Deep Ocean Storm in the Northeastern Equatorial Pacific from Observation and Simulation

Tropical Instability Waves (TIWs) appear at the location where the cold tongue is distributed in the eastern equatorial pacific. They are caused by shears among equatorial under current (EUC), south equatorial current (SEC) and north equatorial counter current (NECC) and are most active from June to December, when the cold tongue is fully developed. In addition, wind-driven Tehuantepec eddies that start in winter from the Mexican Pacific propagate westward to combine with the TIWs at around 110^o W in summer. In this study, we show deep ocean storm events observed by near-bottom current measurements collected at 10.5^o N, 131.3^o W from 2004 to 2013. The time series of velocity and eddy kinetic energy (EKE) reveal energetic events every summer with interannual variation during the 10-year observation period. Numerical simulation results from the CMEMS global ocean physics reanalysis model, GLORYS12V1, show a consistent seasonal variation of velocity and EKE. The simulation results show that high EKE signals propagate westward in the upper layer and northwestward in the deep layer. The deep ocean storm events at our current mooring sites seem to be caused by the energetic eddy activity in the upper layer that triggers deep eddies propagating northwestward from a region around 5^o N, 100 ^o W in early summer. The interannual variation of the seasonal deep ocean storms agree well with the interannual wind changes associated the development of El Nino and/or La Nina.