[A-CG41] Biogeochemical linkages between the surface ocean and atmosphere

[ACG41-04] Evaluation of Asian aerosols and their impact on marine biogeochemistry in the western North Pacific

*Maki Noguchi Aita¹, Kana Nagashima¹, Fumikazu Taketani¹, KIMOTO KATSUNORI¹, Fujiki Tetsuichi¹, Koji Sugie¹, Yugo Kanaya¹ (1.Earth Surface System Research Center, Japan Agency for Marine-Earth Science and Technology)

Keywords:Ocean-Atmosphere Interactions, Marine biogeochemical cycle, Atmospheric aerosols, Primary production

The western North Pacific is one of the world's richest oceans in terms of biological carbon dioxide uptake capacity by marine organisms, and it has the highest fish catches in the world. On the other hand, this area belongs to the mid-to-high latitude westerly wind belt. The East Asian countries are located upwind of the westerly winds, and there are concerns about the impact of anthropogenic emissions from these countries on primary productivity. The western subarctic North Pacific is known as the high-nutrient low-chlorophyll (HNLC) region, where the lack of trace elements and iron deficiency regulates primary production (e.g., Duce et al. 1991). There are two major iron supply processes for this region: one is supplying through the atmosphere, such as dust from Asian deserts and anthropogenic aerosols, and the other from iron-rich intermediate water from the Sea of Okhotsk (e.g., Nishioka et al. 2020). However, it has not been quantitatively clarified that "when" and "how much" supply and to what extent it contributes to primary production. Quantifying the two processes and their changes in time series is critical for advancing future marine ecosystem predictions. On the other hand, it is well known that the abundance of nitrogen mainly determines primary production in the subtropical western North Pacific. Algal cultivation experiments and model simulations have been conducted to estimate the contribution of internal ocean processes such as horizontal advection, vertical mixing, and atmospheric nutrient deposition to primary production. But, understanding these processes in ocean observations has not yet been fully achieved.
To quantify the key processes and availability of nutrients, including trace metal, as well as their spatio-temporal changes and impact on primary production, the Earth Surface System Research Center (ESS) at Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been conducting research cruises since 2020. We conduct seasonal observation cruises in the western North Pacific Ocean, and our observational research is performed from a multidisciplinary perspective using atmospheric chemistry, ocean chemistry, marine ecology, ocean physics, marine geology, and numerical modeling. These will promote a better quantitative understanding of the processes linking the Asian region and marine ecosystems, and the assessment of ecosystem risks, particularly in the western North Pacific region. We will present the results obtained during the cruises and the planned East-West comparative observations in the North Pacific subarctic region in 2024 and 2025.