RECREATING CAMBRIAN CLIMATE IN AN EMIC WITH COMPARISONS TO EVAPORITE PROXIES

The Cambrian climate system is particularly difficult to model because of large uncertainties regarding atmospheric composition, paleogeography, and terrestrial conditions. In this study, best available Cambrian boundary conditions have been utilized in an Earth System Model of Intermediate Complexity (EMIC) to try to recreate climatic conditions consistent with the middle and late Cambrian sedimentary climate proxy record. Five experiments were run with a grid spacing of ~5.6° latitude x 5.6° longitude, late Cambrian continental configuration, atmospheric pCO₂ of 5700 ppm, and a solar constant of 1313.2 W/m². Experiments tested temperature and precipitation responses to terrestrial albedo at 0.37 and 0.1; variations in land surface topography (flat (=50m), “hilly” (≤1000m), and mountainous (≤3500m)); and soil water holding capacities of 0.06 and 0.17 m/m. Higher terrestrial albedo produced the largest changes in the temperature and precipitation patterns seen in this study. Model output for all experiments shows general agreement with climate proxies from the geologic record. Each experiment produced dry climatic conditions on tropical and sub-tropical Gondwana, consistent with middle and late Cambrian evaporite deposits. Favorable conditions for evaporite deposition on Laurentia and Siberia are less spatially consistent with proxies, but such findings are still promising given the lack of reliable constraints on topography and paleo-longitude. While more experiments are warranted, overall, the results from these experiments support continued use of the boundary and initial conditions chosen for this study. In general, results from these experiments represent a more comprehensive look at Cambrian climate dynamics than has previously been available.