Dynamik des Durchflusses durch das kanadisch-arktische Archipel: Eine numerische Studie mit einem Finite Elemente Ozean- und Meereismodell
Bibliographic record
Abstract
The Canadian Arctic Archipelago (CAA) connects the Arctic Ocean and Baffin Bay through narrow channels and is one of the key gateways where freshwater leaves the Arctic. It has therefore the potential to affect the deep convection in the northern North Atlantic. Representing the CAA in traditional global models still poses a challenge due to the small scale nature of the narrow passages. In this study we apply a global, multi-resolution sea ice ocean model (the Finite Element Sea ice Ocean Model, FESOM) with refinement in the CAA up to 5 km, while keeping a coarse resolution setup otherwise. With this model setup, a hindcast simulation for the period 1968-2007 was performed. The first goal of this thesis is to assess the model behavior in the CAA region and in the Arctic Ocean. The model assessment revealed good agreement with sea ice conditions in the Arctic Ocean and with fluxes through the main gates of the Arctic Ocean. During the period 1968-2007 the mean volume transports through Lancaster Sound and Nares Strait amount to 0.86 Sv (1 Sv = 10^6 m^3/s) and 0.91 Sv, respectively. The monthly mean volume transport through western Lancaster Sound is highly correlated with the observational estimate (r=0.81). A comparison of simulated sectionally averaged velocities in Nares Strait with observational estimates reveals good agreement (r=0.57). The simulated mean CAA freshwater export rate is 123 mSv, slightly higher than the observational estimate (101 -10 mSv). The local refinement of 5 km allows to investigate the freshwater contribution of individual narrow straits to the Parry Channel. In the second part of the thesis, the mechanisms driving the interannual variability of freshwater transports through the CAA are analyzed. The interannual variability is determined by sea surface height (SSH) gradients between the Arctic Ocean and northern Baffin Bay. The variability of fluxes through Lancaster Sound and Nares Strait is mainly determined by that of the SSH on the shelf along the Beaufort Sea coast and in the northeastern Baffin Bay, respectively. Sea level variations north of the CAA are explained by changes in the wind regimes (cyclonic vs. anticyclonic) associated to release or accumulation of freshwater from the Beaufort Gyre, whereas sea level in the northeastern Baffin Bay can be attributed to ocean-atmosphere heat fluxes over the Labrador Sea. Both processes are linked with the North Atlantic Oscillation type of atmospheric variability. In the last part of the thesis, the effect of mesh resolution in the CAA area is evaluated by performing experiments with and without highly resolved archipelago (5 km vs. 24 km resolution). Increased resolution in the CAA leads to higher freshwater transports through the CAA; at the same time transports on the eastern side of Greenland are reduced. The `redirection' of Arctic freshwater affects convection in the Labrador Sea and thus the Atlantic meridional overturning circulation. We conclude that multi-resolution models like FESOM are promising tools for global climate modeling, as they are able to present small scale processes in a global setup.
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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 | 0.002 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| 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".