Abstract
Abstract. We assessed and evaluated the performance of five ocean reanalysis products in reproducing essential hydrographic properties and their associated temporal variability for the Weddell Sea, Antarctica. The products used in this assessment were ECMWF ORAS4 (European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4), CFSR (Climate Forecast System Reanalysis), MyOcean UR025.4 (University of Reading), ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and SODA (Simple Ocean Data Assimilation). The present study focuses on the Weddell Sea deep layer, which is composed of the following three main water masses: Warm Deep Water (WDW), Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW). The MyOcean UR025.4 product provided the most accurate representation of the structure and thermohaline properties of the Weddell Sea water masses when compared with observations. All the ocean reanalysis products analyzed exhibited limited capabilities in representing the surface water masses in the Weddell Sea. The CFSR and ECCO2 products were not able to represent deep water masses with a neutral density ≥ 28.40 kg m−3, which was considered the WSBW's upper limit throughout the simulation period. The expected WDW warming was only reproduced by the SODA product, whereas the ECCO2 product was able to represent the trends in the WSDW's hydrographic properties. All the assessed ocean reanalyses were able to represent the decrease in the WSBW's density, except the SODA product in the inner Weddell Sea. Improvements in parameterization may have as much impact on the reanalyses assessed as improvements in horizontal resolution primarily because the Southern Ocean lacks in situ data, and the data that are currently available are summer-biased. The choice of the reanalysis product should be made carefully, taking into account the performance, the parameters of interest, and the type of physical processes to be evaluated.
Highlights
The Southern Ocean is considered an important region for better understanding the global overturning circulation (GOC) because of the regional formation and export of bottom waters to the global ocean (e.g., Talley, 2013)
A good representation of the physical processes occurring in ocean and climate models together with accurate hydrographic data observed in the Weddell Sea, which can be investigated through ocean reanalysis products, should significantly influence the hydrography of the Southern Ocean and South Atlantic (Hellmer et al, 2005)
4.1 Water column structure and simple differences in hydrographic properties showed a similar θ–S structure when compared with observation data
Summary
The Southern Ocean is considered an important region for better understanding the global overturning circulation (GOC) because of the regional formation and export of bottom waters to the global ocean (e.g., Talley, 2013). A good representation of the physical processes occurring in ocean and climate models together with accurate hydrographic data observed in the Weddell Sea, which can be investigated through ocean reanalysis products, should significantly influence the hydrography of the Southern Ocean and South Atlantic (Hellmer et al, 2005). In this way, validation of ocean reanalysis products is needed to evaluate the suitability, consistency, and applicability of these products for long-term investigations in the Southern Ocean.
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