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Flashcards in External Controls Deck (21)
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what does it mean by solar variability

how many sunspots present


define sunspot

dark areas on suns surface which are central parts of active regions

more sunspots = higher solar output


what sunspot cycle are we in now

cycle 25


what happened to sunspots in 2008 and 2019

blank sun
no sunspots visible

like 1954 sun

means lower solar radiation output


2020 sunspots

higher actvity from sun which suggest more spots

2014 they though sun had gone to sleeep


do sunspots impact climate change


during medieval optimum there was warm summers and winters as lots of sunspots

Little Ice age in Maunder minimum = colder winter as less sunspots


what does it mean by orbital forcing

milankovitch cycles

collective effects of changes in earths movements on climate over thousands of years


what are the 3 recognised variations in changes of earths orbit around the sun?

eccentricity roll
obliquity axial tilt
precession wobble


how long does eccentricity take for one cycle

100,000 yrs


how long does obliquity take for one cycle

41,000 yrs


how long does precession take for one cycle

26,000 yrs


describe eccentricity

creates a rounded perfect circle and changes to elliptical circle due to grav forces

not a large impact on amount of insolation recieved in a yr but influneces lengths of seasons

high eccentricity = greater seasonal variation also linked to ice sheet dvelopment


describe obliquity

tilt of earths axis of rotation

varies from 21.5 - 24.5 degrees

influnces solar radiation reaching earth

large tilt - dimishes contrast in insoltaion between low and high latitudes

(low tilt favours ice sheet developemnt due to low SR)

greater seasonal contrast - area towards sun in summer . tilted away in winter - affects high lats most


describe precession

the season during which earths nearest the sun (perihelion) and furthest away (aphrlion) varies.

n. hemis tilted away from sun at aphelion - \

n hemis tilted towards sun at aphelion - / -favours ice sheet development lower sun radiation


EVIDENCE of milankovitch cycles

cyclic deposits in s.spain - hard/soft layer etc

oxygen isotopes - measure size of ice sheet and temp of water


oxygen ratios

16O ligher
18O heavier


where are more 16O found


older water

lighter and colder more

during interglacial periods not enriched in 180 but 16o returns quickly to oceans to maintain balance


where are more 18O found

evaporation removes 16o leaving heavier 18o behind

during glacial periods oceans enriched in 18o as 16o stored in ice sheets and doesn't return quickly to ocean


define el nino

irreuglar warming of sea surface temps off peru and ecuador to central pacific

high air pressure in west/ low pressure in east

weakeneds trade winds


define la nina

colder counterpart of el nino in eastern pacific

intense winds

strengthening of norm


ENSO meaning

el nino southern oscillation

atmospheric pressure changes from east to west which influnces temp and rain on globe