Winter 2017

Winter 2017

Tuesday Afternoons at 3:30 PM
Thimann Lecture Hall, Room 001


January 10, 2017

Speaker:

Title:

Hosts:


January 17, 2017

Speaker: Bernard Hallet, University of Washington

Title: Glacial Erosion: processes and products from microscopic scratches to alpine landscapes.

Hosts: Shalev Siman Tov


February 7, 2017

Speaker: Jena Johnson, University of Colorado - Boulder

Title: Manganese: Minerals, Microbes, and the Evolution of Oxygenic Photosynthesis

Abstract: Oxygenic photosynthesis fundamentally transformed our planet by releasing molecular oxygen and altering major biogeochemical cycles, and this exceptional metabolism requires manganese to function. Not only is manganese essential for producing oxygen, but manganese oxides are also incredibly diagnostic for the presence of environmental oxygen. Thus the history of manganese oxidation recorded in the geologic record provides a valuable perspective on our planet’s environmental past, the ancient availability of oxygen, and the evolution of oxygenic photosynthesis. I will present analyses on manganese minerals in the rock record using microscale techniques to extract primary geochemical signals and process-based laboratory experiments measuring microbial mineral products to interpret ancient geobiological signals. This talk will demonstrate how the evolution of oxygenic photosynthesis and the activity of metal oxide-reducing metabolisms are linked to and recorded in the rich complexity of the manganese mineralogical record.

Hosts: Ana Martinez Fernandez


February 8, 2017

(held in E&MS A340)

Speaker: Jena Johnson, University of Colorado - Boulder

Title: Past and Present Biogeochemistry: Banded Iron Formations and Evolution of Ocean Chemistry

Abstract: The interdependence between geology, chemistry, and biology is remarkable— and also establishes powerful tools that we can harness to understand the evolution of life and environments on Earth. Life continually impacts its surrounding geochemistry, leaving enigmatic clues of its presence and metabolic activities, and these clues are best deciphered using a multi-faceted approach. I use microscale and nanoscale techniques to extract original information from Precambrian rocks, paired with studying modern biogeochemical processes in laboratory experiments and modern analogue environments. In this talk, I will describe projects that I am actively working on, as well as new directions that I plan to explore. I will present how I am investigating a recent discovery of iron-silicate nanoparticle inclusions in Banded Iron Formations (BIFs) and the paradigm shift that these suggest in interpreting ancient seawater chemistry and early life. I will also briefly outline a second research avenue that I intend to embark on, understanding how seawater concentrations of iron and manganese have changed over time as a proxy for paleo-ecology and the oxidation of the ocean. I plan to lead a question-motivated, collaborative lab that links modern aqueous geochemistry and microbe-mineral interactions to the ancient mineral record, focusing in particular on two key elements in biogeochemical cycles throughout Earth history: iron and manganese.


February 14, 2017

Speaker: Hilary Dugan, University of Wisconsin

Title: Salting lakes: A continental scale study of long-term chloride trends in freshwater lakes

Abstract: The highest densities of lakes on Earth are in north temperate ecosystems where increasing urbanization and associated changes to catchment hydrology can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at the global scale remains unknown, leading us to identify broad scale patterns and then investigate how drivers of these patterns are balanced among local and regional factors. Significant decadal trends in lake salinization were identified using a global dataset of long-term lake chloride concentrations from 529 North American and European lakes. Landscape and climate metrics calculated for each site demonstrated that urban land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious surface surrounding a lake increased the likelihood of long-term salinization. In contrast, long-term chloride trends in Scandinavian lakes were driven by regional climate patterns. Considering that 27% of large lakes in the United States have > 1% impervious cover around their perimeter, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for continuous chloride exposure (230 mg L-1) stipulated by the EPA, in the next 50 years if current trends continue unabated.


February 15, 2017

(Held in E&MS A340)

Speaker: Hilary Dugan, University of Wisconsin

Title: Limnology through environmental informatics

Abstract: In limnology, site specific studies provide an invaluable means to understand process, but large-scale analyses across a gradient of sites are essential to forming a generalizable understanding of both ecosystem processes and the interactions between natural systems and humans. This talk will showcase the use data analytics, GIS, and models, in scaling limnology to the continental scale, by focusing on how ecological informatics will enable us to quantify the role of lakes in processing carbon across the US.


February 16, 2017

(Held in E&MS A340)

Speaker: Amy Dale, MIT

Title: Water pollution from the nanotech revolution: Modeling the fate of metal and metal oxide nanoparticles

Abstract: The recent emergence of a global market for textiles, paints, cosmetics, packaging, and other products containing metal or metal oxide nanoparticles (NPs) has incited concerns about the potential ecotoxicity of these NPs following accidental release to the environment during product use or disposal.  NP fate in rivers, lakes, and bed sediments is notoriously difficult to model, since rates of transport and surface transformation depend on complex relationships and feedbacks between nanoparticle properties (e.g., size) and environmental conditions (e.g., fluid flow, sediment transport, and redox conditions).  This seminar introduces the field of environmental fate modeling for NPs and presents my contributions to the development of fate models that better facilitate risk assessment, policy development, and environmental management decision-making for the emerging nanotechnology industry.  I describe three projects and the insights they provide: (1) a comparison of three frameworks for modeling NP "size effects" that represent tradeoffs between simulation runtimes and model accuracy, (2) an aquatic chemistry model of the influence of redox conditions and seasonal variation on nanosilver bioavailability in freshwater sediments, and (3) a coupled hydrologic, land use, and water quality model that explores the influence of overland flow, stream hydrology, and sediment transport dynamics on NP fate in a freshwater watershed.


February 17, 2017

(Held in E&MS A340)

Speaker: Amy Dale, MIT

Title: Integrated multi-scale simulation to support water quality decision-making

Abstract: Population growth, land use change, and climate change place a tremendous burden on the world’s waterways.  Urbanization and agricultural intensification increase surface water loads of nutrients, sediments, and pathogens.  Climate change alters the timing and magnitude of pollutant loads and increases water temperatures.  Water quality degradation threatens human and environmental health and also threatens food and energy production due to the water demands of (e.g.) irrigation, hydropower, and thermoelectric power plant cooling.  Decisions that help mitigate these impacts must be made at all scales, from local to global.  This talk will summarize my current efforts and future research plans in the area of integrated numerical simulation to improve water quality assessment and inform decision-making at multiple scales.  My current research concerns the development of a continent-scale model that predicts the future impacts of climate change on maize production and irrigation water supply and demand across sub-Saharan Africa.  My future research will focus on (1) model design to better assess the environmental fate of particulate and strongly sediment-associating contaminants such as sediments, waterborne pathogens, harmful algal blooms, and metals, and (2) integrated environmental modeling to better inform water quality policy development, investment planning, and risk management in the face of global change.


February 21, 2017

Speaker: Clara Blättler, Princeton

Title: How salty was the sea? Constraining seawater chemistry with ancient evaporites

Abstract: The chemical composition of seawater is a critical boundary condition for reconstructing biogeochemical cycles, interpreting proxy measurements, and understanding the co-evolution of life and Earth’s surface environments. However, many aspects of the evolution of seawater chemistry remain unknown, and very few constraints exist in the Precambrian. I will discuss a new method using calcium isotopes in marine evaporite deposits to constrain seawater chemistry, in particular the relative concentrations of sulfate, calcium, and carbonate alkalinity. I will present examples from the Phanerozoic through the Archean and discuss the implications of these data on the sulfur cycle, oceanic pH, and atmospheric CO2 during critical periods of Earth history.


February 22, 2017

(Held in E&MS A340)

Speaker: Clara Blättler, Princeton

Title: New insights into the carbonate record from calcium and magnesium isotopes

Abstract: Marine carbonates provide one of the most important archives of the Earth’s surface environment. Interpreting this record requires distinguishing local versus global effects and addressing the diagenetic history of samples, both of which can be very challenging. I will present new isotopic tools to help resolve the creation and preservation of geochemical signals in carbonate sediments. This work forms the basis for being able to test the robustness of proxies, including carbon isotope ratios (δ13C), in ancient samples and more effectively use the rich geological record of carbonates.


February 23, 2017

(Held in E&MS A340)

Speaker: Mathias Hain, University of Southhampton

Title: Why study ice age CO2 change?

Abstract: Industrial activities continue are causing a continued rapid increase in the concentration of the greenhouse gas carbon dioxide (CO2) in the atmosphere, giving rise radiative climate forcing that is understood to have a wide range of direct and indirect consequences for the climate and other aspects of the Earth system. The magnitude of current anthropogenic CO2 climate forcing is very similar to that of natural CO2 changes that occurred in lockstep with the recurring ice age climate cycles of the late Pleistocene, which thereby may offer perspective on the significance of ongoing and future changes. In this talk I will review the main biogeochemical processes that caused atmospheric CO2 to be stored in the ice age ocean, and the dynamics of ocean circulation and climate change that gave rise to subsequent deglaciation and the release of CO2 back to the atmosphere. Moreover, inverse carbon cycle modeling and a new high resolution reconstruction of past CO2 change provide strong evidence for a tight coupling between glaciation, climate change and CO2 radiative forcing, illustrating the dual role of the global carbon cycle acting both as a positive feedback and as a driver of climate change. This increasingly comprehensive picture of how natural Earth System processes gave rise to the ice age cycles speaks to many of the outstanding questions with regard to ongoing and future environmental change – ranging from changes in the rate of Southern Ocean uptake of anthropogenic CO2 and heat, geoengineering solutions for CO2 removal from the atmosphere, to the possibility of abrupt climate change caused by instabilities in ocean overturning.


