Recent Circulation Changes at Intermediate Depths (Upper Polar Deep Water) in the Beaufort Gyre Inferred from Water Column Distribution of 230Th
Bibliographic record
Abstract
Surface water circulation in the Arctic Ocean is known to vary with time in response to the Arctic Oscillation. Clear recent changes have been documented in the freshwater budget (Rabe et al., 2011) and in the penetration of 129I (Karcher et al., 2012). In the Atlantic Water Layer, the penetration of a warming anomaly, first observed 1990 in Fram Strait (Quadfasel et al., 1991) has been well documented. Much less is known of circulation changes at greater depths. \nWe compare new 230Th data collected 2007 in the Eurasian and Makarov Basins up to the Alpha Ridge, and 2007-2009 in the southern Canada Basin with previous data from the Arctic Basins. We observe a decreased 230Th content of mid-depth waters (1000-2250m) at the Alpha Ridge compared to data of 1983, and increasing 230Th activities penetrating southward in the Beaufort Sea over the period 2007-2009 in the upper 1500m coincident with the arrival here of the Atlantic temperature anomaly. \nWe propose that the low-particle flux and high-230Th isolated water mass in the Alpha Ridge region described by Bacon et al. (1989) has been ventilated, resulting in decreased activities in Upper Polar Deep Water here in 2007, and included in an anticyclonic circulation that carried it to the southern regions of the Beaufort Sea. \n \n \n \nBacon, M.P, et al., 1989. Vertical profiles of some natural radionuclides over the Alpha Ridge, Arctic Ocean. Earth Planet. Sci. Lett. 95, 15-22. \nKarcher, M.J, et al., 2012. Recent changes of Arctic Ocean circulation revealed by 129 Iodine observations and modelling. Journal of Geophysical Research 117, C08007. \nQuadfasel, D., et al., 1991. Warming in the arctic. Nature 350, 385. \nRabe, B., et al., 2011. An assessment of Arctic Ocean freshwater content changes from the 1990s to the 2006-2008 period. Deep Sea Research Part I: Oceanographic Research Papers 58, 173-185. \n
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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; both teacher heads agree on what is shown here.
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".