Sedimentary gochemical characteristics of the Redox-sensitive elements in Ross Sea, Antarctica: Implications for paleoceanography

Redox conditions of deep ocean are supposed closely related to deep ocean circulation and surface water production. Facts prove that surface water production and deep water circulation may strongly influence the formation of respiration carbon and its migration from ocean interior to atmosphere, which is closely related to the rise of atmospheric pCO₂. Hence, verifying the redox environment evolution of the ocean could help us clarify the mechanism of variation in atmospheric pCO₂ in glacial-interglacial cycles. Samples from core ANT31-R23 and the surface sediment of central Ross Sea, which were taken by R/V Xuelong in the 31^st and 32^th Chinese National Antarctic Research Expedition, are used as research materials in this study. Both the major and minor elements are analyzed, including calcium, titanium and the elements sensitive to paleo-redox environment of deposition, so-called Redox-sensitive elements (RSE), such as manganese, molybdenum, nickel, cobalt and cadmium. RSEs normalized by Ti are adopted as background values to estimate if the RSEs are enriched or depleted. The result shows that enrichment of Mn occurs in the entire core indicating an oxidizing condition. Four strong oxidation pulse events are identified based on Mn peaks in different depths, which may be related to stronger circulation conditions and/or lower surface water production in the Southern Ocean during late Quaternary. The layers enriched by Mo, Co and Ni in addition to Mn, are resulted from absorption, capture or scavenge by Mn-oxyhydroxides. These results suggest that the Ross Sea does not have significant contribution to the reducing of atmospheric pCO₂ during glaciation. The strong oxidation pulse events, however, may play an important role in elevating atmospheric pCO₂ during deglaciation. Nevertheless, the detailed processes of this mechanism will be effectively revealed by follow-up work after the establishment of accurate chronology framework.