A first step towards a complete Southern Ocean proxy compilation for the Last Glacial Cycle: glacial-interglacial changes in Sea Surface Temperature
Bibliographic record
Abstract
Previous research has suggested that different processes in the Southern Ocean contributed to the drawdown and release of atmospheric carbon dioxide (CO2) during the last glacial cycle (0–130 ka), yet their dynamics and interplay are not fully understood. To unravel the interactions between different processes and to allow for more comprehensive analyses, we aim to compile all previously published proxy data and convert them into the Linked open Paleo Data (LiPD) format, overall increasing interoperability, reusability and impact.The PAGES C-SIDE working group recently highlighted substantial open-ocean sea-ice extent changes during the mid-glacial period (Marine Isotope Stage 4, ~72 to 60 ka), coinciding with a significant drop in atmospheric CO2. However, sea-ice changes are notably absent during the early glaciation (Marine Isotope Stage 5d, ~115 to 105 ka), suggesting they cannot account for the early CO2 decrease (Chadwick et al., 2022).As an initial step, we present our compilation of sea surface temperature (SST) reconstructions from marine sediment records across the Southern Ocean (Latitude > 30°S) for the last glacial cycle. This compilation assesses SST changes in different zones and basins, evaluates SST gradients, and explores the interplay between SST and sea ice.Our findings reveal a consistent glacial-interglacial amplitude of 5-10°C across all basins and zones, with uniform timing. SST gradients from the Antarctic to Subantarctic Zone remain unchanged over time, eliminating them as a mechanism for early CO2 decrease. Additionally, we observe that 50% of the total MIS 5e-to-LGM cooling in Southern Ocean SST occurred from MIS 5e to MIS 5d, with a second drop from MIS 5a to MIS 4, essentially reaching LGM cooling. A distinct decoupling of SST cooling and sea ice expansion over MIS 5 suggests that circulation and/or subsurface temperatures may exert a stronger influence than SST on sea ice extent. This emphasizes the necessity for additional proxy compilations to further disentangle these complex relationships.
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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 | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.005 | 0.008 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.003 |
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".