Evidence for Arctic paleothermokarst and melt features controlled by sea-level rise in regional sub-bottom profile data
Bibliographic record
Abstract
Permafrost extends offshore in the Arctic as submarine permafrost. Near the edge of stable, continuous permafrost offshore, fresh groundwater flux contributes to regions of actively deforming thermokarst. Large-magnitude (up to ~30 m) sinkholes have been observed to form over less than a decade, posing a significant threat to offshore infrastructure. Additionally, having recently been discovered in sub-Arctic environments, thermokarst formation may be possible in a wider range of conditions than previously thought. It is critical to understand the evolution of degrading submarine permafrost, thermokarst, and the critical parameters necessary to predict the locations and magnitudes of seabed impacts.We present acoustic sub-bottom profile (3.5 kHz Chirp) data collected in the Canadian Beaufort Sea, highlighting observations just offshore of a well-studied, actively deforming thermokarst field near the shelf edge. We map a seismic horizon that marks the top of ice-bearing sediment in the active thermokarst region; seaward, this horizon becomes a choppy unconformity punctuated by low-amplitude reflections that we interpret as fluid escape pathways. Beneath this horizon, an acoustically transparent layer persists seaward until characteristically and abruptly gaining coherent layering. We map the seaward edge of the acoustically transparent layer and interpret it as paleothermokarst. Laminated shallow seismic stratigraphy and a deep continuous acoustic basement surface are also characteristic of the interpreted paleothermokarst zone and absent from active thermokarst regions. The seaward edge of interpreted paleothermokarst has remarkably consistent seafloor depths at our mapped crossings (-372 m ± 34 m), suggesting an influence of depth-related processes controlling this edge. Lowstand sea level (-120 m) and potentially colder bottom-water temperatures may have allowed lowstand thermokarst to form ~187 m deeper than the thermokarst along the Canadian Beaufort margin today (which has seaward edge depths of -185 m ± 24 m). We suggest that the locus of active thermokarst (de)formation has moved landward over time in response to rising sea level, and expect the most active deformation at the landward edge of the thermokarst field.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".