Contributed Session.
Lead Organizer: Mitchelle Agonsi, University of Georgia (agonsimitchelle@gmail.com)
Presentations
06:00 PM
USING 210PBXS TO TRACK DOWNSLOPE TRANSPORT OF SEDIMENTS IN THE SOUTHERN GULF OF MEXICO: A “PULSE INDEX” AND MASS ACCUMULATION RATE APPROACH (9732)
Primary Presenter: Selby Shipley, Eckerd College (sashipley@eckerd.edu)
Sediment cores collected throughout the Southern Gulf of Mexico (SGoM) in 2015 were used to evaluate downslope transport of sediments which may have associated contaminants and compared to the Northern Gulf of Mexico (NGoM). Their main difference is the SGoM has less terrestrial sediment influence unlike the NGoM’s input from the Mississippi River. Short-lived radioisotope (SLR) analysis of cores for 210-Pb excess (210Pbxs) provided downcore 210Pbxs profiles, which were used to determine age dates and mass accumulation rates (MAR) using the Constant Rate of Supply model. A“Pulse Index” value for each site was determined using profile shape for the number of episodic sedimentation “pulse” events, the percentage of sediments accumulated in each event, and the length of each pulse. This “Pulse Index” provides a relative evaluation of how consistent/stable vs episodic (downslope transport events) sediment accumulation is at each site for the past 100 years. The NGoM has high index values, likely due to Mississippi River input with higher potential for downslope transport of contaminants associated with the 2010 Deepwater Horizon oil spill. The SGOM has lower index values, besides the IXTOC site, with lower potential for downslope transport of contaminated sediments from the 1979 IXTOC oil spill. This indicates more stable sediment accumulation patterns in the SGoM and lower potential for downslope transport of contaminants. Future research can help in understanding the use of SLRs to find downslope transport and recognize patterns in sediment movement throughout the GoM.
06:00 PM
Rates of Shoreline Change on the North Central Basin of Lake Erie (9058)
Primary Presenter: Cooper O'Rourke, University of Waterloo (corourke@uwaterloo.ca)
Coastal erosion is an increasing issue in the Laurentian Great Lakes due to changes in the frequency and magnitude of storm activity, fluctuating lake levels, and the decrease in protective lake ice. The coastal bluffs in Lake Erie have been retreating at an average end point rate of -0.8 m/y between 1909 to 2018, leading to the closure of many roads close to the shoreline as well as properties and infrastructure collapsing into the lake. Due to the absence of aerial imagery prior to the 1950s and a lack of high-quality imagery up until the early 2000s, a comprehensive analysis of bluff erosion was conducted utilizing the Southwestern Ontario Orthophotography Project (SWOOP) imagery and digital elevation model dataset for 2006, 2010, 2015, and 2020. By digitizing the bluff brink, bluff toe, and shoreline for each year in the area between Rondeau and Long Point Provincial Parks, accurate estimates of both erosion, accretion, and the volumetric loss of bluff material to the lake were made for this changing shoreline. Alongshore variation of rates can be attributed to the influence of the structural control that jetties and other coastal infrastructure create by disrupting the transport of sediment within the littoral cell. Increased lake levels as well as diminished protective lake ice indicate that wave erosion at the base of the bluffs is the primary mechanism of sediment loss on this northern shoreline.
06:00 PM
Physical controls of circulation and residence time in the Altamaha River estuary (9339)
Primary Presenter: Mitchelle Agonsi, University of Georgia (mitchelle.agonsi@uga.edu)
The Altamaha estuary is a dynamic and complex ecosystem that connects three adjacent sounds (Altamaha, Doboy and Sapelo Sounds) with the South Atlantic Bight. These environments are constantly changing with mixing of freshwater from uplands and saltwater brought into the estuary primarily by tides and wind forcing. To investigate circulation in the estuary, we use the Delft3D-Flow multidimensional coastal hydrodynamic and transport model with inputs of tides, winds and river discharge as forcing on a structured, boundary fitted grid. Using the Delft3D-Flow model over a 15-month period from December 2016 - February 2018, we implemented a tracer tracking technique to investigate transport processes and provide a quantitative estimate of residence times within the Altamaha estuarine domain. Model simulations of temperature and salinity compared favorably with the continuous temperature and salinity dataset from the Georgia Coastal Ecosystems Long Term Ecological Research hydrographic moorings. We present estimates of transport pathways of freshwater and residence time in the estuary and quantify how those vary seasonally in response to variations in forcing. Our results inform on spatiotemporal variations and distribution of nutrients, contaminants, and other tracers in the estuarine domain and is relevant to several ecological processes.
06:00 PM
HEAT TRANSFER DURING A TROPICAL CYCLONE FORMATION (9057)
Primary Presenter: Sydney Perkins, University of California Berkeley (sydperkins@berkeley.edu)
The Bay of Bengal receives the most rainfall globally and is one of the freshest subtropical regions in the ocean (Mahadevan, 2017). The unique ocean composition and atmospheric conditions interact to create the monsoons that the surrounding 1.4 billion residents and local agricultural economy rely on (Xavier, 2018). Due to the impacts of these weather systems on the coastal population, there is great motivation to understand and predict tropical cyclones and the start of the monsoon season in the Bay of Bengal. This project aims to investigate how heat transfers between the atmosphere, ocean surface layer, and deeper internal layers during the passage of a tropical cyclone. The surface layer is defined as the mixed layer. The interior layer goes from the surface to the 26° C isotherm, also known as the Tropical Cyclone Heat Potential, which is identified by the depth of the 26° C isotherm (Goni, Trinanes, 2003). The change in the heat content over time from the surface to the mixed layer and the mixed layer to the interior layer was compared to surface heat flux. The analysis showed that the ocean had a much higher magnitude of heat change compared to the surface and that tropical cyclones remove temperature structures in the ocean through mixing. Mahadevan (2017). Oceanography C. Xavier (2018). Carnegie Endowment for International Peace G. Goni, J. Trinanes (2003). NOAA/AOML
CS13P - Physical Dynamics
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A