OREGON STATE UNIVERSITY
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Summer Research Internships for Undergraduates
A high-resolution Labrador Sea surface and subsurface foraminiferal δ18O record and its relation to Heinrich EventsHeinrich events are characterized by episodic iceberg discharge events from the Laurentide ice sheet via the Hudson Strait Ice Stream (HSIS) and into the North Atlantic. Although their occurrence throughout late Pleistocene glaciations has been well documented in the oceanic sediment record, the triggering mechanism for Heinrich events is still poorly understood. Recent work (Marcott et al., 2011) has shown that subsurface ocean (~1200 m) warming in response to a shutdown of the Atlantic Meridional Overturning Circulation (AMOC) could lead to accelerated melting and destabilization of an ice shelf fronting the Laurentide Ice Sheet and subsequently trigger Heinrich events. However, evidence for this subsurface warming remains restricted to one core site. Here we use Labrador Sea core HU2006040-006pc from the Hamilton Spur to assess spatial and depth coverage of this signal. We infer surface and subsurface temperature variability using δ18O in benthic and planktonic foraminifera. We also develop a corresponding suite of other sediment core proxies in order to identify Heinrich layers, including X-Ray Fluorescence, Ca/Sr, and % dolomite/calcite data. This research will allow us to evaluate changes in the thermodynamic structure of the Labrador basin due to changes in the strength of the AMOC and their relation to Heinrich events. Results will be used to substantiate existing research and coupled ocean-atmospheric models that suggest a reduced AMOC and associated subsurface warming as the trigger for Heinrich events.
Carbon cycling along the Newport hydrographic line and in Yaquina BayDuring the summer months, the Pacific Northwest coastal margin experiences intense upwelling which delivers nutrients to surface waters. During the winter, nutrients are delivered to the ocean primarily by small mountainous rivers in response to flooding events. The distributions of dissolved and particulate organic carbon and particulate organic nitrogen along the Newport Hydrographic line and in Yaquina Bay were studied in high resolution by collecting water samples and measuring salinity, temperature, and density of the water during the summer months. Longitudinal wind speeds were used to identify various upwelling and downwelling events throughout the summer. The strength and duration of these wind driven events corresponded with the distribution of organic matter along the transect. These results will be used to set a baseline for comparison for the same type of measurements to be collected this winter. The comparison will allow us to evaluate seasonal changes in the overall concentrations and compositions of organic matter in nearshore waters and gain a better understanding of wintertime productivity in the Pacific Northwest ocean margin.
Evaluation of Trace Metal Pollution Associated with Train Traffic in the Pacific NorthwestTrain traffic is anticipated to increase in the Pacific Northwest to meet growing demands for coal and oil in Asia. Additional train traffic will increase toxic trace metal contamination along train routes, including in protected national forests and state parks such as the Columbia River Gorge National Scenic Area (CRGNSA). Lichens are environmental archives of atmospheric metal deposition. Metal concentrations and Pb isotopic compositions of lichen samples collected along coal train lines can be used as indicators of anthropogenic metal pollution associated with trains: from the combustion of diesel fuel, moving metal parts, and cargo (e.g., open cars of coal). To evaluate the impact of train metal emissions on surrounding natural areas, lichen samples were collected at increasing distances along perpendicular transects to the rail line. These lichen samples were measured for metal concentrations using ICP-MS and for Pb isotopic compositions using MC-ICP-MS. Our study found elevated metal concentrations near rail lines that generally decreased with increasing distance from rail lines. These elevated levels are comparable to those found near major roads (e.g. highways, interstates). Elevated levels of Ni, Cr, Cu, Pb, and Zn are largely attributed to material abrasion of train parts, and combustion of diesel. In contrast, elevated As may result from coal dust lost from transportation in open cars. Arsenic levels at sites closest to the rail were up to three times higher than As levels at sites farthest from the rail. Lichens collected near a coal-fired power plant in Boardman, OR are indicators of high N pollution and were notably deformed, presumably from pollution effects. Trace metal concentrations in Boardman were significantly higher than other areas in the CRGNSA, especially in lichens collected along the railroad tracks. Rail car abrasion, train cargo, and nearby roads can contribute to elevated metal concentrations near railroads. Lead and S isotope ratios will be used to fingerprint sources of these elements and determine their relative contributions. Future comparative studies on rail lines where coal is not transported and on rail lines closer to coal mines, where coal is loaded onto trains, may help to distinguish between the importance of the diesel fuel and coal dust as sources.
