Permafrost
Old permafrost carbon dumps just offshore
Open access · cc by · source: Europe PMC
Eroding Arctic coasts drop ancient organic carbon into a 100–300 m nearshore strip, while farther surface waters carry younger carbon.
Study at a glance
- Design
- Cross-sectional — July–August 2017 transect sampling of POC isotopes from thaw streams to ~2 km offshore
- N
- N=49 · 49 Herschel Island–Qikiqtaruk sampling sites
- Population
- Nearshore waters and thaw streams along an eroding Yukon Arctic coast
- Outcome
- Age and pathway of eroded permafrost organic carbon in resuspension vs deposition zones
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Thaw-stream POC averages 2200 mg L−1 and Δ14C −803‰ (8,300–25,000 14C years). Resuspension-zone surface POC is similarly old (mean Δ14C −867‰; 16,400 14C years) and turbid (mean 4.8 mg L−1) versus deposition-zone surface POC <1 mg L−1 and younger. The turbid zone is 100–300 m offshore (5–6 m depth). Nearshore sediment OC is >90% terrestrial.
Methodology
In July–August 2017 the authors sampled 49 Herschel Island–Qikiqtaruk sites (thaw streams to ~2 km offshore), measuring POC, sediment OC, δ13C, C/N, and Δ14C, plus salinity/temperature transects.
Limitations
A two-week campaign at one island cannot quantify pan-Arctic burial efficiency. Waves later resuspend the sink. Mineral association is inferred from OC–surface-area correlations (R2 = 0.75), not incubation fluxes of CO2/CH4.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
This library holds 5 empirical papers on permafrost with measured outcomes rather than reviews.
Evidence for the claim as stated.
Eroding Arctic coasts drop ancient organic carbon into a 100–300 m nearshore strip, while farther surface waters carry younger carbon.
Evidence for the claim as stated.
At 49 Herschel Island–Qikiqtaruk sites (July–August 2017), thaw-stream POC averaged 2,200 mg L⁻¹ and Δ¹⁴C −803‰ (8,300–25,000 ¹⁴C years). Resuspension-zone surface POC a few hundred metres offshore is similarly old (mean Δ¹⁴C −867‰; 16,400 ¹⁴C years) and turbid (mean 4.8 mg L⁻¹), versus deposition-zone surface POC <1 mg L⁻¹ and younger. The turbid strip is 100–300 m offshore (5–6 m depth). Nearshore sediment OC is >90% terrestrial. Mineral association is inferred from OC–surface-area correlations (R² = 0.75), not incubation fluxes of CO₂/CH₄.
Evidence for the claim as stated.
Old ¹⁴C on the Beaufort Sea coast and aged DOC in the Mackenzie basin are not the same carbon pathway. Herschel thaw-stream and resuspension-zone POC is millennial (8,300–25,000 ¹⁴C years; mean resuspension Δ¹⁴C −867‰) and appears to settle 100–300 m offshore. Mackenzie DOC was modern for 15 years, then ~1,300 ¹⁴C years for one June, then modern again. One record is a nearshore particulate dump; the other is a dissolved pulse that reversed. Neither is a pan-Arctic CO₂ flux.
Evidence for the claim as stated.
¹⁴C years and COPRA speleothem years are different clocks. The permafrost papers report uncalibrated ¹⁴C ages and F¹⁴C/Δ¹⁴C on organic carbon. The Maya paper ensembles age models of cave calcite to date a rainfall-seasonality collapse. Treating τpred < significance in 800–1000 CE as a radiocarbon date of Classic Maya drought is a category error, even though the index lists the paper under this method.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Old ¹⁴C on the Beaufort Sea coast and aged DOC in the Mackenzie basin are not the same carbon pathway. Herschel thaw-stream and resuspension-zone POC is millennial (8,300–25,000 ¹⁴C years; mean resuspension Δ¹⁴C −867‰) and appears to settle 100–300 m offshore. Mackenzie DOC was modern for 15 years, then ~1,300 ¹⁴C years for one June, then modern again. One record is a nearshore particulate dump; the other is a dissolved pulse that reversed. Neither is a pan-Arctic CO₂ flux.
¹⁴C years and COPRA speleothem years are different clocks. The permafrost papers report uncalibrated ¹⁴C ages and F¹⁴C/Δ¹⁴C on organic carbon. The Maya paper ensembles age models of cave calcite to date a rainfall-seasonality collapse. Treating τpred < significance in 800–1000 CE as a radiocarbon date of Classic Maya drought is a category error, even though the index lists the paper under this method.
Related papers in this topic
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