Upper Ocean Instability in the Subpolar North Atlantic and Its Implications for Deep Water Formation During Interglacials
Bibliographic record
Abstract
Abstract In this multiproxy study, we used new isotopic data on planktonic foraminifera to highlight the strong instability that characterized surface conditions in the Iceland Basin during Marine Isotope Stage 11 (MIS 11). We produced new oxygen isotope data on the planktonic species Neogloboquadrina incompta and Turborotalita quinqueloba, foraminifera‐bound nitrogen isotope data on N. incompta, and calcareous nannofossil data at coring site IODP Site U1314. The multiproxy record displays two distinct upper ocean regimes: a relatively stable pre‐climate optimum and an unstable post‐climate optimum with high amplitude variations in nutrient utilization and seasonality proxies, and strong enrichment in oxygen isotopes suggesting colder and/or saltier upper waters. The latter regime was concomitant with a resurgence in ice‐rafted debris. Interestingly, this surface instability is not observed in cores from sites affected by the North Atlantic Current. Moreover, deep water ventilation is reconstructed to decrease throughout the eastern North Atlantic, while remaining rather constant in the Labrador Sea. The evidence presented here indicates that deep‐water formation was unstable throughout MIS 11, and that peak periods of deep‐water formation varied across high latitude North Atlantic basins, depending on the prevailing surface conditions in each region. These findings suggest that reconstructing deep‐water formation and ventilation require a comprehensive approach that accounts for the interconnectivity between different components of the overturning circulation system.
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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".