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1. Increased gulf stream warm core ring formations contributes to an observed increase in salinity maximum intrusions on the Northeast Shelf

   https://doi.org/10.1038/s41598-023-34494-0  

   Silver, Adrienne ; Gangopadhyay, Avijit ; Gawarkiewicz, Glen ; Fratantoni, Paula ; Clark, Jenifer ( May 2023 , Scientific Reports)

   We present observational evidence of a significant increase in Salinity Maximum intrusions in the Northeast US Shelf waters in the years following 2000. This increase is subsequent to and influenced by a previously observed regime-shift in the annual formation rate for Gulf Stream Warm Core Rings, which are relatively more saline than the shelf waters. Specifically, mid-depth salinity maximum intrusions, a cross-shelf exchange process, has shown a quadrupling in frequency on the shelf after the year 2000. This increase in intrusion frequency can be linked to a similar increase in Warm Core Ring occupancy footprint along the offshore edge of the shelf-break which has greatly increased the abundance of warm salty water within the Slope Sea. The increased ring occupancy footprint along the shelf follows from the near doubling in annual Warm Core Ring formation rate from the Gulf Stream. The increased occurrence of intrusions is likely driven by a combination of a larger number of rings in the slope sea and the northward shift in the GS position which may lead to more interactions between rings and the shelf topography. These results have significant implications for interpreting temporal changes in the shelf ecosystem from the standpoint of both larval recruitment as well as habitability for various important commercial species.

    

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2. Increasing Frequency of Mid‐Depth Salinity Maximum Intrusions in the Middle Atlantic Bight

   https://doi.org/10.1029/2021JC018233  

   Gawarkiewicz, G. ; Fratantoni, P. ; Bahr, F. ; Ellertson, A. ( June 2022 , Journal of Geophysical Research: Oceans)

   Shelfbreak exchange processes have been studied extensively in the Middle Atlantic Bight. An important process occurring during stratified conditions is the Salinity Maximum Intrusion. These features are commonly observed at the depth of the seasonal pycnocline, and less frequently at the surface and bottom. Data collected from NOAA's National Marine Fisheries Service Ecosystem Monitoring program as well as data collected from the fishing industry in Rhode Island show that the middepth intrusions are now occurring much more frequently than was reported in a previous climatology of the intrusions (Lentz, 2003,https://doi.org/10.1029/2003JC001859). The intrusions have a greater salinity difference from ambient water and penetrate large distances shoreward of the shelf break relative to the earlier climatology. The longer term data from the Ecosystem Monitoring program indicates that the increase in frequency occurred in 2000, and thus may be linked to a recent regime shift in the annual formation rate of Warm Core Rings by the Gulf Stream. Given the increased frequency of these salty intrusions, it will be necessary to properly resolve this process in numerical simulations in order to account for salt budgets for the continental shelf and slope.

    

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3. Interannual and seasonal asymmetries in Gulf Stream Ring Formations from 1980 to 2019

   https://doi.org/10.1038/s41598-021-81827-y  

   Silver, Adrienne ; Gangopadhyay, Avijit ; Gawarkiewicz, Glen ; Silva, E. Nishchitha ; Clark, Jenifer ( December 2021 , Scientific Reports)

   null (Ed.)

   Abstract As the Gulf Stream separates from the coast, it sheds both Warm and Cold Core Rings between $$75^\circ$$ 75 ∘ and $$55^\circ \,\hbox {W}$$ 55 ∘ W . We present evidence that this ring formation behavior has been asymmetric over both interannual and seasonal time-scales. After a previously reported regime-shift in 2000, 15 more Warm Core Rings have been forming yearly compared to 1980–1999. In contrast, there have been no changes in the annual formation rate of the Cold Core Rings. This increase in Warm Core Ring production leads to an excess heat transfer of 0.10 PW to the Slope Sea, amounting to 7.7–12.4% of the total Gulf Stream heat transport, or 5.4–7.3% of the global oceanic heat budget at $$30^\circ \,\hbox {N}$$ 30 ∘ N . Seasonally, more Cold Core Rings are produced in the winter and spring and more Warm Core Rings are produced in the summer and fall leading to more summertime heat transfer to the north of the Stream. The seasonal cycle of relative ring formation numbers is strongly correlated (r = 0.82) with that of the difference in upper layer temperatures between the Sargasso and Slope seas. This quantification motivates future efforts to understand the recent increasing influence of the Gulf Stream on the circulation and ecosystem in the western North Atlantic. 

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4. A Census of the Warm‐Core Rings of the Gulf Stream: 1980–2017

   https://doi.org/10.1029/2019JC016033  

   Gangopadhyay, Avijit ; Gawarkiewicz, Glen ; Silva, E. Nishchitha S. ; Silver, Adrienne M. ; Monim, M. ; Clark, Jenifer ( August 2020 , Journal of Geophysical Research: Oceans)

   A census of Gulf Stream (GS) warm‐core rings (WCRs) is presented based on 38 years (1980–2017) of data. The census documents formation and demise times and locations, and formation size for all 961 WCRs formed in the study period that live for a week or more. A clear regime shift was observed around the Year 2000 and was reported by a subset of authors (Gangopadhyay et al., 2019,https://doi.org/10.1038/s41598-019-48661-9). The WCR formation over the whole region (75–55°W) increased from an average of 18 per year during Regime 1 (1980–1999) to 33 per year during Regime 2 (2000–2017). For geographic analysis formation locations were grouped in four 5° zones between 75°W and 55°W. Seasonally, WCR formations show a significant summer maxima and winter minima, a pattern that is consistent through all zones and both temporal regimes. The lifespan and size distribution show progressively more rings with higher longevity and greater size when formed to the east of 70°W. The average lifespan of the WCRs in all four zones decreased by 20–40% depending on zones and/or seasons from Regime 1 to Regime 2, while the size distribution remained unchanged across regimes. The ring footprint index, a first‐order signature of impact of the WCRs on the slope, increased significantly (26–90%) for all zones from Regime 1 to Regime 2, with the highest percent increase in Zone 2 (70–65°W). This observational study establishes critical statistical and dynamical benchmarks for validating numerical models and highlights the need for further dynamical understanding of the GS‐ring formation processes.

