Predominant orbital forcing on Asian hydroclimate during the Miocene Climatic Optimum
Bibliographic record
Abstract
Abstract The Miocene Climatic Optimum (MCO), spanning from ca. 17 Ma to 14 Ma, marks a pivotal interval in global climate history with elevated greenhouse gas levels and a 3–7 °C increase in global temperatures, disrupting the long-standing Cenozoic cooling trend. However, the dynamics that drove the MCO in the continental realm are not well understood. The driving forces may have conditioned regional scale climate phenomena, such as shifts from an arid to humid environment with a significant temperature rise due to elevated greenhouse gases. Terrestrial outcrops in eastern Asia are particularly valuable for studying the MCO's continental impacts due to their exceptional preservation of orbital-scale sedimentary cycles and sensitivity to monsoonal dynamics, which are pivotal for disentangling hydroclimate-orbital linkages. Notably, the hydrological circulation and orbital influence during the MCO in eastern Asia are still understudied. Employing magneto-cyclostratigraphic chronology, we analyzed samples from a 120-m-thick outcrop section in inland Asia, revealing detailed, orbital-scale, terrestrial responses to the MCO. Based on cyclostratigraphic analysis, our findings emphasize the pronounced influence of two orbital cycles: the dominant 405-k.y. eccentricity and the subtler 173-k.y obliquity band. Based on the magnetic susceptibility, Fe content, and Rb/Sr ratio of rock samples, we concluded that eccentricity and obliquity climate control shifted the summer movement of the Intertropical Convergence Zone in East Asia, impacting northward moisture transport. Significantly, we identified six drought events based on variations in magnetic susceptibility, geochemical proxies (i.e., Fe content and Rb/Sr ratio), and correlation with global phenomena, such as distinct δ13C positive excursions (such as the Monterey Excursion), Antarctic cooling phases (Mi-events), global sea surface temperature changes, and sea-level fluctuations. Our results provide insights into climate variations on both regional and global scales, with implications for past and potential future scenarios.
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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".