Mechanisms of Persistent High Primary Production During the Growing Season in the Chukchi Sea
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Mechanisms of Persistent High Primary Production During the Growing Season in the Chukchi Sea Zijia Zheng,
Hao Wei,
Xiaofan Luo,*
and Wei Zhao
School of Marine Science and Technology, Tianjin University, Tianjin, China
ABSTRACT Persistent high primary production during the growing season in the Chukchi Sea (Arctic Ocean) plays a key role in maintaining an efficient biological carbon pump and diverse Arctic ecosystem. We used a three-dimensional ocean–sea ice–biogeochemical model to simulate monthly averaged net primary production from 1998 to 2015. The results show that the growing season in the Chukchi Sea lasts more than 150 days, with an annual net primary production of 30.85 ± 3.67 Tg C y-1. The mechanisms for maintaining high primary production differ in the southern and northern Chukchi Sea biological hotspots. Nutrient-rich Pacific Winter Water triggers phytoplankton blooms in both hotspots as light intensity increased in spring. After these initial blooms, Bering Summer Water and remnant Pacific Winter Water are the main contributors to nutrient levels and drive primary production during the growing
season (May to September) in the southern and northern hotspots, respectively. Nitrate budget estimations in the euphotic zone reveal that after the spring blooms, persistent high primary production in the southern hotspot is mainly fueled by advecting Bering Summer Water through the Bering Strait. In the northern area, vertical mixing plays a critical role in upwelling nutrient-rich Pacific Winter Water from around the Hanna Shoal, where Pacific Winter Water is trapped for a long duration as a result of topography-influenced ocean circulation. Hence, high primary production exists in the northern Chukchi Sea during the summer and early autumn. Key words: Persistent high primary production; Nitrate budget; Pacific winter water; Bering summer water; Biological hotspots; Chukchi Sea.
HIGHLIGHTS
Received 31 May 2020; accepted 30 August 2020
Author contributions: HW and XL conceived and designed the study. ZZ performed the research and analyzed the data. WZ contributed to the model setup. ZZ and XL wrote the manuscript with suggestions from HW. *Corresponding author; e-mail: [email protected]
Controls on primary production differ in the two Chukchi biological hotspots. Main contributor to southern biological hotspot is advecting Being Summer Water. Remnant Pacific Winter Water plays a key role in the northern biological hotspot.
Z. Zheng and others
INTRODUCTION As the gateway for the Pacific water to enter the Arctic Ocean (Figure 1), the Chukchi Sea has one of the highest primary production rates in the region (Hill and others 2017; Schourup-Kristensen and others 2018), accounting for approximately 58% of the total carbon sequestration capacity of the Arctic Ocean (Bates and others 2006). In addition, high primary productivity supports a complex food web and diverse ecosystems and has created two biological hotspots in the southern Chukchi Sea and the area adjacent to the Hanna Shoal in the n
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