Ocean state estimation and basin‐scale acoustic thermometry.

Abstract

This presentation describes a global ocean state estimation system and explores the role that sustained basin‐scale acoustic thermometry can play in evaluating and constraining the resulting ocean state estimates. The state estimation system is that developed by the ECCO2 project. Solutions are based on an eddying, full‐depth ocean, and sea ice configuration of the Massachusetts Institute of Technology general circulation model. Data constraints include altimetry, hydrography, sea surface temperature, and satellite observations of sea ice extent, thickness, and velocity. Green’s functions and the adjoint method are used to adjust initial and surface boundary conditions and empirical parameters such as vertical diffusivity, albedos, and drag coefficients, in order to reduce model/data discrepancies. Early prototype basin‐scale estimation systems that used acoustic data were deployed in the Eastern Mediterranean for THETIS‐2 and in the North Pacific for ATOC. More recently, 1 decade of North Pacific acoustic thermometry data was compared with ocean simulation and estimation results. The comparisons with acoustic data provide stringent tests of the time mean hydrography and of the large‐scale temperature variability in the models. The differences are sometimes substantial, indicating that acoustic thermometry data can provide significant additional constraints for numerical ocean models. Of particular interest is the deployment of a basin‐scale acoustic array for monitoring changes in the deep ocean interior.