February 24, 2017

(Held in E&MS A340)

Speaker: Mathias Hain, University of Southhampton

Title: Reconstructing the geologic backdrop to ocean acidification

Abstract: Ocean uptake of anthropogenic CO2 is associated with progressive reductions in seawater pH, carbonate ion concentration and calcium carbonate saturation state; a set of changes that is collectively referred to as Ocean Acidification, OA. Based on a growing body of field observations and controlled experiments there is concern that OA is a significant environmental stressor on marine life, and in particular on organisms that build carbonate skeletons. And yet, beyond the immediate effects of OA we know little about the resilience that marine organisms may have evolved from natural changes in seawater acid/base chemistry during geologic time and the range of environmental conditions marine organisms may therefor be able to adapt to as OA proceeds into the future. Here I describe some of my recent work aimed at understanding the chemical principles that govern seawater acid/base and carbonate chemistry on geologic timescales. This work also includes the development of a computational framework to combine the boron isotope pH proxy, reconstructions of seawater major ion composition and records of carbonate burial in deep sea sediments to reconstruct seawater pH, carbon concentration and carbonate saturation as well as atmospheric CO2 back through time. These records offer invaluable information on the limits of resilience of marine life to future OA.


February 28, 2017

Speaker: Katja Meyer, Willamette University

Title: The end-Permian mass extinction: a model for global change biogeochemistry in the 21st century?

Abstract: Ocean anoxia/ euxinia and carbon cycle instability have long been linked to the end Permian mass extinction and the Early Triassic interval of delayed biotic recovery. Many hypotheses to explain this event invoke the release of greenhouse gases during the emplacement of the Siberian Traps, which likely triggered abrupt changes in marine biogeochemical cycling, atmospheric chemistry, and biodiversity. In this talk, I use Earth system modeling to examine the impact of high atmospheric CO2 and enhanced nutrient availability on the distribution of shallow-water anoxia in the end-Permian and Early Triassic. Model simulations show that high nutrient levels and a vigorous biological pump are required to sustain euxinia. I then use carbon isotope measurements from an exceptionally preserved carbonate platform in south China to test model predictions of changes in the biological pump during this interval. Both modeling and geochemical approaches suggest that Early Triassic ocean anoxia and delayed recovery of benthic animal ecosystems resulted from heightened productivity in a warm, nutrient-rich ocean.


March 1, 2017

(Held in E&MS A340)

Speaker: Katja Meyer, Willamette University

Title: The biological pump links Phanerozoic trends in ocean biogeochemistry to the evolution of marine animal ecosystems

Abstract: The net export of organic matter from the surface ocean and its respiration at depth creates vertical gradients in nutrient and oxygen availability that play an important role in structuring marine ecosystems.  Changes in the strength of this biological pump have been hypothesized to account for important shifts in marine ecosystem structure over the course of the Phanerozoic. However, the influence of the biological pump’s strength on ocean biogeochemistry remains poorly quantified, preventing any detailed exploration of how changes in the biological pump over geological time may have shaped long-term shifts in ocean chemistry, biogeochemical cycling, and ecosystem structure. Here I use the cGENIE Earth system model to quantitatively explore the effects of the biological pump on marine chemistry.  I find that changes in the distribution of remineralization enhance the expression of shallow water anoxia and increase carbon isotope gradients at continental shelf depths. Overall, these studies suggest that the changing spatial distribution of photosynthesis and respiration in the oceans has exerted a first-order control on Earth system evolution across Phanerozoic time.


