System Earth Flashcards
what is the feedback factor (Daisyworld)?
ratio of equilibrium response to forcing to the response without feedback. The formula is (temp change with feedback)/(temp change without feedback)
between which values is the feedback factor?
0 and 1
what is a feedback loop?
a series of couplings arranged such that there is a round-trip of information
what is a positive feedback loop?
a loop that amplifies perturbation/ self enhancing
what is a negative feedback loop?
a loop that is self depreciating
what types of steady states do negative feedback loops form?
stable equilibria that are resistant to perturbations.
what types of steady states do positive feedback loops form?
unstable equilibria that is carried to a new state at the slightest disturbance.
can the daisyworld system resist to an increase in luminoisity?
yes, the equilibrium point just changes.
does an equilibrium coincide with optimum daisy growth?
rarely
what is Ekman transport?
the spiralling caused by the Coriolis effect whereby the net movement of the water is at a 90 degree angle to the wind.
what is upwelling?
a phenomenon that occurs at divergent points. The cooler water rises to the surface, bringing nutrients with it.
what is downwelling?
occurs in areas of convergence, the accumulation of water causes a sink process.
what is geostrophic current?
the current as a result of the coriolis effect, whic flows round the gyre clockwise in the Northern Hemisphere and vice versa.
why are gyres assymetrical?
due to vorticity
el nino year temperature anomalies
warm waters in eastern pacific
warm water upwelling in south america
wind flows west to east
more tropical storms in pacific, fewer in atlantic
la nina year temperature anomalies
east to west windflow
global temperature is lower
what causes increasing salt concentrations in oceans?
- evaporation of seawater from shallow seas.
- biological processes with animals
- chemical processes with reactions between seawater and volcanic rocks on the sea floor.
- fomation of sea spray. This salt is returned through rivers .
thermocline
temperature gradient within an ocean coloumn. This varies from 0 to 15 degrees in much of the world. decreases with depth
halocline
salinity gradient within an ocean column. increases with depth.
pycnocline
density gradient within the ocean column. Increases with depth.
AABW
Antarctic Bottom Water - very deep, cold, slow moving water
NADW
North Atlantic Deep Water - Evaporation occurs, increasing the salinity in this region, so it drops near Greenland.
what is the driving force of oceanic circulation?
global distribution of energy and indirectly by temperature differences.
which effect modifies surface ocean currents?
the coriolis effect.
where is cold saline water formed?
north atlantic and Weddell sea off Antarctica
what type of water sinks?
low temperature and high salinity
how does bottom water reach the surface?
through upwelling in another region - a large conveyer belt system.
what is the net effect of oceanic circulation?
redistribution of thermal energy across the globe.
describe the cryosphere
the frozen part of the Earth System. Includes glaciers, ice sheets, frozen lakes and rivers, sea ice and frozen ground.
how do glaciers move?
under the influence of gravity with ice flowing in response to ice-surface slope and by sliding over the bedrock.
how does sea ice move?
due to winds and ocean currents.
what is an ablation zone?
a zone in which ice melts
which season is most significant in determining ice accumulation?
summer - melting occurs much quicker than acccumulation
ice sheet dynamics
you have a diagonal equilibrium line and above this line, ice accumulates. It’s then heavy so pushes down the bedrock causing a sinking effect. As a result, the top of the ice sheet falls below the line and with this lower altitude, starts to melt. The bedrock is no longer under too much pressure and returns to its original position. and the cycle starts again.
sea ice feedback loop
ocean heat flux to atmosphere, increases temp, decreases ice cover, decreases ocean heat flux. Positive feedback loop.
where is new sea floor created?
mid ocean ridges
where is old sea floor destroyed?
subduction zones
which waves do we use to identify inner and outer core etc.?
s waves and p waves
how do we document the creation of sea floor on ridges?
magnetic stripes displaying mirror image patterns across teh mid ocean ridges
Wilson cycles
alternation between assembly and break up of super continents
why do super continents form?
position of mantle downwelling
why do super continents break up?
the insulating effect of super continent lead to sublithospheric heating and mantle upwelling
how deep is the ocean?
4000m
what is the radius of the earth?
6000km
surface area of a sphere
4 pi r^2
% of earth covered in ocean water
70%
residence time
reservoir size/ inflow or outflow
oxidized carbon
is combined with oxygen
reduced carbon
combined with mainly other carbon atoms, hydrogen or nitrogen
organic carbon
a form of reduced carbon. Tends to be highly reactive in the presence of oxygen.
primary productivity
amount of organic matter produced by photosynthesis in a unit time of a unit area
dominant primary producers in the ocean
phytoplankton
plankton
orgnaisms with any type of metabolism that float freely in aquatic environments.
photic zone
upper part of oceanic water column where there is sufficient light for photosynthesis - roughly 100m in open ocean
zooplankton
free floating marine consumers including small invertebrates and microorganisms that cannot photosynthesise.
biological pump
effect of photosynthesis in shallow wters, of the settling of OM and decomposition in deep waters lead to the transfer of CO2 and nutrients from the surface waters to the deep ocean.
redfield ratio
the optimum concentration that favours biological productivity
inorganic carbon cycle
dissolution into rain and sea water, chemical reactions with oxidized carbon.
order of oxidation for carbon
carbonate ion - bicarbonate ion - carbonic acid
carbonate minerals examples
calcite and dolomite
silicate
compounds of silicion and oxygen. They are most commonly found in igneous rocks
carbonates and silicates when it rains..
both dissolve but carbon slighlty quicker. chemical weathering neutralises the acidity of carbonic acid
where does carbonate metamorphism occur?
at destructive plate boundaries
feedback loops in carbonate-silicate cycle
temperature and rainfall
which cycles control biological productivity?
phosphorous and nitrogen, of which phosphorous is the limiting agent.
how is phosphorous supplied to earth?
weathering to the surface
where is the nitrogen supply?
bacterial nitrogen fixation
which UV wavelength is dangerous if not blocked by ozone?
200-320 nm
why is UVB so dangerous?
solar flux is relativley high and ozone absorption coefficient is relatively low
what is the ozone column depth?
measure of overhaed oxygen, but this varies regionally
where is ozone column depth at its highest and lowest?
high near the poles and low at equator. This, and global solar energy distribution = more ground-level UV at equator.
What is the Chapman mechanism?
a set of four reactions that describe ozone chemistry in a pure oxygen-nitrogen atmosphere.
what is important about the first and last equation in the chapman mechanism?
they affect the abundance of odd oxygen. They are both slow reactions.
why do chapman models over estimate O3 levels by 30%?
they exclude trace gasses which produce radicals that affect ozone. eg. nitric oxide, lightning, soils etc.
where and when does the ozone hole form?
over Antarctica in October
why is there a yearly ozone hole?
caused by reactions that occur on the surface of polar stratospheric cloud particles. They remove odd nitrogen, allowing chloring to wreak havoc.
why is there no ozone hole above the arctic?
wintertime polar vortex is notas well developed or long lasting as in the Antarctic
ozone decrease
at a lesser rate at the midlatitude in both hemispheres. Decrease appears to have slowed or stopped in the last few years.
Which protocol is most important for the ozone hole?
Montreal Protocol placed strict limits on freon and halon emissions. If followed, stratospheric chlorine concentrations should decline to their natural levels soon.
