Enhancements of Himalayan and Tibetan Erosion and the Produced Organic Carbon Burial in Distal Tropical Marginal Seas During the Quaternary Glacial Periods: An Integration of Sedimentary Records. Issue 3 (14th March 2021)

• Record Type: Journal Article
• Authors: Xu, Zhaokai; Wan, Shiming; Colin, Christophe; Clift, Peter D.; Chang, Fengming; Li, Tiegang; Chen, Hongjin; Cai, Mingjiang; Yu, Zhaojie; Lim, Dhongil
• Is Part Of: Journal of geophysical research. Volume 126:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-03-14
• Subjects: highland (mountain) erosion -- Indian monsoon -- International Ocean Discovery Program -- organic carbon cycle -- sea level -- terrigenous input; Geomorphology -- Periodicals; 551.3
• DOI: 10.1029/2020JF005828
• Languages: English
• ISSNs: 2169-9003

Abstract

Abstract: The Himalayan and Tibetan highlands (mountains), with high rates of physical erosion, are extreme settings for earth surface processes, generating one of the largest recent terrigenous detritus and organic carbon discharges to the ocean. However, their significance with respect to the global carbon and climate cycles during the Quaternary is still unclear, especially in quantitative terms. Here, we present comprehensive records of continental erosion and weathering, terrestrial supply, marine productivity, and organic carbon burial in the distal Arabian Sea, Bay of Bengal, and southern South China Sea since ∼700 ka over orbital timescales. These records exhibit periodicities corresponding to sea level and Indian summer monsoon intensity changes. During glacial periods, the enhanced highland surface erosion and activation of deep‐sea channels significantly increased inputs of terrigenous detritus, nutrients, and organic carbon into the Arabian Sea and Bay of Bengal, whereas strengthened continental shelf surface weathering and organic matter preservation occurred in the South China Sea. Conclusively, our integrative proxies in the study area demonstrate, for the first time, pronounced glacial burial pulses of organic carbon (∼1.12 × 10 12 mol/yr), dominantly originating from the highland surface erosion and marine productivity. Together with the increased silicate weathering on the exposed tropical continental shelves and in the tropical volcanic arcs, the enhanced burial flux of organic carbon in the tropical marginal seas, therefore, highlights the large contributions that tropical regions can make within the glacial‐interglacial carbon inventory of the ocean and atmosphere and thus cause significant negative feedback on the global climate. Plain Language Summary: Anthropogenic emissions of the greenhouse gas CO2 are significantly changing the global climate and environment, resulting in a warmer state for which there is no historical analog. Marine records hold valuable lessons for the future of our warming world, as marine sediments are an important reservoir of the global organic carbon and then modulate release of CO2 into the atmosphere. Currently, the major river systems originating from the Himalaya and Tibetan Plateau discharge ∼25% of the global fluvial sediment flux to the ocean, acting as an important source of continental organic carbon at tectonic and current timescales. Our integrative mineralogical‐geochemical study demonstrates the enhanced highland (mountain) erosion and activation of deep‐sea channels, increased supplies of the produced materials, strengthened marine productivity, and effective preservation of organic carbon in the deep Arabian Sea and Bay of Bengal during cold periods. In contrast, strengthened chemical decomposition of silicates on the exposed continental shelf was coeval with increased organic carbon storage in the deep South China Sea. The study area contributed ∼1/4 of the current global marine burial flux of organic carbon during sea‐level lowstands and thus represents a key precedent for understanding increasingly severe global warming. Key Points: A first integrative study of Quaternary inputs of Himalayan and Tibetan erosion and weathering products in distal marginal seas is presented Increased highland erosion and terrestrial organic matter burial in the deep Arabian Sea and Bay of Bengal occurred during glacial periods Enhanced continental shelf weathering and terrigenous organic carbon flux in the abyssal South China Sea appeared during sea‐level lowstands