The Pumping SeaSoar: A High-Resolution Seawater Sampling Platform

Abstract

The first results obtained with the Lamont Pumping SeaSoar (LPS), a combination measurement and sampling platform towed by a research ship at speeds of 6?7 kt, are presented. The system allows not only measurement of a suite of oceanographic parameters with in situ sensors, but also delivery of seawater samples through a 750-m tube (5/16-in. inner diameter) to a shipboard laboratory for chemical analyses, while undulating from near the surface to depths near 200 m. Here the performance of the system is demonstrated, and the time lag and signal smearing associated with the seawater sampling scheme are qualitively analyzed. The time lag was determined by comparing salinity determined from measurements of temperature, conductivity, and pressure made in situ by the sensors mounted on the towed body, with salinity determined from temperature and conductivity measurements made in the shipboard outlet of the sample stream. It varied smoothly from 10.8 to 11.5 min over 24 h of sampling, independent of the depth of the fish. The time lag was determined with precision of better than 5 s, corresponding to vertical precision of about 1 m. Smearing of signals due to mixing in the tube was approximated by a Gaussian filter with a time constant of 7.5?10 s, corresponding to a vertical scale of about 2 m.