19405737 Hay It has been common practice to run an atmospheric (AGCM) or oceanic (OGCM) general circulation model and search for results that might be confirmed or rejected by geologic data. AGCM output describes average conditions over large areas, but the non-marine geologic deposits providing the best record of climate were rarely laid down under average conditions. This mismatch between the model results and the geologic data that might be used for their validation has been a major problem in paleoclimate studies. A new AGCM, GENESIS, designed specifically for paleoclimate research, and a new method for validating the results of a paleoclimate model, the Proxy Formation Model (PFM), can be used together to make more realistic simulations that can be validated by comparison with real data. A validated AGCM can then be used to drive an OGCM to investigate circulation of the ocean. GENESIS began as a heavily modified version of CCM1 and differs from it in treatment of water vapor transport, atmospheric convection from the earth's surface, solar radiation related to aerosols, cloud parameterization, vegetation, soil, snow and sea ice. Its ocean is a slab, with heat capacity and ocean heat transport included. GENESIS has independent AGCM and surface grids, allowing for much better representation of surface paleogeographic, vegetation, and soil conditions. The PFM is a quantitative link between climate model data and geologic observations. PFM's are being developed for sedimentary deposits that form under known climatic conditions. 1) evaporites; 2) bauxites and laterites; 3) coal (peat). The PFM prescribes boundary conditions that must have existed at the location where the deposits occur. This additional "grid point" is inserted into the climate model, and the calculated environmental parameters (temperature, humidity, etc.) are compared with conditions required for formation of the deposit. Under this proposal, we will develop 4 additional PFM's : 1) sand deserts; 2) coastal sea ice; 3) mountain glaciers; 4) ice sheets. The climates of the Early and Late Cretaceous were different from each other and both were different from Late Cenozoic climates. In the Early Cretaceous there was high-latitude sea ice, strong mid- latitude seasonality, and a tendency for the "Atlantic" to become anoxic. In the Late Cretaceous there was no high-latitude ice, less seasonality, and a more oxic ocean (with two brief notable exceptions). The differences were a response to changing boundary conditions: 1) from isolation of the western Tethys-Atlantic-Indian seaway from the eastern Tethys-Panthalassic Ocean during the Early Cretaceous to more open connections in the Late Cretaceous: 2) rise in the atmospheric content of CO2 from a lower level in the Early Cretaceous to a high level in the Late Cretaceous: 3) increase in poleward ocean heat transport form a low level during the Early Cretaceous to a high level in the Late Cretaceous: and 4) rise of sea level to a mximum in the Late Cretaceous. The paleogeography, paleoclimatology energy balance of the Earth in the Cretaceous are well enough known to run AGCM's and subsequently OGCM's that can be rigorously validated using PFM's based on geologic data.
