LT John Marburger OC 3570 March 17, 2004 An Investigation Into Spatial Variation of the Deep Sound Channel Off the Central California Coast LT John Marburger OC 3570 March 17, 2004

Overview Background/Project Goals Data Methods Results Conclusions

Background/Goals METOC focus is shifting to near shore/littoral environment Data readily available Some initial prior research performed Project has Navy relevance Characterization of spatial and temporal variation of sound velocity provides a stable foundation to build on information superiority.

Data Lots of CTD data!! Positional data

Line 67

Data Analysis Methods Convert CTD data Conductivity to Salinity Pressure into depth MATLAB code did above conversions and simultaneously made a SVP for each station within a given data set

Data Analysis Methods SVP axis truncated to focus in on Deep sound channel axis (200-900 meters) Scaling factor for waterfall plots

Data Analysis Methods SVP’s contained high frequency noise Butterworth filter Filtering coefficients will vary. Sound reacts to variations based on its frequency Done by inspection

Data Analysis Methods Sound speed minimum gathered for each SVP.

Data Analysis Methods Each sound speed minimum was plotted versus longitude. Longitude was binned and averaged

Results

Results Monthly analysis performed El Nino year analysis performed

February trend

July trend

El Nino trend

Conclusions A statistically significant shoaling of the deep sound channel is observed along Line 67. Monthly/seasonal investigations yielded limited results due to limited data The anomalous El Nino year produced little change in deep sound channel axis depth compared to the ensemble

Further study Dynamics of the trend? Davidson/California currents? Does the trend persist north and south?