Reply on RC1

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The European Alps are hypothesized to have experienced diachronous surface uplift in response to post-collisional processes such as, e.g., slab break-off. Therefore, understanding the geodynamic and geomorphic evolution of the Alps requires knowledge of its surface uplift history. This study presents the simulated response of regional climate and oxygen isotopic composition of precipitation (&delta;¹⁸O_p) to different along-strike topographic evolution scenarios. These responses are modeled to determine if diachronous surface uplift in the Western and Eastern Alps would produce &delta;¹⁸O_p signals in the geologic record that are sufficiently large and distinct for stable isotope paleoaltimetry. This is tested with a series of sensitivity experiments conducted with the water isotope tracking atmospheric General Circulation Model (GCM) ECHAM5-wiso. The topographic scenarios are created from the variation of two free parameters, (1) the elevation of the West-Central Alps and (2) the elevation of the Eastern Alps. Results suggest significant changes in the spatial patterns of &delta;¹⁸O_p, the elevation-dependent rate of change in &delta;¹⁸O_p (&ldquo;isotopic lapse rate&rdquo;), near-surface temperatures, precipitation amounts, and atmospheric circulation patterns in response to the different scenarios. The predictions for the diachronous surface uplift experiments are distinctly different from simulations forced with present-day topography and for simulations where the entire Alps experience synchronous surface uplift. Topographic scenarios with higher elevations in the West-Central Alps produce higher magnitude changes and an expansion of the affected geographical domain surrounding the Alps when compared to present-day topography. Furthermore, differences in &delta;¹⁸O_p values of up to &minus;2 to &minus;8 &permil; are predicted along the strike of the Alps for the diachronous uplift scenarios, suggesting that the signal can be preserved and measured in geologic archives. Lastly, the results highlight the importance of sampling far-field and low-elevation sites using the &delta;-&delta; paleoaltimetry approach to discern between different surface uplift histories.