Subduction in an Eddy-Resolving State Estimate of the Northeast Atlantic Ocean

• Main Author: Gebbie, Geoffrey
• Other Authors: MASSACHUSETTS INST OF TECH CAMBRIDGE
• Format: Text
• Language: English
• Published: 2004
• Subjects: Physical and Dynamic Oceanography; Fluid Mechanics; Statistics and Probability; *EDDIES(FLUID MECHANICS); OCEAN CURRENTS; MODELS; NUMERICAL ANALYSIS; CLIMATE; DATA COMPRESSION; CIRCULATION; NORTH ATLANTIC OCEAN; AZORES; THERMOCLINES; *SUBDUCTION; *GYRES; WATER MASS TRANSFORMATIONS; North Atlantic; Northeast Atlantic
• Online Access: http://www.dtic.mil/docs/citations/ADA427075; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA427075

Are eddies an important contributor to subduction in the eastern subtropical gyre? Here, an adjoint model is used to combine a regional, eddy-resolving numerical model with observations to produce a state estimate of the ocean circulation. The estimate is a synthesis of a variety of in-situ observations from the Subduction Experiment, TOPEX/POSEIDON altimetry, and the MTI General Circulation Model. The adjoint method is successful because the Northeast Atlantic Ocean is only weakly nonlinear. The state estimate provides a physically-interpretable, eddy-resolving information source to diagnose subduction. Estimates of eddy subduction for the eastern subtropical gyre of the North Atlantic are larger than previously calculated from parameterizations in coarse-resolution models. Furthermore, eddy subduction rates have typical magnitudes of 15% of the total subduction rate. Eddies contribute as much as 1 Sverdrup to water-mass transformation, and hence subduction, in the North Equatorial Current and the Azores Current. The findings of this thesis imply that the inability to resolve or accurately parameterize eddy subduction in climate models would lead to an accumulation of error in the structure of the main thermocline, even in the relatively-quiescent eastern subtropical gyre. The original document contains color images. All DTIC reproductions will be in black and white. Performed in collaboration with Woods Hole Oceanographic Institution, Wood Holes, MA.