Lagrangian Salinity Drifters In SPURS

Luca CenturioniVerena Hormann

Scripps Institution of Oceanography

Summary of drifters deployed & Current Status• 101 Salinity

drifters• 54 Temperature

drifters• August 2012-

ongoing

• 41 of the SIO SSS drifters still operating

Goals of our effort• Estimate the surface Eddy fluxes from drifters

and from Satellite assets (Aquarius and Altimetry);

• Question: is <U’S’> (and therefore ,<U’ S’>) measured by satellites realistically;

• Method: compare the following quantities ~

Issues in estimating <U’S’> due to mesoscale eddies include

1) How well AVISO represents U, U’, V and V’ in the SSS max region?

2) Is Aquarius SSS of sufficient accuracy to determine the fluxes?

Issue 1. Probably ok due to good correlation between U’ and V’ and AVISO, but requires correction coefficients obtained from regressing altimetry, wind and drifters observations (Centurioni et al 2008, 2009)

Issue 1. Probably ok too, see Yi Chao work on Aquarius biases.

Direct comparison of drifters’ derived fluxdivergence vs Aviso+ Aquarius

Remarks• Same order of magnitude

and general agreement;• Can be refined by

improving drifters’ SSS QC and drogue presence

• Eddy fluxes are generally small

• 400kmX400 km around mooring;

• Data is bin-averaged over 30 days;

• Only first 6 months of drifter data retained (for drogue presence and SSS accuracy)

~

Wave Glider Configuration• LRI SHARC Vehicle with ADCP Fairing• LRI Auxiliary Battery Payload Box• LRI High Voltage Board• LRI Weather Station• LRI Water Speed sensor• RDI Workhorse ADCP

SIO Additions• Underwater Winch Profiler• SIO Management computer

• ADCP management• Winch control system and algorithm• GPS Wave Spectra • 32GB Data Logger• Secondary Iridium SBD

A new asset for SPURS 2: Profiling WG

Summary

• More than 150 deployed during SPURS, 87 with salinity sensors

• Salt flux divergence computed from drifters and satellite assets both capture, for the most part, the effect of the mesoscale eddies;

• The two quantities computed from independent data are comparable;

• The contribution of the mean flow, ,<U S> is negligible;• A computation of the surface eddy fluxes is likely

meaningful and salt fluxes are being computed (with uncertainty);