New insights of the Heinrich events inferred by speleothems from Northeast Brazil
Bibliographic record
Abstract
Heinrich events (HEs), characterized by massive and rapid ice-rafted debris from Laurentide Ice Sheet into the Labrador Sea as far south as the Iberian Margin, are observed in some stadial periods during the last glacial, however, it is still unclear regarding to the trigger and response mechanism of the HEs. A landmark work by Wang et al. (2004) was one of the first studies to associate tropical rainfall in southern Hemisphere with HEs, showing wet periods in tropical northeastern Brazil, a region that is currently semi-arid but very sensitive to the hydroclimate changes related to the cold events occurred in the northern Hemisphere, are synchronous with HEs in the North Atlantic. After two decades, we have a new chance to study the relationship between hydroclimate in NE Brazil and cold events in the North Atlantic in the light of much more new speleothem records obtained from TBV and TBR caves, NE Brazil. Here we show evidence of stalagmite growth periods and δ18O records during the last 90 kyrs from NE Brazil, in addition to the HEs observed by Wang et al. (2004), we have newly found wet periods during the HE2 and HE3 and GS 5-8 that were not discovered before. It indicates that previous conclusions that the orbital insolation also modulated these events on millennial timescales need to be reinterpreted, and also provides new insights to understand the mechanisms of the HEs and why the HEs only occurred in some Heinrich Stadials. Additionally, we also compare detailed structures of each HE inferred from cave δ18O records in NE Brazil with sea surface temperature and other records in the Atlantic realm, which deepens our understanding of the trigger-response mechanisms of the HEs and its effect on the hydroclimate in the NE Brazil.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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".