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Jeff Sherman

Abstract

An Argos 32-byte message of known content has been transmitted over a 68-day period from a site located at Scripps Institution of Oceanography. The statistical analysis agrees with Service Argos. Due to sparse satellite coverage, only 6% of all transmitted messages are received. Of messages acquired, 9% contain at least one bit error. Error characteristics suggest the occurrence of noise bursts, rather than single-bit random errors. The low probability of seeing a satellite requires transmitting over many hours to ensure a single satellite reception. For such a long transmit duration, it is most efficient to send the same message infrequently (i.e., every 10 min), thus minimizing power consumption. This allows many unique messages to be interleaved, optimizing total information received in the smallest time frame.

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Lionel Gourdeau, William S. Kessler, Russ E. Davis, Jeff Sherman, Christophe Maes, and Elodie Kestenare

Abstract

The South Equatorial Current (SEC) entering the Coral Sea through the gap between New Caledonia and the Solomon Islands was observed by an autonomous underwater vehicle (Spray glider) and an overlapping oceanographic cruise during July–October 2005. The measurements of temperature, salinity, and absolute velocity included high-horizontal-resolution profiles to 600-m depth by the glider, and sparser, 2000-m-deep profiles from the cruise. These observations confirm the splitting of the SEC into a North Vanuatu Jet (NVJ) and North Caledonian Jet (NCJ), with transport above 600 m of about 20 and 12 Sv, respectively. While the 300-km-wide NVJ is associated with the slope of the main thermocline and is thus found primarily above 300 m, the NCJ is a narrow jet about 100 km wide just at the edge of the New Caledonian reef. It extends to at least a 1500-m depth with very little shear above 600 m and has speeds of more than 20 cm s−1 to at least 1000 m. An Argo float launched east of New Caledonia with a parking depth fixed at 1000 m became embedded in the NCJ and crossed the glider/cruise section at high speed about 3 months before the glider, suggesting that the jet is the continuation of a western boundary current along the east side of the island and extends across the Coral Sea to the coast of Australia. In the lee of New Caledonia, the glider passed through a region of eddies whose characteristics are poorly understood.

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