A novel Lagrangian index to compare altimetry products: insights from drifting floats and animal tracking

Alice Della Penna (LOCEAN-IPSL/Univ Paris Cite'- Paris 7/IMAS, France)


Silvia De Monte (Lab « Ecology and Evolution», CNRS UMR 7625, France); Christophe Guinet (CEBC-CNRS, France); Francesco d'Ovidio (LOCEAN - IPSL, CNRS/UPMC/IRD/MNHN, France)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Science Results from Satellite Altimetry: Finer scale ocean processes (mesoscale and coastal)

Presentation type: Type Poster

The tracking of passive (and quasi-passive) tracers at the mesoscale is one of the most challenging uses of satellite altimetry.
This approach provides useful insights for biogeochemical studies (tracking of phytoplanktonic blooms), analysis of transport of pollutants and radionuclids and ecological studies that go from larval dispersals to top predators behaviour. The accuracy and the robustness of these studies are strongly affected by how much the trajectories that we can infer from altimetry-defined current fields are realistic and close to the ones that an actual passive (or quasi-passive) tracer would have at specific times and locations. In this study we define a novel Lagrangian diagnostic, the quasi-passivity index (QPI) that compares the trajectories of drifting floats with the ones we can simulate from the altimetry horizontal velocity field. We use the QPI and a dataset of more than 40 drifters released in the Kerguelen region during the research cruise KEOPS2 to compare Near-Real Time and Delayed Time AVISO products, global and experimental regional ones and purely geostrophic and Ekman-corrected (provided by CLS). Futhermore we apply this diagnostic to animal tracking information to infer information about southern elephant seals' foraging behaviour from a measure of how close their trajectories are to the ones of passive tracer simulated from altimetry.

Alice Della Penna
LOCEAN-IPSL/Univ Paris Cite'- Paris 7/IMAS