    

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5. Warm Core Ring Trajectories in the Northwest Atlantic Slope Sea (2000-2010)

   https://doi.org/10.5281/zenodo.7406675  

   Porter, Nicholas ; Silver, Adrienne ; Gangopadhyay, Avijit ( January 2022 , Zenodo)

   This dataset consists of weekly trajectory information of Gulf Stream Warm Core Rings from 2000-2010. This work builds upon Silver et al. (2022a) ( https://doi.org/10.5281/zenodo.6436380) which contained Warm Core Ring trajectory information from 2011 to 2020. Combining the two datasets a total of 21 years of weekly Warm Core Ring trajectories can be obtained. An example of how to use such a dataset can be found in Silver et al. (2022b).

   The format of the dataset is similar to that of  Silver et al. (2022a), and the following description is adapted from their dataset. This dataset is comprised of individual files containing each ring’s weekly center location and its area for 374 WCRs present between January 1, 2000 and December 31, 2010. Each Warm Core Ring is identified by a unique alphanumeric code 'WEyyyymmddA', where 'WE' represents a Warm Eddy (as identified in the analysis charts); 'yyyymmdd' is the year, month and day of formation; and the last character 'A' represents the sequential sighting of the eddies in a particular year. Continuity of a ring which passes from one year to the next is maintained by the same character in the first sighting.  For example, the first ring in 2002 having a trailing alphabet of 'F' indicates that five rings were carried over from 2001 which were still observed on January 1, 2002. Each ring has its own netCDF (.nc) filename following its alphanumeric code. Each file contains 4 variables, “Lon”- the ring center’s weekly longitude, “Lat”- the ring center’s weekly latitude, “Area” - the rings weekly size in km², and “Date” in days - representing the days since Jan 01, 0000. 

   The process of creating the WCR tracking dataset follows the same methodology of the previously generated WCR census (Gangopadhyay et al., 2019, 2020). The Jenifer Clark’s Gulf Stream Charts used to create this dataset are 2-3 times a week from 2000-2010. Thus, we used approximately 1560 Charts for the 10 years of analysis. All of these charts were reanalyzed between 75° and 55°W using QGIS 2.18.16 (2016) and geo-referenced on a WGS84 coordinate system (Decker, 1986). 

    

   Silver, A., Gangopadhyay, A, & Gawarkiewicz, G. (2022a). Warm Core Ring Trajectories in the Northwest Atlantic Slope Sea (2011-2020) (1.0.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.6436380

   Silver, A., Gangopadhyay, A., Gawarkiewicz, G., Andres, M., Flierl, G., & Clark, J. (2022b). Spatial Variability of Movement, Structure, and Formation of Warm Core Rings in the Northwest Atlantic Slope Sea. Journal of Geophysical Research: Oceans, 127(8), e2022JC018737. https://doi.org/10.1029/2022JC018737 

   Gangopadhyay, A., G. Gawarkiewicz, N. Etige, M. Monim and J. Clark, 2019. An Observed Regime Shift in the Formation of Warm Core Rings from the Gulf Stream, Nature - Scientific Reports, https://doi.org/10.1038/s41598-019-48661-9. www.nature.com/articles/s41598-019-48661-9.

   Gangopadhyay, A., N. Etige, G. Gawarkiewicz, A. M. Silver, M. Monim and J. Clark, 2020.  A Census of the Warm Core Rings of the Gulf Stream (1980-2017). Journal of Geophysical Research, Oceans, 125, e2019JC016033. https://doi.org/10.1029/2019JC016033.

   QGIS Development Team. QGIS Geographic Information System (2016).

   Decker, B. L. World Geodetic System 1984. World geodetic system 1984 (1986).

    

   Funded by two NSF US grants OCE-1851242, OCE-212328 {"references": ["Silver, A., Gangopadhyay, A, & Gawarkiewicz, G. (2022). Warm Core Ring Trajectories in the Northwest Atlantic Slope Sea (2011-2020) (1.0.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.6436380", "Silver, A., Gangopadhyay, A., Gawarkiewicz, G., Andres, M., Flierl, G., & Clark, J. (2022b). Spatial Variability of Movement, Structure, and Formation of Warm Core Rings in the Northwest Atlantic Slope Sea.\u00a0Journal of Geophysical Research: Oceans,\u00a0127(8), e2022JC018737.\u00a0https://doi.org/10.1029/2022JC018737", "Gangopadhyay, A., G. Gawarkiewicz, N. Etige, M. Monim and J. Clark, 2019. An Observed Regime Shift in the Formation of Warm Core Rings from the Gulf Stream, Nature - Scientific Reports, https://doi.org/10.1038/s41598-019-48661-9. www.nature.com/articles/s41598-019-48661-9.", "Gangopadhyay, A., N. Etige, G. Gawarkiewicz, A. M. Silver, M. Monim and J. Clark, 2020. A Census of the Warm Core Rings of the Gulf Stream (1980-2017). Journal of Geophysical Research, Oceans, 125, e2019JC016033. https://doi.org/10.1029/2019JC016033.", "QGIS Development Team. QGIS Geographic Information System (2016).", "Decker, B. L. World Geodetic System 1984. World geodetic system 1984 (1986)."]} 

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