Spatial and Temporal Variation of Dissolved Inorganic Radiocarbon in the East Sea

Abstract

: This study examined the spatial and temporal variation of dissolved inorganic radiocarbon in the East Sea. Five vertical profiles of radiocarbon values were obtained from samples collected in 1999 in three basins (Japan Basin, Ulleung Basin, Yamato Basin) of the East Sea. Radiocarbon values decreased from 63-85‰ at the surface to about -50‰ with increasing depth (up to 2,000 m) and were nearly constant in the layer deeper than 2,000 m in all basins. Radiocarbon values did not show significant basin-to-basin differences in the surface and the bottom layers. In the intermediate layer (200-2,000 m), however, they decreased in the order of Japan Basin > Ulleung Basin > Yamato Basin, which is consistent with the suggested circulation pattern in the intermediate layer of the East Sea. Radiocarbon was found to have decreased at ~2%/year in the surface water of the East Sea. In contrast, in the interior of the East Sea, radiocarbon values have increased with time in all three basins. In the Central Water, the annual increase rate was about 3.3‰, which is faster than the rates in the Deep and Bottom Waters. The radiocarbon in the Deep and Bottom Waters had increased until mid-1990s, after which time it has been almost constant.

Transport of Aged Dissolved Organic Carbon via the Surface Current Revealed by Radiocarbon

“…The DOC results in the East Sea also show a significant linear relationship of the crossplot ( r 2 = 0.61, n = 33, p < 0.0001; Figure 2c). The y ‐intercept of the linear regression, Δ 14 C excess , is +84 ± 48‰, and is within the range of DIC Δ 14 C values in the surface water (<200 m) in the East Sea collected in 1999 (63‰–85‰) (Sim et al., 2014). This result demonstrates that the two‐component model is valid for the East Sea DOC and the major source of the Δ 14 C excess was in situ production of organic matter in the surface water via photosynthesis.…”

“…The mean Δ 14 C value of the DIC in the deep East Sea (collected in 1999) was −49 ± 14‰ (Sim et al., 2014), and is similar to that of the Atlantic deep waters in 1991 (−71 ± 20‰) (Druffel et al., 1992), indicating young ages and the presence of bomb 14 C in the deep waters. The high DOC concentrations together with the high DIC Δ 14 C values imply that the DOC cycle in the East Sea somewhat resembles that in the North Atlantic.…”

Radiocarbon Constraints on Carbon Release From the Antarctic Ice Sheet Into the Amundsen Sea Embayment

“…Efforts have been made to characterize biogeochemical processes in the SIZ and polynya in the Amundsen Sea Embayment using carbon isotopic values in various ocean samples (Fang et al, 2020;B. Kim et al, 2018;M. Kim, 2022;M.…”