DeFord Lecture Series

DeFord Lecture Series Speaker Schedule

The DeFord (Technical Sessions) lecture series has been a requirement and a tradition for all graduate students since the late 1940s. Once the official venue for disseminating DGS graduate student research, the DeFord Lecture series is now the forum for lectures by distinguished visitors and members of our community. Faculty and researchers from the Jackson School have invited prestigious researchers from around the world to present a lecture in this series. This is made possible only through a series of endowments, such as those funding past Distinguished Lectures.

The list below shows all the scheduled talks this semester. If you would like to meet with any of the speakers, please contact them or their hosts directly.

DeFord Lecture Series 2022-23 Speaker Schedule

All talks are Thursdays from 4-5PM (CST) in the Boyd Auditorium (JGB 2.324).  Lectures will be recorded, and most past lectures are posted on the Jackson School YouTube channel.

Date Speaker/
Mar 23
Stephanie Pierce
Harvard University
Functional adaptive landscapes (help) illuminate major transitions in vertebrate evolution
Abstract: The concept of the adaptive landscape has been an invaluable tool to the field of modern evolutionary biology by providing a representation of how fitness and selection vary within populations of organisms. Trait variation can be visualized as a multidimensional “landscape” (analogous to a mountain range) with height on the landscape corresponding to fitness; selection acting on populations is expected to drive populations “up-hill” to cluster around “adaptive peaks” where fitness is maximized. Although originally implemented in the study of population genetics and microevolution, paleontologist G.G. Simpson expanded the idea of the adaptive landscape to explain phenotypic change over macroevolutionary timescales. Specifically, he linked large-scale biological and geological processes, such as extinction and climate change, with shifts in adaptive peaks representing selection acting upon phenotypic traits that were of “functional benefit”. Despite decades passed, the practical application of Simpson’s adaptive landscape in macroevolution has been limited by computational challenges in quantifying the functional performance outcomes of morphological traits and how they vary across a vast phenotypic landscape. Here I will introduce a new method called “functional adaptive landscape analysis” which determines the functional trade-offs associated with morphological adaptation to differing selection regimes. I will then use this method to explore two major transitions in vertebrate evolution. First, I will tackle the fish-to-tetrapod transition and the origin of land locomotion by modelling the evolution of the humerus bone. I will show that the earliest tetrapods occupied a performance valley between water and land adaptive peaks, but that adaptations suggest some capacity for terrestrial locomotion. Second, I will discuss the ‘reptile’-to-mammal transition and the evolution of the mammalian backbone. Using vertebral morphometric data and experimental biomechanics, I will test the lateral-sagittal functional paradigm and demonstrate how this long-held idea is too simplistic to explain mammalian backbone evolution. Together, I will establish the utility of functional adaptive landscapes in quantitatively testing longstanding questions in the vertebrate fossil record and its potential application to unravelling the relationship between form, function, and adaptation across deep time.
Langston Lecture
Mar 30
Dustin Trail
University of Rochester
Traversing the chemical landscape of the early Earth
Abstract: The conditions that gave rise to life on Earth are still unknown. Despite this, there is broad agreement that the early planet was habitable, with interactions between low-temperature water and rock, potentially creating the substrate upon which life arose. While planetary-scale constraints are a crucial part of habitability, it’s likely that key prebiotic chemistry occurred in smaller, more localized environments. This presentation will examine the early Earth environment on a global scale through zircon chemistry, while also delving into possible local environments and scenarios that may have played a significant role in prebiotic chemistry or the emergence of life.
Apr 6
Laure Zanna
Harvard University
Apr 13
Ken Williams
Lawrence Berkeley National Laboratory
Sep 1
Andrew Moodie, Jackson School of Geosciences Leveraging natural delta land-building processes to enable coastal landscape sustainability
River deltas provide many societal benefits, and sustainability of these landforms may be impacted by human modification and global climate change. For example, anthropogenic river control structures inhibit natural sediment dispersal that is necessary to sustain coastal lands in the face of rising sea levels. Declining land area strains human welfare by way of reduced ecosystem services, damaged cultural connections, and hindered economies. To rehabilitate drowning coasts in the Mississippi River delta (Louisiana, USA), engineered river diversions are expected to restore sediment dispersal and promote land growth, but a limited understanding for long-term natural deltaic landscape building processes limits our ability to optimally place diversion structures in space and time. In this presentation, I will demonstrate how reduced-complexity numerical modeling informs natural delta land building processes, supports quantifying societal benefits and costs of diversions, and identifies hazards to land building diversions.
Sep 8
Marc Hesse,

