CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Bush, A.B.G.
Date : 2003.
Title : Changes in ENSO from the Last Glacial Maximum to today.
Publication : Canadian Geophysical Union. Annual Meeting, May 10 -14, 2003. Banff Centre, Banff, Alberta.
Issue :
Page(s) :
Abstract
Transition from glacial to interglacial climates implies a change in the climatological mean state of the atmosphere-ocean system. Changes of the background state are known to alter the behaviour of dynamic oscillations in the atmosphere-ocean system such as the El Ni no Southern Oscillation (ENSO). A sequence of numericalsimulations areperformed with a coupled atmosphere-ocean general circulation model configured for the Last Glacial Maximum (LGM), for 9000 years B.P., for 6000 years B.P., and for today. We examine the changes exhibited in the frequency and amplitude of simulated ENSO events. The control simulation produces Nino 3.4 statistics that are comparable to modern observations. From the LGM to today, ENSO events increase in amplitude and decrease in frequency. Because ENSO events are so rapid in the LGM and 9000 B.P. simulations, the standard deviation of the Ni~ no 3.4 index in these simulations is much smaller than today. The normalized Nino 3.4 index therefore exhibits larger amplitude in the LGM and 9000 B.P. simulations. An additional simulation with doubled atmospheric carbon dioxide indicates that this trend of increasing amplitude and decreasing frequency continues in a warmer climate. Mechanisms that regulate the climatological equatorial easterlies (such as topographic, orbital, and midlatitude eddy forcing) are shown to play an important role in determining the mean climatological state of the atmosphere-ocean system and, hence, the nature of ENSO in the Late Quaternary.
Bibliography of Canadian Geomorphology