Intermittency in the Diurnal and Semidiurnal Temperature Oscillations in the Santa Barbara Channel, California

Maria Fernanda Aristizabal, University of Connecticut, Marine Sciences, Groton, CT, United States, Melanie R Fewings, University of Connecticut, Department of Marine Sciences, Groton, CT, United States and Libe Washburn, University of California Santa Barbara, Marine Science Institute and Department of Geography, Santa Barbara, CA, United States
Abstract:
The Santa Barbara Channel, California, experiences large temperature and velocity fluctuations during summer that have been associated with the input of nutrients to the euphotic zone (McPhee- Shaw et al. 2007). We analyzed data from 40 moorings in 8-200 m water depth. We focus on temperature fluctuations in the diurnal and semidiurnal bands, which account for as much as 65% of the total variance. These fluctuations are strongest during summer but are highly intermittent, showing bursts of activity that last for several days. It has been suggested that the intermittency is regulated by variations in the depth of the regional thermocline, which can control the vertical stratification in the inner-shelf region, allowing or restricting the propagation of internal waves to the inner shelf. The thermocline depth can be controlled by the passage of coastal trapped waves or the large-scale upwelling/downwelling-favorable winds. Our objective is to understand whether the local upwelling/downwelling-favorable winds or the remote winds off Baja California, Mexico, via the propagation of coastal trapped waves, control the diurnal and semidiurnal temperature variability in the inner shelf in this region. In summer, after local wind relaxation events the vertical stratification decreases at the sites along the mainland in the interior of the Santa Barbara Channel and increases at the sites in the Northern Channel Islands. The increase in vertical stratification in the Channel Islands is accompanied by a moderate increase in the diurnal and semidiurnal temperature oscillations after wind relaxation events. The correlation between an index of coastal trapped wave activity generated in Baja California and an index for the strength of the diurnal or semidiurnal oscillations is low. This suggests local, not remote, winds have the greatest influence on the semidiurnal and diurnal temperature oscillations over the inner shelf in the Santa Barbara Channel.
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