Resolving orbital-scale cyclicity in Newfoundland Ridge sediments across the Middle Eocene Climatic Optimum
Bibliographic record
Abstract
The Middle Eocene Climatic Optimum (MECO) was a 500-kyr long thermal event around 40 Ma, which is superimposed on the Eocene cooling trend. Studying the MECO is of interest because it is fundamentally different than the famous and more extensively studied Paleocene Eocene Thermal Maximum (PETM). The duration of the MECO event was longer than the PETM event, which makes the MECO event perfect for assessing biotic response to astronomical cyclicity during a thermal event. The aim of this research is to identify the biotic response to astronomical cyclicity and if this response is the same before as during the MECO. Additionally, it will be assessed if atmospheric CO2 levels rose during the MECO with the use of stable carbon isotopes. Ocean sediments from the Newfoundland Ridge recovered by the International Ocean Discovery Program (IODP) Expedition 342 were deposited at high sedimentation rates and contain large amount of dinoflagellate cysts. The high sedimentation rate makes dinoflagellate cyst assemblage analysis on high resolution possible. Sediment samples were taken, based on cyclic patterns indicated by differences in sediment colour from three different intervals of the MECO. These intervals were the pre-MECO, the MECO-ramp, which is the gradual warming phase of the MECO, and the peak-MECO. Regression analysis on the dinoflagellate cysts assemblages shows that there are relationships between the assemblages and astronomical forcing, and that these relationships change over time. The middle Eocene ecosystem is forced by obliquity through the strength of the Deep Western Boundary Current (DWBC). The dinoflagellate cyst assemblages show an increase in temperature, decrease in nutrient availability, decrease in terrestrial input, increase in salinity and sea level rise throughout the MECO event. Isotope data show a constant level of fractionation difference, suggesting that the atmospheric CO2 concentration did not rise during the MECO, which is contradictory to the results of Bijl et al. (2010). A potential explanation for the difference between the results of this study and the study of Bijl et al. (2010) is polar amplification.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| 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 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".