Investigating ocean deoxygenation and the oxygen minimum zone in the Central Indo Pacific region based on the hindcast datasets.

Abstract

Deoxygenation is increasingly recognized as a significant environmental threat to the ocean following sea temperature rises due to global warming and climate change. Considering the cruciality of the deoxygenation impacts, it is important to assess the current status and predict the future possibility of ocean deoxygenation, for instance, within the Central Indo Pacific (CIP) regions represent climate-regulated marine areas. This study divided CIP into five regions then investigated the deoxygenation parameters (dissolved oxygen, temperature, salinity, and pH) collected from 1993 to 2021 sourced from in situ measurement and long-term hindcast data. The overall error statistics indicate a good accuracy of hindcast data and are comparable to the in situ values. The surface waters were identified to have the most fluctuated seasonal pattern of dissolved oxygen (DO) concentration compared to other water columns. However, DO fluctuation occurred in a different pattern in each region. The study shows ocean deoxygenation is accelerated in all five regions over decades. The strongest oxygen minimum zone (OMZ) is identified in the Bay of Bengal and the Arafura Sea with the lowest oxygen concentration less than 0.5mmol/m3, while the weakest OMZ is located in the South China Sea with 60mmol/m3 of DO concentration. The deoxygenation rates in CIP regions are varied by 0.09-2.75mmol/m3/year depending on the different controlling factors that work in the five regions. Our results indicate that deoxygenation is attributed to ocean warming, seawater salinity increases, and ocean acidification and possibly continue in the future with continued global changes.