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.

The Northeast U.S. continental shelf is characterized by relatively cold and fresh shelf waters of Arctic origin, whereas the adjacent Slope Sea is home to warm and salty, Gulf Stream derived waters. These contrasting watermass properties form a strong Shelfbreak Front, which can act as dynamical barrier of exchange between onshore and offshore waters. A shelfbreak exchange process which has been commonly observed in the Middle Atlantic Bight, south of New England, is the mid‐depth salinity maximum intrusion, occurring predominantly in the stratified season. It is easily identified within salinity profiles, and yet there have been few hydrographic surveys that have resolved the spatial extent of these features. In order to study these features in more detail, a dedicated research cruise was directed in June 2021 toward mapping and characterization of one of these intrusions. Using a combination of shipboard CTD profiles, Autonomous Underwater Vehicle missions, and a towed microstructure profiler, a strong intrusion was mapped in three‐dimensions for the first time. The intrusion penetrated 33 km onshore of the upper portion of the Shelfbreak Front, was 14 km wide in the along‐shelf, and was 10–30 m thick. A warm core ring was directly offshore of the intrusion and likely contributed to the initiation of the intrusion. The intrusion contributed about 2.5% additional salt relative to the ambient salinity structure. These intrusions are relevant for the shelf salinity budget as well as the onshore transport of larval fish and are thus an important process for the shelf ecosystem.

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.

The Northeast US Continental Shelf (NES) is a highly productive marine ecosystem that has experienced wide swings in phytoplankton chlorophyll concentration (CHL). To better understand this variability, we examined changes in CHL over the period 1998-2022, while also considering three indicators of the potential supply of nutrient source waters including cross-shelf advection via deep channels, transport from beyond the shelf edge via Gulf Stream warm core rings (WCR), and input from river and estuarine discharge. Traditionally, deep channel advection of water across the NES was assumed to be derived from Labrador Slope Water (LSW) and Warm Slope Water (WSW). These designations do not fully capture the range of water types contributing to cross-shelf advection. The contribution of LSW and WSW was reciprocal over time, with the presence of WSW at an increased level in recent years. There has been an increase in the number of WCRs off the NES represented by indices of ring occupancy. Precipitation increased over the study period as well, generally over the NES region and in particular in the Mid-Atlantic Bight drainage. We see evidence of the effect of increased precipitation on the NES proper through a change in the area of the ocean surface having 555 nm reflectance with sr-1 > 0.004. Using a canonical analysis, CHL correlated positively with the proportion of LSW and negatively with WSW. These correlations suggest there are aspects of the nutrient content associated with these water masses that are key to phytoplankton growth. WCR frequency negatively correlated with CHL, which was expected since the nutrient loadings of WCRs tends to be low. Finally, CHL negatively correlated with precipitation rate, which suggests terrestrial origin nutrient inputs to the NES are minor. We suggest that in order to understand future CHL dynamics in the NES, careful consideration of advective sources of nutrients in the Northwest Atlantic is necessary.

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−1 over its ~ 400,000 km2 area; 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.

Trends in sea surface temperatures (SST) of the US Northeast Continental Shelf and the adjacent Slope Sea were analyzed using a quantile approach. SST through the period 1982-2021 were analyzed for change in annual mean and range. In addition, the mean of each 25% quantile of the data by year was calculated. Using the full time series, the climatological SSTs at each quantile was determined, which in turn were used with the annual data to determine the number of days temperature fell within the limits of each climatological quantile. The time series of the data parameters were summarized by grid location and for a series of representative index areas. The index areas were analyzed for evidence of change points or regime shifts using the STARS (Sequential T-test Analysis of Regime Shifts) algorithm. The widely reported SST warming in this region was reinforced with our analysis; our findings also revealed new aspects of the change of thermal conditions in important ways. Mean annual temperature trended at approximately 0.36 degree celsius per decade; however, warm quantile SSTs increased by more than 1.25 degree celsius per decade in the Slope Sea, representing a five degree increase over the study period. The change point analysis suggested the change in thermal regime began as early as 2005 or 2007 with the study region fully enveloped by regime change by 2012. A previously identified change point in 1999 appears to be related to the duration of warming as opposed to SST levels. Mean SST alone does not capture the nature of high temperature exposure for living marine species in the study area; these regions may be experiencing a month or more of stressfully higher SST. The thermal effects derived using the quantile approach suggest different types of thermal exposures compared to heat wave analyses, especially related to cumulative exposure.

