Or From Millennia to Hours The Decreasing Scales of the Orbital Theory of Multin Milankovitch Adapted from Dr Randy Cerveny Presidential Professor ASU Milankovitch Theory Milutin Milankovitch ID: 618517
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Slide1
“Being Milutin Milankovitch”
Or “From Millennia to Hours: The Decreasing Scales of the Orbital Theory of Multin Milankovitch”Adapted fromDr. Randy CervenyPresidential Professor, ASUSlide2
Milankovitch Theory
Milutin Milankovitch, Serbian mathematician and astronomerIn 1938, hand-computed insolation at 65° N based on orbital variations for two 6-month seasons (summer & winter)Slide3
Milankovitch Theory
He computed variations in three primary orbital parameters:TiltEccentricity
Precession of the Longitude of Perihelion in relation to the Moving Equinox
(“Precession”)Slide4
Milankovitch Theory
TiltThe variations in the axial tilt of the Earth. This orbital component has a cycle of 42,000 years for the Earth to shift from an axial tilt of 22.1° to 24.5
°
and backSlide5
Milankovitch Theory
EccentricityThe variations associated with the shape of the Earth’s orbit (oblique to circular)The primary cycle of eccentricity is 93,000 years with a secondary cycle at 400,000 years.Slide6
Milankovitch Theory
PrecessionMost complex of the three mechanisms.Refers to the season in which perihelion is occurring as a function of the orientation (or “wobble”) of the Earth’s axisSlide7
Milankovitch
TheoryCurrent PrecessionEarth’s perihelion in early January given the current axial orientation towards the star PolarisBut 11,000 years from now, perihelion will occur in JulyThe primary cycles for precession are 19,000 and 23,000 years.Slide8
Two huge problems in gaining acceptance for his theory
No reliably-dated evidenceUnknown which dates were the most importantTheory put on back burner until more evidence gathered...Slide9
CLIMAP & the ocean corers
International project in mid-1970sHelp better understand when the last ice age occurredIncludes two important research thrustsFirst, a chronology of past climates was begun using deep-sea marine cores.Slide10
Hays, Imbrie & Shackleton: Pacemaker to the Ice Ages
Spectral analyses of cores suggested existence of distinct correlation. Closely matched the cycles computed by Milankovitch for the Earth’s three orbital
mechanisms
.Slide11
Producer vs. consumer?
Remember a producer is a organism that makes a certain chemical.A consumer is an organism or thing that uses a certain chemical.