g Phytoplankton and zooplankton
Where do planktonic biota live?
Pelagic Province
Describe the size of planktonic biota?
-Microscopic to large in size
-Most <2cm
Describe the Migration of Planktonic biota?
Diel and seasonal vertical migration
Describe the lifestyle of Nektonic biota?
Active swimmers which are able to swim against the current, as they are macroscopic animals (have muscles)
Describe the lifestyle of Nektonic biota?
Highly diverse group
Where do Nektonic biota live?
Shallow to deep water?
Describe the Migration of Nektonic biota?
Can migrate long distances
Describe the size of Nektonic biota?
Generally >2cm but VERY diverse
Describe the lifestyle of Benthic biota?
Anythig that lives on or near the sea floor/bed
Where do Benthic biota live?
Associated with marine sedimentary environments e.g tidal pools, continental shelf, abyssal plains
Describe the types of Benthic organisms?
-Most diverse grouping of marine organisms
-Subject to huge pressure differences
Describe the size of Bentic organisms?
Large size range from microscopic to macroscopic?
What are Autotrophs?
Obtain energy from sunlight to fix carbon
What are Heterotrophs?
Cannot fix carbon, rely on organic carbon for growth
How to biologically classify marine biota?
The 3 domains:
1-Bacteria (Prokaryotes)
2-Archaea (Prokaryotes)
3-Eukaryotes (have a nucleus)
Describe the characteristics of Bacteria:
-Dominate microbial communities in al the less extreme habitats
-Specialised to habitat conditions supporting their growths
-Mostly unicellular, some multicellular
-Mostly heterotrophic, some autotrophic
-Important role in ocean nutrient recycling
E.g Cyanobacteria
Decsribe the characteristics of Archaea:
-Most primitive forms of life on Earth
-Unicellular, less complex than bacteria
-Especially adept (proficient) at exploiting environmental extremes., e.g. thermophiles and acidophiles
-Live around hydrothermal vents, hot springs, sea ice, polar environments
-Important ecological functions e.g. nitrogen cycling
What are the four kingdoms in the Eukaryote domain
-Protista
-Fungi
-Plantae
-Animalia
Describe the characterists of Protista?
-Mostly unicellular but may be colonial or more rarely multicellular
-Marine protists typically range in size form 2-200 micrometers
-May be autotrophic, heterotrophic or mixotrophic
-E.g. Dinoflagellates, Coccolithophores, Diatoms
Describe the characteristics of Protista?
-Heterotrophic protists
-Abundant as fossils for last 540 million yrs
-Planktonic and Bentic forms
-Sedimentary deposits across global oceans
-E.g Planktonic/Benthic Foraminifera
Describe the charcteristics of fungi:
-Very few marine fungi (<0.1% of land based fungi)
-Heterotrophic- decompose organic matter
-Associations with marine animals (e.g. corals, and sponges), plants and algae
-Fond in nearly ever marine habitat explored, from surface waters to kms below ocean sediments; abundant in shallow itertidal zone
Describe the Charcateristics of plantae:
-Multicellular eukaryotes
-Autotrophic; conduct photosynthesis, use CO2, produce oxygen
-Mainly inner continental shelf where there is suffiicient light
-3 types; red, brown anf green algae
Dsecribe the characteristics of Animalia:
-Multicellular heterotrophic eukaryotes
-Metazoa (have differentiated body parts)
-2 types; invertebrates and vertebrates
What is the global biodiveristy of marine species?
~15%
What is the biodiversity of marine species?
-~98% Benthic species
-~2% Pelagic species
What is ecology?
The study of the interaction of organisms with each other and with their physical and chemical environments
What do ecological interactions determine?
The distrubution of marine organsims
What is primary productivity?
-The amount of carbon fixed by organisms during photosyntheis of chemosynthesis
-The quantity of organci matter synthesised from inorganic nutrients (C, N, P) by autotrophs
-Measured in g C m^-3 d^-1
What does respiration require?
Metabolic energy
What controls primary productivity?
-Light
-Nutrient availability (food)
-Temperature
-Salinity
What may cause differences in primary productivity?
Size of organisms and efficiency of primary productivity
What are the controlling factors of ecology?
-Light
-Nutrinet availability
-Temperature
-Salinity
-Water chemistry (e.g. pH)\
-Currents
-Waves
-Water pressure
-Substrate
Interactions between ALL of these variables
Distrubution of primary productivity -> marine organisms
Describe the distrubution total primary production in the ocean?
- 81.5% Open ocean
-18% Coastal ocean - 0.5% upwelling areas
What is the distrubution of total fish production in the ocean?
- ~50% Coastal ocean
- ~50% Upwelling areas
- <1% Open ocean
What is the global surface water temperature range?
- -2 to 33 deg C
- Strong seasonal variation
What is the average temp of the deep ocean?
<5 deg C (90% of the global ocean)
What is a thermocline?
Strong temperature gradient below surface mixed layer
What are the temperature characteristics of the Atlantic Ocean and its effect on species distribution?
-Tropical year-round, and temperate in warmer months
-~21-31 deg C
-Water temperature. define latitundinal range of speices distribution
-Warm currents e.g. Gulf Stream affect distribution
What are the temperature characteristics of the Arctic Ocean and its effect on species distribution?
-Average temp ~-1.8 deg C
-Tend to have large fish schools in ice-free wster
-Cold adapted species can tolerate colder conditions due to AFP compounds in blood
Why is temperature sometimes directly influential on rates of biological activity, growth, chemical reactions?
Organismswhich are unable to regulate body temperature are dependent on surrounding temperature
What are the concentrations of dissolved salts in seawater expressed as?
-parts per thousands(‰, g/kg)
-practical salinity units (psu)
-dimemsionless (no units)
What is the mean Ocean salinity?
35‰ (range from 32‰ to 38‰)
What are variations in sea surface salinity driven by?
-Differences in:
-Precipitation, evaporation, river run-off and ice formation and melting
-Seasonal va,ritaion in surface salinity is low in open ocean (<0.3‰)
Where is open ocean salinity highest?
Highest at tropical lattitudes (20-30 deg C), due to high evaporation
Where is salinity lowest in the Open ocean?
Lowest in polar regions, due to high precipitation and ice meltwater
Describe why salinity is high in enclosed seas?
Due to high evaporation rate, hence high salinity
What are Euryhaline species?
Species that tolerate a wide range of salinity e.g. oysters, estuarine environments (0-30‰)
What are Steholaline species?
Species that tolerate a narrow range of salinity e.g. echinoderms, most open ocean organisms
What leads to an unwelling zone?
Trade winds blowing across the open ocean and coastlines
What is primary productivity?
-The amount of carbon fixed by organisms during photosynthesis or chemosynthesis
-The quantity of organic matter synthesised from inorganic nutrients (C,N,P) by autotrophs
How much light is absorbed by the ocean?
45-50%
Describe the disrtubution of light which is absorbed by the ocean?
~50% infrared and ultraviolet - scattered and absorbed near the surface
-~50% Visible spectrum/ photsynthetically active radiation (PAR), decreasing with depth
How much light is scattered, refelcted and absorbed by clouds and the atmosphere?
45-50%
How much light is reflected from th surface ocean via albedo?
4-5%
Describe the photic zone?
Well-lit, good photosynthesis
Describe the dysphotic zone?
Twilight, poorly-lit, no photosynthesis or growing plants
Describe the Aphotic zone?
No light, chemosynthesis only
What nutrients do phytoplankton need to fuel primary production?
N, P , (Si), Fe
