Impact of Medieval Climate Anomaly and Little Ice Age on the Labrador Current flow speed and the AMOC reconstructed by the sediment dynamics and biomarker proxies
Bibliographic record
Abstract
It is widely accepted that the changes in freshwater transport into the Labrador Sea occurred during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), which were instrumental in modifying the climate surrounding the North Atlantic. However, the extent to which paleo proxies accurately reflect freshwater transport is poorly known due simply to lack of data. This study provides the first direct proxy record of freshwater supply by the sediment dynamics sortable silt proxy for the past 1.45 ka. A sediment core MO2009061–0217 (46.387°N, 46.742°W) retrieved off the SE Grand Banks along the flow path of the Labrador Current was used to determine the sortable silt and extract lipid biomarkers. The sortable silt data were converted to current speed (cm/s), which suggests that the Labrador Current was weak during the MCA and most vigorous during the LIA. One concurrent water column temperature proxy, namely TEX86 based on glycerol dialkyl glycerol tetraethers (GDGTs), shows that the outer Labrador Current water was cooler during the LIA than the MCA. In contrast, the converse temperature changes were recorded along the inner Labrador Current, where temperature change was slight. Our data are placed with a few high-resolution (i.e., multi-decadal) published temperature data to reflect broader changes in the subpolar northwestern Atlantic. The temperature variations on the SE Grand Banks are analogous to those between northern Iceland and Greenland shelves over this period and reflect changes in the subpolar gyre geometry of the North Atlantic. We hypothesize that the heterogenous temperatures coupled to changes in the Labrador Current flow speed were modulated by subpolar ocean currents on the SE Grand Banks.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".