Jackson School of Geosciences

Mass transport through Europa’s ice shell and the habitability of Europa’s internal ocean
Jupiter’s moon Europa is thought to have an ocean beneath its ice shell and the habitability of this internal ocean may depend on the availability of redox gradients. Downward transport of radiolytic materials produced at the surface through the ice shell likely sets the flux of oxidants into the ocean. Astronomical observations suggest that Europa’s near surface regolith contains 1014 to 1018 mol of O2 and likely other oxidants. Today I will discuss recent work in my group on three different potential transport mechanism for the oxidants through the ice shell: Convective overturn, brine percolation and impacts. Due to the strong temperature dependence of the thermal conductivity the ice-shell has very thick conductive lid that prevents the transport of oxidants through the ice by convective overturn. A second process is the drainage of large volumes of near-surface brines beneath chaos terrains. I argue that these brines percolate readily and can potentially transport surface-oxidants into the ocean at a rate of 106 to 1010 mol/yr. Finally, I discuss the effect of impacts on mass transport through the ice. We have shown that impacts do not need to penetrate the ice shell to generate vertical mass transport. The foundering of impact generated brines though the ice provides a potential mechanism to bring oxidants into the ocean at a rate of 101 to 105 kg/yr. Assuming sufficient production of reductants due to weathering of Europa’s seafloor, our estimated oxidant fluxes are deemed sufficient to sustain primitive life in Europa’s internal ocean. Our simulations also imply that large volumes of near surface brine are not be stable in long timescales, a hypothesis that is testable by NASA’s Europa Clipper mission.

