Searching for Pathways of Cross-Equatorial Water Mass Return Flow

Typical temperature (a) and salinity (b) profiles in the Anegada Passage region, as well as approximate ranges of the major water masses (c). Without the use of dissolved oxygen (d), two distinctly different water masses in the Central Water range cannot be distinguished from each other based on temperature and salinity alone.

Identifying a water mass’ hemisphere of origin based on temperature and salinity alone is imperfect as the major water masses from either hemisphere have common formation mechanisms and thereby have similar temperature and salinity characteristics. Fortunately, those same formation mechanisms lead to unique dissolved oxygen signals for the major water masses below the surface layer. Thus, when combined with temperature and salinity, dissolved oxygen can be used to infer the hemisphere of water mass origin. I am presently investigating the different cross-equatorial meridional overturning circulation (MOC) return flow pathways in the Caribbean. This research utilizes the unique temperature, salinity, and dissolved oxygen characteristics of South Atlantic and North Atlantic Water (SAW/NAW) in existing glider datasets in the Northern Caribbean and planned glider deployments in the Southern Caribbean. This work is in progress as Chapter 2 of my PhD.

Glider RU29 Windward Island Passages Deployments (October and November 2022)

Revisiting Anegada Passage Transport

Glider tracks in the Anegada Passage region from 2020-2022 glider deployments.

Caribbean through-flow is an important source of heat and salt for the Atlantic Meridional Overturning Circulation (AMOC). The presence of water masses that originated in the South Atlantic (SAW) in the Northern Hemisphere is indicative of cross-equatorial AMOC return flow. Ship-based observations in the 1990’s identified major pathways for this AMOC return flow but there is still a significant amount of SAW that is taking an unknown, alternate route northward. Working with Travis Miles and Scott Glenn of Rutgers and Doug Wilson from the University of the Virgin Islands, we have now conducted 4 glider deployments in the Anegada Passage region since 2020 collecting the first observations of temperature, salinity, and subsurface velocity in nearly 20 years. These observations suggest that the total transport and SAW transport through the Anegada Passage is larger than previously estimated. This work has been submitted to the JGR: Oceans and comprises Chapter 1 of my PhD.

E(+)/W(-) (top row) and N(+)/S(-) (bottom row) transport time-series’ calculated from the repeat transect lines between St. Thomas and St. Croix for the RU29 October 2020 deployment (left column) and RU36 March 2022 deployment (right column). Black dashed line represents the deployment mean transport.

Onboard Processing for Glider ADCPs

There is a growing number of increasingly complex instruments have been integrated into autonomous underwater vehicles over the past two decades. While these newly glider integrated sensors provide unprecedented insight into ocean processes, the large data volumes collected by these instruments cannot be efficiently telemetered to shore. There is a need for a sensor agnostic real-time processing software and hardware architecture for autonomous underwater vehicles. Working with Travis Miles, Eli Hunter, Julia Engdahl, and the software team at Teledyne Webb Research, we have begun integrating a Raspberry-Pi into a G3S Slocum Glider to perform real-time processing of Acoustic Doppler Current Profiler (ADCP) data. While this is ongoing work, initial findings from this work can be found in our Marine Technology Society Conference paper. The Python code used for ADCP processing can be found here.

Schematic of glider ADCP data processed into a single velocity profile.

Slocum Glider Development

Prior to coming to Rutgers, I worked as a Customer Support Applications Engineer on Slocum gliders for Teledyne Webb Research. I was primarily involved with testing and developing new glider software features while also supporting customers via remote field campaigns and technical trainings. During my time with TWR, I worked on lab and field testing of the under-ice and station keeping behaviors as well as development and testing of the STM-32 processor. Naturally I became very good at breaking gliders, of course with the goal of improving and hardening the system! I also was one of the lead pilots during the last two legs of Silbo’s Trans-Atlantic Challenger Mission, where this glider went from the Canary Islands to St. Thomas (417 days, 6256 km) and then from St. Thomas to Cape Cod (348 days, 6236 km).

Silbo and her total Trans-Atlantic Challenger Mission Track.

Kinetic Energy and Phytoplankton

I conducted Master’s work at the University of Delaware with Matt Oliver in the ORB Lab. While at UD, my research investigated sea surface kinetic energy as a proxy for phytoplankton light limitation in the Southern Ocean through the use of SOCCOM floats as well as satellite and modeled parameters. Our JGR: Oceans’ publication showed that low surface kinetic energy behaves like a necessary but not sufficient condition for high chlorophyll concentrations. In high kinetic energy conditions, high chlorophyll concentrations arer are. Conversely, under low kinetic energy conditions, both high and low chlorophyll concentrations were observed. We showed that higher kinetic energy conditions are related to deeper mixed layers, which is likely a proxy for local light conditions.

Mean surface kinetic energy and mean surface chlorophyll concentration relationship derived in the Southern Ocean from 2003 to 2017.