A study of the seasonal variation in temperature and salinity along the Oregon - Northern California coast

Graduation date: 1972This study examines the seasonal variability in temperature and\ud salinity of the nearshore waters off Oregon and Northern California.\ud Specifically, temperature and salinity variations during summer and\ud winter were ana1yzed from data gathered at shore stations along the\ud coast and from hydrographic data collected within 25 nautical miles\ud of shore.\ud At each of five shore stations a modal cell technique was used\ud to establish the temperature-salinity characteristics of the "normal"\ud water type existing at each station during summer and winter. A\ud classification scheme was employed to determine what local processes\ud were influential in altering the "normal" T-S characteristics at each\ud station.\ud In summer mixing with Columbia River plume water was found to be the\ud major modifying process along the Northern Oregon coast. Off Central and\ud Southern Oregon local heating and mixing with water from the shelf/slope\ud region were found to be most influential. In winter dilution due to precipitation\ud and subsequent runoff is the major modifying factor along the\ud entire coast except off Northern Oregon where mixing with shelf/slope\ud waters is slightly more influential.\ud The temperature and salinity structure of the near surface waters\ud (< 200 meters) was examined for four latitudinal zones off the Oregon-\ud Northern California coast. Within each zone profiles were constructed\ud at 5, 15, and 25 nautical miles offshore.\ud Surface waters are warmer and more saline in summer than in winter.\ud Surface temperatures increase seaward in both seasons. Surface salinities\ud increase seaward only during winter; in summer the increase is shoreward.\ud Offshore gradients of temperature and salinity are one to two orders of\ud magnitude greater than longshore gradients.\ud A strong thermocline to 30 meters and a strong halocline to 75 meters\ud is present in summer. In winter the water is isothermal to 50 meters\ud while a strong halocline is present to 100 meters. Below these levels\ud temperatures and salinities continue to slowly decrease and increase,\ud respectively, until at 200 meters they become constant throughout the\ud study area. Variability with distance from shore is significant only\ud in summer and is constrained to the upper 150 meters of the water column