The Role of Topography on Continental Water Cycling and Water Stable Isotope Compositions over Geological Time Scales

Abstract:

The rise and collapse of orogens through geologic time has been a major forcing on terrestrial climate and water cycling. Orogens substantially affect the type, amount, and distribution of precipitation on continents through their influence on atmospheric dynamics and circulation, vapor transport, and precipitation processes. Stable isotope compositions (δ¹⁸O/δD) of authigenic minerals can preserve a record of ancient meteoric waters and, in this way, offer a glimpse into past water cycles and their response to topographic evolution. In practice, however, stable isotope records can be difficult to interpret, both due to the complex response of the water cycle to topographic change and due to coeval climate change.

Isotope-enabled global climate models (GCMs) provide a tool for quantifying the response of water isotopes to topography and climate, and can be used in collaboration with proxy records to refine our understanding of long-term paleoclimate change. Our previous work using isotope-enabled GCMs has demonstrated that Cenozoic uplift of the Andes and the North American Cordillera had a large and complicated influence on the water cycle and stable isotope compositions. In this talk, we report on a series of experiments simulating surface uplift of the Tibetan Plateau and Himalayas using an isotope-enabled GCM (ECHAM5-wiso), and compare stable isotope and water cycle responses to those resulting from uplift of the Andean and North American orogens. Our preliminary results indicate that as in the central Andes and western North America the response to surface uplift is regionally large, spatially heterogeneous, and nonlinear. In contrast to the Andes and North American Cordillera however, surface uplift of the Tibetan Plateau and Himalayas has a more widespread influence on stable isotope compositions that extends across the Northern Hemisphere.