UC San Diego

Spray glider surveys in the California Current System (CCS) resolve upper ocean processes at scales from a few kilometers to a few hundred kilometers over monthly to interannual timescales. These observations are used to understand eddies and effluent transport, the structure and variability of poleward currents, the regional effects of El Niño, and thermohaline structure. Repeated glider surveys of the greater San Pedro Bay region within the Southern California Bight (SCB) are used to describe coastal processes during the fall of 2006. Elevated subsurface chlorophyll levels within a small cyclonic eddy correspond to an inferred increase in nitrate availability to the euphotic zone. The low-salinity signature of the effluent plume from a coastal ocean outfall is used to show that the plume was advected poleward while remaining subsurface. Glider observations and a numerical state estimate are used to describe the mean and variability of poleward flows in the CCS. Persistent poleward currents are observed near Point Conception, within the SCB, and offshore of the SCB. The poleward current offshore of the SCB migrates westward with across-shore wave number and frequency that are consistent with first-mode baroclinic Rossby dynamics. This westward propagation is tied to westward propagating density anomalies originating in the SCB during the spring-summer upwelling season. The effects of the 2009--2010 El Niño in the CCS are investigated using glider observations. Positive upper ocean temperature anomalies and depression of isopycnals coincide with equatorial SST anomalies, while isopycnal salinity and alongshore transport anomalies are shown to be insignificant. Glider observations rule out advection of subtropical waters into the CCS during the 2009--2010 El Niño and suggest that an atmospheric teleconnection was important. Glider observations show the distribution of temperature and salinity variations along isopycnals at mesoscales and submesoscales. Along-isopycnal salinity variance is used to identify distinct layers; increased variance is found in the seasonally restratifying layer and within a layer below the thermocline. Adjoint passive tracer calculations in a numerical state estimate show the differing histories of waters in each layer