Observations of a California Current Jet Meandering off the Continental Shelf into a Deep Ocean Region

During early August 2006, a series of meteorological and near surface oceanographic measurements (-0-200 m) were conducted from R/V Mt. Mitchell in an ocean region in the northeast Pacific, near 46degN, 126deg W, west of the North America continental shelf break, and in 2000 m deep water. The test region was roughly 20 nmi west of the main path of the California Current, however, observations of a jet meandering off the California Current and intruding into the deep water test region were captured in both in situ measurements from the R/V and remote satellite observations of the ocean surface. The horizontal boundaries of the jet intrusion in the test region are apparent in both in situ and satellite remote sensed temperature measurements as well as in ocean currents measured by ADCP and Lagrangian style surface drifters. Temperature and salinity profiles show waters associated with the jet are significantly cooler and slightly fresher than the ambient water in the test region. After initial observations of the intruding jet, measurements in the test region continued for the duration of seven days. Winds were initially relatively calm, in the 5-12 knot range, but after about three days, winds suddenly increased to over 20 knots, and high winds (NNW) persisted for three days. A corresponding increase in near surface, wind driven circulation was observed, moving approximately 90 degrees to the right of the wind direction. Eventually, wind driven currents dominated near surface circulation across the test region and the presence of the jet boundaries became less evident in CTD profiles collected over transects that cross in and out of the initial jet boundaries, after the wind speed increase. These results show the water in the test region gradually transitioning back to a horizontally homogeneous state as a result of wind induced mixing of the jet water and ambient water in the surrounding region. Detailed observations of the initial characteristics of the California - Current jet intrusion into the deep water test region are presented along with the observations of the jet waters mixing with the local wind driven currents.