Accueil > Actualités > Séminaires > Séminaire de Mark D. Ohman


Titre : Abrupt Changes in a Pelagic Ecosystem: Insights from the California Current Ecosystem LTER site
Nom du conférencier : Mark D. Ohman
Son affiliation : Scripps Institution of Oceanography/University of California, San Diego
Laboratoire organisateur : LOCEAN
Date et heure : 09-10-2017 10h30
Lieu : UPMC - 4 place Jussieu - Paris 5e - salle de réunion LOCEAN, tour 45/55, 4eme étage
Résumé :

The California Current Ecosystem Long-Term Ecological Research (CCE-LTER) site seeks to understand the mechanistic basis for abrupt changes in ecosystem state in this major Eastern Boundary Current upwelling ecosystem.  We are analyzing the consequences of multiple scales of forcing – including ENSO, the Pacific Decadal Oscillation, and long-term secular trends – on the planktonic ecosystem at the base of the food web.  At times there are abrupt changes in ecosystem state in this region that have been attributed to changes in dynamic “regimes.”  However, we have advanced a simpler Double Integration Hypothesis that explains such abrupt ecological shifts as a consequence of reddening of the variance spectrum, illustrated by a simple Autoregressive I model. Our CCE-LTER site is actively involved in developing a mechanistic understanding of these shifts, in order to develop a quantitative framework for forecasting the future state of the planktonic food web and the organisms that depend upon it.  Our site research includes a multidisciplinary group of scientists who utilize complementary approaches in an iterative manner: experimental work at sea, extensive multi-scale ocean observations, integrated with modeling.  The CCE-LTER site is fortunate to build upon the nearly 7-decade observational record of the CalCOFI program, an important space-resolving ocean time series.

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