Characteristics and biogeochemical effects of oxygen minimum zones in typical seamount areas,Tropical Western Pacific

摘要

As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline of DO is characterized by the expansion of oxygen minimum zones(OMZs)in the ocean interior.Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific(TWP),but have gained very little attention.In this study,we focus on characteristics of OMZs in three typical seamounts areas(named Y3,M2,and Kocebu,respectively)of the TWP.Based on distributions of DO,the OMZs of the three seamounts areas are very different in scope,thickness,and the minimum oxygen content.The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic.To quantitatively describe the intensity of OMZs,a parameter,IOMZ,is firstly proposed.According to this quantitative parameter,the intensity order of OMZs for the three seamounts areas is Kocebu>M2>Y3.Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using IOMZ.With higher IOMZ,the degradation of particulate organic carbon(POC)tends to be lower.Yet because of the limited data,their relationship still need more research to prove.However,if this relationship holds in global oceans,the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump.Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump.