Cryospheric sciences 寒冷圏 科学 Heinz Blatter presently: ILTS, Hokkaido University, Sapporo...
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Transcript of Cryospheric sciences 寒冷圏 科学 Heinz Blatter presently: ILTS, Hokkaido University, Sapporo...
Cryospheric sciences寒冷圏 科学
Heinz Blatterpresently: ILTS, Hokkaido University, Sapporo
Special lecture on cryospheric Science
International Antarctic Institute
Graduate School of Environmental Science
Hokkaido University, Sapporo
Program 2013
Fridays, 16.30-18.00
•October 18: Cryosphere and climate •October 25: Land ice and snow •November 1: Sea ice •November 8: Glaciers •November 22: Ice sheets •November 29: Past of the cryosphere •December 6: Future of the cryosphere
ftp://iacftp.ethz.ch/pub_read/blatter/IAI-2013/
ppt and pdf files are available (see subdirectories)
Cryosphere:
κρύος: cold 「さむい」 σφαῖρα: sphere 「球、圏」
glaciers 「氷河」 , ice sheets 「氷床」permafrost 「永久凍土」
sea ice 「海氷」 , lake ice 「湖氷」 , river ice 「川氷」
snow 「雪」ice clouds 「氷の雲」 , hail 「氷雨」
hoar frost 「霧氷」
Climate system
• Atmosphere: – thermodynamics, wind, clouds, precipitation
• Hydrosphere (ocean): – heat transport, evaporation, roughness
• Pedosphere (solid Earth surface): – surface fluxes of heat, momentum, water
• Biosphere: – surface fluxes, evapotranspiration
Where is the cryosphere?
Cryosphere
• integral part of the climate system• many different sub-systems• many different processes• strong feedback mechanisms• strong influence to
– atmospheric dynamics and precipitation– ocean surface energy exchange– terrestrial water balance
this lecture presents an individual selection of topics:a physicists view
processes:
• dynamics:– wind, convection, ocean currents
• thermodynamics:– insolation: surface, atmosphere, ocean– thermal radiation: „greenhouse effect“– surface energy flux– meridional energy transport in atmosphere
and ocean
• weather:– clouds and precipitation (rain, snow, hail)
schematic of the climate system
IPCC
Weather vs. Climate
• weather: transient situation, days to weeks
• climate: mean state of the climate system, mostly atmosphere
– averaging time 30 years– high temporal and spatial variability on time
scales of 2, 5-10, 50-1000, 20‘000-400‘000, millions of years and longer
– gap around 30 years
spectrum of periodic variabilities of climate
Solar radiation
Solar „constant“
Mean solar radiative flux at Earth
rs: solar radius
ae: mean distance between Earth and the sun
Bs: radiative energy flux through the surface of the sun
(black body radiation at 5700 K: 6.28 · 107 Wm−2)
Latest corrected value: S = 1362 Wm-2
Global mean solar radiation on the surface of the Earth
A: Albedo (fraction of reflected solar radiation) (Earth: A=0.3)
e: eccentricity of Earth orbit
mean insolation:
Area of circle: r2
Surface area of sphere: 4r2
Global mean energy fluxes
seasonal variation of daily insolation in percent of the solar constant S=1362 W m−2
Radiation laws
Stefan-Boltzmann law:
B = T4 with σ = 5.67×10−8 W m−2 K−4
B=1368 W m−2 T=395 K (122oC)
B/4=342 W m−2 T=279 K (5oC)
0.7*B/4=239 W m−2 T=255 K (-18oC)
Radiation in the planetary system
``solar constant``: S proportional to 1/r 2
Temperature: T proportional to S1/4
T proportional to 1/r1/2
radiation temperature in the planetary system
Venus, Earth, Mars
• Venus: runaway greenhouse, only vapor
• Earth: water in all three phases
• Mars: runawy icehouse, only ice
Ice• solid state of water
• anomalies:– ice floats on water (expansion at freezing)– melting point decreases with pressure
• hexagonal lattice
• phase diagram of ice
ice crystal halos
role of ice in the climate system
• Albedo: most important– albedo: reflectivity of solar spectrum– snow and ice have high albedo– strong positive feedback
• latent heat flux– melt and freezing: snow, sea ice, land ice– sublimation: high altitude– crystallisation: ice clouds
albedo:fraction of reflected sunlight
• rock: 0.1• forest: 0.1-0.2• ocean: 0.05• desert: <0.3• snow: 0.4-0.9• glacier ice: 0.3-0.5
ice albedo feedback氷のアルベドの帰還
• controll circuit– negative feedback: perturbation is damped– positive feedback: perturbation is enhanced
regulator
target va lue
regulatedquantity
sensor
perturbation
ice albedo feedback• example:
– large closed snow cover in Eurasia,
– longer winter
• example:– decrease of sea ice cover
in arctic ocean– more absorption of solar
radiation– warmer in arctic ocean– further decrease of sea ice
cover
• polar climate more sensitive to changes in radiative forcing (greenhouse)
summary
• cryosphere is an important part of the climate system
• snow and ice play an important role in many fundamental processes in the climate system
as Goethe already mentioned 200 years ago:
ice is more important than you think