CHAOCEAN (low-frequency intrinsic variability in the eddying ocean : observations, simulations and processes)
The aim of this proposal is to exploit the above advances with a view to low-frequency ocean variability, motivated by evidence that both external (atmospheric) and intrinsic sources contribute importantly to the ocean variability observed by altimetry and other means, that the latter is poorly known (and is indeed absent from current climate models), and that analyses and projections of climate variability are likely sensitive to it. The foundations for these statements will be outlined below, where we argue that distinguishing the internal (intrinsic) and external (atmospherically-forced) components of the ocean variability is central to understanding and using observational (altimeter and other) timeseries for ocean/climate science: climate monitoring, climate reconstruction/projection, and detection of climate change in the ocean.
The improvement of OGCMs is evidenced in the convergence of model statistics towards observations, in particular sea level variability (Penduff et al., 2010). In order to analyze the features and origin of the observed signals, we propose to simulate and extract the low-frequency intrinsic ocean variability from ensemble-like OGCM simulations, and study its dynamics using dynamical concepts developed in process-oriented settings. The objectives of this French project are to
Accordingly, this proposal, along with its American counterpart that was just submitted to the partnered NASA/ROSES OST-ST program, gathers French, European and American scientists/engineers who work on the ocean variability from complementary perspectives: namely 'realistic ' ocean modelers, making routine use of altimeter/satellite/in-situ observations, specialists in non-linear dynamics and dynamical systems theory with insights into the foundations of ocean variability, and experts in statistical analysis of large datasets applied to climate. Our international group will produce, share and analyze an ensemble of observed/simulated fields and will take advantage of the complementarity between their own approaches to address several scientific questions with operational relevance (ocean/climate observation, monitoring, reconstruction, modeling) on climatic timescales. The PIs will coordinate the collaboration between French and American members, who will meet at least once every year at OSTST meetings.