Geology Reference
In-Depth Information
Precession
ε
Obliquity
Ψ
Earth
ϕ
Rotation
H
Dynamical
ellipticity
Eccentricity
e
Sun
Π
Figure 5.1
Astronomical
parameters affecting Earth-
Sun position. Source: Hinnov
and Ogg 2007.
ω
Longitude of the
perihelion measured from
moving vernal equinox (
Ψ
+
Π
)
Longitude of the
perihelion measured from
the equinox of reference
Eccentricity: e
0.6
0.4
0.2
405-kyr cycles
e
e
e
95-128 kyr cycles
e
0
Obliquity:
ε
25
24
+
+
+
+
+
23
22
41 kyr cycles
19-24 kyr cycles
Precession Index: esin
ω
+0.6
0
-0.6
ETP
6
4
2
0
-2
-4
-6
0.0
0.2
0.4
0.6
0.8
1. 0
1.2
1. 4
1.6
Time (Ma)
Figure 5.2
The astronomical parameters 10
4
-10
5
years oscillations for the past 1.6 million years according to the La2004
nominal solution (Laskar et al. 2004). Main periodicities in kiloyears are indicated in red. ETP is the sum of the standardized
eccentricity E, obliquity (i.e., tilt T) and precession index P (Imbrie et al. 1984). Source: Hinnov and Ogg 2007.
The parameters that affect climate are (i) Earth's orbital eccentricity e, which
determines Earth-Sun distance, (ii) Earth's axial tilt, or obliquity ε, and (iii) the
precession of Earth's rotation axis or the
precession of the equinoxes
ψ, which
determines the timing and location of the seasons with respect to the Earth's
orbit. Numerical solutions (e.g., Laskar et al. 2004, 2011) have been calculated
for hundreds of millions of years into the past, revealing complex modulating
behavior in the astronomical parameters (Figures 5.2 and 5.3). The orbital
