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An intercomparison study has been carried out on the analysis of inorganic nutrients at sea following the operation of two nutrient analysers simultaneously on the GO-SHIP A02 trans-Atlantic survey in May 2017. Both instruments were Skalar San ++ Continuous Flow Analyzers, one from the Marine Institute, Ireland and the other from Dalhousie University, Canada, each operated by their own laboratory analysts following GO-SHIP guidelines while adopting their existing laboratory methods. There was high comparability between the two data sets and vertical profiles of nutrients also compared well with those collected in 1997 along the same A02 transect by the World Ocean Circulation Experiment. The largest differences between data sets were observed in the low-nutrient surface waters and results highlight the value of using three reference materials (low, middle and high concentration) to cover the full range of expected nutrients and identify bias and non-linearity in the calibrations. The intercomparison also raised some interesting questions on the comparison of nutrients analysed by different systems and a number of recommendations have been suggested that we feel will enhance the existing GO-SHIP guidelines to improve the comparability of global nutrient data sets. A key recommendation is for the specification of clearly defined data quality objectives for oceanic nutrient measurements and a flagging method for reported data that do not meet these criteria. The A02 nutrient data set is currently available at the National Oceanographic Data Centre of Ireland: 10.20393/CE49BC4C-91CC-41B9-A07F-D4E36B18B26F and 10.20393/EAD02A1F-AAB3-4F4E-AD60-6289B9585531. [ABSTRACT FROM AUTHOR]

An inter-comparison study has been carried out on the analysis of inorganic nutrients at sea following the operation of two nutrient analysers simultaneously on the GO-SHIP A02 trans-Atlantic survey in May 2017. Both instruments were Skalar San++ Continuous Flow Analysers, one from the Marine Institute, Ireland and the other from Dalhousie University, Canada, each operated by their own laboratory analysts following GO-SHIP guidelines, while adopting their existing laboratory methods. High quality control of the nutrient analysis was achieved on both instruments and there was high comparability between the two datasets. Vertical profiles of nutrients also compared well with those collected in 1997 along the same A02 transect by the World Ocean Circulation Experiment. The comparison of the two 2017 datasets and individual laboratory methods, did however raise some interesting questions on the comparison of nutrients analysed from different systems, in particular the calibration range of daily standards and its influence on low nutrient samples, and the importance of using certified reference materials of high and low concentrations to identify bias in the data. Based on the results from this inter-comparison, a number of recommendations have been suggested that we feel will enhance the existing GO-SHIP guidelines to improve the comparability of global nutrient datasets. [ABSTRACT FROM AUTHOR]