CTD Temperature, Salinity, Oxygen and Potential Density

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	To assist in the interpretation of the data, it can be displayed using the Hawaii Ocean Time-series Data Organization & Graphical System (HOT-DOGS©).

Results

Profiles of temperature, salinity, oxygen and potential density (σ_θ) were obtained from data collected at Stations Kahe, ALOHA, WHOTS, and Kaena. Downcast CTD profiles from 2021 are presented in the figures below, together with the results of bottle determinations of oxygen and salinity. The offset between bottle salinities and CTD profiles apparent in some of the cruise's salinity vs. pressure plots is due to the mismatch between the downcast CTD profile and the bottle salinities, which are taken during the upcast. This salinity mismatch is caused mostly by vertical displacements of the density structure and disappears when plotted against potential temperature (lower right panel). In some instances mismatches are caused by the freshening of the surface water due to rain during the cast.

Figure 1 & Figure 2 show the contoured time-series for potential temperature and density (σ_θ) in the upper 1000 dbar for all HOT cruises through 2021. Seasonal variation in temperature for the upper ocean is apparent in the maximum of the near-surface temperature of about 26 Deg C and the minimum of approximately 23 Deg C. Oscilations in the depth of the 5 Deg C isotherm below 500 dbar appear to be relatively large with displacements up to 100 dbar. The main pycnocline is observed between 100 and 600 dbar, with a seasonal pycnocline developing between June and December in the 50-100 dbar range (Figure 2). The cruise-to-cruise changes between February and July 1989 in the upper pycnocline illustrate that our quasi-monthly sampling does not always resolve variabilty in density.