Eulerian inflow observations for Lagrangian analyses of coherent structures using low-cost short-term real-time moorings
Abstract
Coherent pathways for export of water from the surface mixed layer into the ocean interior are a poorly understood aspect of the functioning of the dynamical system in the upper ocean. Much of the theoretical work to date based on the concepts of ???Lagrangian coherent structures??? (LCS) has focused on the horizontal flow distributions and trajectories. CALYPSO intends to help extend these to 3D and vertical motion. Initial theoretical attempts for this were made by Bettencourt et al. (2012), Sulman et al. (2013), Allshouse and Peacock (2015) and others. A novel approach is that of Feppon & Lermusiaux (2018) who compute so-called ???flow maps??? which can be used to calculate fully 3D FTLE fields very efficiently. Many of the related observational techniques based on LCSs and FTLE analysis require a numerical field based on altimetry, model hindcasts, or data assimilation. The MSEAS team of Lermusiaux et al. have developed tools for data assimilation which can produce these model fields for analysis by other CALYPSO partners.CALYPSO will study the front which usually forms in the eastern Alboran Sea, resulting from the convergence of the Algerian Current deflected into the East Alboran Gyre (EAG) and the Northern Current which flows south along the French and Spanish coast. Our objective is to observe these two inflow branches during the two targeted observing periods in 2019 and 2020. For this we will test a new design of light-weight real-time low-cost moorings for short duration deployments in year 1, and in years 2 and 3 operate three geostrophic end-point moorings during the targeted observing periods to capture the inflow and upstream boundary condition. We will provide data, in delayed-mode and in real-time, to CALYPSO modelers for hindcasts, nowcasts, and forecasts of the frontal region, and collaborate with partners to understand what constraints the inflow conditions can provide for 3D LCSs in this front. We will place the moorings based on previous-day altimeter maps, on real-time analyses of the flow field (from SOCIB and from the MIT MSEAS system), and based on planning for the frontal field work in the subsequent days. The moorings would remain deployed for the approximately two weeks of the intensive frontal surveys. In order to make the mooring low-cost, light-weight, and real-time, we would merge our standard subsurface mooring type having inductive T/S sensors clamped onto the wire with the new mini-moorings under development for a small surface expression, and re-use older wire. This concept will be tested off Mallorca in collaboration with the SOCIB partners in year 1. Years 4 and 5 will have a low level of analysis work, with more science applications planned through an externally funded graduate student
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 04, 2018
- Source ID
- N000141812802
Entities
People
- Uwe Send
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego