New Caledonia

What are the internal tides and mesoscale interactions in the South-West Tropical Pacific Ocean? How do these fine-scale processes affect this area of important biodiversity?

In the region around New Caledonia in the South-West Tropical Pacific, strong internal tides are observed, generated by complex topographic obstacles and numerous seamounts. These internal tides interact with the ubiquitous mesoscale and sub-mesoscale eddies, and impact the hydrodynamics, the water mixing, and the biology in this area of important biodiversity.

The SWOTALIS cruise, phased with the SWOT fast sampling phase, will take advantage of a SWOT swath south of New Caledonia, above the seamounts and the internal tides generation area. It will be dedicated to the study of internal tides and their interactions with meso- and sub-mesoscale structures. The objectives of the field campaign are to describe the variability of the internal tides genesis, propagation, and dissipation, with a focus on the physical processes explaining their coherence loss. Deployments of moorings highly instrumented, fixed stations and ship-borne sections using underway CTDs and ADCP will be used to observe the vertical structures and their variability; additional measurements (GPS buoys, GPS blanket) will allow to infer their surface signatures, a key final objective being the observability of these processes by the sea level measured by the future SWOT satellite mission.

Surface currents (left panel) and relative vorticity ( ζ=vxuy) normalized by Coriolis frequency (f) (right panel) for the New Caledonia study site with SWOT grid overlaid (black lines). Images were generated using output from a high-resolution MITgcm simulation and are instantaneous snapshots from 1 July 2012.

Principal investigators: F. Marin, S. Cravatte, L. Gourdeau (LEGOS, France)

Institutes involved in the cruise/project: LEGOS (Toulouse), MIO (Marseille), LOPS (Brest), LIENSs (La Rochelle), IGE (Grenoble), ENTROPIE (New Caledonia), SPC (New Caledonia)

Contact point for the study site: S. Cravatte (

Sea Surface Height M2 stationary baroclinic tide Amplitude (colors) from altimetry (Ray and Zaron, 2016); sea level anomalies of mesoscale eddies from altimetry (snapshot, white contours), and SWOT Fast Sampling Phase (red). The area of focus for the SWOTALIS cruise in shown in black.