Orbital Theory of the Ice Ages. Interglacial. Glacial. Milankovitch Theory of the Ice Ages. Milutin Milankovitch (1941) Kanon der Erdbestrahlung und seine Anwendung auf das Eiszeitenproblem (Canon of Insolation of the Earth and Its Application to the Problem of the Ice Ages).
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Orbital Theory of the Ice Ages
Milankovitch Theory of the Ice Ages
Milutin Milankovitch (1941)
Kanon der Erdbestrahlung und seine Anwendung auf das Eiszeitenproblem
(Canon of Insolation of the Earth and Its Application to the Problem of the Ice Ages)
Orbital forcing of Earth’s climate
Changes in Earth’s orbital geometry
(eccentricity, tilt, precession)
Changes in the seasonal distribution of
Insolation (heat) as a function of latitude
Amplified by other processes
Glacial-interglacial climate change
decreases in winter radiation would favor snow accumulation, coupled this to the idea
of a positive ice-albedo feedback to amplify the solar variations.
Latitude of equivalent insolation
Obliquity is responsible for seasons
Obliquity creates inter-hemispheric heat imbalance (caloric equator shifts seasonally)
Effect of Obliquity on Insolation
difference in obliquity from 22 to 24.5o with other parameters held at present values
Effect on insolation is greatest at high latitudes
Same sign for respective summer season (hemispheric response is in phase).
varies at a period of
frequency [1/ky] Period [ky] Amplitude
0.02439 40.996 0.011168
0.02522 39.657 0.004401
0.02483 40.270 0.003010
0.01862 53.714 0.002912
0.03462 28.889 0.001452
Earth travel around the sun in an elliptical orbit with the Sun at one focus
What makes eccentricity vary?The gravitational pull of the other planets
the total insolation
received by the
Earth but the
difference is small!
0.5/342.7 = 0.15%
Dominant periods are
at ~400 and 100 kyrs
frequency [1/ky]Period [ky]Amplitude
Precession of the axis of the earth
Effect of precession from its minimum value (boreal winter at perihelion) to its
maximum value (boreal summer)
Precession affects insolation at both high and low latitudes.
Opposite sign in northern and southern hemispheres for respective season
(out of phase)
at ~19, 22 and 24 kyrs
frequency [1/ky]Period [ky]Amplitude
Eccentricity modulates precession
Insolation anomaly at 10 ka relative to present
The equilibrium line of a glacier is the location where winter
accumulation of snow is equal to the summer loss.
Decreased summer insolation lowers the equilibrium line
and glacier advances.
Shackelton & Opdyke, 1972
Pacific deep core V28-238
Variations in the Earth's Orbit: Pacemaker of the Ice Ages
J. D. Hays, John Imbrie, N. J. Shackleton
Science, 194, No. 4270, (Dec. 10, 1976), pp. 1121-1132
Marine oxygen isotope record shows
the same periodicities predicted by
Power spectrum of June Insolation at 65oN
The 100-kyr Problem
Classic Milankovitch forcing
(might consider alternatives)
Why does the climate system have so much 100-kyr power
Traditionally explained by non-linear response involving internal feedbacks.
Non-linear ice volume models invoking threshold response
Ice Sheet Growth Lags Summer Insolation
V = ice volumei = summer insolation at 65°N
i0 = insolation threshold
k = kA (accumulation) if i < i0
k = kM (melting) if i > i0
In climate record
(time series might
be too short)
V = ice volume
i = summer insolation at 65°N
t = tM if V > i (melting)
t = tA otherwise
Note weak forcing here
due to low eccentricity
Response (Imbrie and Imbrie, 1980)
Ice volume lags insolation forcing by a constant or varying
amount of time.
The “Stage 11” Problem
Ice volume model
Imbrie and Imbrie
Weak glacial (g)
Full glacial (G)
"Ignoring anthropogenic and other possible sources of variation acting at frequencies
higher than one cycle per 19,000 years, this model predicts that the long-term cooling
trend which began some 6,000 years ago will continue for the next 23,000 years."
(Imbrie and Imbrie, 1980)
George Kukla, Czechoslovakian Academy of Sciences, Prague
Robley Matthews, Brown University, Providence
A conference summary appeared in Science in October 1972.