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

The 2009-2010 El Niño marked the first occurrence of this climate phenomenon since the initiation of sustained autonomous glider surveillance in the California Current System (CCS). Spray glider observations reveal the subsurface effects of El Nio in the CCS with spatial and temporal resolutions that could not have been obtained practically with any other observational method. Glider observations show that upper ocean waters in the CCS were unusually warm and isopycnals were abnormally deep during the El Nio event, but indicate no anomalous water masses in the region. Observed oceanic anomalies in the CCS are nearly in phase with an equatorial El Nio index and local anomalies of atmospheric forcing. These observations point toward an atmospheric teleconnection as an important mechanism for the 2009-2010 El Nio's remote effect on the midlatitude CCS. Copyright 2011 by the American Geophysical Union.