Skip to Main Content
GEOREF RECORD

Obliquity forcing with 8-12 times preindustrial levels of atmospheric pCO (sub 2) during the Late Ordovician glaciation

Achim D. Herrmann, Mark E. Patzkowsky and David Pollard
Obliquity forcing with 8-12 times preindustrial levels of atmospheric pCO (sub 2) during the Late Ordovician glaciation
Geology (Boulder) (June 2003) 31 (6): 485-488

Abstract

Results from coupled ice-sheet and atmospheric general circulation models show that the waxing and waning of ice sheets during the Late Ordovician were very sensitive to changes in atmospheric pCO (sub 2) and orbital forcing at the obliquity time scale (30-40 k.y.). Without orbital forcing, ice sheets can grow with pCO (sub 2) level as high as 10 times preindustrial atmospheric level (PAL). However, with orbital forcing, ice sheets can grow only with pCO (sub 2) levels of 8 times PAL or lower. These results indicate that the threshold of pCO (sub 2) for the initiation of glaciation is on the lower end of previously published estimates of 8-20 times PAL. The ice-sheet model results further indicate that during exceptionally long periods of low summer insolation and low pCO (sub 2) levels (8-10 times PAL), large ice sheets could have formed that were able to sustain permanent glaciation under subsequently higher pCO (sub 2) values. This finding suggests that in order to end the Late Ordovician glaciation with a rise in pCO (sub 2) , atmospheric pCO (sub 2) must have risen to at least 12 times PAL. Ice sheets therefore introduce nonlinearities and hysteresis effects to the Ordovician climate system. These nonlinearities might have also played a role in the initiation and termination of other glaciations in Earth history.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 31
Serial Issue: 6
Title: Obliquity forcing with 8-12 times preindustrial levels of atmospheric pCO (sub 2) during the Late Ordovician glaciation
Affiliation: Pennsylvania State University, Department of Geosciences, University Park, PA, United States
Pages: 485-488
Published: 200306
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 33
Accession Number: 2003-045524
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200314
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal