Presentation: Coastal Ocean Carbon Cycling – Current Understanding and Challenges.
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Biographical Information: In addition to being a Cheung Kong Chair Professor of Marine Biogeochemistry at Xiamen University, Minham Dai currently serves as the Director of the State Key Laboratory of Marine Environmental Science and is the Dean of the College of the Ocean and Earth Sciences. His research interests include carbon and trace metal biogeochemistry in marginal and estuarine systems, and the geochemistry of radioactive elements in surface and ground water. He has published more than 80 papers in leading international journals and is a leading PI of a “973” program on “carbon cycling in China Seas - budget, controls and ocean acidification”. He has served on many national and international committees. He is currently a member of advisory committee for the Earth Science Division of NSF-China, a SSC member of SOLAS, and the Secretary General of Asia Oceania Geosciences Society (AOGS).
Coastal ocean carbon cycling is an important component of the Earth’s climate system yet very complex because multiple-scale processes occurred to the coastal ocean where atmosphere, ocean and land interplay, which makes their inclusion in any realistic prognostic climate simulation an immense challenge. While global estimates of coastal air-sea CO2 fluxes have dramatically improved during the past several years as a result of the rapid growing of regional studies on carbon flux measurements, we still lack a mechanistic understanding on why some of the coastal ocean systems act as sinks for atmospheric CO2 while others are sources. The temporal and spatial variability of these CO2 fluxes both at the global and regional scales also present challenges. Adding to that are multiple stressors such as anthropogenic pressures which has likely led to the rapid changes seen in many of the world’s coastal ocean carbon systems. For example, ocean acidification in the coastal ecosystem is not only driven by the perturbation of anthropogenic CO2 but also impacted by coastal eutrophication and likely hypoxia as well.
This presentation will start with our current understanding of carbon fluxes and their controls in the global coastal ocean. We emphasize that physical settings such as the basin/mesoscale circulation including their interactions with open ocean basins in many coastal systems determines the carbon fluxes to a large extent. We will then look at the South China Sea as an example of the variability of coastal carbon fluxes at various temporal and spatial scales, spanning from diurnal changes to decadal changes, and in different physical-biogeochemical domains such as river plumes, upwellings, and meso-scale eddies. Emphasis will be given to the carbon connection between riverine input, its response on the shelf system and exchange with the open ocean interior. Also examined in this presentation are the interactions between carbon cycling and other biogenic elements such as nitrogen and silicate in the coastal ocean. This presentation will end with comments on the potential future changes of coastal ocean carbon biogeochemistry under the influence of both climate change and various anthropogenic effects.