Holocene oceanographic variability in the Subtropical Northeast Atlantic
Bibliographic record
Abstract
• Early Holocene featured weak stratification and possibly year-round upwelling. • Subsurface warming peaked and upwelling weakened during the Middle Holocene. • Late Holocene marked by SST cooling, weaker NASTG, and seasonal upwelling. • Proxies suggest changes in NEABW composition and corrosivity during the Holocene. • Precession and remote forcings shaped complex monsoon–gyre–upwelling interactions. Cabo Verde hosts unique, highly biodiverse marine ecosystems that thrive on volcanic seamounts and island slopes. These ecosystems are shaped by distinct oceanographic dynamics, influenced by the southeastern edge of the North Atlantic Subtropical Gyre (NASTG) and by seasonal upwelling. To explore regional oceanographic variability over time, this study investigates Holocene (last 11.7 ka) sediments using multi-proxy palaeoenvironmental reconstructions from a short core retrieved from ∼ 4,400 m water depth off Cabo Verde. During the Early Holocene, year-round upwelling, or an intensified Guinea Dome, may have inhibited the development of the strong summer stratification characteristic of the modern regional non-upwelling season. Despite humid conditions over the continent, sea surface temperatures (SSTs) remained relatively low during this subepoch, diverging from the present-day pattern in Northwest Africa, where the wet season is marked by weaker upwelling and higher SSTs. This oceanographic state was likely driven by precession-induced insolation changes associated with the precession minimum, which may have modified seasonal regional wind regimes and influenced broader atmospheric processes. Teleconnections related to transitional postglacial conditions and/or continental climate feedbacks, may also have played a role. The Middle Holocene, corresponding to the most humid conditions of this epoch in Northwest Africa, is characterized by reduced upwelling and an eastward expansion of the NASTG, inferred from warmer subsurface conditions at our study site. This interval also provides tentative evidence for enhanced input of North Atlantic Deep Water (NADW) into the Northeast Atlantic Bottom Water (NEABW). During the Late Holocene, intensified upwelling and a reduced influence of the NASTG, possibly due to a westward retraction of its eastern boundary, are suggested at our site, occurring under arid conditions in Northwest Africa. These results highlight that, despite the overall climatic stability of the Holocene, oceanographic conditions off Cabo Verde experienced significant changes in seasonal upper ocean stratification, upwelling, subtropical gyre influence, and deep-water structure. Such insights improve our understanding of regional climate-ocean interactions, helping to refine climate models and improve predictions of ecosystem responses in this sensitive marine region.
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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 | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".