A Century of Southern California Coastal Ocean Temperature Measurements

Scripps Institution of Oceanography Pier has been the site of daily temperature measurements since the original structure was built in 1916. The time series is the longest continuous record of temperature on the Pacific Rim and is frequently cited as an indicator of ocean temperature trends in the region. The over 100‐year long record of daily surface temperature and slightly shorter bottom temperature data are presented here, with adjustment for bias owing to changes in sampling time of day. Data were generally collected near 8:00 a.m. in the early years, when water temperatures are cooler, and gradually shifted later in the day, when temperatures are warmer. In addition, cold surges from irregular internal tidal bores complicated attempts to estimate daily heating‐cooling cycles solely as a function of time of day. To isolate the effect of the solar heating cycle, adjustments were calculated based on seasonally variable diurnal solar heating using a surface ocean heating model and locally measured insolation data. Although the observed warming trends in nearshore temperatures are reduced by about 0.2 °C per century in the adjusted data, they still retain a significant increase of 1.24 °C per century at the surface and 1.67 °C per century in bottom waters. Key Points Once‐daily measurements taken on Scripps Pier since 1916 provide a long‐term record of ocean temperature in the northeast Pacific Ocean Temperatures adjusted for the time of day of sampling using a solar heating model better capture long‐term means and warming trends Coastal ocean temperatures at this location have increased by 1.24 °C per century at the surface and 1.67 °C per century in bottom waters