Week 6

Question 1

What is the percentage of carbon that goes into the ocean, land/biosphere/atmosphere?

Answer 1

25% in ocean

25% in land/biosphere

50% in the atmosphere

Question 2

What impact has humans had on the carbon reservoirs?

Answer 2

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

Question 3

Can you do a quick recap on poleward energy transport?

Answer 3

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

Question 4

Can you give an example of an ice sheet? What is the speed of their flow?

Answer 4

Greenland and Antarctica

1km or more per year of flow - fast for a glacier

Question 5

What are some of the fluxes in the carbon cycle?

Answer 5

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

Question 6

Without humans what is the state of fluxes?

Answer 6

they are roughly balanced - changes in reservoirs are not huge without the impact of humans

Question 7

How have humans perturbed the cycle?

Answer 7

• 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

Question 8

Can you tell me a little about fluxes in the cryosphere?

Answer 8

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

Question 9

What is the role of the biosphere in terms of co2?

Answer 9

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

Question 10

What is the biological pump in the ocean?

Answer 10

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

Question 11

What is the solubility pump?

Answer 11

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

Question 12

When Co2 dissolves in the sea water what does it form?

Answer 12

Carbonic acid

lowers the ph - higher acidity

Question 13

The Mauno Lao carbon graph what are the red wiggles caused by?

Answer 13

Day to day or month to month variation

Question 14

How thick on average is the ocean?

Answer 14

4km

Question 15

What would happen if all the water in the ocean was to warm and expand 1%?

Answer 15

sea level would rise by 40m

Question 16

What is the relationship with old ice sheets and sea level change?

Answer 16

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

Question 17

How is sea level being predicted in models?

Answer 17

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

Question 18

How historically has climate changed?

Answer 18

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

Question 19

How is the past climate reconstructed?

Answer 19

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

Question 20

What are milankovitch cycles?

Answer 20

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

Question 21

What are the three parameters of milankovitch cycles? can you explain them individually and what do they do together?

Answer 21

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

Question 22

Some natural explanations for glacial cycles please?

Answer 22

• 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

Question 23

What is uncertain about the temperature and Co2 relationship with glacial and interglacial cycles?

Answer 23

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

Question 24

When was the last glacial maximum?

Answer 24

20,000 yrs ago

Question 25

Where was the last glacial maximum?

Answer 25

Much of north america and norther europe was covered in large ice sheets - up to 4km thick

Question 26

What impact does glaciation have on sea level?

Answer 26

large ice sheets means lower sea level

Question 27

What is the post-glacial rebound?

Answer 27

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

Question 28

How has sea level changed historically?

Answer 28

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

Question 29

What is the idea of the snowball earth?

Answer 29

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

Question 30

What is el nino?

Answer 30

when there are warmer than average tropical east pacific and cooler in the west pacific

Question 31

what is la nina?

Answer 31

cooler than average tropical east pacific and warmer than average west pacific

Question 32

What is ENSO stand for and what is it?

Answer 32

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

Question 33

Can you expand on how the atmospheric and sea surface temperature interact in ENSO?

Answer 33

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

Question 34

What is the impact of ENSO on precipitation?

Answer 34

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)

Question 35

What is ENSO impact on temperature>

Answer 35

El nino

wamer
- south america
-south africa
-europe

Colder
- Sweden and the scandis
- new Zealand
- Mexico

Question 36

What is the north atlantic osciliation?

Answer 36

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

Question 37

What is the NAO cycle?

Answer 37

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

Question 38

What does volcanic erruptions release into what part of the atmosphere?

Answer 38

sulphur dioxide into the strateosphere (15km)

Question 39

What is the imapct of volcanic erruptions?

Answer 39

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

Question 40

Where is the carbon in the earth system?

Answer 40

resevoirs, including the atmosphere, land, biosphere, and ocean but with large fluxes between them

Question 41

How is the carbon in the earth system modified by humans?

Answer 41

the resevoirs were roughly balanced, humans have changed this balance through the burning of ff

Question 42

What do future changes in sea level look like?

Answer 42

Increases in thermal expansion and ice sheet melt, at a much longer timescale than the atmosphere
continuing to 2300 and beyond

Question 43

What did climate look like in the past?

Answer 43

large variation in temperature which can be reconstructed using proxies

Question 44

what caused historical climate variation?

Answer 44

natural forcing such as volcanoes and orbital changes (milankovtich) and anthropogenic forcing - GHG emissions

there are also cycles and natural variability