Étude multi-traceurs de la productivité primaire et du paléoclimat dans le nord de la baie de Baffin
Bibliographic record
Abstract
RÉSUMÉ: Cette étude lie les changements de la productivité primaire et les conditions marines de surface dans le nord de la baie de Baffin depuis 1560 AD à partir d'une carotte de sédiments récoltée à l'été 2008. Des reconstitutions quantitatives des conditions marines de surface, dérivées d'assemblages de kystes de dinoflagellés et de fonctions de transfert utilisant la technique des analogues modernes (MAT), ont été combinées à la composition isotopique du carbone et de l'azote et à l'analyse des biomarqueurs organiques. Plus particulièrement, IP25 (Ice Proxy avec 25 atomes de carbone) et les dinostérols ont été analysés. IP25 est un isoprénoïde hautement ramifié (higly branched isoprenoïd, ou HBI) apparemment produit par une diatomée vivant dans la glace de mer, genre Haslea, alors que le dinostérol est un stérol principalement produit par des dinoflagellés. Nos résultats montrent un climat relativement stable, avec deux intervalles de productivité primaire maximale et un léger réchauffement depuis 1560 AD. Par ailleurs, nos reconstitutions quantitatives des conditions marines de surface utilisant la MAT suggèrent que le biomarqueur IP25 est plus utile pour évaluer la productivité primaire que la concentration de glace de mer dans un environnement de glace de mer relativement stable. Finalement, notre étude montre un écosystème dominé par les diatomées en interaction avec la glace de mer, où le couvert de glace semble être le principal facteur limitant la productivité primaire depuis 1560 AD. -- Mots clés: productivité primaire, baie de Baffin, dinoflagellés, reconstitutions, biomarqueurs, IP25, dinostérol, diatomées, composition isotopique. --ABSTRACT: This study links the evolution of primary productivity and sea-surface conditions in northern Baffin Bay since 1560 AD from a sediment core collected in the summer of 2008. Quantitative reconstructions of sea-surface conditions derived from dinoflagellate cyst assemblages and transfer functions using the Modern Analogue Technique (MAT) were combined with the stable isotope composition of organic carbon and nitrogen and the concentration of organic biomarkers (IP25 , lce Proxy with a 25 carbon atom skeleton and dinosterol) in bulk sediment. IP25 is a highly branched isoprenoid (HBI) produced in the Arctic Ocean by the sea-ice diatom Haslea ostrearia, whereas dinosterol is a sterol produced mainly by dinoflagellates. Our results show a relatively stable climate with two intervals of maximum primary productivity and a slight warming since 1560 AD. Moreover, comparison between quantitative reconstitutions of sea-surface conditions using MAT and organic biomarkers results indicate that IP25 could be more useful in evaluating the primary productivity in a sea-ice environment (e.g. stable ice-edge conditions) th an the fluctuations of the sea-ice coyer. Finally, the region shows an ecosystem dominated by diatoms in close interaction with the sea-ice, in which temperature seems to be the main factor controlling primary productivity since 1560 AD. -- Keywords: Baffin Bay, Arctic, quantitative reconstruction, dinoflagellate, isotopic composition, transfer function, biomarkers, dinosterol, IP25.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".