Week 6 Flashcards
What is the percentage of carbon that goes into the ocean, land/biosphere/atmosphere?
25% in ocean
25% in land/biosphere
50% in the atmosphere
What impact has humans had on the carbon reservoirs?
they have pertrubed the balance between the resevoirs- they are imbalanced and their sizes have been altered
human influences are not balanced from the changes in fluxes
Can you do a quick recap on poleward energy transport?
The earth recieves more energy in the tropics than at high latitudes
the difference in heating fuels the circulation of the atmosphere, which works to transport excess heat from the tropics to the poles
the ocean also transports energy from the tropics to the poles - but less efficiently than the atmosphere
Can you give an example of an ice sheet? What is the speed of their flow?
Greenland and Antarctica
1km or more per year of flow - fast for a glacier
What are some of the fluxes in the carbon cycle?
there is rapid cycling due to plants photosynthesising and respiring and decomposing
this can remove Co2 but also put it back in - cant remove all the Co2 from the atmosphere but the fluxes can be large
Without humans what is the state of fluxes?
they are roughly balanced - changes in reservoirs are not huge without the impact of humans
How have humans perturbed the cycle?
- extracted carbon from the geological reservoir through ff
- through land use change such as deforestation
- cemend production
nb this perturbation cannot be balanced easily because it takes a long time to put carbon back into the geological reservoir
about 3 petagrams of carbon a year but sufficient to perturb the system
Can you tell me a little about fluxes in the cryosphere?
there are very small fluxes in terms of the formation of new rocks - however this takes time
there are volcanoes
fossil carbon is being redistributed into different places in the atmosphere - and there is more in the ocean as well
What is the role of the biosphere in terms of co2?
plants takeup Co2 and emit oxygen in photosynthesis
since plants need Co2 to grow this can increase in higher Co2 climate however there is a limit and doesn’t apply to all plants
using satellites it is clear that there has been an increase in the size of the land res. because of an increase in Co2
What is the biological pump in the ocean?
the idea that organisms take up Co2 as they grow
deposit this back onto the sea floor wen they die and sink
this forms ff in eons
What is the solubility pump?
CO2 is direclty taken up by seawater
- you can dissolve Co2 in the water - Co2 can be dissolved in the water under high pressure- once you release the pressure CO2 can escape
When Co2 dissolves in the sea water what does it form?
Carbonic acid
lowers the ph - higher acidity
The Mauno Lao carbon graph what are the red wiggles caused by?
Day to day or month to month variation
How thick on average is the ocean?
4km
What would happen if all the water in the ocean was to warm and expand 1%?
sea level would rise by 40m
What is the relationship with old ice sheets and sea level change?
We used to have massive ice sheets over the land which pushed the land underneath down - these have now gone but the land is still responding to this and is moving upwards
therefore we need to account for the changing in the height of land surface to ensure a good understanding of sea level rise
How is sea level being predicted in models?
in the future with more emissions, there will be more warming and thus sea level rise
there is more sea level rise regardless of the scenario due to the delay in ocean response - high heat capacity
How historically has climate changed?
There have been large changes over 500 m yrs
last 10k yrs have been relatively stable
but the temperatures are uncertain and may not be representative of the entire globe - use of proxies
there have been glacial/interglacial cycles over periods of about 100,000 yrs
How is the past climate reconstructed?
paleoproxies
= indirect evidence of former cliamte conditions
eg. tree rings, isotopes of oxygen and carbon, fossilised pollen and plankton, lake and ocean sediments, animal bones, charcoal and landscape feature
req. when there are no direct measurements of climate variables - eg. temperature or precipitation
eg. Dome C ice core in Antarctica - about 800ys of records for climate - very detailed paleoproxy
What are milankovitch cycles?
The cause for the glacial cycles lies in variations in the earths orbit
the earths orbital parameters vary naturally over this of yrs with regular or predictable cycles
What are the three parameters of milankovitch cycles? can you explain them individually and what do they do together?
Eccentricity - how oval/circle shaped the earths orbit is (eggs centricity)
the bigger the eccentricity the more oval it is - the bigger the variation, when it is less eccentric more circular and get less variation
Obliquity - the angle of the tilt - varies how strong the seasons are
Precession - spin around the earths axis - i.e. the idea that the location of the north star changes- sometimes it is close to polaris and sometimes close to valaga
these all change on different time scales however, together the parameters control the spatial distribution of insolation, and the seasonal cycles
Some natural explanations for glacial cycles please?
