Old permafrost carbon dumps just offshore
Eroding Arctic coasts drop ancient organic carbon into a 100–300 m nearshore strip, while farther surface waters carry younger carbon.
Source
Nearshore Zone Dynamics Determine Pathway of Organic Carbon From Eroding Permafrost Coasts
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.
What they did
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.
What they found
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.
The limits
What it doesn't show
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.
Key terms
- Resuspension zone
- A high-energy nearshore strip where waves keep sand moving and old, mineral-bound POC is concentrated.
- Δ14C
- Radiocarbon depletion; large negative values mean millennia-old permafrost carbon.
- Retrogressive thaw slump (RTS)
- A rapidly retreating permafrost coast landform delivering ice-rich, OC-rich sediment to the sea.
Flashcards
Research intelligence for this paper
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Quiz yourself
Resuspension-zone POC radiocarbon age is about:
Common questions
Does eroded permafrost carbon all become greenhouse gas immediately?
Not necessarily: old POC appears to settle quickly nearshore, which can bury carbon if it stays put.
Why is offshore surface water younger?
It mixes marine production and modern terrestrial debris, unlike the old resuspension-zone plume.
How fast is this coast eroding?
Mean 0.45 m yr−1 (1970–2000) rising to 0.68 m yr−1 (2000–2011); some RTS headwalls 22 m yr−1.
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