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This dataset consists of weekly trajectory information of Gulf Stream Cold Eddies (CE) that existed between 2017 and 2023. The format of this Cold Eddy dataset is similar to the Warm Core Ring (WCR) Trajectory data from Porter et al. (2022, 2024) and Silver et al. (2022), and the following description is adapted from those datasets. This dataset is comprised of individual files containing each eddy’s weekly center location and its surface area for 181 CEs that existed and were tracked between January 1, 2017 and December 31, 2023 (28 CEs formed in 2017; 24 formed in 2018; 25 formed in 2019; 26 formed in 2020; 35 formed in 2021; 23 formed in 2022; and 20 formed in 2023). Each Cold Eddy is identified by a unique alphanumeric code 'CEyyyymmddX', where 'CE' represents a Cold 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 an eddy 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 eddy formed in 2021 has a trailing alphabet of 'J', which signifies that a total of nine eddies were carried over from 2020 which were still present on January 1, 2021 and were assigned the initial nine alphabets (A, B, C, D, E, F, G, H, and I). Each eddy trajectory has its own netCDF (.nc) filename following its alphanumeric code. Each file contains 4 variables every week, “Lon”- the eddy center’s longitude, “Lat”- the eddy center’s latitude, “Area” - the eddies size in km^2, and “Date” in days – which is the number of days since Jan 01, 0000. Note that in this dataset, which ended tracking all eddies up to 2023, there were six eddies that formed in 2023, and were carried over into 2024 were included with their full trajectories going into the year 2024. These eddies are: ‘CE20230515P’, ‘CE20230818U’, 'CE20230925V', 'CE20231030Y', 'CE20231103Z', and 'CE20231106a'. Findings from Jensen et al. (2024) suggest three different cyclonic eddy formation types: pinch-off cyclonic rings, hook-type cyclonic eddies, and Sargasso Sea cyclonic eddies. Pinch-off cyclonic rings form from a Gulf Stream meander trough amplifying, then encircling Slope Sea water and eventually detaching from the Gulf Stream as a cyclonic cold-core ring in the Sargasso Sea. Hook-type eddies form from a southward extending filament of the southern flank of the Gulf Stream establishing as a hook-like entity cyclonically encircling a body of Sargasso Sea water at its core. Sargasso Sea cyclonic eddies are isolated from the Gulf Stream and occur in the Sargasso Sea. A separate file is also created to help identify the cold eddy's formation type. Two files are provided here. These are: (1) The trajectories of all Gulf Stream Cold Eddies formed from 2017 to 2023. Filename – CE_2017_2023_ncfiles.zip (2) Information on the formation type of each Cold Eddy. Filename – CE_FormationTypes_2017to2023.doc The process of creating the CE weekly tracking dataset follows the same GIS-based methodology of the previously generated WCR census (Gangopadhyay et al., 2019, 2020). The Jenifer Clark’s Gulf Stream Charts described in Gangopadhyay et al. (2019), and continued through 2023 were used to create this dataset and were available 2-3 times a week from 2017-2023. Thus, we used approximately 840+ Charts for the 7 years of analysis. All of these charts were reanalyzed between 75°W and 55°W using QGIS 2.18.16 (2016) and geo-referenced on a WGS84 coordinate system (Decker, 1986). A single eddy trajectory is then obtained following an eddy through all of the available charts during the eddy's lifespan on a weekly basis. This process is repeated for every individual eddy.
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Observational evidence of a new type of cyclonic eddy of the Gulf Stream
Based on over four decades of satellite and in-situ observations, we present evidence that there are two types of cyclonic Gulf Stream eddies formed to the south of the Gulf Stream. One of these types is the well-known pinch-off rings generally formed over and to the east of the New England Seamount Chain (NESC) when a large amplitude meander trough of the Gulf Stream occludes and traps cold slope water in the eddy core. A large number of cyclonic eddies formed across the entire Gulf Stream follow a “hook-type” formation process, in which an offshore filament from the southern flank of the Gulf Stream elongates by extracting flow from the Stream, eventually acquiring cyclonic rotation and capturing Sargasso water (colder than the Gulf Stream-derived annulus) in its core. The hook-type cyclonic eddies have a distinct seasonality with formation peaking in spring, while the pinch-off rings do not show any discernible seasonal pattern. The pinch-off rings form predominantly on and east of the NESC, whereas hook-type eddies form across the entire Stream, possibly resulting from trapped and radiating instabilities and have shallower thermoclines. Shifts in the longitude of the Gulf Stream destabilization point relate to the pinch-off rings on both sides of the Stream. The shifts are not associated with the flank-generated aneurysm and hook-type eddies. The abundance of smaller and shallower aneurysm-type anticyclonic eddies to the north and the newly observed hook-type cyclonic eddies to the south suggests Gulf Stream barrier characteristics west of the NESC, while pinch-off rings appearing mostly on and east of the NESC seem to explain the blender nature of cross-stream exchange of the Gulf Stream on and east of the NESC.
