Observed features of stable surface seawater isotopes across the Pacific, Indian and Southern oceans

The marine hydrological process is still unclear due to scarce observations. Based on stable water isotopes in surface seawater along the 33rd Chinese National Antarctic Science Expedition from November 2016 to April 2017, this study explored the hydrological processes in the Pacific, Indian and Southern oceans. The results show that the Northwest Pacific (0°–26°N) is a region with strong evaporation (the δ¹⁸O-δD slope is 6.58), while the southern Indian Ocean is a region with strong precipitation (the δ¹⁸O-δD slope is 9.57). The influence of continental runoff and water mass mixing reduces the correlation between δ¹⁸O and salinity in the eastern Indian Ocean. The characteristics of the isotopes and hydrological parameters indicate that the Agulhas Front and sub-Tropical Convergence do not merge in the Antarctic–Indian Ocean region. The freezing of sea ice near the Antarctic continent decreases the δ¹⁸O and δD by 0.40‰ and 7.0‰, respectively, compared with those near 67°S. This study is helpful for understanding marine hydrological processes and promoting the understanding and research of the nature of ocean responses in the context of climate change.