OREGON STATE UNIVERSITY
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Summer Research Internships for Undergraduates
Evolution of the Coast RangeAccretion, deposition, and uplift have been occurring west of where the modern cascades are located since the early Eocene. Above the accreted island terrane known as the Siletz terrane, a forearc basin formed and accumulated sediment that now makes up the formations found in the Oregon coast range and Willamette Valley. By radiometrically dating minerals found in those sedimentary formations, they can be traced to source areas that had volcanism at that time. Detrital muscovite from the Tyee formation and Umpqua group, the latter having a confirmed Klamath source area, will allow us to determine if both of the formations had the same source area. This will in turn provide insight on what direction the depositing rivers came from and the topography of the coast range at the time of deposition.
Presence and succession of cable bacteria at Hydrate Ridge, NE Pacific OceanTwo competitive filamentous microbes called cable bacteria and Beggiatoa oxidize sulfide for energy, resulting in a seasonal cycle that prevents natural oxygen depletion (hypoxia) in coastal marine environments. Hydrate Ridge (HR) is a seafloor environment where surface sediments are saturated by methane gas and hydrogen sulfide rising from deeper reservoirs due to tectonic activity along the Cascadia convergent margin. At 775m, Hydrate Ridge is located in the northeast oxygen minimum zone which is permanently hypoxic. In benthic regions such as HR, Beggiatoa fields are a natural occurrence while traces of cable bacteria have never been found. This study attempts to understand if the growth of cable bacteria is limited by scarce dissolved oxygen in HR sediment. After exposing HR sediment to higher oxygen levels for 3 weeks, cable bacteria were found but Beggiatoa were still dominant. Our results suggest that oxygen may not be the only environmental factor affecting the competition between Beggiatoa and cable bacteria. The discovery of cable bacteria in HR sediment suggests that they are widespread throughout the ocean.
Microbial Martians: How Earth’s microbial communities can tell us about extraterrestrial onesIron redox cycling is an ancient metabolic process that many microbes in a myriad of environments still use to derive their energy. Understanding the diversity in these microbial communities yields insight into the environments in which they thrive, how they play into our ecosystems, and helps us understand where we would expect to find them elsewhere in the universe. In order to do so, we examined the environments on earth in which they are found. A good model for the distribution of this microbial life is the Copper River Delta, a high latitude wetland. Our goal was to determine the types of microbes present in wetland sediments samples taken along glacier-to-ocean and sediment-depth axis on the delta. We successfully extracted and sequenced the DNA from these sediment samples and using QIIME 2 we identified the microbes that colonize each region of the wetland. Using non-metric multidimensional scaling (NMDS) we are filtering through the microbial community data to determine abiotic factors that influence community composition. With sediment-depth and glacier-ocean distance as key variables. Preliminary findings appear to suggest that depth is not as influential a factor as positioning along the outwash-uplift plains. With more context for the optimal regions of habitability for these organisms, we can begin to fit them into the ecosystem and to examine where analogous conditions may exist elsewhere in the universe.
A new conceptual model for interpolar climate coupling during the Ice AgesThe thermal bipolar seesaw model by Stocker and Johnsen is widely used to explain the connection between abrupt Dansgaard-Oeschger events in Greenland and their climate response in Antarctica. We now have better-dated records from Greenland and Antarctica with higher resolutions which provide critical information into furthering our understanding of interpolar climate coupling. Records of water isotopic composition from Greenland and Antarctic ice cores were used as a proxy for past temperatures. MatLab was the primary tool used for data analysis, combining statistical correlation and modeling on the updated data sets. The data were first used to replicate the bipolar seesaw. WAIS Divide, Talos Dome, and EPICA Dome C (EDC) produced the best depiction of the seesaw, whereas EPICA Dronning Maud Land (EDML) and Dome Fuji had much lower correlations even though their proximity is much closer to the South Atlantic. Next, we suggest a simple conceptual model that can replicate both millennial and orbital-scale Antarctic climate during the last ice age using greenhouse gas forcing, surface albedo, and the AMOC. Modeling results suggest Antarctic climate simply reflects the mean ocean temperature; in this view it is the global ocean interior, rather than the Southern ocean, acting as the heat reservoir in the bipolar seesaw. By using three AMOC states (strong, weak, and off), we can simulate the D/O cycle and glacial terminations, confirming the seesaw is a necessary part of the machinery of glacial cycles. The success of our simple model approach suggests a revised view of the seesaw concept may be warranted.
