| Title: | Twenty Years of Cretaceous Climate Modeling |
| Author: | Eric J Barron |
| Date Submitted: | 05/01/2002 |
| Address: | 2217 Earth-Engineering Sciences Building
EMS Environment Institute
University Park
PA
USA
16802
|
| Phone: | 814-865-1619 |
| Email: | eric@essc.psu.edu |
| Co-Authors: | |
| Affiliation: | Penn State University |
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| Abstract URL: | http://cis.whoi.edu/science/GG/ccod/viewAbstracts.cfm?RefNumber=19725584 |
| Keywords: | Cretaceous, General Circulation Models, Climate Modeling |
| Abstract: | The first General Circulation Model simulations of Cretaceous climates were published exactly twenty years ago. By modern standards, the models were primitive. These early experiments were based on a 60 to 90 day simulation with fixed insolation (January or July), with an energy balance ocean lacking any heat capacity (so called "swamp" ocean that providing a source of moisture and enabled evaporative cooling and albedo to be included in the surface temperature equation), and a terrestrial albedo to account for surface vegetation. Our focus was on the extent to which continental geometries would alter the structure of the circulation, whether sea level had a direct impact on atmospheric warmth, and whether these changes would allow simulation of a reduced equator-to-pole temperature gradient. The progress of the last two decades is noteworthy. Paleoclimate modeling has followed closely in the footsteps of climate modeling in general with improvements in radiative transfer calculations, the addition of a mixed layer ocean and the seasonal cycle, the addition of fully resolved ocean models, and the inclusion of vegetation as an interactive component of the climate system. Our ability to collect and interpret the wealth of geochemical, physical and biologic information about the Cretaceous has also expanded considerably. It is clearly the marriage of models with Cretaceous observations that has yielded remarkable advances in our understanding. We are much closer to recognizing that "the Cretaceous" includes a remarkable diversity of climates. We have made substantial progress in attempting to "predict" climate parameters that can be closely tied to proxy information. In the near future, we can expect to see such things as biomes, isotopic composition, and ocean biogeochemical cycles as standard elements of paleoclimate modeling. To a considerable degree, we now recognize what types of observations really challenge the models and visa versa. The marriage of models and data has focused our attention on tropical sea surface temperatures and the nature of high latitude continental interiors. We are approaching a whole new set of problems as we begin to explore the significance of the coupled system response, including such remarkable avenues as the role of run-off in governing the deep circulation. Yet, explaining (and simulating) the nature of Cretaceous warmth and the nature of poleward heat transport during times of polar warmth have remained intriguing problems. Without a doubt, the Cretaceous is an example of how a single forcing factor is inadequate to describe the climate change recorded in Earth history, and is an example of how the coupled system must play a key role in climate change. |
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