Seasonal Water Mass Evolution and Non-Redfield Dynamics Enhance CO Uptake in the Chukchi Sea.
Zhangxian Ouyang, Andrew Collins, Yun Li, Di Qi, Kevin R Arrigo, Yanpei Zhuang, Shigeto Nishino, Matthew P Humphreys, Naohiro Kosugi, Akihiko Murata, David L Kirchman, Liqi Chen, Jianfang Chen, Wei-Jun Cai
Author Information
Zhangxian Ouyang: School of Marine Science and Policy University of Delaware Newark DE USA. ORCID
Andrew Collins: School of Marine Science and Policy University of Delaware Newark DE USA.
Yun Li: School of Marine Science and Policy University of Delaware Newark DE USA.
Di Qi: Polar and Marine Research Institute Jimei University Xiamen China. ORCID
Kevin R Arrigo: Department of Earth System Science Stanford University Stanford CA USA. ORCID
Yanpei Zhuang: Polar and Marine Research Institute Jimei University Xiamen China.
Shigeto Nishino: Institute of Arctic Climate and Environment Research Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokosuka Japan. ORCID
Matthew P Humphreys: Department of Ocean Systems (OCS) NIOZ Royal Netherlands Institute for Sea Research Texel The Netherlands. ORCID
Naohiro Kosugi: Meteorological Research Institute Tsukuba Japan. ORCID
Akihiko Murata: Global Ocean Observation Research Center Research Institute for Global Change Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokosuka Japan. ORCID
David L Kirchman: School of Marine Science and Policy University of Delaware Newark DE USA.
Liqi Chen: Key Laboratory of Global Change and Marine-Atmospheric Chemistry of Ministry of Natural Resources Third Institute of Oceanography MNR Xiamen China. ORCID
Jianfang Chen: Key Laboratory of Marine Ecosystem Dynamics Second Institute of Oceanography Ministry of Natural Resources Hangzhou China. ORCID
Wei-Jun Cai: School of Marine Science and Policy University of Delaware Newark DE USA. ORCID
The Chukchi Sea is an increasing CO sink driven by rapid climate changes. Understanding the seasonal variation of air-sea CO exchange and the underlying mechanisms of biogeochemical dynamics is important for predicting impacts of climate change on and feedbacks by the ocean. Here, we present a unique data set of underway sea surface partial pressure of CO (CO) and discrete samples of biogeochemical properties collected in five consecutive cruises in 2014 and examine the seasonal variations in air-sea CO flux and net community production (NCP). We found that thermal and non-thermal effects have different impacts on sea surface CO and thus the air-sea CO flux in different water masses. The Bering summer water combined with meltwater has a significantly greater atmospheric CO uptake potential than that of the Alaskan Coastal Water in the southern Chukchi Sea in summer, due to stronger biological CO removal and a weaker thermal effect. By analyzing the seasonal drawdown of dissolved inorganic carbon (DIC) and nutrients, we found that DIC-based NCP was higher than nitrate-based NCP by 66%-84% and attributable to partially decoupled C and N uptake because of a variable phytoplankton stoichiometry. A box model with a non-Redfield C:N uptake ratio can adequately reproduce observed CO and DIC, which reveals that, during the intensive growing season (late spring to early summer), 30%-46% CO uptake in the Chukchi Sea was supported by a flexible stoichiometry of phytoplankton. These findings have important ramification for forecasting the responses of CO uptake of the Chukchi ecosystem to climate change.