Acoustical measurements and modeling of mixed grainsize sediment under breaking wavesCoastal erosion is a nearshore process that is complicated to model and requires integration of experimental measurements to provide accurate parameters to include in a single model for prediction. An accurately parameterized model is increasingly important with rapidly occurring changes to the coast due to climate change. The current theoretical models lack representation of real sediment and currently are not well validated for predicting the relationships between suspended sediment concentration and particle size with breaking wave type. The planned experiment aims to contribute data to accurately define sediment transport at Duck, NC, based on data collected by an acoustic backscatter sensor (ABS) to collect backscatter intensity profiles from suspended particles with known characteristics. Acoustic parameters measured in the lab can be added to an acoustic inversion model that will be used to extract suspended sediment concentration and particle size from in-field backscatter intensity profiles taken by the same ABS in Duck, NC which is also accompanied by lidar scans of wave type. Pairing both ABS and lidar data then illuminates how sediment is moved by each specific wave at a level of detail that has rarely, if ever, been achieved in past field studies.
Mechanics of fissure eruptions at Newberry VolcanoNewberry Volcano experienced fissure eruptions ~7,000 years BP resulting in numerous lava flows aligned in a NW trend extending from the caldera. These lava flows cover an extensive area and reach only 12 km away from the city center of Bend, OR. By computing the volume of lava ejected from the fissure during this eruption, conceptual models of the geometrical dimensions of the fissure opening will be created. The stress it takes to break open a fissure and the volume which results from this amount of applied stress will be quantified. Once these variables are determined, a simplified model will be created to model fissure opening during the 7,000-year BP eruption.
Encouraging K-12 Math Interest Through Sea Ice DynamicsBringing research and real-world data into the classroom highly engages students with core math and science concepts. The Oregon State SMILE program presents lesson plans for elementary, middle and high school students that satisfy next generation science standards and engage students in their grade appropriate mathematics curriculum. In a lesson designed to increase public understanding of climate processes and modeling, high school students will participate in a sea ice drift forecast project, developing persistence forecasts whose performance will be compared to model-derived sea ice drift forecasts. Through the lesson, students will be introduced to the concept of forecasting and the real-world significance of their forecasts in ensuring safe operations in the polar regions. Math skills such as fractions, geometry, and the concept of differentiation will be explored in the context of their use in our research. The students will develop their persistence forecasts by working directly with near-real time buoy data reported by the International Arctic Buoy Programme, a resource used widely by cryospheric researchers. Students may also choose to extend the lesson, developing persistence forecasts independently and collaborating with researchers who are developing their own sea ice forecasts. In 2019-2020 the lessons will be tested in Oregon schools and SMILE clubs. Lesson plans will become freely available, after trials, to encourage development of the math and conceptual skills relevant to this project in a broad range of students. We invite you to join these students in providing a sea ice drift forecast. Can you do better than persistence?
Examining the effects of air bubbles on tidewater glacier meltCurrent tidewater glacier models underestimate the rate of ambient melting by up to two orders of magnitude. We propose an experiment to examine the impact of air bubbles trapped in glacier ice as a possible explanation for this discrepancy. If our hypothesis is correct, popping bubbles disrupt the viscous sublayer at the ice-ocean interface, enhancing mixing and increasing the rate of heat exchange. Our experiment will measure the flow profiles over residual pressurized glacier ice, normal atmospheric pressurized ice, and bubble-free ice in a controlled laboratory environment, allowing us to understand how bubbles influence the momentum exchange, and by proxy the heat mixing rates, in the near boundary region.. Finding evidence of increased mixing or turbulence over the glacier ice will motivate further study into this previously uncharacterized phenomenon.
Iron-rich rhyolite in the Central Volcanic Zone of northern ChileThe Central Volcanic Zone of the Chilean Andes contains a multitude of high potassium, silicic ignimbrites produced by explosive volcanism. An anomaly to most of these eruptions is the Caspana ignimbrite of the APVC. The Caspana ignimbrite is composed of a high-silica, fayalite-bearing rhyolite (75% SiO2), underlying a more mafic andesite (59% SiO2). The two pumices are thought to be erupted from the same chamber, where extensive convective fractionation produced the iron-rich rhyolite. To the author’s knowledge, this is the only fayalite-rhyolite found within the APVC. Investigation into these pumices can provide one method by which this rare and explosive composition can be produced at a subduction zone. Geochemical, thermodynamic, petrologic, and spatial data will be used to constrain the convective fractionation process that led to eruption. The large compositional gap is thought to follow a shallow cotectic curve due to the fractionating assemblage, promoted by the geometry of the magmatic chamber.
