Characterizing the warm water flow through Pine Island Thwaites West Trough

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

This project will collect novel observations of turbulent fluid motions at the Amundsen Sea shelf break to examine how the resulting diffusion of heat and salt changes the properties of water entering the shelf. Circumpolar Deep Water (CDW) enters the Amundsen Sea shelf through the Pine Island Thwaites West Trough within an undercurrent and travels toward the shrinking Pine Island and Thwaites Ice Sheets. An existing NERC-funded project entitled “Drivers of Oceanic Change in the Amundsen Sea” (DECADES) plans to explore heat transport on the shelf at seasonal timescales; this work would utilize DECADES ship time to target high-frequency heat transport through the trough. Goals are to: 1) expand the observational capabilities in DECADES to directly measure transformation of CDW as it enters the trough; 2) understand the processes driving the transformation; and 3) examine possible mechanisms by which the undercurrent turns into the trough. The work would contribute to a better understanding of the processes driving ice sheet melt, which could improve modeling and predictions of sea level rise. New turbulence measurements in this data-sparse region will help refine the emerging processing standards for turbulence data. This proposal supports an early career investigator, and includes two education and outreach components:vthe data will provide basis projects for a summer intern and a “Nerd's Rule Ocean Ambassador.” PIs are involved in the Ocean Ambassador program, which aims to expose 10- to 25-year-olds from underserved backgrounds to community education and mentoring opportunities focused on ocean and climate justice. High-resolution ship-based state of the art instrumentation will be used: the "FastCTD" (5 m/s descent rate, rated to 2000m, profiles to 600m can be done every 20 minutes) and the custom-built "Epsifish" (a loosely tethered free-falling microstructure turbulence profiler with pumped CTD, shear probes, and fast-response thermistors). Three profiling moorings - two overwintering and one additional measuring turbulence during the shipboard observations - in addition to 5 planned DECADES moorings. Ship based work would occur in early 2024 (austral summer) with the turbulence mooring deployed and recovered the same summer, and the other two moorings recovered in early 2025 along with the DECADES moorings. Velocity and temperature microstructure data from these measurements will be used to calculate the dissipation rates of turbulent kinetic energy and thermal variance, respectively. Dissipation rates are calculated from shear probe data using standard techniques that involve fitting observed shear spectra in the inertial sub-range of turbulence to standard spectral shapes. 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.