Winter 2021

Tuesdays at 3:30 PM

Zoom information can be found on the EPS advising Google calendar

January 5, 2021

Speaker: Rowan Martindale, University of Texas Austin

Title: Synthesizing records of marine extinction and environmental change in the Early Jurassic (~183 Ma)


Host: Matthew Clapham

January 12, 2021

Speaker: Natalie Burls, George Mason University

Title: How will the tropical Pacific respond to global warming? The influence of the extra-tropical ocean and cloud-feedbacks

Abstract: Several oceanic and atmospheric mechanisms have been put forward to describe the response of the tropical Pacific to global warming. Still uncertainties persist in their interaction and relative importance, with projections varying substantially across climate models. Adding to this complexity is the time-scale dependance of specific processes, wherein the wind-driven subtropical overturning circulation and adjustment of the equatorial thermocline plays a key role. We will review these mechanisms within both complex and idealized models and their role in the transient and equilibrium response of the tropical Pacific to warming. We will contrast fully-coupled and slab-ocean perturbed CO2 simulations, as well as a unique set of climate simulations across which we systematically scale the strength of the low cloud cover (LCC) feedback under abrupt 2xCO2 forcing within a single model, thereby isolating the impact of this feedback. Finally, in search of an observational constrain on the equilibrium response to warming, we will turn to the last time in Earth’s history that atmosphere CO2 estimates exceeded 400pm, the Pliocene.


Host: Nicole Feldl

January 19, 2021

Speaker: Danny Sigman, Princeton University

Title: The role of the Southern Ocean in glacial/interglacial CO2 change

Abstract: In the effort to identify the cause of the lower atmospheric concentration of CO2 during ice ages, the potential impact of the Southern Ocean, the circumpolar ocean around Antarctica, has long been recognized. I will describe an increasing body of nitrogen isotope evidence – from the organic matter bound within sedimentary microfossils – that both the (higher latitude) Antarctic and (lower latitude) Subantarctic Zones of the Southern Ocean played roles in lowering the atmospheric concentration of CO2 during the ice ages. In the Subantarctic, the data indicate dust-driven iron fertilization of phytoplankton during the peak ice age conditions, which enhanced the flux of organic carbon out of the surface ocean. In the ice age Antarctic, the exchange of water between the surface and subsurface was apparently reduced, a state that I summarize here as “isolation” of the Antarctic surface; this could have stanched the leak of biologically derived, deeply stored CO2 that occurs there today. As to the physical cause, a range of observations point to weakening of westerly wind-driven Antarctic upwelling. Moreover, new high-resolution nitrogen isotope records suggest orbital controls on the upwelling that can explain important aspects of glacial/interglacial CO2 change, such as the lag of CO2 behind climate at the initiation of the last ice age and the gradual rise in CO2 over the Holocene.


Host: Mathis Hain

January 26, 2021

Speaker: Nikki Seymour, Stanford University

Title: Discovery of the Orocopia Schist in northern Plomosa Mountains and ongoing investigations into Laramide subduction and metamorphism in west-central Arizona


Host: Jeremy Hourigan

February 2, 2021

Speaker: Margaret Shanafield, Flinders University, Australia

Title: Hydrologic aspects of rivers Down Under: from the coast to the Red Centre


Host: Margaret Zimmer

February 9, 2021

Speaker: Phil Bart, Louisiana State University

Title: New constraints on the post-LGM retreat of the Bindschadler Ice Stream from the Ross Sea continental shelf, Antarctica


Host: Slawek Tulaczyk

February 16, 2021

Speaker: Jill Marshall, University of Arkansas

Title: How trees grow their own pot- Quantifying the role of trees as wind-wiggling, tap-dancing and crowbar-wielding Critical Zone architects


Host: Margaret Zimmer

February 23, 2021

Speaker: Jenny Middleton, Columbia University


Host: Tamara Pico

March 2, 2021

Speaker: Maryjo Brounce, UC Riverside


Host: Jasmeet Dhaliwal

March 9, 2021

Speaker: Eva Scheller, Cal Tech


Host: Francis Nimmo