Examination of the impact of one-dimensional crustal structures on Cascadia subduction zone earthquake locationsOver the last several years, multiple earthquake events have been detected and recorded off the coast of Oregon, yet their epicenter locations have great uncertainty with the assumed simple crustal structures. Solutions to determine the locations of a particular earthquake based on observed arrival times at a network of seismic stations will differ depending on the assumed crustal structure. Because the relationship between the earthquake locations and crustal structure can be diagnostic of tectonic activity, it is important to determine more accurate locations. Knowing how location estimates depend on the assumed crustal structure leads to a better understanding of the earthquake activity in the Cascadia region and what can be expected from this region in the future. Using earthquake waveform data taken in the Cascadia region, arrival times of the primary and secondary earthquake waves were used to calculate the location of three earthquakes using HYPO71 and related software. By assuming different crustal structures for the same earthquake the impact of uncertainties in the crustal structure on earthquake location can be quantified. Two one-dimensional crustal structure models were used for the three earthquakes, one thicker model that has been used in the past by seismic networks and one thinner model that is thought to resemble the crust in the region where the earthquakes occurred. As expected, the thicker crustal structure resulted in deeper earthquake locations while the thinner crustal model resulted in shallower locations. Although the thinner crustal model is thought to resemble the subduction zone better, the model yields a higher uncertainty than the thicker model, possibly because the thicker structure is a better representation of the structure in the vicinity of the stations. While the exact location of the earthquakes is still not known, comparing the two models has allowed for a better understanding of the actual uncertainties. The next step will be to explore the effect of more complex and realistic 3D crustal structure.
Pacific (Crassostrea gigas) and Olympia (Ostrea lurida) shell dissolution rates in Yaquina Bay, ORHealthy oyster reefs require a positive shell budget, in other words the rate shell generation must outpace shell loss. A large focus of ocean acidification research has examined changes in biocalcification rates with far less on dead shell dissolution. Oyster reefs are subjected to shell degradation through two primary environmental controls, decreased saturation state and burrowing organism attacks. With increasing ocean acidification, CaCO3 saturation states will decrease which will increase shell dissolution rates and thus potentially affect juvenile recruitment, coastal erosion, and habitat loss due to possibly shrinking reefs. Previous research quantified shell dissolution rates on other oyster species in east coast estuaries, however little is known regarding Ostrea lurida and Crassostrea gigas. Here we seek to quantify shell degradation rates by conducting field and laboratory experiments, to determine field rates, as well as isolate chemical dissolution in the laboratory. We accomplished this by placing shell bags along Yaquina Bay, OR to represent the gradient associated with estuarine chemistry, resulting from both freshwater input and net community metabolism. We measured mass loss over time (mg g-1 month-1) to determine shell degradation. During the wet season, we observed increased dissolution rates along the estuarine gradient, with higher rates up the estuary with the lowest alkalinity. However, during the dry season we observed ~0.5% loss per month at the site with the highest alkalinity, which is greater than the site with intermediate alkalinity. We hypothesize that the ~0.5% average loss is due to upwelling events and associated decreases in saturation state occurring concurrently with the dry season.
Implementing a Variable Mesoscale Eddy Parameterization Scheme on Global Ocean Models: Modern Oceans and the Last Glacial MaximumMesoscale eddies, vortical currents which arise from steepened density gradients and exist on scales of 10km to 100km, are a ubiquitous ocean phenomena. They play a crucial role in ocean dynamics, possessing a bulk of the oceans kinetic energy as well as transporting heat, salinity and various biogeochemical tracers across the globe. The impact of mesoscale eddies on ocean models is significant, but they are too small to be resolved by global coarse-resolution models, and as a result must be parameterized in simulations. Most models employ the Gent and McWilliams (1990) eddy-mixing scheme, parameterizing the eddies via the thickness diffusivity KGM and isopycnal diffusivity KISO, which together account for the mixing action along isopycnal surfaces. Standard practice has been to use constant values of KGM and KISO, but observation and theory suggest spatially and temporally variable coefficients are more appropriate. We apply parameterization of variable thickness and isopycnal diffusivities to the paleocean of the Last Glacial Maximum (LGM), as well as the modern ocean, in order to evaluate the parameterization and test the impact of variable diffusivities on global ocean models.
Incorporating radiometric constraints in dynamic programming algorithms to align chemostratigraphic time seriesDynamic programming algorithms can produce optimal alignments of two geochemical time series. An optimal alignment is defined as the path of adjoining elements in a generated cost matrix with the smallest cumulative sum of squared differences. At present, such algorithms determine alignment paths without accounting for possible stratigraphic tie points, such as ash beds or other lithologic markers, between the stratigraphic sections at which the two time series were sampled. Adding stratigraphic tie points into these algorithms can decrease the number of optimal alignments of the geochemical time series and produce more geologically realistic relationships between geochemical time series. Here we propose to incorporate stratigraphic tie points into an existing alignment algorithm by adding either bonus or penalty functions to the algorithm that encourage the alignment to pass through a determined point, or stratigraphic time control, whose uncertainty equals that of the radiometric date measurement.
