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Abstract
The deep ocean temperatures from 6 years of CTD profiling at the Hawaii Ocean Time-series site exhibit robust interannual variations. A total of 63 (62) casts were made which reached to at least 3600 (4500) dbar between October 1988 and November 1994. (Figure 1.) In the North Pacific Deep Water between 3500-3600 dbar, potential temperature had a mean value of 1.200°C, with variations over a range of 54.0 m°C and a standard deviation of 10.8 m°C. In the Pacific Bottom Water between 4400-4500 dbar, the mean potential temperature was 1.115°C, with variations over a range of 11.0 m°C, and a standard deviation of 2.1 m°C. (Figure 2.) Smoothing splines fit to the time-series in each pressure interval are used to separate interannual variability from instrumental and natural high frequency noise. In the Deep Water, the interannual variability had an RMS value of 7.4 m°C, with a signal-to-noise (S/N) ratio of 1.1. In the Bottom Water, interannual variations had an RMS value of 1.5 m°C with a S/N ratio of 1.6. The interannual variations of potential temperature were not coherent between the Deep Water and the Bottom Water. The apparent dominant time scale in the Deep Water was near 2 years, and close to 3 years in the Bottom Water. Previous observations of interannual baroclinic Rossby waves in the North Pacific are suggested as an explanation for the deep ocean interannual temperature variability.
Reference:
Lukas, R. and F. Santiago-Mandujano, 1996: Interannual variability of Pacific Deep- and Bottom-waters observed in the Hawaii Ocean Time-series. Deep-Sea Res. II, Vol. 43, No. 2-3, pp. 243-255.
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