History of Cordilleran Ice Sheet activity recorded in core MD02-2496: Vancouver Island, British Columbia.
Bibliographic record
Abstract
MD02-2496, a marine core from the continental slope off Vancouver Island, contains detailed late Quaternary Cordilleran Ice Sheet records. Multi-proxy data establish depositional patterns related to glacial phases while stable isotopes allow correlation between Cordilleran Ice Sheet activity and global climatic change. Magnetic susceptibility, color reflectance, and mass accumulation rates (MAR) of lithogenic sediment document the initiation of glaciomarine sedimentation (Fraser Glaciation) at ∼30 Ka. Reduced magnetic susceptibility validates a brief ice retreat ∼23 Ka (19.2 14 C kyrs BP, Port Moody). MARS, grainsize, and cyclic sedimentation suggest the ice margin became proximal to the shelf edge at ∼19 Ka. Spectral analysis of the interval 19 to 17 Ka suggests either lunar or solar forcing of ice sheet instability. Catastrophic ice sheet retreat is indicated by the gradual onset and abrupt cessation of ice rafted detritus deposition (IRD, >250mum grains g -1 ), between ∼17 Ka and ∼16.2 Ka. Another IRD pulse identifies a second ice sheet retreat at ∼14.6 Ka. Glacial advance (the Sumas Events), between ∼12.8 and 11.5 Ka, is indicated by increased abundance of medium-coarse silts, sands, with high magnetic susceptibility and poor sorting. Based on the sediment characteristics of this sequence of events, an older ice sheet advance with associated catastrophic retreat has been identified. Submillennial climate variability is revealed by the planktonic delta 18 O record. Between stadial and interstadial conditions, sea surface temperatures (SSTs) ranged between 1.5 to 3°C. Interstadial SSTs (7 to 9°C) off southern British Columbia were ∼2.5°C cooler than those off Southern California, while stadial SSTs (∼5 to 6.5°C) were similar between the regions. Increased western North American margin SST gradients during interstadials may have strengthened the North Pacific High and related northerly winds associated with upwelling. Environmental conditions during interstadials were similar to warm Pacific Decadal and negative North Pacific America Oscillations. The MD02-2496 planktonic delta 18 O record decoupled from other Pacific SST records between 28.5 and ∼15 Ka. This anomalous negative regional delta 18 Owater indicates either freshening of local surface waters, or a precipitation shift from predominantly rain to snow. Evidence for freezing air temperatures could explain the absence of ice sheet response to submillennial climate change.
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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 | 0.002 | 0.004 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".