Mid ocean ridges are large interruptions in the expansive abyssal plains that dominate ocean basins. Volcanically active ridges release heat and chemicals into the surrounding ocean through hydrothermal plumes. Benthic organisms are dependent on these plumes for nutrients and distribution of their larvae. Quantifiable changes in hydrothermal plumes have been documented in response to volcanic eruptions. These plumes experience increases in fluid temperature and rise height after eruptions and become event plumes. This study investigates the effects on circulation from the 2015 eruption at Axial Seamount: a submarine volcano located along the Juan de Fuca Ridge, 300 miles off the coast of Oregon. After the eruption, an unusual temperature increase was measured within the summit caldera. This increase is unique compared to other eruptions in that it is widespread, uniform, and has a large amplitude of 0.6 to 0.7 °C. Two hypotheses exist for the temperature anomaly: a large brine layer was expelled from the subsurface after the eruption, and a neutrally buoyant event plume formed above a lava flow and was advected above the summit. Since no salinity data is available, I evaluate the two hypotheses using the mean flow direction, magnitude, and variation of currents measured at a site within the caldera. There was an abnormal sustained flow to the southeast lasting 12 days with high speed coinciding with the rising temperature. This observation is consistent with the movement of a large volume of warm fluid. The increase in standard deviation and by proxy, turbulence, are not significant enough in the presence of increased flow speed to imply either a brine layer or event plume as the cause. Understanding fluid motion after eruptions will help give insight into how microorganisms are distributed amongst and establish new communities in hydrothermal vent fields.

Better understanding the circulation of the ocean's deepest waters is critical to predicting how the world ocean will respond to a rapidly heating atmosphere. The deep and abyssal circulation across 30°S in the Brazil Basin is inferred from multiple decades of full-depth CTD data by an angular momentum and salt conserving inverse model which parameterizes mixing across ocean layers as a function of the roughness of the seafloor. This inverse model was originally designed by my advisor for use in the North East Pacific basin. My work was writing an extensible software library in Python to apply the same inverse technique to other ocean basins like the Brazil basin. From this inverse we learned the Brazil basin exhibits strong diapycnal mixing especially towards its boundaries, and weak lateral mixing. The largest transport outside of boundary currents across 30°S is the southward flow of Antarctic Bottom Water (AABW) at a rate of ~10^10 kg s-1. AABW flows northward through the Vema Channel and southward in the interior of the basin creating a cyclonic circulation around the Rio Grande Rise. Flow along -30°S is westward in the Antarctic Intermediate Water (AAIW) and Upper Circumpolar Deep Water (UCDW), and eastward in the North Atlantic Deep Water (NADW). Southward east of the Rio Grande Rise would have large impacts on the mixing and heat budgets of the Brazil basin.

Dam removals are becoming more common as many dams reach the end of their lifespans. As a consequence, it is important to understand the characteristics of the sediment accumulated behind them for sometimes over 100 years when it is released. These sediments can contain organic matter that is deposited in river deltas and reservoirs and can have an impact on the ecosystem. The Elwha River dams were removed starting in 2011, releasing 19Mt of sediment, and also a fraction of organic material that is unknown, some of which made its way to nearshore subtidal deposits. To characterize the relationship specifically between organic content and sediment size in sub-tidal deposits, box cores were collected and examined using x-radiography, wet sieving, and loss on ignition procedures. In subsamples with a lower percent of mud, the percent of organic matter is less than in subsamples that contained more mud. There is also a relationship between both percent mud and organic matter with the distance that the samples were collected from the river, with more mud and organic matter being found farther from the river mouth. These relationships can be explained by the settling velocity of flocculated sediment because organic matter better combines with mud particles and flocs sink slower than sediment of a larger size. This study is useful for future dam removals to determine what range of impacts it might have downstream.

