The impact of insolation, greenhouse gas forcing and ocean circulation changes on glacial inception
Bibliographic record
Abstract
In this study we employ the NCAR CCSM3 coupled model to investigate the onset of high northern latitude perennial snow cover. Two periods of Earth’s insolation history, that of the pre-industrial period and that of 116 ka before present (BP), are used as benchmarks in an investigation of the influences of interglacial greenhouse gas (GHG) concentration and insolation upon the occurrence of permanent summer snow cover. An additional two experiments at 10 ka and 51 ka into the future (AP) using a typical interglacial GHG level are used to investigate the length of the current interglacial. Results from this set of multicentury sensitivity experiments demonstrate the relative importance of forcings due to insolation and atmospheric greenhouse gases at the millennial scale, and of Atlantic ocean overturning strength (AMOC) at the century scale. We find that while areas of perennial snow cover are sensitive to GHG concentrations, they are much more sensitive to the contemporaneous insolation regime. The goodness of fit of the climatology of the control model to the modern observed climatology is found to influence the modeling results. While there is a strong correlation between AMOC decadal variability and high latitude surface temperature in our control climates, we find little change in AMOC strength during our simulations of 116 ka BP climate nor do we find significant correlation between high latitude snow accumulation and the AMOC. Both the 10 ka AP and 51 ka AP future simulations produce inception events which are much stronger than that of the equivalent pre-industrial simulation. The simulation of inception at 10 ka into the future suggests a maximum duration of the current interglacial of approximately 20 ka in the absence of modern anthropogenic forcing.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".