What do Atlantic δ13C measurements indicate about AMOC shutdown and reinvigoration during the LGM-HS1 and HS1-Bølling-Allerød transitions? δ13C isotope records contain information about carbon storage in the ocean, air-sea gas exchange, and the functioning of circulation systems. It is currently believed that the Atlantic Meridional Overturning Circulation (AMOC) underwent dramatic changes in strength during the most recent deglacial period (20,000-10,000 ybp). Through impact on efficiency of the biological pump, the cessation and restart of the AMOC are reflected in δ13C records. Geographically wide-ranging 13C data taken from benthic foraminifera in sediment cores were organized and compiled from a several of sources into a new database to create the most comprehensive existing record of δ13C. Records from the Atlantic Ocean during the last deglacial period were drawn from this database, and δ13C millennial averages for the Atlantic were synthesized and spatially averaged into latitude and depth zones. Averages of isotope records were used to assess Atlantic circulation changes over the course of climate events: Last Glacial Maximum (LGM), Heinrich-Stadial 1, and the Bølling-Allerød.
Detection of heavy metal pollution from Trail, B.C., through Colville National Forest, WAHeavy metal pollution has been detected in the Upper Columbia River Valley and the Colville National Forest. Due to their uptake of nutrients from the atmosphere and wide availability, lichens have been used as archives of heavy metal pollution. Previous work shows that Teck's Trail smelter, located approximately 6 miles north of the US- Canada border, emits a large number of heavy metals into the atmosphere. This smelter is hypothesized to be the main contributor of heavy metal pollution in this region. To evaluate the impact of this smelter in the surrounding area and cross- border along the Columbia River and in Colville National Forest lichen samples were collected and analyzed for heavy metal concentrations and Pb isotope composition. Previous work (Shiel et al. 2010) shows that the lead refined at this smelter has a characteristic isotopic composition that can be used to fingerprint Pb emissions from the smelter. Our study shows that there is high pollution around the smelter that dissipates and returns to normal levels further from the smelter. Heavy metals Pb, Zn, and Cd have concentrations at levels as high as 182, 673 and 5.27 ppm respectively. These maximum Pb, Zn, and Cd concentrations are 55, 15, and 13 times USFS threshold values, respectively. The majority of extracted In and Bi is produced as a by-product of Zn and Pb production. Ore concentrates processed at Trail contain small quantities of In and Bi. Our study indicates that significant In and Bi are released during processing and reach natural areas as far as 24 miles downwind of the smelter. Lichen samples exhibit In and Bi concentrations as high as 0.70 and 2.6 ppm, respectively. Lead isotope fingerprinting will be used to identify the relative contribution of the smelter and other sources to the identified pollution. This will complement the metal concentration study providing further evidence for the source of metal pollution along the Columbia River.
Isolation and function of the Pacific oyster larvae's organic matrixBivalves are seeing massive losses in population due to increased ocean acidification (OA) and saturation states. Bivalve larvae are especially sensitive to OA before the development of their dissoconch shell. The organic matrix of the bivalve larvae has been isolated in this study to look closely at its functional role in precipitation of calcium carbonate. Isolation of the organic matrix was carried out through a series of steps involving the removal of larval soft tissue with a bleach solution, and then the removal of the shell minerals with weak and strong acids. Metals analysis on an ICP-MS and ICP-OES were carried out as well as the determination of C/N ratios to verify the methods. The organic matrix was then filtered with recirculating artificial seawater to reprecipitate calcium carbonate. Precipitation rates were compared with abiotic aragonite and glass beads. While reprecipitation levels where undetectable, this study has led to better insight into the behavior of bivalve larvae.
Autonomous research vessels in the oceanA "Remotely Operated Surface Sampler" is a remotely operated research platform that is both inexpensive and capable of remote and autonomous data-collection. It is designed to be an ocean going instrument initially to assist in researching Air-Sea interaction. This system will be designed, built and tested at Oregon State University, then deployed in the Bay of Bengal for further field testing and for data-collection.