Sep 13
Ashley Matheny, Jackson School of Geosciences
Sensing, synthesizing, and integrating plant ecohydrology for understanding and predicting land-atmosphere feedbacks in response to environmental extremes
My research explores how forests respond to different stressors across multiple dimensions and scales. This is important because vegetation provides a critical nexus between the subsurface, biosphere, and atmosphere through the mediation of the exchange of water, carbon, and energy. Plants respond dynamically to local microclimates at both short and long time scales via mechanisms ranging from physiological behaviors, such as stomatal closure, to acclimation and adaptation. These responses influence land-atmosphere fluxes directly and are therefore crucial to understanding and predicting Earth system responses to a changing climate. For example, how will ecosystems respond to the coupled extremes of high temperatures and water limitations? By exploring water-use dynamics and photosynthetic rates in trees near the furthest edge of their range limits, we gain insights into how these species will respond to predicted climate shifts in the coming decade. Likewise, through the development of a mechanistic understanding of how trees manifest stress responses, we can better predict the complex feedbacks to carbon, water, and energy fluxes that subsequently develop. In this seminar, I will discuss the work conducted by my team, which is tightly integrated with my graduate and undergraduate education and research programs, to develop novel observational systems and advanced field datasets in conjunction with holistic interpretation methods that facilitate direct data incorporation into multiple model systems leading up to our newest directions and future research.
Sep 15
Daniella Rempe, Jackson School of Geosciences
How forests connect the solid earth to its atmosphere
Earth’s crust is penetrated by plant life. Tree roots commonly extend into bedrock where they exchange water and carbon with the atmosphere leading to mineral transformations. This has consequences for the availability of Earth’s freshwater resources and how these resources evolve over time and space with climate change. In this talk, I describe new insights about how forests interact with underlying bedrock. These insights are gleaned from novel sampling systems, geophysical tools, and remote sensing capabilities that allow us to document how hydrologic and biogeochemical processes in the root-zone manifest at larger scales. I will focus on observations from recent droughts in the western US that motivate a new framework for incorporating bedrock properties into projections of ecosystem and streamflow response to drought.
Sep 22
Liannie Velazquez Santana, Jackson School of Geosciences
Revealing magmatic and tectonic processes through a multifaceted study of the monogenetic volcanic record of the Eastern Bolivian Altiplano
Abstract: The volcanic products of continental arc volcanoes provide comprehensive insights into the complex nature of magmatic systems. For example, current understanding supports the presence of complex, dynamic transcrustal magmatic systems (TCMSs) that consist of interconnected regions of magma storage where liquid-poor, crystal-rich mushes exist and variably interact. However, the extent to which these petrogenetic pathways affect storage, differentiation, and final eruption (or emplacement) of magmas at different crustal regions within the magmatic system remains challenging to address. In this talk, I will address this through a study of andesitic-dacitic lavas, hornblendite cumulates, and crustal xenoliths from the Pampa Aullagas and Quillacas monogenetic volcanic centers on the Bolivian Altiplano, Central Andes. Through this work, I use a multifaceted analytical approach to 1) characterize the magmatic and crustal components of TCMSs and 2) constrain the tectono-magmatic processes and petrogenetic pathways of magmas at varying timescales and stages within TCMSs. 
Sep 27
David Goldsby, Department of Earth and Environmental Science,
University of Pennsylvania
Mechanisms of Rate and State Friction: Insights from Atomic Force Microscopy, Nanoindentation, and Atomistic Simulations
Abstract: In spite of their widespread use in earthquake models, rate and state friction ‘laws’ still lack a robust physical basis.  Without knowledge of the underlying physical/chemical mechanisms of rate and state friction, there is uncertainty in extrapolation of these equations beyond the relatively limited range of conditions explored in the experiments that provide their basis. To explore the contact-scale mechanisms of rock friction, we are conducting ‘single-asperity’ experiments using atomic force microscopy and nanoindentation coupled with atomistic modeling and simulations.  Here I will attempt to merge results of these nano- to micro-scale single-asperity experiments and simulations with those from friction experiments on rocks to help constrain the mechanisms of rate and state friction.
Oct 6 Brad Foley, University of Pennsylvania Planetary interior controls on the habitability of rocky exoplanets
Abstract: An essential factor for the habitability of rocky exoplanets is climate regulation via the carbonate-silicate cycle. Without such regulation, uninhabitably hot or cold climates can form, even for planets lying within their host star’s habitable zone. The planetary interior plays a critical role in driving the carbonate-silicate cycle, as it controls how volatiles are cycled between surface and interior over time. I will explore these links between interior dynamics and climate evolution considering the role of a planet’s tectonic state, thermal evolution, and area of exposed land. While it has long been thought that plate tectonics might be essential for the carbonate-silicate cycle to regulate climate, I show that the same stabilizing feedbacks can also operate on planets lacking plate tectonics. However, these results point to the importance of active volcanism, which is in large part controlled by the budget of radiogenic elements (U, Th, and K) a planet acquires during formation. Radiogenic heat producing element (HPE) abundances are not directly measurable in other planets, but estimates can be made based on the composition of stars planets orbit. I therefore use measured HPE abundances in stars to determine the likely range of heat budgets for rocky exoplanets and estimate how long they can stay volcanically active in a stagnant-lid regime. The results show many known exoplanets, including the Trappist system, may be too old to still be volcanically active today. Finally, I discuss the role of exposed land in sustaining habitable surface conditions. Whether sea floor weathering provides a climate regulating feedback, like weathering of exposed land, has been long debated. Based on recent estimates of the seafloor weathering rate and its dependence on temperature, ocean pH, and spreading rate, I show that planets lacking exposed land can potentially regulate their climates better than planets with land. This result opens up the possibility of habitable climates on waterworld planets.
Oct 20 Elowyn Yager, University of Idaho It’s not always rainbows and butterflies: vegetation influences on rivers beyond sediment deposition and meander formation
