Decadal variation of biological settling particle fluxes controlled by physical process in the subarctic western North Pacific

Naomi Harada1, Hiromichi Ueno2, Isao Fujita3, Nozomi Matsudera3, Jonaotaro Onodera4, Makio C Honda5, Maki Noguchi Aita6, Tetsuichi Fujiki1, Kitamura Minoru1 and Miyako Sato1, (1)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan, (2)Hokkaido University, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan, (3)Hokkaido University, Japan, (4)JAMSTEC, Yokosuka, Japan, (5)JAMSTEC, Kanagawa, Japan, (6)Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Yokohama, Japan
Abstract:
The subarctic western North Pacific is one of the most effective area in terms of biogenic pCO2 draw down in the world (Takahashi et al., 2002). Aquatic resource is also rich there. In order to understand the missing link between physical, chemical and biological production to create the rich marine ecosystem and effective biogeochemical dynamics in the subarctic western North Pacific, new interdisciplinary study, “Ocean Mixing Processes: Impact on Biogeochemistry, Climate and Ecosystem (OMIX)” is ongoing in Japan. As a part of OMIX study, we have a time-series mooring system at St.K2 in the subarctic western North Pacific to observe biogenic fluxes by sediment trap to find missing link between physical processes, nutrient supply and associated biological production there. According to decadal data from 2005 to 2017 at St.K2, total mass fluxes changed ranging from 0.07 to 949.5mg m-2 day-1 composed to mainly opal which is the frustules of diatom, silicoflagellate, and radioralia. There is a seasonal change namely, relatively high in the beginning of summer to autumn and low during winter-spring. The total mass, opal and organic carbon fluxes showed decreasing trend since Jan 2011. On the other hand, alkenone flux which is the biomarker of Emiliania huxlyei, coccolithophorid showed increasing trend since Jan 2011. Emiliania huxleyi distributes mainly in subtropical and transition area in the western North Pacific (Harada et al., 2006) and thus the increasing of alkenone flux since 2011 implies the north migration of subarctic frontal zone (SAF). What physical mechanism control the decadal variation of biogenic flux and component through the latitudinal migration of SAF? We will compare the strength of local jet current with biogenic fluxes and will discuss the potential process to move SAF in this presentation.