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Abstract The Gulf Stream system is dominated by strong mesoscale variability that can obscure any seasonal signals in Gulf Stream strength. Nevertheless, seasonal variability of the Gulf Stream is important for local weather and climate and can influence amplification of hurricane intensity and storm tracks. We investigate seasonal variability of the speed of the Gulf Stream after it detaches from Cape Hatteras, using high‐resolution along‐track altimeter data. The altimeter data show a significant seasonal cycle in the Gulf Stream axis speed, peaking in summer. The seasonal variability in the Gulf Stream axis velocity is related to changes in the local wind stress curl and changes in the density difference across the Gulf Stream. Wind forcing affects the Gulf Stream year‐round, while changes in the density difference have the largest impact in summer. Overall, changes in the wind stress curl and upper ocean density difference across the Gulf Stream can explain roughly 40% of the seasonal Gulf Stream speed variability in summer. 

Abstract The Gulf Stream, a major ocean current in the North Atlantic ocean is a key component in the global redistribution of heat and is important for marine ecosystems. Based on 27 years (1993–2019) of wind reanalysis and satellite altimetry measurements, we present observational evidence that the path of this freely meandering jet after its separation from the continental slope at Cape Hatteras, aligns with the region of maximum cyclonic vorticity of the wind stress field known as the positive vorticity pool. This synchronicity between the wind stress curl maximum region and the Gulf Stream path is observed at multiple time-scales ranging from months to decades, spanning a distance of 1500 km between 70 and 55W. The wind stress curl in the positive vorticity pool is estimated to drive persistent upward vertical velocities ranging from 5 to 17 cm day⁻¹over its ~ 400,000 km²area; this upwelling may supply a steady source of deep nutrients to the Slope Sea region, and can explain as much as a quarter of estimated primary productivity there. 

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. 

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.     

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).         

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). 

{"Abstract":["This dataset includes multiple fields: (i) files for monthly and annual fields for the max curl line and the zero curl line at 0.1 degree longitudinal resolutions; (ii) files for monthly and annual GS path obtained from Altimetry and originally processed by Andres (2016) at 0.1 degree longitudinal resolution. The maximum curl line (MCL) and the zero curl line (ZCL) calculations are briefly described here and are based on the original wind data (at 1.25 x 1.25 degree) provided by the Japanese reanalysis (JRA-55; Kobayashi et al., 2015) and available at https://zenodo.org/record/8200832 (Gifford et al. 2023). For details see Gifford, 2023. <\/p>\n\nThe wind stress curl (WSC) fields used for the MCL and ZCL calculations extend from 80W to 45W and 30N to 45N at the 1.25 by 1.25-degree resolution.  The MCL is defined as the maximum WSC values greater than zero within the domain per 1.25 degree longitude. As such, it is a function of longitude and is not a constant WSC value unlike the zero contour. High wind stress curl values that occurred near the coast were not included within this calculation. After MCL at the 1.25 resolution was obtained the line was smoothed with a gaussian smoothing and interpolated on to a 0.1 longitudinal resolution. The smoothed MCL lines at 0.1 degree resolution are provided in separate files for monthly and annual averages (2 files). Similarly, 2 other files (monthly and annual) are provided for the ZCL.    <\/p>\n\nLike the MCL, the ZCL is a line derived from 1.25 degree longitude throughout the domain under the condition that it's the line of zero WSC. The ZCL is constant at 0 and does not vary spatially like the MCL. If there are more than one location of zero curl for a given longitude the first location south of the MCL is selected. Similar to the MCL, the ZCL was smoothed with a gaussian smoothing and interpolated on to a 0.1 longitudinal resolution.   <\/p>\n\nThe above files span the years from 1980 through 2019. So, the monthly files have 480 months starting January 1980, and the annual files have 40 years of data. The files are organized with each row being a new time step and each column being a different longitude. Therefore, the monthly MCL and ZCL files are each 480 x 351 for the 0.1 resolution data. Similarly, the annual files are 40 x 351 for the 0.1 degree resolution data.  <\/p>\n\nNote that the monthly MCLs and ZCLs are obtained from the monthly wind-stress curl fields. The annual MCLs and ZCLs are obtained from the annual wind-stress curl fields.<\/strong><\/p>\n\nSince the monthly curl fields preserves more atmospheric mesoscales than the annual curl fields, the 12-month average of the monthly MCLs and ZCLs will not match with the annual MCLs and ZCLs derived from the annual curl field.  The annual MCLs and ZCLs provided here are obtained from the annual curl fields and representative metrics of the wind forcing on an annual time-scale. <\/p>\n\nFurthermore, the monthly Gulf Stream axis path (25 cm isoheight from Altimeter, reprocessed by Andres (2016) technique) from 1993 through 2019 have been made available here. A total of 324 monthly paths of the Gulf Stream are tabulated. In addition, the annual GS paths for these 27 years (1993-2019) of altimetry era have been put together for ease of use. The monthly Gulf Stream paths have been resampled and reprocessed for uniqueness at every 0.1 degree longitude from 75W to 50W and smoothed with a 100 km (10 point) running average via matlab. The uniqueness has been achieved by using Consolidator algorithm (D\u2019Errico, 2023). <\/p>\n\nEach monthly or annual GS path has 251 points between 75W to 50W at 0.1 degree resolution.  <\/p>"],"Other":["Please contact igifford@earth.miami.edu for any queries.","{"references": ["Andres, M., 2016. On the recent destabilization of the Gulf Stream path downstream of Cape Hatteras. Geophysical Research Letters, 43(18), 9836-9842.", "D'Errico, J., 2023. Consolidator (https://www.mathworks.com/matlabcentral/fileexchange/ 8354-consolidator), MATLAB Central File Exchange. Retrieved June 17, 2023.", "Gifford, Ian. H., 2023. The Synchronicity of the Gulf Stream Free Jet and the Wind Induced Cyclonic Vorticity Pool. MS Thesis, University of Massachusetts Dartmouth. 75pp.", "Gifford, Ian, H., Avijit Gangopadhyay, Magdalena Andres, Glen Gawarkiewicz, Hilde Oliver, Adrienne Silver, 2023. Wind Stress, Wind Stress Curl, and Upwelling Velocities in the Northwest Atlantic (80-45W, 30-45N) during 1980-2019, https://zenodo.org/record/8200832.", "Kobayashi, S., Ota, Y., Harada, Y., Ebita, A., Moriya, M., Onoda, H., Onogi, K., Kamahori, H., Kobayashi, C., Endo, H. and Miyaoka, K., 2015. The JRA-55 reanalysis: General specifications and basic characteristics.\\u202fJournal of the Meteorological Society of Japan. Ser. II,\\u202f93(1), pp.5-48. Kobayashi, S., Ota, Y., Harada, Y., Ebita, A., Moriya, M., Onoda, H., Onogi, K., Kamahori, H., Kobayashi, C., Endo, H. and Miyaoka, K., 2015. The JRA-55 reanalysis: General specifications and basic characteristics.\\u202fJournal of the Meteorological Society of Japan. Ser. II,\\u202f93(1), pp.5-48."]}"]}