Abstract: Vegetation is ubiquitous in river and delta systems and is often used to restore river channels with the assumption that vegetation addition will cause sediment deposition and stabilize channel banks. Uncertainties remain as to whether vegetation actually enhances sediment deposition because of the competing influences of vegetation drag and vegetation induced turbulence. Vegetation can also cause significant spatial variability in deposition/erosion that complicate common correlations between vegetation and channel planform. We use laboratory experiments at a wide range of spatial scales (stem to river reach) to understand the mechanics of turbulence and sediment transport through vegetation, and the impact of vegetation and flow hydrographs on channel morphology. We demonstrate that complex feedbacks between flow hydraulics, channel morphology, and sediment transport during flow hydrographs control whether vegetation causes local deposition or erosion. The role of vegetation in promoting a certain type of channel planform (e.g., meander) may depend on vegetation location within the channel and the upstream sediment supply.
Oct 27
Jessica Guo,
University of Arizona
Sensitivity of plant water use to a changing environment
Abstract: The global carbon and water cycles are inextricably linked through plant stomata, as water loss is an inescapable consequence of photosynthesis. Characterizing the sensitivity of plant processes to environmental controls becomes even more urgent as climate warms and precipitation regimes change. As a dryland plant ecophysiologist, I study the sensitivity of water use strategies to seasonal variability and the consequences for ecosystem productivity. In well-watered riparian ecosystems, desert trees differ in their stomatal sensitivity to cumulative atmospheric dryness, which is associated with differences in xylem anatomy. Among dryland species such as creosote bush and Utah juniper, regulation of midday water potential shifts rapidly to allow for greater productivity under episodic precipitation. Broadening our understanding of plant water use strategies as temporally dynamic has the potential to explain why dryland ecosystems are largely responsible for high inter- and intra-annual variability in the terrestrial carbon cycle.
 Nov 3
Tim Lyons,
University of California, Riverside
 How three billion years of Earth history may help us find life on exoplanets
Abstract: Life and life-sustaining environments, including oceans, have existed on a dynamic Earth for more than four billion years. Each of our many past planetary states was associated with a particular atmospheric composition, and those atmospheres contained gases that were produced by Earth’s early life. Using ancient Earth to understand when and how these biosignature gases accumulated is allowing us to select targets and techniques for exploring the many Earth-like planets beyond our solar system.
Nov 10
Bruce Fouke,
University of Illinois
Life on the Edge of Entombment: 3.8 Billion Years of Biomineralization
Abstract: The survival of all forms of Life on Earth through geological time has depended on successfully responding to, and eventually controlling, mineral growth within the environment. This process, called biomineralization, has been an essential, unavoidable, and ubiquitously distributed force of nature that has provided essential strategic benefits (such as coral skeletons), as well as profound practical problems and impediments (such as kidney stones). This presentation will explore the scientific renaissance being driven by convergence of the geological, biological, and medical sciences (GeoBioMed), as a means to reframe our basic approach to tackling the grand challenges that face society regarding the environment, energy, health, and space exploration.
Nov 17
Barbara Carrapa,
University of Arizona
Rising from the ashes: marine and continental feedback responses to Andean volcanism and Miocene climateAbstract: The late Miocene is a critical time within the generally cooling trend of the Cenozoic, characterized by a warmer climate than today, shifts in global geo- and bio-chemistry and sea surface temperatures, and modern-like atmospheric pCO2. Although the cause(s) of these shifts remains unresolved, we show a strong correlation between Andean volcanism and diatom occurrence and abundance. This combined with increased Si flux from the Amazon river into the Atlantic starting at ~9Ma, and increased aridity, supports a connection between an increased flux of nutrients (Fe, Si) to the oceans in the Late Miocene that could have led to increased marine primary production associated with the Late Miocene Carbon Isotope Shift (LMCIS), the Late Miocene Biogenic Bloom (LMBB), and, through an enhanced biological pump and increased organic carbon burial, Late Miocene cooling. Peak late Miocene magmatism in the Central Andes coincides with global SST cooling. Peak Andean magmatism also correlates with a sharp increase in marine megafauna extinction rates. We suggest that the combination of Andean volcanism, climate and tectono-morphic regime contributed to ocean fertilization, enhancement of the biological pump, biogenic carbon burial, CO2 drawdown, and cooling in the last ca. 12 Ma, which disrupted marine ecosystems, especially in coastal waters, and contributed to the extinction of marine megafauna and the establishment of modern marine communities. Horton
Dec 1
Isaiah Bolden,
Georgia Tech
Biogeochemical Fingerprints of Change in Coral Reef Ecosystems Across Space and Time
Abstract: Coral reef ecosystems are known to be in a global state of decline, largely attributed to sea-surface warming, ocean acidification, pollution, disease, and other direct human contributions. The impending transition away from calcified substrates to macroalgae dominance and other alternative stable states within these environments could translate to major losses in marine biodiversity, erosion of protective coastal barriers, stress on major fisheries, and numerous other sociocultural and economic impacts. My research combines discrete and autonomous measurements of carbonate chemistry, trace metal, and carbon isotope variability within coral reef environments, quantitative decomposition models of biogeochemical fluxes within reefs, and high-resolution mass spectrometry to investigate various geochemical proxies as fingerprints of stress-induced changes in reef metabolism and community composition. I also apply similar tools to understand the utility and nuances of coral skeletons as paleoclimate archives in modern and ancient reef ecosystems. Here, I will primarily report on (1) the use of temporal variability in modern reef seawater Sr/Ca ratios as an indicator of calcifier community composition shifts under compounding environmental stressors and (2) ongoing efforts to construct comprehensive paleoclimate records of Southern Caribbean temperature and aridity using co-located coral skeleton and speleothem geochemical analyses. The ultimate aim of research in my group is to build and apply sophisticated analytical and quantitative tools for detecting and monitoring environmental change on reefs and better protect the ecosystem services these dynamic environments provide.
Dec 6
Julia Cisneros
Jackson School of Geosciences
The morphology of alluvial sand dunes
Abstract: In the process of sediment transport through a shearing flow, dunes are forming and simultaneously recording their surrounding conditions. These records offer clues about the movement of wind and water across an ancient, otherwise unknown, landscape. In turn, dunes are influencing how sediment is transported. Key to leveraging these records of ancient environments is our understanding of the links between flow, sediment transport, and bedform morphodynamics. To gain that critical understanding, we use modern bedforms to understand the conditions of the Earth and planetary systems and improve how contemporary environments are managed.

