An overlooked freshwater source contributed to the extreme fresheningevent in the eastern subpolar North Atlantic after 2014
Bibliographic record
Abstract
Abstract. Outflows of low-salinity waters from the Arctic to the upper layers of the subpolar North Atlantic (SPNA) are central in redistributing freshwater from river runoff, melting sea ice, and precipitation. They act to reduce shallow, as well as deep, convection; thereby affecting both biological production and the Atlantic Meridional Overturning Circulation. The two main sources of low-salinity water to the SPNA are the flows through the Canadian Arctic Archipelago and through the Denmark Strait. A potential additional source of low-salinity water is the shelf/slope region south of Iceland, mainly fed by Icelandic runoff. Normally this water passes into the Nordic Seas, but in some periods, it may instead flow into the upper layers of the central parts of the Iceland Basin in the eastern SPNA. This low-salinity water has previously been overlooked as a freshwater supply to the SPNA. Using a range of observational data sets, we show that the conditions for a diversion of this water mass from the south Iceland shelf into the Iceland Basin were favourable during the 2014–2018 period. In those years the Iceland Basin became extraordinarily fresh, characterized by surface salinity lower than previously seen in a 120-year long time series. The event is thought to have been mainly caused by unusual winter wind stress patterns that diverted freshwater from the western SPNA to the eastern basin and caused a zonal shift of the subpolar front. Here, we show that the low-salinity signal near the surface was locally reinforced in the central Iceland Basin by anomalous diversion of low-salinity water originating in the shallow shelf areas south of Iceland and that this can help explain why the surface salinity of the Iceland Basin became so exceptionally low. The diversion was generated by anomalous wind conditions over the Iceland Basin and caused slightly enhanced freshening of the warm waters crossing the Greenland-Scotland Ridge from the SPNA into the Nordic Seas. The low-salinity Icelandic-source water also increased the near-surface stratification and reduced the depth of convection in the Iceland Basin during two consecutive winters with reduced nutrient renewal of near-surface waters as a consequence. Although especially pronounced after 2014, this extra freshwater input probably occurs more generally, which may help explain why the central Iceland Basin may be an oligotrophic region, as has previously been suggested.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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".