Wind-Event-Induced Ocean Upwelling, Relaxation and Chlorophyll Response in the Southern California Bight

Abstract

Abstract. The consequences of a large wind event occurring in the Southern California Bight on 31 January 2016, are analyzed using data from nearshore island and mainland seabed thermographs (10 to 20 m depths), NOAA meteorologic and wave-rider buoys, a CalCOFI cruise and SST and Chl a data products from satellite remote sensing. Discernible upwelling was discovered approximately 7 hr after the northwesterly wind surpassed 10 m/s, and ultimately coastal water shoaled by at least 90 m. The upwelling character varied according to where the measurements were taken. Leeward seabed thermographs and near mainland shore buoys registered an impulse-like temperature decrease, whereas open-ocean and windward sites measured a more gradual change. The approximately one day long event was followed by an increase in Chl a throughout the bight, with the largest increase being adjacent to the mainland. The Chl a signal vanished after about one week and the temperatures returned to pre-event levels after 11 d. Various upwelling and temperature-relaxation mechanisms are discussed, with two separate upwelling mechanisms suggested and the most likely candidate for relaxation being lateral diffusion of warm offshore water into the nearshore upwelled water.