This talk will highlight research that aims to investigate dune formation and dune shape in big and small rivers and in shallow laboratory flows. This investigation allows the comparison and validation of the key processes controlling the formation of low-angle dunes. I then identify and discuss the conditions when one process may dominate in creating complex dune shapes. This talk highlights the balance between bedform superimposition and sediment suspension as controls on the formation of low-angle dunes. This information is vital to improving our approach to managing contemporary rivers under modern stressors and revealing the deposits of ancient rivers.


Dec 8
Jonathan Ajo-Franklin,
Rice University
Exploring the Subsurface with Regional DAS Networks: Results from the Imperial Valley Dark Fiber Project

Abstract: With recent advances in the large-scale deployment of distributed acoustic sensing (DAS) approaches utilizing telecommunication infrastructure, the asymmetry between the per-channel cost of high-resolution passive seismic recording and corresponding active source deployments continues to increase. This has motivated renewed interest in both large-scale ambient noise studies as well as improved utilization of shallow natural seismicity for imaging applications. In this study, we highlight three approaches for using DAS, ambient noise, and shallow earthquakes to constrain larger scale S-wave velocity and reflectivity structure utilizing data acquired as part of the Imperial Valley Dark Fiber Project (IVDFP). The project targets structures near the Brawley Geothermal Field relevant to understanding the seismic signatures of hidden geothermal systems; to date, almost 19 months of continuous DAS data has been acquired on a 27 km (7000+ channel) dark fiber array stretching from Calipatria to Imperial, CA. In our first example, we show on-going work seeking to combine the high spatial density of DAS and anthropogenic ambient noise imaging to constrain zones of hydrothermal alteration directly beneath the Brawley field. In the second example, we attempt to utilize the abundant natural seismicity in the Brawley Seismic Zone (BMZ) recorded by DAS, and local earthquake tomography to improve constraints on S-wave structure over a larger region. In the third example, we image large lateral reflectivity features near the field using coherently scattered S-waves and 3D migration, an approach not possible using the classical sparse seismic arrays. These results are compared to existing datasets and interpreted to be related to deep hydrothermal alteration and fault-related structures at the southern termination of the Brawley Seismic Zone (BSZ).
Further information in: Ajo‐Franklin, J., Rodríguez Tribaldos, V., Nayak, A., Cheng, F., Mellors, R., Chi, B., Wood, T., Robertson, M., Rotermund, C., Matzel, E. and Templeton, D.C., 2022. The Imperial Valley Dark Fiber Project: toward seismic studies using DAS and telecom infrastructure for geothermal applications. Seismological Society of America, 93(5), pp.2906-2919.

