Modeling Late Cretaceous climate and vegetation.

DeConto, Robert M., Hay, William W. and Bergengren, J. C. (1998) Modeling Late Cretaceous climate and vegetation. Open Access Zentralblatt für Geologie und Paläontologie / Teil 1, 1996 (11/12). pp. 1433-1444.

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Abstract

The Late Cretaceous was much warmer than today. There was
no significant ice at high latitudes, meridional thermal gradients were low,
and continental interiors remained warm during winter. Late Cretaceous
atmospheric C02 concentrations were about four times greater than today
and an enhanced "greenhouse" effect contributed to the overall warmth
of the Late Cretaceous. However , increases in atmospheric C02 tend to
increase temperatures at all latitudes and do not explain the very low
thermal gradients recognized in the geologic record. Increased poleward
ocean heat transport has been cited as a mechanism for maintaining low
meridional thermal gradients during the Cretaceous. However , ocean heat
transport values larger than the present day are difficult to reconcile. In
addition, low meridional thermal gradients suggest sluggish atmospheric
circulation, implying that the advection of heat from the warm oceans
into the continental interiors was limited. In general, paleoclimate simulations
using Atmospheric General Circulations Models (AGCMs) have not
been successful in simulating the low meridional thermal gradients and
warm winter continental interiors of the Cretaceous, forcing the concept
of "equability" to be questioned.
Until recently, the physical effects of vegetation on pre-Quaternary
climates have largely been ignored. Terrestrial ecosystems influence global
climate by affecting the exchange of energy, water, and momentum between the land surface and the atmosphere. In a new approach to pre-Quaternary
paleoclimate modeling, Campanian (80 Ma) climate and vegetation
have been simulated using a global climate model (GENESIS Version
2.0), coupled to a predictive vegetation model (EVE), resulting in a realistic
simulation of Late Cretaceous climate. The predicted distribution of
Late Cretaceous vegetation played an important role in the maintenance
of low meridional thermal gradients, polar warmth, and equable continental
interiors. High latitude forests reduced albedo, especially during snowcovered
months, and increased net surface radiation and latent heat flux.

Document Type: Article
Keywords: Modeling, climate, vegetation, Late Cretaceous
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
ISSN: 0340-5109
Date Deposited: 11 Feb 2016 09:44
Last Modified: 06 Feb 2018 11:03
URI: http://oceanrep.geomar.de/id/eprint/31318

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