HiWASE: calibration of surface salinity measurements

Between 1978 and 2009 the Norwegian weather ship Polarfront made continuous meteorological measurements at Station Mike (66oN 2oE). In September 2006, as part of the HiWASE project the ship’s existing measurement systems were complemented by the AutoFlux system to measure the transfers of momentum, heat and CO2 between the atmosphere and the ocean. Surface salinity was measured using a thermosalinograph (TSG) as part of the AutoFlux system. The TSG data were calibrated by comparison to surface CTD measurements, Nansen surface bottles and underway bottle samples. The corrected TSG salinity data has a residual difference from the calibration data, which is generally less than ±0.1 psu except for the summer months when this increases ±0.2 psu. This is sufficient for this study since salinity was only used for the calculation of CO2 solubility in the surface water. The corrected salinity data show a sharp decrease in salinity of about 1 psu during July and August each year. The salinity measured during this time is highly variable and must be used with caution. The data are available from the British Oceanographic Data Centre, UK (http://www.bodc.ac.uk/).