Jan 19
Alicia Wilson
University of South Carolina
Subseafloor Hydrogeology: Moving Beyond Watersheds
Abstract: The field of submarine groundwater discharge (SGD) was launched in the 1990s by the remarkable discovery, via naturally-occurring isotopic tracers, that saline groundwater was discharging to the South Atlantic Bight in very large volumes. Subsequent studies confirmed that saline groundwater discharges to the Atlantic Ocean in volumes that rival river discharge. All available evidence indicates that this saline groundwater is highly enriched in nutrients compared to river water, so the nutrient contributions of this submarine discharge exceed that of river discharge. These findings have been slow to find widespread acceptance, however, because it has been exceedingly difficult to confirm this flow by means other than the original isotropic tracers. This discharge does not occur near the shoreline, and no conceptual models for SGD far from shore existed. 
Cardenas Darcey Lecture
Jan 26
Ekaterina Larina
Jackson School of Geosciences
Paleoenvironmental and paleoecological trends leading up to the end-Triassic mass extinction
Abstract: The end-Triassic mass extinction (ETE) is one of the biggest biotic crises that has occurred during geological history and the main cause is generally attributed to the emplacement of the Central Atlantic Magmatic Province (CAMP) ~201.51 million years ago. The amount of CO2 injected into the atmosphere during each CAMP magmatic pulse rivals anthropogenic CO2 emission projected for the 21st century. Although the ETE and its aftermath are well documented, the conditions leading up to the ETE remain poorly understood. This study aims to resolve environmental conditions in Panthalassic and Tethys basins that acted in the leadup to the ETE and its impact on the complexity of marine benthic ecosystems. The study of upper Rhaetian sections in Tethys realm reveals an ecologically diverse and robust marine benthic community across different depositional environments all the way up to the main phase of CAMP volcanism implying the sudden tempo of ecological changes in Tethys compared to the more protracted nature of ecological shifts recorded in the Panthalassa. Despite disparities in paleoenvironmental and paleoecological trends in the lead up to the ETE across the basins, the severity of the extinction is apparent across the globe once the main phase of CAMP volcanic activity was initiated.
Feb 9
Demian Saffer
Jackson School of Geosciences (UTIG)
Wiring the Subduction Megathrust: Recurring and Triggered Slow Slip Events Near the Trench Along the Nankai Subduction Zone
Abstract: The offshore reaches of subduction megathrusts fail in a broad spectrum of slip modes, spanning from coseismic slip in great earthquakes, to tsunami earthquakes, to tremor and low frequency earthquakes, to slow slip events (SSE) and aseismic creep. Understanding the nature of strain accumulation and release in this region is central to assessing hazards associated with shallow earthquake rupture and tsunamigenesis. In this talk I describe a family of newly discovered repeating SSE in the Nankai subduction zone offshore of Honshu Japan, updip of rupture zone of great (M8) earthquakes, using formation pore pressure data from instrumented borehole observatories.

