Paleoclimate of the Kimmeridgian/Tithonian (Late Jurassic) world: II. Sensitivity tests comparing three different paleotopographic settings

Abstract

Topography and location of continents largely determine present-day climate. We conclude that in the geologic past paleotopographic expression was equally important. However, in the geologic record paleotopography is difficult to asses and compile because it is largely a self-destructive environment without record and is rarely addressed in the literature. An objective of this study is to test the sensitivity of paleoclimate to paleotopography by comparing three different Late Jurassic scenarios.Paleotopography influences many paleoclimate parameters to varying degrees. To test the sensitivity of paleoclimate to modeled paleotopography for simulations incorporating a Late Jurassic reconstruction, we ran three simulations using the same boundary conditions of paleogeography (land and ocean) and atmospheric CO2 concentration, 4x the pre-Industrial level (1120 ppm). One simulation contained mountain ranges of variable height of 3 km. In another, all the mountain ranges were reduced to 1 km highlands. The third simulation used a constant 500 m height for all land grid cells.The sensitivity tests indicate that paleotopography is an important boundary condition. Without realistic paleotopography, flat or idealized continents surrounded by bodies of water do not produce realistic paleoclimate results. We conclude that in paleogeographic reconstructions the location and extent of mountain ranges and highlands should be recognized and given suitable elevations consistent with their plate tectonic origins, settings, and geologic ages.