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Abrupt climate change and transient climates during the Paleogene: a marine perspectiveDetailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.
Document ID
20040090320
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Zachos, J. C.
(University of Michigan Ann Arbor 48109)
Lohmann, K. C.
Walker, J. C.
Wise, S. W.
Date Acquired
August 21, 2013
Publication Date
March 1, 1993
Publication Information
Publication: The Journal of geology
Volume: 101
Issue: 2
ISSN: 0022-1376
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: OCE-9012389
CONTRACT_GRANT: OCE-9101861
CONTRACT_GRANT: NAGW-176
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Exobiology
NASA Discipline Number 52-30
Non-NASA Center
NASA Discipline Exobiology

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