During the course of the HOT program, corrections have been applied to the salinity data if needed. When salinity samples were being measured on the Minisal by Ted Walsh (HOT 1-26), the Minisal was not capable of standardizing by adjusting a standardization knob like an Autosal. Thus, adjustments to the salinity data measured by the Minisal had to be determined by measuring an IAPSO standard seawater ampoule. In this way, the difference between the measured IAPSO value and the expected IAPSO value was applied as correction to standardize the salinity data.

Other instances that required corrections to the salinity data were when 1) the IAPSO value at the end of a run differed from the previous IAPSO value by +1 mpsu or more, or 2) a drift or variability more than +1 mpsu was detected in the substandard measurements throughout the measurement run. Both of these instances were an indication of drift in the Autosal measurements, and the data captured during that session or run were corrected accordingly. Thus, it is important to keep an eye out for abnormal IAPSO or substandard values during a measurement session (see Section 2.1.3, #8), and if noted, the salinity supervisor must be consulted before taking further action.

Corrections have also been applied in the past if conditions around the Autosal were not maintained. These conditions have included failure of flashing light bulbs that control the thermistor to maintain constant bath temperature (for instance HOT-51) as well as large fluctuations in ambient temperature (see Section 2.1.2). Evaporation corrections have been applied to samples collected in plastic bottles, if not measured within 15 days after the cruise (see Section 1.1.2).

Sharon DeCarlo noticed that HOT-51's second deep cast (S2c19) was noticeably saltier than almost 200 deep casts in history due to failure of the Autosal's flashing light bulb (see Figure 1 in Sharon DeCarlo's "HOT-51 Salinity measurement corrections," Appendix N). Details of the corrections are explained in Sharon DeCarlo's report, but corrections to this cruise's data done before DeCarlo's corrections were difficult to find or if found, incomplete. This emphasizes the importance of documentation, especially at times when no experienced person is present during measurements. All corrections done to the salinity data must be consolidated in the written Salinity Measurement Report. Maintaining continuity of the HOT salinity history is only possible through clear and consistent documentation.

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