The Sea Journal of the Korean Society of Oceanography ISSN:1226-2978(Print) 2671-8820(Online) 한국해양학회지 바다

Seawater salinity refers to the total amount of dissolved inorganic salts in 1 kg of seawater and provides crucial information for understanding changes in the physical and chemical properties of the ocean interior, as well as the ocean’s influence on global climate. In oceanographic studies, salinity is typically measured by immersing conductivity and temperature sensors directly into seawater and calculating salinity from the measured conductivity and temperature values. The SBE 4C conductivity sensor, commonly used for high-resolution vertical salinity observations from research vessels, demonstrates high precision and stability in field conditions. However, changes in its electrical characteristics can cause monthly salinity measurement deviations of up to ±0.0023 psu. To achieve the salinity measurement accuracy of ±0.001 psu recommended by the World Ocean Circulation Expedition (WOCE), observations must be conducted within two weeks of sensor calibration to minimize the effects of electrical drift. In coastal areas where observations are conducted multiple times over short periods, the impact of electrical drift is reduced, but physical changes to the sensor caused by biofouling or oil contamination necessitate frequent calibration. In Korea, there is no calibration facility for the SBE 4C sensor, therefore, the sensor must be sent to the manufacturer, Sea-Bird Electronics, in the United States for the calibration. This process takes approximately two to four months, resulting in frequent use of sensors that have been calibrated more than a month prior or continuous observations without regular calibration. This study presents methods for checking the operational status of sensors when pre- and post-observation calibration is not frequently available, correcting observed values using calibration constants before and after observations that last more than one month, and adjusting processes for salinity data observed with sensor using salinity sample analysis.