1997-98 EL NINO EFFECTS ON SOUND SPEED IN THE SOUTH CHINA SEA BASIN LT Adria Schneck-Scott SEP 2004 OC3570 Cruise Project

Contents Introduction/Navy Relevance Data Collection Background Data Processing Analysis and Findings Recommendations

Introduction Why? Political/Strategic Sea Power 21 Quantification/Prediction Ocean Variability Current Databases Good Enough Thesis Work Sea Poer 21 - information superiority and accurate battle space characterization provide “unprecedented offensive power, defensive assurance, and operational independence” quantification and prediction of spatial and temporal ocean variability becomes more valuable These products do not always provide sufficient prediction of the acoustic environment. Resolution of these models is equally inadequate to meet the high spatially sensitive needs of today’s operations; however, with scarce computing resources and the demands of the right information at the right time, we must ask ourselves what is good enough.

Data Collection 2 USNS Silas Bent cruises (Prof. Steve Ramp) April 28-May 17, 1997 April 4-18, 1998 CTD data Limited to Deep Basin Thesis Work

Background - El Niño displays the development of the 1997-98 El Niño. In April, during the 1997 data collection, an oceanic Kelvin wave reached South America (topex.com) approximately one month after being triggered by east-blowing winds near Australia. The El Niño peak is seen in November at about 35 centimeters above average in the eastern Pacific, near the Galapagos Islands. In May 1998, just after the second Silas Bent China Sea cruise, typical conditions of a decaying El Niño are exhibited. What is El Niño? Characterized by sustained warming over a large part of the central and eastern tropical Pacific Ocean .

Background - El Niño Global Impacts

Data Processing Convert CTD data Used MATLAB GDEM from NAVO Depth into pressure (db) SSP for station GDEM from NAVO April, May MATLAB – SSP

Results – SSP GDEM “good enough” very deep water?

Results - SSP 150-400 db GDEM 5m/s faster than mean

Upper 100db of SSP

Temperature Cross Section

50db Temperature Contour

50db Salinity Contour

50db Salinity Contour

Ship UDAS Readings

Recommendations Explanation for: Deeper MLD in 1998 Stronger seasonal thermocline in 1998 Increase sound speed in upper 20db 1997 Verify cause of fresh waters of 1997 Sea Poer 21 - information superiority and accurate battle space characterization provide “unprecedented offensive power, defensive assurance, and operational independence” quantification and prediction of spatial and temporal ocean variability becomes more valuable These products do not always provide sufficient prediction of the acoustic environment. Resolution of these models is equally inadequate to meet the high spatially sensitive needs of today’s operations; however, with scarce computing resources and the demands of the right information at the right time, we must ask ourselves what is good enough.

Conclusion El Niño did impact South China Sea 1998 SSP: Deeper isospeed layer Deeper isothermal layer (mixed layer depth) Stronger seasonal thermoclines 1997 SSP marked by increase in upper 20db METOC needs to understand and develop tools to predict temporal and spatial variations Information Superiority and Battle Space Characterization Sea Poer 21 - information superiority and accurate battle space characterization provide “unprecedented offensive power, defensive assurance, and operational independence” quantification and prediction of spatial and temporal ocean variability becomes more valuable These products do not always provide sufficient prediction of the acoustic environment. Resolution of these models is equally inadequate to meet the high spatially sensitive needs of today’s operations; however, with scarce computing resources and the demands of the right information at the right time, we must ask ourselves what is good enough.