ATM 623: Climate Modeling

Brian E. J. Rose, University at Albany

Lecture 12: Orbital variations, insolation, and the ice ages

About these notes:

This document uses the interactive IPython notebook format (now also called Jupyter). The notes can be accessed in several different ways:

Many of these notes make use of the climlab package, available at https://github.com/brian-rose/climlab

In [1]:
%matplotlib inline
import numpy as np
import matplotlib.pyplot as plt
from climlab import constants as const

1. The ice ages


Recent Earth history (past few million years) has been dominated by the repeated growth and retreat of large continental ice sheets, mostly over the land masses of the Northern Hemisphere.

Extent of glaciation

The images below show typical maximum extents of the ice sheets during recent glaciations (grey) compared with present-day ice sheets (black)

In [2]:
from IPython.display import display, Image
url = []
url.append('http://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Iceage_north-intergl_glac_hg.png/480px-Iceage_north-intergl_glac_hg.png')
url.append('http://upload.wikimedia.org/wikipedia/commons/thumb/4/44/Iceage_south-intergl_glac_hg.png/480px-Iceage_south-intergl_glac_hg.png')

for u in url:
    display(Image(u))

Pacing of ice ages: evidence from ocean sediments

This figure shows a global record of oxygen isotopes recorded in the shells of marine organisms. This record tells us primarily about variations in global ice volume -- because the net evaporation of water from the oceans to build up the ice sheets leaves the oceans enriched in heavier isotopes.

The x axis is plotted in Thousands of years before present (present-day is at zero on the left).

In [3]:
Image('../images/Lisiecki_Raymo_Fig.4top.png', width=800)
Out[3]: