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

Title: Glacially-driven changes in submarine hydrothermal activity

Host: Tamara Pico

March 2, 2021

Speaker: Maryjo Brounce, UC Riverside

Title: Enrichment in H2O and elevated Fe oxidation states are linked to material recycling in Izu-Bonin-Mariana lavas


Host: Jasmeet Dhaliwal

March 9, 2021

Speaker: Eva Scheller, Cal Tech

Title: The Fate of Water on Mars: Tracing Water-rock Interactions Through Modelling, Satellites, and Rovers


Abstract: There is abundant geological and mineralogical evidence for large volumes of liquid water forming hydrated minerals (such as clays), fluvial features, and potential ocean shoreline features early in Martian history (~3-4 Ga). For present-day Mars, we observe that most water is stored in the polar cap or subsurface ice. Based on observation, liquid water availability on Mars has decreased over geological time. However, the processes dictating the loss of water remain unresolved. Measurements of meteorites, rover samples, and the atmosphere show that the hydrogen isotope ratio of deuterium to hydrogen (D/H) of the atmosphere has increased over time. Previous studies suggested that the fractionation of atmospheric D/H can be explained by significant water loss on Mars due to atmospheric escape. However, these models cannot explain both the isotopic fractionation and large amounts of water in Mars’ past. We hypothesize instead that the sequestration of water into the crust during the first 1-2 billion years caused the long term drying of Mars and explains the atmospheric D/H evolution. We model Martian water history through a new integrated hydrogen isotopic model that simulates the three key processes affecting the Martian water budget and hydrogen isotopic composition including crustal hydration or the sequestration of water into the crust, volcanic outgassing of water, and atmospheric escape of water. Our model results show that long-term drying of Mars was caused by the sequestration of ocean-scale volumes of water in the crust simultaneously explaining the hydrogen isotopic budget of Mars and geological observations of large past water volumes. This has tremendous implications for considerations with regards to understanding climate and the continuous habitability potential of Mars on a geological time scale as aqueous environments are considered to provide both solvents and adequate thermophysical conditions for life as we know it. We find that ancient Mars (~ 4 Ga) had the most habitable conditions and that sequestration of water to the crust rapidly decreased the amount of liquid water early on in Martian history. The recently landed Perseverance rover will seek to constrain the processes involved in crustal hydration, the loss of water on Mars, and evidences for past habitability. The models presented in this study presents a possible framework for experiments and sampling by the Perseverance rover.

Host: Francis Nimmo