A toolbox for secondary quality control on ocean chemistry and hydrographic data

Siv K Lauvset,Toste Tanhua

doi:10.1002/lom3.10050

Abstract

High quality, reference measurements of chemical and physical properties of seawater are of great importance for a wide research community, including the need to validate models and attempts to quantify spatial and temporal variability. Whereas data precision has been improved by technological advances, the data accuracy has improved mainly by the use of certified reference materials (CRMs). However, since CRMs are not available for all variables, and use of CRMs does not guarantee bias-free data, we here present a recently developed Matlab toolbox for performing so-called secondary quality control on oceanographic data by the use of crossover analysis. This method and how it has been implemented in this toolbox is described in detail. This toolbox is developed mainly for use by sea-going scientists as a tool for quickly assessing possible bias in the measurements that can—hopefully—be remedied during the expedition, but also for possible post-cruise adjustment of data to be consistent with previous measurements in the region. The toolbox, and reference data, can be downloaded from the Carbon Dioxide Information Analysis Center (CDIAC): http://cdiac.ornl.gov/ftp/oceans/2nd_QC_Tool_V2/.

Highlights

High quality, reference measurements of chemical and physical properties of seawater are of great importance for a wide research community, including the need to validate models and attempts to quantify spatial and temporal variability
Improvements in the instrumentation has reduced the achievable precision to about 2 lmol kg21 for dissolved inorganic carbon (DIC) and, with the use of certified reference materials (CRMs), an accuracy better than 5 lmol kg21 can be routinely obtained
The toolbox presented here is a continuation of scripts and functions developed during the Carbon in Atlantic Ocean (CARINA), PACIFICA, and GLODAPv2 projects, and an earlier version of the toolbox was used to do the quality control on new cruises submitted to the GLODAPv2 data product

Summary

Introduction

Reference measurements of chemical and physical properties of seawater are of great importance for a wide research community, including the need to validate models and attempts to quantify spatial and temporal variability. Since CRMs are not available for all variables, and use of CRMs does not guarantee bias-free data, we here present a recently developed Matlab toolbox for performing so-called secondary quality control on oceanographic data by the use of crossover analysis. This method and how it has been implemented in this toolbox is described in detail. CRMs are not available for all variables or used on each cruise and measurements performed without the aid of CRMs are more prone to show biases, the use of CRMs is no guarantee for accurate measurements as several factors. Differences in the reported values obtained during different ship campaigns can be due to systematic biases in, Lauvset and Tanhua

Methods

Findings

Conclusion