Winter 2019
Winter 2019
Tuesday Afternoons at 3:30 PM
Nat Sci Annex 101
January 15, 2019
Speaker: Lydia Staisch, USGS Menlo Park
Title: A simple case of shear: the onset of strike-slip faulting in Northern Tibet and implications for plateau evolution
Host: Neil Foley
January 22, 2019
Speaker: Brenhin Keller, UC Berkeley
Title: Insights into the operation of the Earth system from the compositional evolution of the continental crust
Host: Terry Blackburn
January 23, 2019
Special WES Seminar at 12:00PM in E&MS A340
Speaker: Tyler Mackey, MIT
Title: A clumped isotope test for Neoproterozoic Snowball Earth deposits of NE Svalbard
Host: Neil Foley
January 23, 2019
Special WES Seminar at 2:30PM in E&MS A340
Speaker: Tyler Mackey, MIT
Title: Antarctic microbial mats as windows into ancient ecosystems
Host: Neil Foley
January 29, 2019
Speaker: Sarah Slotznick, UC Berkeley
Title: Magnetism as a lens into redox conditions in ancient environments
Host: Matthew Clapham
February 5, 2019
Speaker: David Wahl, USGS
Title: Climate and Land Use Change in the Maya Lowlands
Host: Sarah WhiteFebruary 12, 2019
Speaker: Holly Oldroyd, UC Davis
Title: Turbulent Land-Atmosphere Interactions in the Swiss Alps:
Abstract: Steep terrain poses several challenges to interpreting and modeling turbulent surface-atmospheric exchanges because it violates key assumptions (e.g., horizontal terrain) necessary for traditional parameterizations and classical theories to hold. State-of-the-art numerical weather, climate, hydrologic and remote sensing models rely on empirically-based, surface-atmosphere exchange parameterizations that were developed for horizontal and homogeneous terrain. These classical parameterizations translate how surface conditions, such as roughness, temperature and soil moisture, influence the atmosphere, and vice versa, via turbulent fluxes of momentum, heat and water vapor. Therefore, they cannot represent the fundamental physical processes that arise from the atmosphere's interactions with heterogeneous and sloping terrain. As micrometeorological research shifts to increasingly non-idealized environments, the lens through which we view classical atmospheric boundary layer theory must also shift to accommodate unfamiliar behavior. In this presentation, near-surface observations of nocturnal flows over a steep (35.5 degree), Alpine slope will be compared to classical theories for nocturnal boundary layers (NBL) over uniform, horizontal terrain and over gentle slopes. In each case, the NBL is characterized by a strong, terrain-aligned, stable thermal stratification. Over flat terrain, this temperature inversion tends to stabilize perturbations (suppress turbulence) and inhibit vertical motions. Hence, the buoyancy flux term in the turbulence kinetic energy (TKE) budget equation acts as a sink. Over sloping terrain, however, streamwise (upslope) buoyancy fluxes, contribute to the total vertical buoyancy flux since the gravity vector is non-orthogonal to the underlying terrain. If the ratio of the streamwise to surface-normal heat fluxes is greater than the cotangent of the slope angle (which decreases with increasing slope angle) then buoyant TKE production occurs, despite the NBL thermal stratification. Due to a dearth of observations over steep terrain, the turbulence structure of such flows and the implications of buoyant TKE production in modeling them have gone largely unexplored. As an important consequence of this characteristic, conventional stability characterizations require careful coordinate system alignment and interpretation. In addition, traditional flux-gradient relations are shown to inadequately parameterize scalar transport over steep terrain. Finally, the observations provide an avenue to propose new theories for the steep-slope katabatic flow regime and explore key objectives for future field observation strategies.
Host: Margaret Zimmer
February 19, 2019
Speaker: Dr. Fernanda Santos, UC Merced
Title: The effects of fire on soil carbon mobility and transport
Absrtact: Fire is a common, widespread phenomenon in many parts of the world, and has multiple, complex effects on soil chemical and physical processes. Fire can transform the chemical composition of bulk soil organic matter (SOM) and its soluble component and convert organic matter into more stable forms of organic carbon collectively known as pyrogenic carbon (PyC). Although much progress has been made in describing the thermal transformations in bulk SOM and estimating PyC stocks and mineralization rates, there is limited data available on the thermally induced chemical changes of the soluble portion of SOM. Additionally, the controls of PyC persistence in soils remain unclear. In this talk, I will present results from my past and ongoing research work that examined: 1) changes in the chemical composition of water-extractable organic matter from soils heated at low and intermediate temperatures; and 2) the effects of physicochemical composition and soil depth on PyC leaching. I argue that examining the terrestrial controls of fire-derived DOC dynamics is key to understand PyC cycling at the soil-stream interface.
Host: Andi Greene
February 25, 2019 - Special WES at noon in E&MS A340
Speaker: Jess Adkins, Caltech
Title: The mechanism of CaCO3 dissolution in seawater and a possible way forward on CO2 sequestration
Host: Jim Zachos
February 26, 2019
Speaker: Jess Adkins, Caltech
Title: Coupling between the carbon and sulfur cycles from measurements of modern rivers and Phanerozoic carbonates
Host: Jim Zachos
March 5, 2019
Speaker: Paul Koch
Title: Plio-Pleistocene decline of African megaherbivores – hominin or environmental drivers?
March 12, 2019
Speaker: Xiaoli Dong, UC Davis
Title: Ecosystem Spatial Self-organization in South Florida
Host: Margaret Zimmer
