Spatial and Temporal Variability of Oceanic Oxygen Changes and Underlying Trends

A recent analysis of observed oxygen changes shows a 2% decline in marine oxygen during the 50 years since 1960. However, these oxygen changes vary on time scales related to climate modes and by regions, including areas of increasing oxygen. Hence, any local oxygen change is related to various subsets of these drivers for the different regions and time scales. Here we provide an overview of drivers presently known for the different regions in the upper and deep ocean and the regional influence of climate modes, focussing on decadal and longer time scales for open ocean regions. We identify and compile regions where changes in solubility, stratification, decadal to multidecadal variability, source waters (either increases or decreases), overturning circulation or circulation-driven changes, and biological or nutrient stimulation have been shown to play a role in oxygen changes. The superposition and interaction of drivers and processes makes the decomposition of the impact on oxygen distribution difficult. Nevertheless, the description of the different drivers identified will help in better understanding the oxygen changes observed and lead to better verification of numerical models of future ocean oxygen levels.

Automated summary

The recent analysis of observed oxygen changes reveals a 2% decline in marine oxygen over the past 50 years, with variations in different regions and time scales linked to various drivers. These drivers include solubility, stratification, source water changes, and circulation patterns, making it challenging to accurately determine the impact of each driver on oxygen levels. Efforts to better understand these complex interactions will improve future verification of numerical models for ocean oxygen levels.