Week 5 Flashcards
What happens if F>0
the earth needs to warm in order to emit more infrared energy to space and re-establish radiative balance
What is λ? and what are the measurments?
w/m^2/oC
determines how efficiently the earth cools to space per unit of global warming
Why does the atmosphere circulate?
fuelled by solar energy
- it works to redistribute heat horizontally (eddy currents circulate circularly and correolis effect) and vertically (convection)
- more energy is focused in the tropics and less in high latitudes therefore there is more heating in some areas
What is the meriodional distribution of radiative heating?
Idea that there is an uneven distribution of solar radiation = there is more heating near the equator than at the poles - the beam is spread over a larger area which decreases the flux of energy per unit of area
What is the consequence of meridional distribution of radiative heating?
in the tropics the atmosphere recieves more heat than it can radiate away
the excess radiative energy in the tropics is transported to higher latitudes by the circulation of the atmosphere and the ocean
this varies depending on the season
what would a net short or long wave mean?
Net short = net solar radiative heating
net long = net infrared radiative cooling
What is the biggest source of energy transport?
the atmosphere but oceans are also important for energy transport
Can you describe the energy transport between the poles and the tropics?
Northward is defined as postive so the transport is positive to the NH
negative in the SH - but oceans also important for transport especially in the tropics
the graph for this is a flipped S with a line down the middle for the southern hemisphere it is negative for the northern is it positive
What are the two ways that meriodional energy is transported?
The mean meridional circulation - north south
eddy (turbulent) motions - spinning motion or turbulence
Can you explain how heat and convection work?
Air is heated from the surface, it becomes less dense than the air above it and start to rise = convection
air will stop rising when it is sufficiently cooled by radiation
the air has to be replenished from the surface and this created cells - due to the rotation of the earth the cells break up –> 3x per hemisphere
this is further influenced by the trade winds, westerlies and polar easterlies
rising air is warm, sinking air is cool - contributes to the transport of heat in the tropics to the polls
Tell me about the Hadley cell?
tropical cell - profound impact on the climate - important for rainfall and cloud distribution
What are the three kind of winds and where do they move to and how?
Trade winds - equator to the west - bend in both hemispheres
westerlies - west to east
easterlies - east to west
Why are the winds not straight?
The rotation of the earth deflects the waves therefore the turn in a different direction
What is the Coriolis force?
the force that affects flow in a rotating frame of reference
- we are spinning around an axis - at the poles there is a small circle at the equator it is a much bigger circle in terms of distance travelled
What is the effect of the coriolis force?
the velocity at which the earth’s surface rotates varies with latitude
this has an impact on the atmosphere and ocean circulation
this can be more noticeable in some regions compared with others due to this idea of the distance travelled in each rotation being different at the poles compared to the equator
What is the impact of the coriolis effect on deflection?
Northern - to the right
Southern- to the left
there is low pressure in the middle - therefore a lack of air there and air likes to flow to low pressure therefore the air surrounding it starts to go inwards
correolis force happens and the air moving to the centre will bend to the right (n)/left(s) depending on the hemisphere - therefore the air flows inwards and bends creating a spiralling motion around the area of low pressure
they are counter clockwise in the north and clockwise in the south in a spinning motion
What are low and high pressure systems associated with?
Low pressure is associated with storms - low pressure has weak descent and as it cools it causes condenssation and cloud formation
high pressure has less clouds - high pressure has descent and the air is dry
What do storms contribute to energy mixing?
They are a large source of energy transport or heat transport in the atmosphere
they mix cold and warm air
What gives rise to the jet stream?
the difference in temperature - warmer regions on one side and cold on the other - drives winds
add the effect of rotation
What is the jet stream?
belts of strong eastward winds in the mid-latitudes of each hemisphere in the upper atmosphere of about 10km
- coincident with strong temperature gradients - typically warm air is in the south and cold air is in the north
get their energy from the temperature difference between tropics and high latitudes
What drives ocean currents?
- surface winds
- temperature and salinity differences - both of which control density
What is the relationship between denisty and temperature of the ocean?
Density increases with decreasing temperatures and increasing salinity
the densiest waters are found near the sea ice margins, very cold water and high salinity - because salt is left behind when ice forms
density reduces with temperature as water increases it expands and the same mass of water takes up more volume
Why is water density important for the heat transfer in the ocean ?
Dense water sinks - it is cold so cold water sinks - this is critical for the overturning of water as it mixes things
What is the Atalantic meridional overturning circulation
ocean circulation that transports heat from low to high latitudes on average
- very complicated pattern of deep water formation and surface level warm currents
Deep water formation near the poles as close to sea ice - heat is being released to the atmosphere warm waters are flowing towards the norm - heat release thus transport
What percentage of extra heat in the climate goes into the ocean? why?
