LANDSCAPES WITH LATITUDE: QUANTIFYING THE INFLUENCE OF CLIMATIC REGIMES ON GEOMORPHIC EFFECTIVENESS (Invited Presentation)

Geomorphic processes across a landscape are responsible for the production, transport, and export of sediment out of a watershed. Therefore, improving the fidelity of climate and tectonic histories from sedimentary archives requires a robust understanding of the how these systems influence landscape evolution. We use a gradient of climatic regimes set-up by the N-S latitudinal trend of the Andes to parameterize a suite a model runs using the CHILD landscape evolution model. Specifically, latitudinal variations in storm duration, intensity, and frequency statistics from NCEP/NCAR Reanalysis data are used to explore the influence of modern climate regimes on geomorphic effectiveness. Synthetic landscapes with steady and uniform rock-uplift and erodibility are modeled to a quasi-steady state. Geomorphic effectiveness is measured by the modeled steady-state elevation, where higher elevations represent less effective regimes. Geomorphic effectiveness varies along latitude by 2-30 fold, depending on the specifics of model parameterization, such as inclusion of an erosion threshold. In general, geomorphic efficiency is highest in the tropics (5-15°S) and mid latitudes (30 to 35°S), and is lowest in the subtropics (20 to 25°S) and upper-mid latitudes (45 to 50°S). Geomorphic efficiency also varies across the width of the orogen as a result of orographic effects. Additionally, latitudinal trends generated using stochastic storms diverge from those generated using mean annual precipitation (MAP) suggesting that MAP may not capture the true geomorphic efficiency of the modern climate system in some locations. This point is considered further by comparing the trend in the modern climate’s geomorphic efficiency with long-term metrics of erosion. The model results and comparison with trends in erosion rates provide further constraints of climate’s importance in geomorphic processes and topography. We suggest that the latitudinal control on climate regime may explain some discrepancies in previous studies comparing erosion rates with climate metrics.