Quantifying Degradative Loss of Terrigenous OrganicCarbon in Surface Sediments Across the Laptevand East Siberian Sea
| Parent link: | Global Biogeochemical Cycles Vol. 33, iss. 1.— 2019.— [P. 85-99] |
|---|---|
| Corporate Author: | |
| Other Authors: | , , , , |
| Summary: | Title screen Ongoing permafrost thaw in the Arctic may remobilize large amounts of old organic matter.Upon transport to the Siberian shelf seas, this material may be degraded and released to the atmosphere,exported off-shelf, or buried in the sediments. While our understanding of the fate of permafrost-derivedorganic matter in shelf waters is improving, poor constraints remain regarding degradation in sediments.Here we use an extensive data set of organic carbon concentrations and isotopes (n= 109) to inventoryterrigenous organic carbon (terrOC) in surficial sediments of the Laptev and East Siberian Seas (LS + ESS).Of these ~2.7 Tg terrOC about 55% appear resistant to degradation on a millennial timescale. Afirst-orderdegradation rate constant of 1.5 kyr-1is derived by combining a previously established relationshipbetween water depth and cross-shelf sediment-terrOC transport time with mineral-associated terrOCloadings. This yields a terrOC degradationflux of ~1.7 Gg/year from surficial sediments during cross-shelftransport, which is orders of magnitude lower than earlier estimates for degradationfluxes of dissolvedand particulate terrOC in the water column of the LS + ESS. The difference is mainly due to the lowdegradation rate constant of sedimentary terrOC, likely caused by a combination of factors: (i) the loweravailability of oxygen in the sediments compared to fully oxygenated waters, (ii) the stabilizing role ofterrOC-mineral associations, and (iii) the higher proportion of material that is intrinsically recalcitrant dueto its chemical/molecular structure in sediments. Sequestration of permafrost-released terrOC in shelfsediments may thereby attenuate the otherwise expected permafrost carbon-climate feedback. |
| Language: | English |
| Published: |
2019
|
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1029/2018GB005967 |
| Format: | Electronic Book Chapter |
| KOHA link: | https://koha.lib.tpu.ru/cgi-bin/koha/opac-detail.pl?biblionumber=660442 |