'Intraseasonal Variability of Surface Ocean Currents and Upwelling off the U.S. West Coast'

The variability of surface ocean currents and upwelling along the United States west coast has been extensively studied over a range of spatial and temporal scales.  While it is known that the dominant oceanic variability in that region occurs due to wind forcing with time scales on the order of ten days, connections between shorter-term, intraseasonal variability of the climate system and surface ocean currents in the region remains unresolved.  The Madden Julian Oscillation (MJO) is the primary mode of intraseasonal variability in the tropics, and it is known to have important teleconnections outside the tropics, including the modulation of mid-latitude atmospheric circulation.  This study examined variations in surface currents along the U.S. west coast as they related to the MJO.  The primary hypothesis tested was that MJO modulation of surface winds would be reflected as intraseasonal variability in surface ocean currents.  To accomplish this objective, surface current variability was examined by phase of the Real-time multivariate MJO (RMM) index.  Surface current data were obtained from NASA’s Ocean Surface Current Analyses Real-time (OSCAR) gridded product at 1/3° resolution.  The OSCAR surface current anomalies were calculated for days in each active MJO phase by season from 1993-2016 to test for intraseasonal variability.  Given the continued increase in predictive skill of the MJO, work such as this that establishes statistical relationships between the MJO and smaller-scale, less predictable phenomena may lead to increased predictability of upwelling and fishery production along the U.S. west coast on intraseasonal timescales.