A control section south of Sri Lanka for near-shore fresh water transport into the Arabian Sea
Abstract
The Arabian Sea exchanges heat and fresh water with the Bay of Bengal through a strong boundary current system that passes around Sri Lanka. The ASTraL program recognizes the importance of these exchange flows, and their seasonal changes, to the ocean stratification in the “mini warm pool area” of the Arabian Sea. However, probably around 50% of the freshwater flux happens in the inner 50km of the boundary current which cannot be sampled with gliders. In addition, satellite salinity cannot resolve the low-salinity cores of nearshore flows of with expected 20km scales. Here, an observational system is proposed that builds on previous efforts in the ASIRI and MISO-BoB initiatives and would close these gaps. This system seeks to fully monitor the flow and transport of salt and freshwater for several years, to assess its variability and provide the results as benchmarks to other ASTraL projects. There are substantial uncertainties in present knowledge of the variability of both the currents and their salinity in the nearshore region south of Sri Lanka, where the signal is largest. Data from further offshore exist from the previous ASIRI and MISO-BoB programs, using both gliders and pressure-sensing inverted echo sounders (PIES). These have been analyzed together with a reanalysis model to guide and justify the proposed work. We intend to re-deploy a pair of seafloor PIES from MISO-BoB in a location that brings them closer to shore, and to augment these with a near-shore mooring that measures currents and salinity directly at one location. This can fill the gaps and quantify the salinity transport in the inner 50km of the boundary current south of Sri Lanka. It needs to be paired with glider observations farther offshore on the same section, as had been done in ASIRI and MISO-BOB. The planned duration of the field observations is three years, consisting of one three-year deployment of the PIES and three successive, nominally one-year, mooring deployments. The work is carried out in collaboration with partners in Sri Lanka. This research addresses the following of the ASTraL science questions, by providing the observational data needed from the boundary currents off Sri Lanka: What processes control the maintenance and dissipation of the Arabian Sea warm pool? What exchange processes are misrepresented in coupled models leading to moisture & precipitation dry biases in forecasts?
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2023
- Source ID
- N000142312811
Entities
People
- Uwe Send
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego