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- Title
Controls on Upper Ocean Salinity Variability in the Eastern Subpolar North Atlantic During 1992–2017.
- Authors
Siddiqui, Ali H.; Haine, Thomas W. N.; Nguyen, An T.; Buckley, Martha W.
- Abstract
The upper ocean salinity in the eastern subpolar North Atlantic undergoes decadal fluctuations. A large fresh anomaly event occurred during 2012–2016. Using the ECCOv4r4 state estimate, we diagnose and compare mechanisms of this low salinity event with those of the 1990s fresh anomaly event. To avoid issues related to the choice of reference salinity values in the freshwater budget, we perform a salt mass content budget analysis of the eastern subpolar North Atlantic. It shows that the recent low salt content anomaly occurs due to the circulation of anomalous salinity by mean currents entering the eastern subpolar basin from its western boundary via the North Atlantic Current. This is in contrast to the early 1990s, when the dominant mechanism governing the low salt content anomaly was the transport of the mean salinity field by anomalous currents. Plain Language Summary: On decadal time scales, the eastern subpolar North Atlantic shifts between a salty and fresh upper ocean. Between 2012 and 2016, there was a large event which freshened this region more than at any other time in over a century. A similar event occurred in the early 1990s, but with a smaller magnitude. We use a numerical model of the ocean to figure out why these events occurred. Our study shows that there were two different mechanisms at play. The recent event occurred because a lot of fresh water came in from the west by the mean currents. The 1990s event occurred because ocean currents shifted and brought fresh water from outside the region. Key Points: Two fresh anomalies observed in the eastern subpolar North Atlantic upper ocean during 1992–2017 share similar spatial characteristicsSalt budget analysis shows the 2012–2016 fresh anomaly in the upper 1,000 m occurs due to transport of anomalous salinity by mean currentsIn contrast, the fresh anomaly in the 1990s is due to anomalous circulation of the mean salinity field
- Subjects
FRESH water; BUDGET; SALINITY; REFERENCE values; OCEAN
- Publication
Journal of Geophysical Research. Oceans, 2024, Vol 129, Issue 8, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2024JC020887