March 2, 2017

(Held in E&MS A340)

Speaker: Matthew Winnick, Stanford

Title: Characterizing the Controls of Subsurface Flow on Chemical Weathering Fluxes from the Critical Zone

Abstract: Despite its importance for global biogeochemical cycling and climate, the transport and transformation of carbon in the subsurface remains the least characterized aspect of the terrestrial carbon cycle. Of particular interest are the controls of subsurface hydrology on biogeochemical reactions, both in terms of water flowpaths and residence times and the regulation of reactive gases (CO2, O2) in the subsurface. In this talk I will present a field study demonstrating direct regulation of the balance of oxidative v. acid-base weathering fluxes by snowmelt hydrology through concentration-discharge relationships in the shale-dominated East River, CO watershed. Specifically, the transitions between snowmelt and baseflow regimes control the coupled dynamics of pyrite oxidation and carbonate dissolution, as well as the amount of petrogenic carbon released to the atmosphere. Finally I will discuss future research directions aimed at quantifying the role of hydrology in modulating subsurface concentrations of reactive gases and the chemical weathering potential of infiltrating waters.


March 3, 2017

(Held in E&MS A340)

Speaker: Matthew Winnick, Stanford

Title: Quantifying Terrestrial Moisture Recycling Dynamics from Lateral Gradients of Isotopes in Precipitation

Abstract: Averaged across the globe, roughly 40% of precipitation that falls on land has been recycled through terrestrial evapotranspiration processes. This recycling of water through terrestrial systems is an integral part of the hydrologic cycle, and constraining the response of recycling dynamics with changing climate is of vital importance for predicting future change. In this talk, I will present a quantitative framework for constraining atmospheric transport dynamics and evapotranspiration rates from synoptic-scale lateral gradients of isotopes (δ18O, δD, deuterium-excess) in precipitation. This framework will be extended to address the monitoring of changes in moisture recycling rates and the partitioning of recycling between plant transpiration and soil evaporation with future climate change, as well as the reconstruction of terrestrial hydrologic change in past climates through the use of paleoclimate proxy records.


March 7, 2017

Speaker: John Knowles, University of Colorado - Boulder

Title: Mountain hydrology and ecosystem function

Abstract: Climate change is affecting the hydrology of high-elevation mountain ecosystems, with implications for ecosystem functioning and water availability to downstream consumers. My research thus uses an interdisciplinary approach to advance mechanistic understanding of ecohydrological processes in the mountains at multiple scales. In this seminar, I first investigate the hydrological controls on carbon fluxes across a broadly representative alpine tundra soil moisture, vegetation, and possible permafrost gradient, within the footprint of ongoing eddy covariance measurements at Niwot Ridge, Colorado, USA. I then broaden to the watershed scale to characterize energy versus water limitation to hydrological cycling within a 5.36 km2 catchment that spans the alpine treeline. Finally, source water contributions to streamflow are contrasted across a headwater catchment elevation gradient using a hydrologic mixing model. At the plot scale, this work identifies the presence of ecohydrological “hotspots” and suggests that an alpine tundra permafrost feedback to climate change, similar to that observed in arctic tundra ecosystems, may be currently underway. At the watershed scale, I show that a common assumption of water balance closure has the potential to mask important uncertainty and/or storage terms, and further quantify how surface/groundwater connectivity is variably influenced by the timing, type, and magnitude of recharge at different elevations.


March 8, 2017

(Held in E&MS A340)

Speaker: John Knowles, University of Colorado - Boulder

Title: Scaling mountain ecohydrological processes using modeling and remote sensing techniques

Abstract: In the western United States, most natural and managed systems are limited by water supply, and effective water distribution is predicated upon accurate estimates of basin-wide water storage in the mountains. However, field observations are often limited by remote locations and complex mountain terrain, and climate change is affecting hydrological cycling in high-elevation ecosystems that may be particularly to disturbance. As a result, this work leverages a combination of models and satellite observations to scale and project the links between climate, snowpack, streamflow, and vegetation over space and time in the Rocky Mountains, USA. I then explore the potential for deviations from these baseline ecohydrological relationships with respect to the major ongoing disturbances of snow drought and bark beetle infestation. This research contributes to a novel multi-scale understanding of the effects of snow accumulation and melt on plant growth, streamflow generation, and hydrological connectivity with broad implications for predicting both the ecohydrological response to climate change and the ensuing consequences for water resources throughout the western United States. Additionally, this work raises ecohydological questions that can be addressed with future experimentation and/or model development.


