Coccolithophore assemblage composition during the Greenland Interstadial–Stadial 20 transition and their response to the Youngest Toba Tuff (YTT) supereruption ∼74,000 years ago in the northeastern Arabian Sea
Bibliographic record
Abstract
Here we present a new 850-year long coccolithophore record from core SO130-289KL in the northeastern Arabian Sea that spans the Greenland Interstadial 20-Greenland Stadial 20 transition including the timing of the ∼74 ka Youngest Toba Tuff (YTT) supereruption. During the warm interstadial, the coccolithophore assemblage is characterized by Gephyrocapsa oceanica (41%) and Florisphaera profunda (30%) while the succeeding cold stadial is distinguished by the abundance of small placolith species (Emiliania huxleyi + G. ericsonii) (52%). However, the oldest samples of the study interval seem to show a stadial-like coccolithophore assemblage. Spectral analysis revealed an interdecadal cycle imprinted in the coccolithophore record during the interstadial that was also independently reported in other terrestrial and marine proxies. Immediately after the YTT eruption, small placoliths increased by 42% from 5% right below the YTT layer to 47% ∼1 mm above the YTT layer, while G. oceanica and Helicosphaera carteri increased and F. profunda decreased within the ∼1.15 cm layer representing about 8-19 years. Subsequently, the coccolithophore assemblage returned to a composition similar to the warm interstadial period before abruptly changing to a stadial composition characterized by the abundance of small placoliths about 100-130 years after the YTT eruption. Therefore, the YTT eruption had a significant impact on the overall coccolithophore assemblage but appears to have not caused the climate transition from interstadial to stadial conditions, supporting proxy and modeling data. However, the overall mechanism driving the observed changes and cyclicities remains unknown but might be related to rapid atmospheric teleconnections of North Atlantic climate variability to the low latitudes.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".