Subsea permafrost as a potential major source of dissolved organic matter to the East Siberian Arctic Shelf

Meilian Chen; Ji-Hoon Kim; Yun Kyung Lee; Dong-Hun Lee; Young Keun Jin; Jin Hur

doi:10.1016/j.scitotenv.2021.146100

Subsea permafrost as a potential major source of dissolved organic matter to the East Siberian Arctic Shelf

Sci Total Environ. 2021 Jul 10:777:146100. doi: 10.1016/j.scitotenv.2021.146100. Epub 2021 Feb 28.

Authors

Meilian Chen¹, Ji-Hoon Kim², Yun Kyung Lee³, Dong-Hun Lee⁴, Young Keun Jin⁵, Jin Hur⁶

Affiliations

¹ Environmental Program, Guangdong Technion - Israel Institute of Technology, Shantou 515063, China. Electronic address: chen.meilian@gtiit.edu.cn.
² Petroleum and Marine Research Division, Korea Institute of Geoscience and Mineral Resources, 124 Gwahak-ro, Yuseong-gu, Daejeon 34132, South Korea.
³ Department of Environment & Energy, Sejong University, Seoul 05006, South Korea.
⁴ Hanyang University ERICA Campus, 15588 Ansan, South Korea; Marine Environment Research Division, National Institute of Fisheries Science, 216, Gijanghaean-ro, Gijang-eup, Busan 46083, South Korea.
⁵ Korea Polar Research Institute (KOPRI), Incheon 21990, South Korea.
⁶ Department of Environment & Energy, Sejong University, Seoul 05006, South Korea. Electronic address: jinhur@sejong.ac.kr.

PMID: 33684745
DOI: 10.1016/j.scitotenv.2021.146100

Abstract

Arctic subsea permafrost contains more organic carbon than the terrestrial counterpart (~1400 Pg C vs. ~1000 Pg C) and is undergoing fast degradation (at rates of ~10 to 30 cm yr^-1 over the past 3 decades) in response to climate warming. Yet the flux of organic carbon sequestered in the sediments of subsea permafrost to overlying water column, which can trigger enormous positive carbon-climate feedbacks, remain unclear. In this study, we examined the dissolved organic matter (DOM) diffusion to bottom seawaters from East Siberian Sea (ESS) sediments, which was estimated at about 943-2240 g C m^-2 yr^-1 and 10-55 g C m^-2 yr^-1 at the continuous-discontinuous transition zone of subsea permafrost and the remainder shelf and slope sites, respectively. The released DOM is characterized by prevailing dominance (≥ 98%) of low molecular weight (M_n < 350 Da) fractions. A red-shifted (emission wavelength >500 nm) fluorescence fingerprint, a typical feature of sediment/soil DOM, accounts for 4-6% and 7-8% in the fluorescence distributions of seawaters and pore waters, respectively, on ESS shelf. Statistical analysis revealed that seawaters and pore waters possessed similar DOM composition. The estimated total benthic efflux of dissolved organic carbon (DOC) was ~0.7-1.0 Pg C yr^-1 when the estimate was scaled up to the entire Arctic shelf underlain with subsea permafrost assuming the width of continuous-discontinuous transition zone is 1 to 10 m. This estimation is consistent with the established ~10-30 cm yr^-1 degradation rates of subsea permafrost by estimating its thaw-out time. Compiled observation data suggested that subsea permafrost might be a major DOM source to the Arctic Ocean, which could release tremendous carbon upon remineralization via its degradation to CO₂ and CH₄ in the water column.

Keywords: Arctic sediment; Benthic efflux; Carbon release; Fluorescence; Low molecular weight fraction; Subsea permafrost.