AGU: Geophysical Research Letters

 

Editors' Highlight

Orbital variations and the rate of change in global ice volume

The famous research of Milutin Milankovitch, completed in 1941, suggested that periods of low summertime insolation in the northern high latitudes resulting from variations in Earth's orbit coincided with instances of glacial advances in Europe. To try to separate the general question of how orbital variations are expressed in climate changes and paleoclimate proxies from the specific question of what causes changes in ice sheet extent, Roe (2006) studied previous research and model results to better define Milankovitch's hypotheses. Using basic physical arguments, he showed that rather than specifying absolute global ice volume, as many previous studies recommend, it is much more informative to consider the time rate of change in global ice volume. This shift in perspective revealed that available records support a zero-lag, antiphased relationship between the rate of global ice volume change and summertime insolation in the northern high latitudes. Furthermore, variations in atmospheric carbon dioxide appear to lag behind the rate of global ice volume changes, implying only a secondary role for carbon dioxide in driving changes in global ice volume.

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