Monitoring Boundary Currents Using Ocean Observing Infrastructure

Abstract

0° FIGURE 2. Trajectories and nearsurface velocity estimates from Global Drifter Program drifters in the western Pacific and marginal seas. Paths of various boundary currents are clearly visible. From Todd et al. (2018) Boundary currents dominate the poleward transport of warm water and the equatorward transport of cold water and are major drivers of climate variability, extreme weather events (e.g.,hurricanes), and marine heatwaves (Figure 1). The western boundary regions have some of the most dynamic and energetic currents in the ocean and are key to the transport of mass, heat, salt, biogeochemical properties, and plankton. The eastern boundary currents are often upwelling systems that comprise some of the most biologically productive regions in the world. Boundary currents in marginal seas provide the major means of exchange with the open ocean and impact regional ecosystems. Communication between the coast and open ocean is regulated by the boundary currents that flow along the continental slopes, affecting ecosystems, sea level, flood levels, erosion, and commercial activity. Current strategies used to monitor boundary currents vary and are composed of individual and partially coordinated efforts. At global scales, the Argo array of profiling floats collects a growing suite of ocean physical and biogeochemical parameters, providing comprehensive coverage offshore of the continental shelf. Satellite measurements of sea surface height, temperature, salinity, and ocean color clearly identify the signals of mesoscale features at the ocean surface. Surface drifters take measurements of currents (e.g., Figure 2). The need for finer spatial and temporal resolution closer to shore is addressed with more regionally focused efforts (Figure 3). Ocean gliders provide sustained or targeted observations across a few boundary current systems that connect the coast to the open ocean. The OceanSites network of moorings has some of the longest in situ time series at strategic locations within Monitoring Boundary Currents Using Ocean Observing Infrastructure