Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

Methods for these LCS results can be found in Veatch, et al., (2024), In revision.

Finite Time Lyapunov Exponents assign scalar values to points on a gridded velocity field that characterizes the horizontal separation distance between two drifters about a point over a defined

 time interval. From particle trajectories in a velocity field, FTLE will define stretching as the integrated separation rate between two particles. To calculate repelling FTLEs, a forward trajectory is used, and to calculate attracting FTLEs, a backward trajectory is used. In this study, attracting FTLEs were calculated. FTLE differs from the instantaneous separation rate (Weiss 1991; Okubo 1970) by integrating over trajectories, providing a more realistic interpretation (one with particle position “memory”) of transport in the velocity field. Coherent structures are defined by the FTLE metric as ridges in the flow field where neighboring particles are converged toward, and then diverged along the ridge. This relative motion between two

neighboring particles is the key way in which the FTLE metric differs from the RPD metric. FTLE will vary over space and time when applied to a discrete set of velocity data. FTLE calculations result in a material surface that then can be projected at a set resolution back onto the study region. FTLE results were projected at the resolution of the HFR so as to not stretch the observations further than the input data should be able to resolve. FTLE calculations were performed using a MATLAB software toolbox (Haller) that was modified for use on HFR data and available at https://github.com/JackieVeatch/SWARM_LCS.
* Curatorial note: See supplemental file SWARM_LCS-related_to_bcodmo_917926_917914_v1.zip which contains a release corresponding to commit (10931d9).

All data were processed using MATLAB 2019b. Scripts used for data analysis can be found at https://github.com/JackieVeatch/SWARM_LCS.
* Curatorial note: See supplemental file SWARM_LCS-related_to_bcodmo_917926_917914_v1.zip which contains a release corresponding to commit (10931d9).

* netcdf file imported into BCO-DMO. No changes made.
* A copy of code repository supplied by submitter https://github.com/JackieVeatch/SWARM_LCS (commit 10931d9) forked to BCO-DMO for curatorial purposes and a release was made on 2024-01-08
https://github.com/BCODMO/SWARM_LCS/releases/tag/related_to_bcodmo_91792.... No changes to the code were made. Zip file of this release attache as a supplemental file.

NSF Award Abstract:
Undersea canyons play disproportionately important roles as oceanic biological hotspots and are critical for our understanding of many coastal ecosystems. Canyon-associated biological hotspots have persisted for thousands of years Along the Western Antarctic Peninsula, despite significant climate variability. Observations of currents over Palmer Deep canyon, a representative hotspot along the Western Antarctic Peninsula, indicate that surface phytoplankton blooms enter and exit the local hotspot on scales of ~1-2 days. This time of residence is in conflict with the prevailing idea that canyon associated hotspots are primarily maintained by phytoplankton that are locally grown in association with these features by the upwelling of deep waters rich with nutrients that fuel the phytoplankton growth. Instead, the implication is that horizontal ocean circulation is likely more important to maintaining these biological hotspots than local upwelling through its physical concentrating effects. This project seeks to better resolve the factors that create and maintain focused areas of biological activity at canyons along the Western Antarctic Peninsula and create local foraging areas for marine mammals and birds. The project focus is in the analysis of the ocean transport and concentration mechanisms that sustain these biological hotspots, connecting oceanography to phytoplankton and krill, up through the food web to one of the resident predators, penguins. In addition, the research will engage with teachers from school districts serving underrepresented and underserved students by integrating the instructors and their students completely with the science team. Students will conduct their own research with the same data over the same time as researchers on the project. Revealing the fundamental mechanisms that sustain these known hotspots will significantly advance our understanding of the observed connection between submarine canyons and persistent penguin population hotspots over ecological time, and provide a new model for how Antarctic hotspots function.

To understand the physical mechanisms that support persistent hotspots along the Western Antarctic Peninsula (WAP), this project will integrate a modeling and field program that will target the processes responsible for transporting and concentrating phytoplankton and krill biomass to known penguin foraging locations. Within the Palmer Deep canyon, a representative hotspot, the team will deploy a High Frequency Radar (HFR) coastal surface current mapping network, uniquely equipped to identify the eddies and frontal regions that concentrate phytoplankton and krill. The field program, centered on surface features identified by the HFR, will include (i) a coordinated fleet of gliders to survey hydrography, chlorophyll fluorescence, optical backscatter, and active acoustics at the scale of the targeted convergent features; (ii) precise penguin tracking with GPS-linked satellite telemetry and time-depth recorders (TDRs); (iii) and weekly small boat surveys that adaptively target and track convergent features to measure phytoplankton, krill, and hydrography. A high resolution physical model will generalize our field measurements to other known hotspots along the WAP through simulation and determine which physical mechanisms lead to the maintenance of these hotspots. The project will also engage educators, students, and members of the general public in Antarctic research and data analysis with an education program that will advance teaching and learning as well as broadening participation of under-represented groups. This engagement includes professional development workshops, live connections to the public and classrooms, student research symposia, and program evaluation. Together the integrated research and engagement will advance our understanding of the role regional transport pathways and local depth dependent concentrating physical mechanisms play in sustaining these biological hotspots.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.