Trends and drivers of Arctic lake color change from Landsat time series
Bibliographic record
Abstract
• Declining red and green surface reflectance in western Canadian Arctic lakes. • Abrupt changes in lake color and NDTI associated with slumping and wildfire. • Lake color change follows warm summer temperature with a 2-year lag. • Tailored cross-sensor calibration of Landsat essential for Arctic lake studies. Arctic lake color and quality are changing in response to the warming climate, permafrost degradation, and intensifying disturbances. These changes have important implications on carbon and nutrient cycling, wildlife habitat, and water resources planning. However, the drivers, spatial distribution, and long-term trajectories of these changes remain poorly characterized on regional scales (∼100 km). In this study, we examined over 3,000 lakes in part of the Mackenzie Delta, Tuktoyaktuk Coastlands, and adjacent upland tundra in the Northwest Territories, Canada, to quantify both gradual and abrupt changes in lake color using harmonized Landsat time series from 1985 to 2022. Across the region, we found average declines of surface reflectance in the red and green bands by 13 % and 15 % over the last four decades, respectively. In comparison, the Normalized Difference Turbidity Index (NDTI) trends differed between sub-regions, with a decadal increase in the Tuktoyaktuk Coastlands and a decrease in the Mackenzie Delta. We identified a positive, lagged correlation between abrupt lake color change and mean summer air temperature (MSAT), particularly in the Tuktoyaktuk Coastlands (R = 0.7, lag = 2 years), indicating a delayed impact of warm summers on lake color. One important mechanism of such impact was lakeshore thaw slumping intensified by rising summer temperatures, with slump-affected lakes experiencing abrupt increases in surface reflectance and NDTI driven by sediment input. We identified fire as another important driver of lake color dynamics, which led to greater changes in lake surface reflectance (p < 0.01) and NDTI (p = 0.1) compared to surrounding lakes. These findings demonstrate the value of harmonized Landsat time series for characterizing multifaceted Arctic lake color dynamics, along with their drivers and impacts.
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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 | 0.001 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".