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Nearshore Zone Dynamics Determine Pathway of Organic Carbon From Eroding Permafrost Coasts
Author(s) -
Jong Dirk,
Bröder Lisa,
Tanski George,
Fritz Michael,
Lantuit Hugues,
Tesi Tommaso,
Haghipour Negar,
Eglinton Timothy I.,
Vonk Jorien E.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088561
Subject(s) - permafrost , total organic carbon , arctic , oceanography , environmental science , submarine pipeline , sediment , thermokarst , geology , radiocarbon dating , settling , hydrology (agriculture) , environmental chemistry , geomorphology , environmental engineering , paleontology , geotechnical engineering , chemistry
Collapse of permafrost coasts delivers large quantities of particulate organic carbon (POC) to Arctic coastal areas. With rapidly changing environmental conditions, sediment and organic carbon (OC) mobilization and transport pathways are also changing. Here, we assess the sources and sinks of POC in the highly dynamic nearshore zone of Herschel Island‐Qikiqtaruk (Yukon, Canada). Our results show that POC concentrations sharply decrease, from 15.9 to 0.3 mg L −1 , within the first 100–300 m offshore. Simultaneously, radiocarbon ages of POC drop from 16,400 to 3,600 14 C years, indicating rapid settling of old permafrost POC to underlying sediments. This suggests that permafrost OC is, apart from a very narrow resuspension zone (<5 m water depth), predominantly deposited in nearshore sediments. While long‐term storage of permafrost OC in marine sediments potentially limits biodegradation and its subsequent release as greenhouse gas, resuspension of fine‐grained, OC‐rich sediments in the nearshore zone potentially enhances OC turnover.