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

lydia

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

brenhin

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

tyler

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

tyler2

Host: Neil Foley


January 29, 2019

Speaker: Sarah Slotznick, UC Berkeley

Title: Magnetism as a lens into redox conditions in ancient environments

 sarah

Host: Matthew Clapham


February 5, 2019

Speaker: David Wahl, USGS

Title: Climate and Land Use Change in the Maya Lowlands

Host: Sarah White

February 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.

holly

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.

fernanda

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