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1. Warm Core Ring Trajectories in the Northwest Atlantic Slope Sea (2021-2023)

   https://doi.org/10.5281/zenodo.10392322  

   Porter, Nicholas; Gangopadhyay, Avijit; Silver, Adrienne; Gangopadhyay, Avijit; Silver, Adrienne; Porter, Nicholas (January 2024, Zenodo)

   Porter, Nicholas; Gangopadhyay, Avijit (Ed.)

   This dataset consists of weekly trajectory information of Gulf Stream Warm Core Rings (WCR) that existed between 2021 and 2023. This work builds upon two previous datasets: (i) Warm Core Ring trajectory information from 2000 to 2010 -- Porter et al. (2022) (https://doi.org/10.5281/zenodo.7406675) (ii) Warm Core Ring trajectory information from 2011 to 2020 -- Silver et al. (2022a) (https://doi.org/10.5281/zenodo.6436380). Combining these three datasets (previous two and this one), a total of 24 years of weekly Warm Core Ring trajectories are now available. 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 Porter et al. (2022) and Silver et al. (2022a), and the following description is adapted from those datasets. This dataset is comprised of individual files containing each ring’s weekly center location and its surface area for 81 WCRs that existed and tracked between January 1, 2021 and December 31, 2023 (5 WCRs formed in 2020 and still existed in 2021; 28 formed in 2021; 30 formed in 2022; 18 formed in 2023). Each Warm Core Ring is identified by a unique alphanumeric code 'WEyyyymmddX', 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 'X' represents the sequential sighting (formation) of the eddy in that particular year. Continuity of a ring which passes from one year to the next is maintained by the same character in the previous year and absorbed by the initial alphabets for the next year. For example, the first ring formed in 2022 has a trailing alphabet of 'H', which signifies that a total of seven rings were carried over from 2021 which were still present on January 1, 2022 and were assigned the initial seven alphabets (A, B, C, D, E, F and G). Each ring has its own netCDF (.nc) filename following its alphanumeric code. Each file contains 4 variables every week, “Lon”- the ring center’s longitude, “Lat”- the ring center’s latitude, “Area” - the rings size in km^2, and “Date” in days – which is the number of days since Jan 01, 0000. Five rings formed in the year 2020 that carried over into the year 2021 were included in this dataset. These rings include ‘WE20200724Q’, ‘WE20200826R’, ‘WE20200911S’, ‘WE20200930T’, and ‘WE20201111W’. The two rings that formed in 2023, and were carried over into the following year were included with their full trajectories going into the year 2024. These rings include ‘WE20231006U’ and ‘WE20231211W’. 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 (Gangopadhyay et al., 2019) used to create this dataset are 2-3 times a week from 2021-2023. Thus, we used approximately 360+ Charts for the 3 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). 

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2. Spatial Variability of Movement, Structure, and Formation of Warm Core Rings in the Northwest Atlantic Slope Sea

   https://doi.org/10.1029/2022JC018737  

   Silver, Adrienne; Gangopadhyay, Avijit; Gawarkiewicz, Glen; Andres, Magdalena; Flierl, Glenn; Clark, Jenifer (August 2022, Journal of Geophysical Research: Oceans)

   Abstract Gulf Stream Warm Core Rings (WCRs) have important influences on the New England Shelf and marine ecosystems. A 10‐year (2011–2020) WCR dataset that tracks weekly WCR locations and surface areas is used here to identify the rings' path and characterize their movement between 55 and 75°W. The WCR dataset reveals a very narrow band between 66 and 71°W along which rings travel almost due west along ∼39°N across isobaths – the “Ring Corridor.” Then, west of the corridor, the mean path turns southwestward, paralleling the shelfbreak. The average ring translation speed along the mean path is 5.9 cm s⁻¹. Long‐lived rings (lifespan >150 days) tend to occupy the region west of the New England Seamount Chain (NESC) whereas short‐lived rings (lifespan <150 days) tend to be more broadly distributed. WCR vertical structures, analyzed using available Argo float profiles indicate that rings that are formed to the west of the NESC have shallower thermoclines than those formed to the east. This tendency may be due to different WCR formation processes that are observed to occur along different sections of the Gulf Stream. WCRs formed to the east of the NESC tend to form from a pinch‐off mechanism incorporating cores of Sargasso Sea water and a perimeter of Gulf Stream water. WCRs that form to the west of the NESC, form from a process called an aneurysm. WCRs formed through aneurysms comprise water mostly from the northern half of the Gulf Stream and are smaller than the classic pinch‐off rings. 

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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. 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)

   Abstract 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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5. Warm Spiral Streamers over Gulf Stream Warm-Core Rings

   https://doi.org/10.1175/JPO-D-20-0035.1  

   Zhang, Weifeng; McGillicuddy, Dennis J. (November 2020, Journal of Physical Oceanography)

   Abstract This study examines the generation of warm spiral structures (referred to as spiral streamers here) over Gulf Stream warm-core rings. Satellite sea surface temperature imagery shows spiral streamers forming after warmer water from the Gulf Stream or newly formed warm-core rings impinges onto old warm-core rings and then intrudes into the old rings. Field measurements in April 2018 capture the vertical structure of a warm spiral streamer as a shallow lens of low-density water winding over an old ring. Observations also show subduction on both sides of the spiral streamer, which carries surface waters downward. Idealized numerical model simulations initialized with observed water-mass densities reproduce spiral streamers over warm-core rings and reveal that their formation is a nonlinear submesoscale process forced by mesoscale dynamics. The negative density anomaly of the intruding water causes a density front at the interface between the intruding water and surface ring water, which, through thermal wind balance, drives alocalanticyclonic flow. The pressure gradient and momentum advection of the local interfacial flow push the intruding water toward the ring center. The large-scale anticyclonic flow of the ring and the radial motion of the intruding water together form the spiral streamer. The observed subduction on both sides of the spiral streamer is part of the secondary cross-streamer circulation resulting from frontogenesis on the stretching streamer edges. The surface divergence of the secondary circulation pushes the side edges of the streamer away from each other, widens the warm spiral on the surface, and thus enhances its surface signal. 

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