Tracing Pan‐Canadian Arctic Water Masses and Dissolved Inorganic Carbon Cycling Using Stable and Radiocarbon Isotopes
Bibliographic record
Abstract
Abstract The Canadian Arctic is warming four times faster than the global average, yet the impact of this perturbation on the marine carbon cycle remains unknown. Dissolved inorganic carbon (DIC) stable isotope (δ13C) and radiocarbon (Δ14C) values are powerful tools for tracing water mass transport, residence times and carbon cycling. While the hydrography of the Canadian Arctic Archipelago (CAA) is well documented, few DIC δ13C and Δ14C values exist for the region. Here, we present new DIC δ13C and Δ14C depth profiles from 19 stations across the CAA sampled in 2021 and place them into the context of five recently published Baffin Bay values. CAA DIC δ13C and Δ14C values ranged from −0.68‰ to +1.86‰, and −90.7 to +49.5‰, respectively. Several negative DIC Δ14C values (−44.7‰ and −51.9‰) were observed near the Mackenzie River, indicating riverine permafrost carbon is actively incorporated into the nearshore DIC pool. “Bomb” DIC Δ14C values in the Kitikmeot Sea were attributed to enhanced tidal mixing and heterotrophy together with high regional water mass residence times. A comparison of historical DIC Δ14C depth profiles from 2009 to 2021 reveals significant dilution of “bomb” 14C and minor contributions (2.1%–4.4%) of fossil anthropogenic CO2 within Pacific Summer Water (PSW), Pacific Winter Water (PWW) and Atlantic Fram Strait Water (ATLFS) in the Beaufort Sea. Finally, the contrast between deep Beaufort Sea and Baffin Bay DIC δ13C and Δ14C values reveal differences in residence time and carbon sources in the two regions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".