Evolution of West‐East Contrast in the Subarctic Pacific Gyre During the Plio‐Pleistocene Based on Palynological Evidence at ODP Sites 882 and 887
Bibliographic record
Abstract
Abstract Fragmentary and contradictory evidence prevents a clear understanding of the possible role of the North Pacific Ocean surface on the ice‐sheet evolution. New palynological data encompassing the Pliocene and Pleistocene at Ocean Drilling Program Site 882 in the northwest Pacific document sea‐surface conditions from dinoflagellate cysts in addition to atmospheric trajectories from pollen grains and spores. The comparison of the Site 882 record with that of Site 887 from the northeast Pacific also permits documenting West to East contrasts across the subarctic North Pacific. The dinocyst assemblages at the two sites indicate strong temperature contrasts until 4.2 Ma, with much warmer conditions in the East. From 4.2 to 3.6 Ma, dinocyst assemblages of both sites are characterized by alternated dominance of the extinct taxa Habibacysta tectata and Impagidinium detroitense suggesting homogenous and cool conditions across the subarctic Pacific gyre. A major transition is recorded in the palynological assemblages at Site 882 around 2.7 Ma. It is marked by the highest occurrence of Habibacysta tectata and high percentages of Filisphaera microornata additionally to thermophilic taxa. Dinocyst record indicates high seasonality and warmer surface conditions due to reinforced stratification, which support the hypothesis of high evaporation at the origin of atmospheric moisture supply to high latitudes. During the last 1.2 Ma, the increase of Operculodinium centrocarpum relative to Nematosphaeropsis labyrinthus is tentatively interpreted as a reinforced influence of the subtropical waters. Hence, we suggest that the warm surface ocean fostered the inception and growth of northwestern North American ice‐sheets during the Pliocene and Pleistocene.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".