Indexed on: 17 Jun '16Published on: 23 May '16Published in: Geology
Late Cenozoic surface uplift of the southern Sierra Nevada (Sierra; California, United States) is widely debated. Recent interpretations of lee-side isotope records from the southern Sierra suggest that the elevation of the southern Sierra has been sufficiently high to induce atmospheric flow patterns similar to modern patterns since the mid-Miocene, at ca. 12 Ma. The tendency for flow to deflect around a topographic barrier can be determined by the atmospheric stability, barrier height, and incoming wind speed. We test the sensitivity of flow deflection to elevation to determine what elevation would have been sufficiently high to establish modern flow patterns in the mid-Miocene. Using global paleoclimate models and idealized regional weather models, we find that the Miocene atmosphere was more stable than modern. We suggest that in a Miocene climate, flow patterns similar to modern patterns could have been achieved for elevations as low as 2 km, and that while Miocene lee-side isotope records from the southern Sierra may indicate that the southern Sierra has been a longstanding topographic feature, they may not have changed significantly in response to proposed late Cenozoic surface uplift of the southern Sierra.