In the winter of 1997-1998, a NOAA-P3 aircraft was used to perform airborne expendable bathythermograph (AXBT) surveys off the U.S. West Coast in the region of the California Current. These soundings profiled the upper ocean, providing a dense mesoscale sampling of the ocean mixed layer and upper-ocean heat content. A comparison of mean ocean mixed layer depths and temperatures with climatology using nearly 100 AXBT's shows the presence of deeper mixed layers, and warmer near surface waters. Upper ocean heat contents from the AXBT's are compared to satellite altimeter estimates, using three different altimeter data sets. The first was based on TOPEX data alone. The second was obtained by blending TOPEX and ERS-2 altimeter data which allowed more mesoscale information to be present than in the TOPEX alone data. The third data set is an operational product that is produced by heavily filtering and combining ERS-1 and ERS-2 altimetric data, with an emphasis on only retaining the ocean mesoscale structure. The analysis shows that the blended TOPEX/ERS-2 data set provides the best correlation with the AXBT data, and does a very good job of estimating the upper-ocean heat content, with a correlation coefficient of 0.72. Time series of the upper-ocean heat content for the region of AXBT sampling were then computed using each of the three methods, for the period of 1995-1999. These data show that upper-ocean heat content off California was greatest during the 1997-1998 El Nino event.