March 14, 2017

Speaker: Darren Ficklin, Indiana University

Title: The Past, Present, and Future of Western United States Hydroclimate

Abstract: One of the most urgent challenges facing the world today is ensuring an adequate supply and quality of water for human and ecosystem needs in the face of climate variability and change. Recent increases in air temperature are resulting in increases in evaporation/evapotranspiration and changes in precipitation, leading to an overall intensification of the hydrologic cycle. This intensification is projected to continue into the 21st century at potentially faster rates. Using observed climate data and projected climate data from General Circulation Models, this talk examines how these changes in the hydrologic cycle will affect water resources and their quality throughout the western United States. These changes will not only impact agricultural and urban communities that depend on these resources, but also aquatic species that are adapted to particular hydrologic regimes and stream temperatures. This work indicates that changes in air temperatures and precipitation will lead to changes in streamflow magnitude and timing (shifting streamflow peaks earlier into the year by 1-2 months), as well extreme events such as flooding and droughts. The streamflow changes coupled with air temperature increases will also result in stream temperature changes by 1-5 °C, subsequently affecting habitat ranges for aquatic species such as trout and salmon that are both culturally and economically significant. These results indicate a very different hydroclimatic future for the western United States, thus requiring an adaptation of water resource and aquatic species management.


March 15, 2017

(Held in E&MS A340)

Speaker: Darren Ficklin, Indiana University

Title: Current Issues and Unanswered Questions in Hydroclimatology

Abstract:

Many questions remain unanswered in the field of hydroclimatology. This talk will introduce some of these issues in detail and will be divided into four separate themes (hydrologic modeling, citizen science-aided modeling, stream temperature modeling, and drought modeling), each raising their own issues and questions. Future research directions on these issues will also be discussed.

Large-scale hydrologic modeling – Calibrating hydrologic models for large watersheds (i.e., Mississippi River Basin) is a complex, computationally-expensive problem in hydrology and hydroclimatology. A calibration tool was developed that uses parallel processing to calibrate large-scale hydrologic models for multiple observations and objective functions. Initial applications and results of this tool will be discussed and remaining issues will be examined.

Citizen science aided-hydrologic modeling – Hydrologic and eco-hydrologic models are dependent on observed data for model calibration and validation. This data, however, exists at locations more appropriate for agricultural or urban needs (i.e., flooding, water supply) than locations appropriate for aquatic species (i.e., headwater streams). Can citizen scientists fill this data availability gap sorely needed for hydrologic and aquatic species modeling?

Stream temperature modeling – A stream temperature model was previously developed that simulates stream temperature as function of both air temperature and the temperature of contributing hydrology. This model, however, is still missing key components that also contribute to changes in stream temperature. Adaptations and improvements to the stream temperature will be discussed.

Drought modeling – Droughts are one of the costliest natural disasters in the world. Many drought maps or data released to the public are at a scale much too large for site-specific analyses or lack methodological transparency. A user-friendly drought modeling tool was developed that can quantify drought at any spatial scale where climate data is located. Background and applications of this tool are discussed.


March 16, 2017

Speaker: Margaret Zimmer, Duke University

Title: Linking subsurface and surface flow regimes from hillslopes to rivers

Abstract: There is a significant knowledge gap regarding streamflow generation processes in low relief, humid landscapes. To address this, we instrumented an ephemeral-to-intermittent drainage network in the Piedmont region of North Carolina to gain new understanding about the controls on streamflow generation, stream-groundwater interactions, and expansion and contraction of the surface drainage network. We characterized streamflow and overland, shallow soil, and deep subsurface flow across a variety of landscape positions using hydrometric and chemical data. Our results showed bi-directionality in stream-groundwater head gradients that led to annual groundwater recharge magnitudes that were similar to streamflow magnitudes. Active surface drainage lengths were highly correlated to runoff independent of catchment wetness. That said, shallow, perched, transient water table and deep water table contributions shifted in dominance with changes in catchment wetness, which produced distinct hydrograph recession constants. Together, these results indicate the mechanisms and source areas that produce runoff can be highly variable and difficult to discern from runoff alone. These streamflow generation processes and catchment characteristics have significant implications for stream biogeochemistry across season and catchment wetness.


March 17, 2017

(Held in E&MS A340)

Speaker: Margaret Zimmer, Duke University

Title: Pushing the boundaries of watershed science through coupled hydrologic observations and models

Abstract: Water quality and quantity are complex issues that span local to global scales. There are still significant gaps in our understanding about the stores, fluxes, and chemical signatures of the major components of the hydrologic cycle. As a watershed hydrologist, I plan to 1) continue to improve discipline-specific frameworks in the hydrologic sciences, 2) target research toward understanding human-induced change on hydrologic systems, and 3) provide a process-based understanding that can be used toward sustainable management of hydrologic systems. I will utilize new data observations, models, and frameworks to address these three main short term career goals. For this talk, I will introduce active research addressing these topics as well as my future research I plan to conduct in my first years as an assistant professor.