Assessment of the Accuracy of Global Oceanic Reanalysis in Reproducing the Temperature and Salinity of the Waters of the Avacha Bay (the Pacific Ocean)

The objective of this study is to assess the accuracy of reproducing the vertical distribution of temperature and salinity in the waters of Avacha Bay (the Pacific Ocean) in the coastal area, based on data from two global ocean reanalysis products: CMEMS GLORYS12v1 and GOFS3.1. The results of in situ measurements performed on a repeating grid of stations in April 2019 and 2020 were used as independent data. The results showed that both products reproduce the general trends in thermohaline characteristics, but the accuracy varies depending on the depth and area. The average temperature anomaly was 0.6 °C for CMEMS GLORYS12v1 and 0.4 °C for GOFS3.1, and for salinity — 0.3 and 0.4, respectively. The largest deviations were observed at the shelf stations, where the reanalysis products failed to reproduce both the mean values and the near-surface halocline. This is likely due to limitations in the models’ resolution and a lack of sufficient data for accurate calculations. In the deepwater part of the bay, both products demonstrate higher accuracy, although inaccuracies in reproducing the characteristics and features of the vertical structure of the cold intermediate layer and the upper boundary of the warm intermediate layer are noted at individual stations. In particular, GLORYS12v1 reproduces the salinity distribution better, whereas GOFS3.1 more accurately reflects the temperature structure. However, both products demonstrate poor accuracy in reproducing the vertical structure of salinity on the shelf, which indicates the need for more accurate accounting of local processes such as freshwater runoff and the dynamics of coastal currents. In general, it is preferable to use temperature and salinity data from the GOFS3.1 product to track the state of marine ecosystems in the deep-water areas of Avacha Bay, including the “Northern” canyon area, which is the epicenter of spawning of the East Kamchatka pollock population.