Introduction to CCE-LTER: Responses of the California Current Ecosystem to climate forcing

The California Current Ecosystem Long Term Ecological Research (CCE-LTER) site has been in existence since 2004. One of its primary objectives is to understand the response of the southern California Current ecosystem to climate forcing. The CCE-LTER site cooperates with the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program and complements CalCOFI׳s work through more extensive observations, process studies, and a modeling program. This special issue is focused on the long-term observations made by the CCE-LTER and CalCOFI programs, describing and understanding long-term changes in the physical, chemical, and biotic environment in the region. The papers in this issue highlight the climatological conditions during recent years and employ modeling to diagnose the principal forcing of meridional currents and eddy transport, both of which affect biotic responses. Changes in source waters in the region, and altered flushing of the Santa Barbara Basin, are considered. Temporal variations in inherent optical properties and in higher trophic levels, including seabirds and marine mammals, are presented. Key methodological developments presented include the incorporation of subsurface phytoplankton and light distributions in order to improve remotely sensed measures of primary production, and the validation of multi-frequency acoustic estimates of mesopelagic fish biomass. Results also highlight significant spatial differences across the CCE-LTER region, including cross-shore trends in microbial assemblages, and glider-resolved frontal features and zones of mixing associated with abrupt topography. Alterations to the spatial structure of the pelagic ecosystem must also be considered when evaluating future climate-related changes.