World Ocean Circulation Experiment – Argo Global Hydrographic Climatology

Abstract. The paper describes the new gridded World Ocean Circulation Experiment-Argo Global Hydrographic Climatology (WAGHC). The climatology has a 1∕4∘ spatial resolution resolving the annual cycle of temperature and salinity on a monthly basis. Two versions of the climatology were produced and differ with respect to whether the spatial interpolation was performed on isobaric or isopycnal surfaces, respectively. The WAGHC climatology is based on the quality controlled temperature and salinity profiles obtained before January 2016, and the average climatological year is in the range from 2008 to 2012. To avoid biases due to the significant step-like decrease of the data below 2 km, the profile extrapolation procedure is implemented. We compare the WAGHC climatology to the 1∕4∘ resolution isobarically averaged WOA13 climatology, produced by the NOAA Ocean Climate Laboratory (Locarnini et al. , 2013) and diagnose a generally good agreement between these two gridded products. The differences between the two climatologies are basically attributed to the interpolation method and the considerably extended data basis. Specifically, the WAGHC climatology improved the representation of the thermohaline structure, in both the data poor polar regions and several data abundant regions like the Baltic Sea, the Caspian sea, the Gulf of California, the Caribbean Sea, and the Weddell Sea. Further, the dependence of the ocean heat content anomaly (OHCA) time series on the baseline climatology was tested. Since the 1950s, both of the baseline climatologies produce almost identical OHCA time series. The gridded dataset can be found at https: //doi. org/10. 1594/WDCC/WAGHCV1. 0 (Gouretski, 2018).