- variations in the northern hemisphere summer insolation is critical for glacial cycles
- weaker summer insolation in NH favours coolder climate
Growth of land ice controlled by the accumulation in the summer - mainly down to summer temperatures - if you glacier melts away completely in the summer then is it harder to have a glacial period
- global ice volumes have varied in tandem with temp over global cycles
- large ice sheets in NH - ice sheet changes are associated with large positive albedo feedback
What is uncertain about the temperature and Co2 relationship with glacial and interglacial cycles?
warming leads to Co2 release from the oceans however the mechanism is not entirely certain
the effect is that CO2 changes are a large positive feedback in the glacial and interglacial cycles
could be the microphysical processes at the top of the ocean - turbulence effects the solubility at the top of the ocean - net flux of Co2 going out at certain points therefore temperature increases - impacts the solubility of te oceans
When was the last glacial maximum?
20,000 yrs ago
Where was the last glacial maximum?
Much of north america and norther europe was covered in large ice sheets - up to 4km thick
What impact does glaciation have on sea level?
large ice sheets means lower sea level
What is the post-glacial rebound?
the ice sheets from the last glacial max were v thich and they compressed the earths mantel = crust deformation
disappeared relatively recently therefore the mantel is still bouncing back - rebound is fastest is where sea level is falling
How has sea level changed historically?
Relative to the last 1m yrs sea level is at peak high
global sea level was more than 100m lower 18,000 yrs ago
sea level varies in sync with glacial and interglacial cycles - in sink with temperature
What is the idea of the snowball earth?
ice caps gets close enough to the equator therefore preventing the earth to warm
potential causes
- volancoes, eccentricity - combination of natural factors that mean that the outgoing radiation is more than incoming and there is cooling sufficient for the formation and maintenance of glaciers
key takeaway is that the earths climate varies naturally as well as through human induced climate change
What is el nino?
when there are warmer than average tropical east pacific and cooler in the west pacific
what is la nina?
cooler than average tropical east pacific and warmer than average west pacific
What is ENSO stand for and what is it?
El Nino-Southern Oscillation (ENSO)
- coupled ocean and atmosphere variability
El Nino/nino refer to the ocean conditions - it is measured using sea surface temperature but there is natural variability and a random component associated with this cycle as well
the south osciliation is the atmospheric part
Can you expand on how the atmospheric and sea surface temperature interact in ENSO?
in El Nino
- warmer east pacific –> more convcetion in the east paciic –> anomalous winds push warm water east
convention where the water is warmest
- trade winds east to west and warm wateris pushed to the west pacific - el nino trade winds are wekaed, no longer pushing the water west, the water slides back to the centre through convcetion - different air circulations occur which brings the warm water east
What is the impact of ENSO on precipitation?
El nino shifts rainfall pattersn in many different parts of the world however, this can vary between el ninos
the strongest shifts are mainly a drying over Australia and a wetness over the south of Amrica (not south America)
What is ENSO impact on temperature>
El nino
wamer
- south america
-south africa
-europe
Colder
- Sweden and the scandis
- new Zealand
- Mexico
What is the north atlantic osciliation?
a change in jet stream position over the north Atlantic
positive NAO = low pressure over iceland and jet stream shifts north
storms are directed further north in positive - negative they are directed south
if the jet stream moves further south - the UK gets cooler, drier air - harsher winter
What is the NAO cycle?
it is not really an oscilation it is regular but chaotic
- varies on timescales of weeks/months - more presistent than just a random occurrence
it is a WEATHER REGIME
- internal to the atmosphere - no forcing from the ocean required but it can also be forced
What does volcanic erruptions release into what part of the atmosphere?
sulphur dioxide into the strateosphere (15km)
What is the imapct of volcanic erruptions?
produces a haze - suphate aersol which can block sunlight
negative radiative forcing - this is an external forcing
large eruptions can cause global cooling but only for a few yrs
Where is the carbon in the earth system?
resevoirs, including the atmosphere, land, biosphere, and ocean but with large fluxes between them
How is the carbon in the earth system modified by humans?
the resevoirs were roughly balanced, humans have changed this balance through the burning of ff
What do future changes in sea level look like?
Increases in thermal expansion and ice sheet melt, at a much longer timescale than the atmosphere
continuing to 2300 and beyond
What did climate look like in the past?
large variation in temperature which can be reconstructed using proxies
what caused historical climate variation?
natural forcing such as volcanoes and orbital changes (milankovtich) and anthropogenic forcing - GHG emissions
there are also cycles and natural variability
