Changes in global climate may significantly alter the circulation, biogeophysical processes, and biological productivity of marine ecosystems (IPCC 2007, Hoegh-Guldberg and Bruno 2010). These effects are expected to cascade up from changes in the physical environment to the bio-geophysical systems and then to top ocean predators such as whales and dolphins. The potential impacts of ocean climate change on the range, distribution, and migratory behavior of these apex predators are of significant importance to developing adaptive management strategies for the future. Cetaceans respond to the integrated effects of changing physical and biological processes and act as sentinels for understanding the aggregate effects of broad changes in ocean climate. Our ability to assess their current and future distributions will provide critical baseline information for monitoring aggregate effects of global change. This proposed project brings together a multidisciplinary team of marine ecologists and climate modelers toconnect changes in physical forcing to changes in top predators. The core of this team is built from an ongoing NASA-ROSES supported collaboration between Duke University and the NOAA Southwest Fisheries Science Center (SWFSC). In this proposal we extend the scope of this work to project cetacean species distributions and habitats under future climate with and expanded team including ocean modelers from NOAA-ERD and NOAA-Geophysical Fluid Dynamics Laboratory (GFDL). The efforts of our team have already resulted in the development of robust, spatially explicit predictions of cetacean distribution for years with contrasting oceanic conditions (Ferguson et al. 2006; Best et al. 2007; Redfern et al. 2008; Barlow et al. 2009; Becker et al. in press, Schick et al. in review). The most recent models apply remotely sensed and modeled oceanographic data as input variables, allowing hindcasts and short-term forecasts of distribution and abundance for cetacean species, including some endangered whales (Becker et al. in prep). To advance our projection capacity to multi-decadal and centennial scales, we propose to implement such models in the context of output from numerical models simulating the ocean's response to climate change under future scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). Our approach is to obtain relevant physical (e.g., SST, thermocline depth, currents, salinity) and biogeochemical (phytoplankton, nitrogen, oxygen) variables from three-dimensional, high-resolution simulations for the regions of interest and forced by IPCC projections as recommended by Stock et al. (in review). Two models from the upcoming IPCC 5th Assessment, developed at GFDL, will provide ocean biogeochemistry and lower trophic level ecological distributions at 1° and ultimately 0.25° resolution (TOPAZ; Dunne et al. 2010). This output will also be used to force a high-resolution (1/12°) physical and biological model (ROMS-CoSINE) for the California Current System, in collaboration with Chavez et al. (pending). Parallel modeling efforts will be conducted on the US Atlantic coast suing the HYCOM modeling framework. These model outputs will provide input scenarios for models to assess responses of cetaceans to climate variability and characterize biases and uncertainty in these predictions. Potential changes in the distribution patterns of cetacean species will be assessed in relation to current and historical ranges, as available on mapping portals such as OBIS-SEAMAP (Halpin et al. 2009) and the associated Spatial Decision Support System recently enhanced under NASA funding. Elevated risk will be evaluated based on the level of human use, such as shipping lanes and fisheries, along with management status, such as EEZ boundaries and marine protected areas (MPAs). These analyses will help focus attention to areas of particular need for adaptive management interventions.