How Do Ocean Currents Impact Our Lives ?

The atmosphere drives entire ocean motions, and yet the exchange of momentum between the atmosphere and ocean occurs in the thin layer where they meet, involving the smallest scales of turbulence. The Ocean Surface Current Analyses Real-time (OSCAR) project attempts to better understand this exchange using satellite observations with simplified physics to calculate global ocean currents. The goal is to continually improve the physics in OSCAR and more accurately model the currents. The theoretical study will help coupled ocean-atmosphere modeling efforts whereas the societal benefits of measuring ocean currents are broad, e.g., fish larval dispersion, heat transport, commercial shipping, and search and rescue. 1. How Do Ocean Currents Impact Our Lives? The ocean is constantly in motion. It is at the surface where much of human activity in the ocean occurs. Ocean currents affect boating, fishing, and commercial shipping where knowledge of surface currents can not only aid in navigation but also significantly impact fuel consumption [Bialystocki and Konovessis, 2016]. Seasonal and interannual variability of currents has a significant impact on fish larval dispersion [Qian et al., 2015]. Tracking methods utilizing the surface currents [Parker, 2014] can be used for to track marine debris, for search and rescue, to map the spread of pollutants, or to backtrack paths to the original source such as with pieces of the Malaysian Airlines Flight 370 airplane. Heat and salt transports can be calculated using currents, sea surface temperature (SST), and sea surface salinity. Ocean eddies are an important source of upwelling, a process that brings nutrient-rich deep waters to the surface to supply the food chain [McGillicuddy et al., 2003]. Surface currents play a crucial role in El Nino Southern Oscillation (ENSO) dynamics. In the equatorial Pacific, the trade winds generate currents that carry the warm surface waters to the west, pulling up cold deep waters in the east. Occasionally (every 3–7 years), the trade winds relax, reversing the currents and creating an El Nino event. When the trade winds resume, westward currents restore conditions to normal. Unusually strong trade winds and currents create a La Nina event. The changes in the Pacific equatorial currents typically lead the more commonly used SST observations by 2–3 months. This can be seen in the surface current-based ENSO index (http://www.esr.org/enso_index.html) [Lumpkin et al., 2016]. In this way, surface currents are a valuable early indicator of ENSO events. Monthly maps of currents and their anomalies are used routinely to monitor ENSO in the Climate Diagnostic Bulletin (Climate Prediction Center, NOAA). We now have 24 years of satellite currents allowing us to track long-term changes and help us to redefine our present state and to better predict the future. This provides the context to better understand the role that circulation plays in drastically changing conditions such as the recent massive oyster die-off along the U.S. West Coast [Cheng et al., 2016] and to guide recovery efforts. Flooding, droughts, super storms, frequencies and intensities of hurricanes, etc. are all connected to oceanic conditions. They affect us today and they will continue to affect us tomorrow. 2. How Do the Atmosphere and Oceans Interact? Ocean currents contain a vast range of interacting scales and a variety of dynamical regions. Alternating bands of planetary-scale winds such as the jet stream and the trade winds drive large-scale water circulation in the oceans. Because most oceans are bounded by the continents and because of the dynamics on a rotating Earth, the result is water circulations within ocean basins, with intensified currents along the Special Section: Earth and Space Science is Essential for Society Key Points: Ocean surface currents strongly influence human activity The OSCAR project develops ocean surface currents from satellite-sensed fields Satellite data are used to study the momentum transfer between the atmosphere and ocean Correspondence to: K. Dohan, kdohan@esr.org Citation: Dohan, K. (2017), Ocean surface currents from satellite data, J. Geophys. Res. Oceans, 122, 2647–2651, doi:10.1002/2017JC012961.