ings, the U.S. CLIVAR and Ocean

communities came together for a daylong session to discuss opportunities for collaborative research. The relevant science questions span physical topics such as variability and trends in sea surface temperature (SST), ocean heat content, and the wind-driven and ther-mohaline components of ocean circu-lation to biogeochemical issues such as ocean carbon dioxide (CO2) uptake, declining oxygen levels, shifts in rates of biological productivity, and changes in ecosystem patterns and structure. Here I address some of the scientific synergies across the two commu-nities and common observational approaches, emphasizing ship-based and in-situ autonomous platforms. There are natural linkages between the sets of physical and biogeochemical questions addressed by the CLIVAR and OCB research communities, respec-tively. The air-sea fluxes of momentum, heat, freshwater, CO2, and other trace gases are modulated by similar kinetic processes such as winds, turbulence, and wave breaking. Ocean circulation, heat content, and marine biogeochemistry are coupled on seasonal to decadal time scales. A good example is the oceanic response to El Niño-Southern Oscil-lation (ENSO) in the tropical Pacific, in which reduced equatorial upwelling and relaxation of the east-west tilt of the thermocline during El Niño events lead to warmer SSTs and reduce outgassing of CO2. In the extratropics, surface chlorophyll is correlated with SST, reflecting a combination of varying mixed layer depth (which affects the light environment experienced by the phytoplankton), nutrient supply, temperature-dependent physiological processes, and loss mechanisms. Both programs also are motivated, in part, by historical data from the past several decades, which indicate how the ocean and the Earth system as a whole evolve with time (Fig. 1). Well known examples include rising atmospheric levels of CO2 and other greenhouse gases, increases in the heat content of the ocean thermocline, an