ARGO floats are a fleet of autonomous robots that measure various oceanographic data while drifting with ocean currents and moving through the water column using a buoyancy engine. This buoyancy engine utilizes oil and air which is pumped in and out of a bladder at the base of the float. A typical function of an ARGO float is to sink to depth in the water column and then float back up to the surface, this is called a “profile”. When the float reaches the surface again, it communicates to satellites across the globe using an antenna which must emerge from the water completely to transmit its collected data. Recently, there have been suspicions of bladder problems in floats being produced as well as in deployed floats due to communication issues with the telemetry system which may be caused by the antenna not getting fully out of the water. I have refined a method of identifying bladder problems in ARGO floats using the data the float transmits. Preliminary analyses I have done shows that a decrease in vacuum with an increase in air pump runtime overtime has identified floats with bladder problems with high confidence. I then found all the floats that have been deployed since 2012 that have bladder problems and compiled data visualizations showing the relation between these floats and other data variables. Finally, I will analyze the data to decide whether this problem affects the overall lifespan and/or functionality of the floats. From this analysis I will then possibly find a solution for future floats to resolve the bladder problems detected and additionally to set up a system to automatically monitor for more problems.

Each year, snow-melt runoff flows through the Snohomish River and pours into the Snohomish River Estuary in Possession Sound, located in the Whidbey Basin of Washington State, resulting in a water-layering phenomenon. Cold snow-melt freshwater layers above relatively warmer, saltier Sound water. The Ocean Research College Academy (ORCA) collects data from two instruments in the Everett Marina, located just south of the Snohomish River mouth. Data from ORCA and the United States Geological Survey (USGS) were analyzed to investigate seasonal variations in current velocity, water temperature, and Snohomish River discharge; variables that have not been previously investigated in this region through a correlational lens. The current working hypothesis is that observed water current patterns over time in Possession Sound can be correlated to trends in water velocity, temperature, and discharge. This study uses data collected during deployments of an Acoustic Doppler Current Profiler (ADCP) in 2017 and 2020. The ADCP was located 0.45 meters above the seafloor of the main river channel near Everett Marina, providing consistent water temperature measurements at the instrument fixed base and current velocity measurements at 0.5- to 1-meter increments throughout the water column. A conductivity, temperature, and depth sonde (CTD) was attached to a dock at Everett Marina, 2 meters below the water surface, allowing the CTD to rise and fall with the tide. Water temperatures from the CTD and ADCP give a comprehensive overview of the middle and bottom layers of the estuary. Seasonal current changes can be determined with current velocity data measured by the ADCP and correlated against USGS river discharge data. Preliminary results indicate some temporally condensed variations, such as autumnal semimonthly current velocity changes in deeper waters. This investigation and analysis can offer insight into some of the effects these variables may have on the local water system.

 Euphausia superba, commonly known as Antarctic krill, are the dominant krill species in the Southern Ocean, and one of the most abundant species on Earth. This project focused on the swimming patterns of Antarctic krill in increasing chlorophyll concentrations to help understand the relationship between food availability and krill response by using 3-D data points from synchronized videos. Samples were collected aboard the RV Gould throughout Autumn of 2019 at both the South Shetland Islands and Gerlaches Straight at depths of 100-150m using 750 micrometer mesh square 2 x 2m nets. Samples were stored in a 500L tank and kept at 6 degrees Celsius. For the trials, 5 krill were placed in a 50L tanks in varying chlorophyll-a concentrations and recoded for 10 minutes using synchronized cameras. Afterwards, krill movement was analyzed using MATLAB’s DLTdv8 software. R Studio was used to assign ‘bins’ to various tank depths and count the number of individuals in each bin at a given time. Currently, I am still working on the results, however, it is hypothesized that the time spent in multiple bins will decrease as the chlorophyll concentration increases, since the krill will develop a more horizontal swimming pattern. It is important to understand this mechanism because in future climates, phytoplankton abundance is uncertain, which could have negative consequences for krill and the surrounding environment because of their keystone species status.