The RVIB Nathaniel B. Palmer is equipped with a SeaBird Electronics Model SBE-911plus conductivity, temperature, and depth instrument, which is mounted on a SeaBird, epoxy coated 24-bottle rosette sampler. The sampler is equipped with a SeaBird pylon and 10-liter Bullister bottles. Data from dual temperature, dual conductivity, pressure, oxygen, and other instruments were transmitted in real-time to the SBE-11 deck unit via conducting cable. Onboard, the data were recorded digitally on a Windows computer running SBE Seasave software (ver.5.37d).
Prior to the start of each hydrocast, the CTD was lowered to a depth of 10 m to allow time for the CTD pumps to activate and the sensors to equilibrate. During this washing period, the differences between the primary and secondary readings of the temperature and conductivity were monitored as well as dissolved O2 levels. Once stability was achieved, the CTD was brought back to the surface in preparation for the hydrocast. During all hydrocasts, the CTD was lowered at a rate of 30 m min-1 through the upper water column (usually 150 m) and then at 50 m min-1 at greater depths. The distance between the sensor package and the bottom was determined using a Datasonics pinger. A mechanical safety switch notified the CTD operator when the package had reached a distance of 3 to 5 m from the bottom. We reached the seabed on about half of the hydrocasts conducted during both NBP0601 and NBP0608. The remaining casts focused on sampling the uppermost, biologically active portion of the water column. Ten-liter Bullister bottles were tripped at selected depths on the upcast to provide in situ sampling of chemical, biological, and physical properties of the water column as well as to provide calibration data for the CTD. Once the CTD was back onboard, the temperature, conductivity, and dissolved oxygen sensors were flushed with deionized water and covered with rubber boots to minimize instrument fouling between casts.
Detailed descriptions of calibration and processing are available in the full cruise reports (see the cruise specific data documentation). Those reports, along with the original data contributions were downloaded from Rob Dunbar's site at Stanford University on 15 May 2009: CTD data from Rob Dunbar.
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