Permafrost
Aged permafrost carbon surged in Arctic rivers in 2018
Open access · cc by · source: Europe PMC
June 2018 Mackenzie basin rivers exported previously modern-looking DOC that was suddenly centuries old, with a nitrate spike, then modern again in 2019.
Study at a glance
- Design
- Other — Spring-freshet DOC Δ14C sampling in Mackenzie basin rivers vs ArcticGRO record
- N
- N=28 · June 2018 mean DOC-F14C from n=28 samples (2017 comparison n=22)
- Population
- Mackenzie, Peel, and Arctic Red river DOC during spring freshets 2017–2019
- Outcome
- Abrupt aging of exported DOC and nitrate spike in June 2018
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
2003–2017 DOC was modern (F14C ≈ 1.00). In June 2018 mean F14C fell to 0.85 (about 1,300 14C years), as low as 0.51 in northern tributaries, with a two- to threefold nitrate increase, consistent with supra-permafrost talik flow. 2019 returned to F14C ≈ 0.99.
Methodology
Authors measured DOC Δ14C, concentrations, and major ions in the Mackenzie, Peel, and Arctic Red during 2017–2019 spring freshets and compared them with ArcticGRO samples back to 2003.
Limitations
Snapshot sampling cannot time the event’s duration or Arctic-wide carbon feedback; 2018/19 June discharges were the lowest in the set, though still not hydrograph outliers versus F14C.
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.
June 2018 Mackenzie basin rivers exported previously modern-looking DOC that was suddenly centuries old, with a nitrate spike, then modern again in 2019.
Evidence for the claim as stated.
Mackenzie, Peel and Arctic Red DOC was modern from 2003–2017 (F¹⁴C ≈ 1.00). In June 2018 mean F¹⁴C fell to 0.85 (about 1,300 ¹⁴C years), as low as 0.51 in northern tributaries, with a two- to threefold nitrate increase, consistent with supra-permafrost talik flow. June 2019 returned to F¹⁴C ≈ 0.99. Snapshot sampling cannot time the event’s duration or an Arctic-wide carbon feedback; 2018/19 June discharges were the lowest in the set but not hydrograph outliers versus F¹⁴C.
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.
- Supports · Old permafrost carbon dumps just offshore
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.
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