Optical measurements of ship wake celerity for hydrographyShips passing through the mouth of the Columbia River (MCR) create internal waves as they move through stratified layers of salt and fresh water. The propagation speed (celerity) of the waves theoretically depends on the density and thickness of the layers through which they are propagating; this relationship is approximately [insert equation here]. This suggests that measurements of wake celerity could be used for hydrography. To test this hypothesis, we measured the propagation speed of 6 wakes and compared the results with expected celerities calculated from in situ measurements. For each wake, two users each took two measurements of wake propagation speed. Using these measurements, we calculated average celerity and standard deviation for each wake. We also tested how repeatable our measurements were: we found the root mean square (RMS) difference between measurements taken by the same user, the bias for each measurement, the RMS difference between measurements taken by different users, and found the extent of geographical overlap between measurements. The RMS difference between measurements taken by the same user averaged 0.143 m/s; between two different users it was .179 m/s. We then used in situ CTD and velocity-depth measurements to calculate theoretical celerity from 10 May 2013 to 11 June 2013. We compared these theoretical celerities to the average measured celerity for six wakes with strong signals. The first wake had an average measured celerity of 0.632 +/- 0.019 m/s with a theoretical range of 0.498 to 0.518 m/s. The second wake had an average measured celerity of 0.667 +/- 0.457 m/s with a theoretical range of 0.498 to 0.518 m/s. The third had average measured celerity of 0.741 +/- 0.055 m/s and a theoretical range of 0.518 to 0.584 m/s. The fourth wake had average measured celerity of 0.795 +/- 0.047 m/s and a theoretical range of 0.694 to 0.722 m/s. The fifth wake had average measured celerity of 0.697 +/- 0.24 m/s and a theoretical range of 0.662 to 0.732 m/s. The six wake had average measured celerity of 0.815 +/- 0.70 m/s with a theoretical range of 0.756 to 0.784 m/s. The percent difference from wake to wake varied widely – the first three measured wakes fell outside the predicted range by 15.6%, 16.6% and 14.9% respectively; the fourth wake fell outside the predicted range by only 3.5%. The average measured celerity of the final two wakes fell within the predicted range.
3D visualization of global ocean circulationAdvanced 3D visualization techniques are seldom used to explore the dynamic behavior of ocean circulation. Streamlines are an effective method for visualization of flow, and they can be designed to clearly show the dynamic behavior of a fluidic system. We employ vector field editing and extraction software to examine the topology of velocity vector fields generated by a 3D global circulation model coupled to a one-layer atmosphere model simulating preindustrial and last glacial maximum (LGM) conditions. This results in a streamline-based visualization along multiple density isosurfaces on which we visualize points of vertical exchange and the distribution of properties such as temperature and biogeochemical tracers. Previous work involving this model examined the change in the energetics driving overturning circulation and mixing between simulations of LGM and preindustrial conditions. This visualization elucidates the relationship between locations of vertical exchange and mixing, as well as demonstrates the effects of circulation and mixing on the distribution of tracers such as carbon isotopes.
Warm winter winds: building a case study for the Oregon Coast RangeWarm, high pressure systems are measured from a weather station on a high elevation peak in the Oregon Coast range during the winter months. The readings have abnormal characteristics in relation to the surrounding areas. Characterizing the spatial and temporal variability of the high elevation warm mass of air around the Oregon Coast range was the general purpose of this research. Correlating each event to find common factors will determine its significance in the seasonality changes around the Coast Range. Temperature, relative humidity, height and wind were the main variables of data collected from radiosonde soundings, satellites and various weather stations. These sources showed wind directions, pressure systems, cloud formation and possible inversions which furthered the understanding of how and where the warm air formed. Analyses of the vertical structure of temperature and wind from the National Center for Atmospheric Prediction's (NCEP) North American Regional Reanalysis (NARR) provided high resolution depictions of what occurred during these warm periods. The anomalous warm events that were observed affecting the summit of Mary's Peak are likely caused by strong subsidence of warming air in the centers of high pressure ridges. These subsidence inversions may be originating from the semi-permanent North Pacific High pressure system at lower latitudes.
Do Indian and Pacific Ocean carbon isotopes reflect a change in the biological pump during the last deglaciation (~19,000---11,000 years ago)?The biological pump is a significant control on atmospheric carbon dioxide levels due to its ability to sequester carbon in the deep ocean. δ13C measured from the carbonate shells of benthic foraminifera serves as a proxy for biologic pump efficiency, so analyzing these carbon isotope ratios from sediment cores can provide information about the pump's efficiency in the past. Here we compile and analyze δ13C data from the Pacific and Indian Ocean basins during the last deglaciation (19,500 to 10,500 years ago), when atmospheric carbon dioxide levels increased about 80 ppm. Hundreds of published results and unpublished data were assembled into a database and selected for deglacial records of at least millennial time resolution. The resulting 59 records were analyzed in 8 regions, divided based on depth (intermediate [< 2 km] and deep [> 2 km]), and geographic location (North-, Equatorial-, and South-Pacific and Indian Ocean). Overall, in both basins, δ13C increased throughout the deglaciation, indicating that the deglacial biological pump became more inefficient.