STATE OF THE CALIFORNIA CURRENT 2009-2010: REGIONAL VARIATION PERSISTS THROUGH TRANSITION FROM LA NIÑA TO EL NIÑO (AND BACK?)

This report summarizes observations of the California Current System (CCS) from Baja California, Mexico to Oregon for the period from spring 2009 through spring 2010. During this period, changes in the state of the CCS reflected a transition from cool La Nina conditions into and through a short-lived, relatively weak El Nino event. Weaker than normal upwelling and several extended relaxation events contributed to warming over much of the CCS during summer 2009, especially in the north. Moderation of La Nina conditions in the CCS coincided with the development of El Nino conditions in the equatorial Pacific, yet manifested well in advance of any evidence for direct effects of El Nino on the CCS. Responses to El Nino in fall 2009 and winter 2009–2010 appear to have varied substantially with latitude: conditions off southern California returned to near climatological values with the decline of La Nina,