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- PAR ID:
- 10654214
- Publisher / Repository:
- Nature Scientific Reports
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Associated Dataset(s):
- View Associated Dataset(s) >>
- Sponsoring Org:
- National Science Foundation
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Abstract Downstream of Cape Hatteras, the vigorously meandering Gulf Stream forms anticyclonic warm core rings (WCRs) that carry warm Gulf Stream and Sargasso Sea waters into the cooler, fresher Slope Sea, and forms cyclonic cold core rings (CCRs) that carry Slope Sea waters into the Sargasso Sea. The Northwest Atlantic shelf and open ocean off the U.S. East Coast have experienced dramatic changes in ocean circulation and water properties in recent years, with significant consequences for marine ecosystems and coastal communities. Some of these changes may be related to a reported regime shift in the number of WCRs formed annually, with a doubling of WCRs shed after 2000. Since the regime shift was detected using a regional eddy‐tracking product, primarily based on sea surface temperatures and relies on analyst skill, we examine three global eddy‐tracking products as an automated and potentially more objective way to detect changes in Gulf Stream rings. Currently, global products rely on altimeter‐measured sea surface height (SSH), with WCRs registering as sea surface highs and CCRs as lows. To identify eddies, these products use either SSH contours or a Lagrangian approach, with particles seeded in satellite‐based surface geostrophic velocity fields. This study confirms the three global products are not well suited for statistical analysis of Gulf Stream rings and suggests that automated WCR identification and tracking comes at the price of accurate identification and tracking. Furthermore, a shift to a higher energy state is detected in the Northwest Atlantic, which coincides with the regime shift in WCRs.more » « less
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This dataset consists of a census of warm core ring formation locations, times, and sizes from the Gulf Stream between 2018 and 2023. This work builds upon the following dataset: Gangopadhyay, A., Gawarkiewicz, G. (2020) Yearly census of Gulf Stream Warm Core Ring formation from 1980 to 2017. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2020-05-06 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.810182.1 [access date] In addition, it is related to two additional datasets containing warm core ring weekly tracking data: (i) Warm Core Ring trajectory information from 2011 to 2020 -- Silver et al. (2022a) (https://doi.org/10.5281/zenodo.6436380). (ii) Warm Core Ring Trajectories in the Northwest Atlantic Slope Sea (2021-2023) – Porter et al. (2024) (https://doi.org/10.5281/zenodo.10392322) The format of this data set is similar to the datasets mentioned above, and the following description is adapted from those. This dataset contains a yearly census of Gulf Stream Warm Core Ring formation from 2018 to 2023. This continuous census file contains the formation and demise times and locations, and the area at formation for warm core rings that lived a week or more. Each row represents a unique Warm Core Ring and 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. For example, the first ring formed in 2018, having a trailing alphabet of 'G', indicates that six rings were carried over from 2017, which are still observed on January 1, 2018. Creating the WCR tracking dataset follows the same methodology as the previously generated WCR census (Gangopadhyay et al., 2019, 2020). This census was created from Jenifer Clark’s Gulf Stream Charts. These charts show the location, extent, and temperature signature of currents (GS, shelf-slope front), warm and cold-core rings (WCRs and CCRs), other eddies, shingles, intrusions, and other water mass boundaries in the Gulf of Maine, over Georges Bank, and in the Middle Atlantic Bight. An example chart is shown in Figure 1a of Gangopadhyay et al. (2019). A year-long animation for these charts for 2017 is presented in the supporting information of Gangopadhyay et al. (2020) https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JC016033. The charts are generated 2-3 times a week from 2018 to 2023. Thus, we used approximately 624+ Charts for the 6 years of analysis. These charts were then reanalyzed between 75°W and 55°W using QGIS 2.18.16 (2016) and geo-referenced on a WGS84 coordinate system (Decker, 1986).more » « less
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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.more » « less
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Abstract Despite the ubiquity of eddies at the Mid‐Atlantic Bight shelf‐break front, direct observations of frontal eddies at the shelf‐break front are historically sparse and their biological impact is mostly unknown. This study combines high resolution physical and biological snapshots of two frontal eddies with an idealized 3‐D regional model to investigate eddy formation, kinematics, upwelling patterns, and biological impacts. During May 2019, two eddies were observed in situ at the shelf‐break front. Each eddy showed evidence of nutrient and chlorophyll enhancement despite rotating in opposite directions and having different physical characteristics. Our results suggest that cyclonic eddies form as shelf waters are advected offshore and slope waters are advected shoreward, forming two filaments that spiral inward until sufficient water is entrained. Rising isohalines and upwelled slope water dye tracer within the model suggest that upwelling coincided with eddy formation and persisted for the duration of the eddy. In contrast, anticyclonic eddies form within troughs of the meandering shelf‐break front, with amplified frontal meanders creating recirculating flow. Upwelling of subsurface shelf water occurs in the form of detached cold pool waters during the formation of the anticyclonic eddies. The stability properties of each eddy type were estimated via the Burger number and suggest different ratios of baroclinic versus barotropic contributions to frontal eddy formation. Our observations and model results indicate that both eddy types may persist for more than a month and upwelling in both eddy types may have significant impacts on biological productivity of the shelf break.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41598-025-10796-3
