Ocean changes in the North Atlantic over the Late Holocene: \nA multi-proxy approach
Bibliographic record
Abstract
In today's North Atlantic, warm and salty surface waters are transported northwards from the subtropics, releasing their heat and eventually sinking to form a deep southward-flowing water mass. This process in the meridional-vertical plane is termed the Atlantic Meridional Overturning Circulation (AMOC). Changes in the strength and structure of the AMOC play a critical role in the Earth’s climate system and have been thought to be implicated in the climate variability of the Late Holocene. \nIn this thesis, two sediment cores RAPiD-35-25B and RAPiD-17-5P recovered from the Eirik Drift (South of Greenland) and the Iceland Basin are used to produce Late Holocene palaeoceanographic reconstructions of some of the main constituents of the AMOC at sub-decadal to multidecadal resolution. \nUpper water column reconstructions from the Eastern Labrador Sea based on multi-species planktonic foraminiferal δ18O, Mg/Ca and faunal assemblages indicate millennial to centennial variability in the influence of polar waters reaching the Labrador Sea which likely led to reductions in deep water convection in the Labrador Sea. Inferred shifts of Labrador Sea Water formation appear concomitant with climatic anomalies recorded in the North Atlantic region. It is suggested that these climatic oscillations may have resulted from a coupled ocean-atmosphere response to reductions in solar irradiance. \nThe paired δ18O and Mg/Ca composition of the thermocline-dweller G. inflata, shows multi-centennial shifts in the temperature and salinity of the North Atlantic Current during the last millennium with a potential link to solar forcing. The recorded hydrographic variability is explained in terms of the effects of atmospheric blocking events on subpolar gyre dynamics. \nSortable silt mean grain size measurements show millennial-scale trends towards slower and faster vigour of the overflows east and west of Iceland during the Late Holocene. Potential upstream and downstream mechanisms are investigated and it is concluded that the millennial-scale variability in the strength of the overflow likely resulted from insolation driven Neoglacial changes in the freshwater budget and atmospheric circulation in the Nordic Seas. Furthermore, an antiphasing relationship between the strength of the two overflows is found, supporting previous predictions from modelling studies.
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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 | 0.004 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.004 | 0.001 |
| Research integrity | 0.001 | 0.005 |
| 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".