Lake archives in Canada and Alaska: Do we see effects of polar climate change during the Early Holocene?
Bibliographic record
Abstract
Terrestrial deposits provide valuable information about past landscape development in the Arctic. Especially lake sediments as continuous records are highly important to comprehend the post-glacial dynamic of the periglacial environment in northern Canada and Alaska. It is crucial to evaluate already studied and published paleoenvironmental archives as well as to fill gaps of knowledge to gain a better understanding of the past, present and future polar climate change. \nVarious literary sources were studied to get an overall picture of climate records in the North American Arctic. Since environmental archives are relatively rare in the western Canadian Arctic a lake sediment record from Herschel Island (Yukon Territory) was analyzed as a case study using radio carbon age determination and several sedimentological and geochemical methods. \nMany authors draw the conclusion that a progressive amelioration of climate conditions with warmer-than-modern levels of air temperatures was reached during the period of 11,000 to 8,500 cal. a BP in the western Canadian Arctic and Alaska (e.g. Szeicz and MacDonald 2001, Bigelow and Edwards 2001). Also Herschel Island’s lake archive demonstrate an early Holocene warming by about 10,300 to 8,800 cal. a BP: variations in nitrogen, total organic carbon content and stable carbon isotopes indicate the lake onset by pooling of water and thaw subsidence of the ice-rich permafrost. \nThe Pleistocene-Holocene transition was a period of dramatic and rapid environmental changes, particularly at coastal sites. The formation of thermokarst lakes in permafrost regions was extremely intense during the Holocene Thermal Maximum (HTM). On the coastal plain in the western Canadian Arctic thermokarst lakes developed especially between 11,600 and 10,300 a BP (Rampton 1988) – so did the lake on Herschel Island in all likelihood. According to Kaufman et al. (2004) the HTM was time-transgressive, which means the western Canadian Arctic warmed earlier (11,300+/-1,500 a BP) than northern continental Canada (7,300+/-1,600 a BP). Also the duration of the HTM in eastern Canada was about 1,000 years shorter. Both can be explained due to the remnants of the Laurentide Ice Sheet and the cooling effect of the Greenland ice cap. \nThe overall pattern of Holocene climate change is expressed in several records in the North American Arctic. We are recently noticing thermokarst processes and effects of permafrost degradation due to global climate change. Thus, understanding the past environmental effects on polar landscapes and especially on lake systems is extremely valuable to appraise present und future polar climate change. \nReferences: \nBigelow, N.H.; Edwards, M.E. (2001). A 14000 yr paleoenvironmental record from Windmill Lake, Central Alaska: Lateglacial and Holocene vegetation in the Alaska range. Quaternary Science Reviews, 20: 203-215. \nKaufman, D.S.; Ager, T.A.; Anderson, N.J. et al (2004). Holocene thermal maximum in the western Arctic (0-180°W). Quaternary Science Reviews, 23: 529-560. \n \nRampton, V.N. (1988). Quaternary geology of the Tuktoyaktuk Coastlands, Northwest \nTerritories. Geological Survey of Canada. Memoir, 423. \nSzeicz, J.M.; MacDonald, G.M. (2001). Montane climate and vegetation dynamics in \neasternmost Beringia during the Late Quaternary. Quaternary Science Reviews, 20: 247-257.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.007 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".