Interconnections between the physical, biological and chemical processes that regulate carbon cycling in the ocean span a tremendous range of space and time scales. For example, regional to global-scale variations in the biogeochemical constituents of the water column are closely linked with the general circulation of the ocean. At finer scales, such relationships are just as striking, if not more so. A particularly strong manifestation of these linkages occurs at the oceanic mesoscale, sometimes referred to as the “internal weather of the sea.” Highly energetic currents, fronts and eddies are ubiquitous features of ocean circulation, with characteristic spatial scales of 10-100 km and temporal scales of weeks to months. Their space scales are thus smaller and time scales longer than their counterparts in atmospheric weather, but the dynamics of the two systems are in many ways analogous. Both are characterized by large-amplitude departures from mean conditions on relatively small spatial scales, over relatively short periods of time.