90%
have a high heat capacity and can take a lot of energy to heat water by a certain amount compared to the low heat capacity of air and land
this means it will take a long time for oceans to reach an equilibrium even if we stopped emitting Co2 today the oceans would continue to warm
What is the difference between an ice sheet and an ice shelf?
Ice sheet = large mass of continental ice - flow on long timescales - idea of ablation and accumulation for growth
ice shelf = a thick floating platform of ice that forms where a glacier or ice sheet flows onto the sea
What is the relationship between ice sheets and ice shelves?
ice sheets can become unstable when ice shelves disappear
potential for accelerated sea level rise if this happens
- ice shelves are floating - holds the ice sheet back due to this bouyancy - if this is gone, the flow of the ice sheet into the ocean will increase potential for ACC. melting and sea level rise
warming of ocean melts the ice sheet from below - lubricant to accelerate flow into warm oceans - ACC. warming
What is the issue with ice sheets?
They are non-linear - the only way to build an ice sheet is accumulation over years and can be lost v quickly - tipping point
Briefly describe the water cycle?
It is the exchange of water over reseviours, laakes, vegetation etc. water is transported from the oceans/bodies of water to land as vapour
flows back to the ocean/water bodies through runoff - surface and groundwater
formation of clouds and rainfall - exchange of water
What determines global wet and dry regions?
The distribution is determined by the circulation of the atmosphere which transports heat and moisture
- idea of the circulation cells - warming and cooling air and differing amount of cloud and rainfall - peaks at mid-latitiudes - cell convergence
What are the future changes for the water cycle?
on average - wet gets wetter and dry gets drier - wind patters are exacerbated - more moisture away from the sub tropics and brinign more into the mid-lat
direct consequence of the higher oisture content in the atmosphere - Clausius- Clayperson
important for future water management in the sub-top, med regions
How will precipitation change in the future?
Projected to decrease over the Med, South Africa and Aus
more precp - Equitorial regions and at high lat
pattern is not symmetrical - what happens is dependenton winds and this is a great uncertainty
Can you briefly describe the carbon cycle? like what are the major components? and how have humans messed this up?
Atmosphere, ocean, land and geological reservoirs
rapdi cycling btween land, atmosphere and ocean reservoirs
much slower cycling between geological and other reservoirs
without human activity the fluxs are in balance - the size of each reservoir stays constant
HUMANS…
- perturbed the cycle - extracting carbon from the geological res. in ff.
- land use - deforestation
this cannot be balanced easily because it takes a long time to put carbon back into the geological res.
How much of the total carbon budget has gone into the ocean and the land?
the ocean accounts for 25% of ALL the CO2
25% in the land
the remaining has gone into the atmosphere
What is the impact of the biosphere?
Plants take up Co2 and emit oxygen in photosynthesis
plants required CO2 for respiration - grow better with more co1
What is the role of the ocean in terms of CO2?
the ocean takes up Co2 in two ways
- the biological pump - tiny organisms take up C02 as they grow and deposit on sea floor as they die and sink
= form ff - the solubility pump - Co2 is directly taken up by seawater
Describe the process of ocean acidification?
When Co2 disolves in water - it forms Carbonic Acid
this lower the pH - makes it more acid
What are the white cliffs of dover made out of?
Carbonate
formed by the sedimentation of tiny organisms at the bottom of the ocean over millions of years
What is the relationship between carbonate and ocean acidification?
carbonate tends to dissolve as water becomes more acidic
organisism that rely on carbonate eg. coral or mollusks - struggle to build their shells
ocean acidification interuprs this biological cycle
Why does global warming cause sea level rise?
- water expands as it warms - thermal component
- glaciers melt
- ice sheets melt
NB MELTING SEA ICE DOES NOT CAUSE SEA LEVEL RISE - THIS IS BECAUSE IT IS FLOATING THINK ABOUT A GLASS WITH ICE IN IT
What sort of time scale will oceans warm?
Long time scales - idea of the high heat capacity of oceans - even if we stop emitting carbon the seas will continue to warm
there is a delayed ocean waring in response to present and past emissions
Can you briefly outline the different time scales of the climate spheres? Fastest–>slowest
response to forcing occur at different scales
FAST
- atmosphere
- oceans - decades (top layer) to thous (deep ocean)
- ice sheets - tho to adjust
What is the imapct of the different climate sphere time scales for climate models?
Makes it very difficult to predict the long term impacts of GHG emissions
What are the five spheres?
Lithosphere
Cryosphere
Biosphere
Hydrosphere
Atmosphere
