This study is led by Dr. Ma Jun and Dr. Song Jinming from Institute of Oceanology, Chinese Academy of Sciences. Focusing on the research of OMZ, the research team clarified that the DO threshold range of OMZ in the global ocean is 20-100 μmol L-1. They pointed out the differences in the horizontal and vertical distributions of OMZ in different sea areas, expounded that the continuous consumption of DO in the ocean interior and the restriction of water exchange caused by ocean stratification are the two core mechanisms for the formation of OMZ, and analyzed that two positive-feedback regulation methods, namely the increase in microbial oxygen consumption and the increase in oxygen consumption by anaerobic metabolites, are the maintenance mechanisms for the hypoxic state of OMZ.
In the context of global change, the OMZ is evolving rapidly. The researchers indicated that its expansion can usually be attributed to two core controls: the temperature and the ocean circulation. On the one hand, rising temperature provides direct impetus for the expansion of OMZ by reducing the solubility of O2, increasing the rates of organic matter respiration and remineralization, and enhancing the stratification of the upper ocean. On the other hand, global change alters the intensity, structure, and spatial distribution patterns of ocean circulations represented by thermohaline circulation, wind-driven circulation, and upwelling, significantly influencing the formation, maintenance, and transmission of hypoxic waters. In addition, wind stress, mesoscale vortex, and freshwater flux can also further regulate the structure and evolution process of OMZ.
The researchers suggested that in the future, attention should be paid to establishing OMZ gradient thresholds and classification criteria that conform to the laws of deoxygenation, improving the systematic understanding of the spatio-temporal changes of OMZ, and continuously strengthening in-depth research on OMZ in sea areas such as the Western Pacific Ocean, which has a relatively weak OMZ intensity and is greatly affected by global change. This will help to better understand the evolution process of global ocean hypoxia and deoxygenation, providing scientific support for formulating future-oriented sustainable development strategies.