After filtering oceanographic noise using a local hydrostatic reference, the records over a 6 year period from 2010-2016 reveal 8 events. Of these, 6  arise spontaneously, and occur at ~1 yr intervals with durations of ~7-21 days. The remaining 2 events are larger and immediately follow: (1) the 2011 M9 Tohoku earthquake; and (2) the 2016 M7 Kumamoto earthquake. In some cases, the SSE are accompanied by swarms of low-frequency tremor and low-frequency earthquake activity that appear to migrate trenchward. The data are well fit by slip of ~1-4 cm on a patch at the plate interface that extends 20-40 km in the dip direction. A key implication is that the SSE accommodate ~30-50% of plate convergence across the outer ~40 km of the forearc. This coincides with a region of the shallow-most megathrust characterized by: (1) elevated pore fluid pressure; (2) transitional frictional behavior that promotes the nucleation of unstable slip at low sliding velocities; and (3) low stress magnitudes as constrained by analysis of wellbore failures. The repeating nature of the events, taken together with apparent triggering by regional earthquakes and the inference of low in situ stress magnitudes, indicates that the outermost reaches of the megathrust are highly sensitive to perturbation and are perched near a state of failure. 
Feb 16
Veronika Bray
University of Arizona
Kuiper Belt Geology, as revealed by New Horizons
Abstract: This talk will  cover how impacts helped build our solar system, change planetary orbits and rotation, and create the environments and geology that we see today.   This talk will cover these topics as part of a tour of the geology of the Pluto System and of KBO Arrokoth.
Gulick/Hesse Barnes Lecture
Feb 23
Amy East
Measuring and attributing geomorphic and sedimentary responses to modern climate change: Challenges and opportunities
Abstract: Modern climate change is affecting virtually all terrestrial and nearshore settings to some extent today. This presentation will focus on some of the challenges of measuring climate-driven physical landscape responses to modern global warming, and identify opportunities to better characterize and quantify the extent and nuances of climate-change effects on geomorphic systems. Better understanding sedimentary and geomorphic responses to ongoing warming and hydrologic changes in myriad environmental settings will prepare societies to manage the risks to human health and safety, infrastructure, water–food–energy security, economics, and ecosystems that follow from climate-driven physical landscape change.
Mar 2
Kristin Bergman
Towards a temperature record across the advent of complex life
Abstract:The ecology and habitability of Earth is fundamentally shaped by its surface temperature. But, the further back in time we look, this history becomes increasingly difficult to reconstruct. This is particularly true over the ∼4 billion years when microbes ruled and before animals like corals began making skeletons and shells out of seawater. Consequently, Earth’s temperature history in deep time is, and has been, the subject of a vigorous, decades-long debate.

In my work, we are developing multi-mineral isotopic and petrographic methods to understand the role of temperature, fluid chemistry, and diagenesis on two isotopic systems—oxygen isotopes and clumped isotopes—that reefs and other carbonates record as they grow. We are developing local records and present details of those alongside a new high-resolution record of bulk carbonate oxygen isotopes for the last billion years of Earth’s history.

My results suggest one solution to the previous ambiguity surrounding seawater oxygen isotope composition through time. Based on our results to date, and other distinctive features of our high resolution oxygen isotope record, we hypothesize that temperature, and not just atmospheric oxygen levels, was a key factor for understanding emergence, diversification and subsequent trajectory of complex life.

Mar 9
Renyi Zhang
Texas A&M University
Do industrial emissions play a role in the catastrophe during Hurricane Harvey?
Abstract: Hurricane Harvey caused catastrophic flooding (about 555 mm in the Houston urban area) and more than 100 deaths during 25-27 August 2017. It is tied with 2005’s Hurricane Katrina as the costliest tropical cyclone on record, inflicting $125 billion in damage, primarily from catastrophic rainfall-triggered flooding in the Houston metropolitan area and Southeast Texas. Although several recent studies have linked Hurricane Harvey’s devastation to climate change or changes in land use due to urbanization, the cause of the catastrophic flooding remains uncertain. Tropical cyclones are driven by latent heat release from condensation and are inevitably linked to the abundance of aerosols by acting as cloud condensation nuclei. In this talk, I will present results from both measurements and numerical model simulations to investigate the impacts of anthropogenic aerosols on deep moist convection, precipitation, and lightning activities during hurricane Harvey. Our work shows a non-negligible effect of anthropogenic aerosols on this regional extreme weather event, highlighting the necessity of accounting for the aerosol effects in hurricane forecast models to accurately predict precipitation and to minimize the storm damage along the heavily industrialized Gulf of Mexico region.