[A-CG68] Science in the Arctic Region

[ACG68-P06] Increasing shelf-derived material transport to the southwestern Beaufort Sea of the Arctic Ocean from 2010 to 2023

*Jonaotaro Onodera¹, Motoyo Itoh¹, Mariko Hatta¹, EIJI WATANABE¹, Kohei Mizobata², Yuichiro Tanaka³, Takuhei Shiozaki⁴, Naomi Harada⁴, Takashi Kikuchi¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.Tokyo University of Marine Science and Technology, 3.National Institute of Advanced Industrial Science and Technology, 4.The University of Tokyo)

The reduction in Arctic sea ice extent affects ocean circulation and chemical conditions, thereby influencing lower-trophic marine ecosystems and material transport in the Arctic Ocean. Sediment traps were deployed in the southern Northwind Abyssal Plain (NAP: 74.5°N 161.9°W) and north of Barrow Canyon (NBC: 72.5°N 155.4°W) in the southwestern Beaufort Sea to monitor the biogeochemical dynamics with changing physical oceanographic conditions. The obtained particle flux data showed peaks in summer and during oceanic events, such as eddy passages. Low silicon concentrations in supernatants of recovered collecting sample bottles of sediment traps suggested minimal artificial loss of biogenic material, unlike similar Atlantic Arctic experiments. Most particles were lithogenic, with some biogenic components, indicating advection from the shelf to the Canada Basin. Comparing years around 200 m depth at NAP, the median of daily total mass and particulate organic carbon (POC) fluxes increased notably from the early 2010s (31.9 and 2.0 mg m^-2 day^-1) to the late 2010s (101.8 and 5.2 mg m^-2 day^-1), respectively. At NBC, settling fluxes also rose from 2015 to 2023, with abundant lithogenic material. In the late 2010s, the molar ratio of biogenic silicon to POC and the δ¹³C values of POC increased at NAP, approaching levels observed in Chukchi Sea sediments, indicating increased shelf-derived organic matter. Related physical oceanographic studies have revealed a southeastward shift of the Beaufort Gyre and strengthening of the westward shelf-slope current since 2017. The stronger northward current observed at NAP in 2018 was likely linked to this shift. If late-2010s conditions recur and persist, ongoing hydrographic changes could further influence marine ecosystems and biogeochemical conditions around the NAP.