“Fjord” for thought: Early findings from the LeConte glacier datasetRecent investigations of tidewater fjords have detailed unexpectedly high melt rates and unaccounted-for circulation patterns, highlighting the need for a better understanding of near-glacial processes. To offer insight into these processes, we deployed moorings within approximately 20 meters of the terminus of LeConte Glacier for 10 days in September 2018; these collected near-terminus velocity profiles, CTD (conductivity, temperature, and depth) measurements, and hydroacoustic recordings. Additionally, we collected transects of velocity, salinity, and temperature, as well as time-lapse imagery of the terminus region. We present initial analyses of these data. We find that fluctuations in the measured currents near the terminus are considerably higher than those measured 500m down-fjord, indicating flow patterns are more complex than reported previously. Further, we divide the fjord circulation into four “regimes” (i.e. periods of time with distinct velocity and acoustic signals, characterized in terms of the mean and variance of these parameters); these regimes do not represent the spatial and temporal variability of the near-terminus velocities, but they do helpfully isolate instances of abrupt change in the circulation pattern. We propose movement of the subglacial discharge outlet location as the primary driver of regime change. Finally, we identify a possible relationship between large calving events and regime changes, and we suggest directions for future research.
The effect of microzooplankton grazing on phytoplankton in the Northern California Current: assessment through an imaging flow cytobot and dilution experimentsMicrozooplankton are a crucial component of pelagic food webs. We are interested determining the cross-shelf patterns of phytoplankton growth, microzooplankton growth and grazing, and mesozooplankton effects in the Northern California Current. This research will be conducted using an Imaging Flow Cytobot (IFCB) to determine counts and identity of phytoplankton and microzooplankton as part of a dilution method experiment. This method has yet to be accessed with this instrument which provides high taxonomic resolution and precise cell counts of organisms less than 200 um. The results of this experiment will inform our understanding of trophic cascades in dynamic upwelling-influenced marine ecosystems.
Quantifying Chukchi Polynya occurrence using passive microwave and local observational data Polynyas are recurring areas where sea ice thins or opens to reveal an ocean-atmosphere interface. They have the potential to affect moisture and heat flux, warming local temperatures, and initiating feedbacks on Arctic atmospheric and oceanographic systems. The Barrow Coastal Polynya and the Chukchi Polynya, found in the Northeastern Chukchi Sea off the Alaskan coast, have widespread implications as they foster the survival of biodiverse marine animals and impact sea ice hunting practices. We develop a database of the timing and spatial extent of the Barrow Coastal Polynya (between Utqiagvik and Icy Cape, Alaska) and Chukchi Polynya (between Icy Cape and Cape Lisburne) between November 1 and May 31, for the years 2002 through 2019 using 12.5 km resolution satellite passive microwave data from the Japan Aerospace Exploration Agency’s Advanced Microwave Scanning Radiometer (AMSR-E/AMSR-2) sensors. An automated system identifies polynya events based on annual time series of total water percent over each polynya’s domain area. Polynya timing and spatial characteristics are verified with sea ice concentration maps, and integrated with local Iñupiat observations from near Utqiagvik, Alaska using the Seasonal Ice Zone Observing Network and Alaska Arctic Observatory & Knowledge Hub. This database of polynya events reveals inter-annual variability in the timing and frequency of both polynyas in response to synoptic scale wind forcing. Between 2002 and 2019 the Chukchi Polynya has typically opened more frequently, but with lower total water coverage than the Barrow Coastal Polynya. Comparing passive microwave-derived polynya identifications to local observations of polynya indicators reveal that these two datasets should be used in tandem to thoroughly characterize the polynyas. By accurately quantifying these polynya events, we lay the groundwork to understand the impacts of coastal polynyas on regional wintertime atmospheric moisture and heat flux.
Earthquakes and megafloods: extreme events recorded in marine sediments of the Pacific Northwest since the Last Glacial MaximumMarine sediment core OC1706B-02J ( 46° 15.4178 N, 125° 42.4543 W, at water depth 2263m), was collected on the lower continental slope near the base of the Willapa Canyon. It is a rapidly accumulating site (~30cm/kyr) located near the thrust front of the Cascadia Subduction Zone. The site is also adjacent to the mouth of the Columbia: the largest river to discharge to the Northeast Pacific Ocean. As such, sediment delivery to the core site could be sensitive to earthquakes and/or extreme discharge events from the Columbia River. Dozens of coarse-grained layers reflecting energetic sediment deposition have been identified in the core via CT-scan. To understand the origin of these events we evaluate variability in sediment composition via X-ray fluorescence (XRF) and magnetic susceptibility on a chronology informed by a combination of foraminiferal stable oxygen isotopes, and radiocarbon. By comparing the timing of the energetic deposits preserved in the core to the known timing of large regional earthquakes in the Holocene and megaflood events through the late glacial, we evaluate the extent to which either of these processes influence sediment transport to the site.