Aged permafrost carbon surged in Arctic rivers in 2018
June 2018 Mackenzie basin rivers exported previously modern-looking DOC that was suddenly centuries old, with a nitrate spike, then modern again in 2019.
Source
An Abrupt Aging of Dissolved Organic Carbon in Large Arctic Rivers
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.
What they did
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.
What they found
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.
The limits
What it doesn't show
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.
Key terms
- DOC
- Dissolved organic carbon passing ~0.22 μm filters.
- F14C
- Fraction modern radiocarbon; values <<1 mean aged carbon.
- Talik
- Unfrozen ground in permafrost that can route deeper water.
- Spring freshet
- High discharge just after ice breakup.
- Active layer
- Seasonally thawing soil above permafrost.
Flashcards
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Quiz yourself
2018 Mackenzie-network mean DOC F14C:
Common questions
What changed in June 2018?
DOC became aged across three catchments, with higher nitrate.
Did it last into 2019?
June 2019 F14C looked modern again.
Was discharge wildly unusual?
Not enough to explain F14C; similar hydrograph stage.
Proposed pathway?
Deeper groundwater and supra-permafrost taliks tapping frozen soils.
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