Hawaii Ocean Time-series (HOT)
in the School of Ocean and Earth Science and Technology at the University of Hawai'i at Manoa
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Continuous near-surface salinity and temperature data were collected during every 2018 HOT cruise (HOT-299 through HOT-308) using Sea-Bird thermosalinograph and temperature sensors aboard R/V Kilo Moana and R/V Ka'imikai-O-Kanaloa. The details of each thermosalinograph system varied from ship to ship, but each system consisted of a remote temperature sensor measuring near-surface temperature close to the intake of the ship's uncontaminated seawater supply in conjunction with a thermosalinograph sensor that measured both conductivity and temperature further down the seawater supply line. The salinity of seawater was then calculated using the internal temperature and conductivity as well as the internal pressure of the pump.
Thermosalinograph conductivities were calibrated using bottled salinity samples taken periodically (approximately every 4 hours) from the continuous seawater line outtake near to the thermosalinograph. Thermosalinograph data from each cruise were also compared with the CTD temperature and conductivity data collected at roughly the same time and from near the same depth as the seawater supply intake for a final data quality control.
The thermosalinograph system aboard the R/V Kilo Moana was comprised of the SBE-38 external temperature sensor (SN 0396), which was located in the bow-thruster chamber in the starboard bow close to the seawater intake. The depth of the intake was 8 meters below the surface, and the internal pressure of the pump was approximately 6 dbar. A SBE-45 Seacat thermosalinograph (SN 0267) measuring internal conductivity and temperature was located in the IMET lab at the port bow of the ship. Data were acquired every second.
The thermosalinograph system aboard the R/V Ka'imikai-O-Kanaloa was comprised of an internal SBE-21 Seacat thermosalinograph unit (SN 1392 and SN 2045) along with an SBE-3 external temperature sensor (SN 4073) installed in a sea-chest at the bow of the ship. The depth of the seawater intake was approximately 4 meters below the surface, and the internal pressure of the pump was 8.5 dbar. Data were acquired every 10 seconds.
Thermosalinograph measurements of near-surface temperature (NST) and near-surface salinity (NSS), as well as navigation for the 2018 HOT cruises are presented in the Figures below. Thermosalinograph data recorded while on station can be compromised by ship effects such as temperature changes in the water due to the ship's hull and engine temperatures. Salinity can also be influenced by the ship when on station as the ship provides a potential source of contamination and disturbs the water being sampled.
In general, cooler near-surface temperatures and, in most cases, saltier near-surface salinities were observed at Station ALOHA compared to the data recorded near Oahu.