The Shelfbreak Front in the Northern Middle Atlantic Bight delineates the boundary between colder, fresher shelf water and warmer, saltier slope water. The location of the foot of the Shelfbreak Front, where the frontal isohalines and isopycnals intersect the bottom, is highly dynamic, impacting several commercial fisheries. In this work, we present new indices to quantify seasonal and interannual variability in the movement of the foot of the Shelfbreak Front. One index is generated from over three decades of observational Conductivity, Temperature, and Depth (CTD) data, and the other from GLORYS reanalysis fields. After detrending and removing seasonality, both indices capture similar variability and were found to be statistically significantly correlated with upstream along-shelf geostrophic velocities derived using satellite altimetry data. Using the lag correlation between the along-shelf geostrophic velocities from the Scotian Shelf to Georges Bank, skillful forecasts for the frontal indices were obtained up to three seasons in advance. This work provides a useful methodology for including variability of the foot of the Northern Middle Atlantic Bight Shelfbreak Front into ecosystem and stock assessment models using readily available near-real-time satellite altimetry data.

We demonstrate how the wind-driven Ekman transport enhances the advection and mixing of cells from the colder waters of the Surface Antarctic Waters from the south to the warmer waters of the northern Polar Front (PF) belt. This mechanism provides cells a mean ambient temperature near optimum levels for specific species and, ultimately, for community growth rates high enough to develop blooms under non-light limiting macronutrients and iron conditions. A Lagrangian trajectory model was constructed for tracking plankton cells as tracers forced by winds and surface currents. Depending on the region along the circumpolar front, increased winds can enhance this process across temperature gradients, and further accelerate such temperature-controlled growth. These results indicate that favorable temperature may enhance the growth rate even further when iron is sufficiently available, and thus have far-reaching implications for increased productivity in a future warming climate.

The United States Northern Shortfin squid fishery is known for its large fluctuations in catch at annual scales. In the last 5 years, this fishery has experienced increased availability of Illex illecebrosus along the Northeast US continental shelf (NES), resulting in high catch per unit effort (CPUE) and early fishery closures due to quota exceedance. The fishery occurs within the Northwest Atlantic, whose complex dynamics are set up by the interplay between the large-scale Gulf Stream, mesoscale eddies, Shelfbreak Jet, and shelf-slope exchange processes. Our ability to understand and quantify this regional variability is requisite for understanding the availability patterns of Illex, which are largely influenced by oceanographic conditions. In an effort to advance our current understanding of the seasonal and interannual variability in this species' relative abundance on the NES, we used generalized additive models to examine the relationships between the physical environment and hotspots of productivity to changes in CPUE of I. illecebrosus in the Southern stock component, which comprises the US fishery. Specifically, we derived oceanographic indicators by pairing high-resolution remote sensing data and global ocean reanalysis physical data to high-resolution fishery catch data. We identified a suite of environmental covariates that were strongly related to instances of higher catch rates. In particular, bottom temperature, warm core rings, subsurface features, and frontal dynamics together serve as indicators of habitat condition and primary productivity hotspots, providing great utility for understanding the distribution of Illex with the potential for forecasting seasonal and interannual availability.

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.

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).

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 degrees W. The WCR dataset reveals a very narrow band between 66 and 71 degrees W along which rings travel almost due west along similar to 39 degrees 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 contains weekly trajectory information of Gulf Stream Warm Core Rings from 2011-2020. This dataset is comprised of individual files containing each ring’s weekly center location and its area for 282 WCRs present between January 1, 2011 and December 31, 2020. Each 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. 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 2017 having a trailing alphabet of 'E' indicates that four rings were carried over from 2016 which were still observed on January 1, 2017. 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 week 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 2011-2020. 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). 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).

Fluctuations in the path of the Gulf Stream (GS) have been previously studied by primarily connecting to either the wind-driven subtropical gyre circulation or buoyancy forcing via the subpolar gyre. Here we present a statistical model for 1 year predictions of the GS path (represented by the GS northern wall-GSNW) between 75 degrees W and 65 degrees W incorporating both mechanisms in a combined framework. An existing model with multiple parameters including the previous year's GSNW index, center location, and amplitude of the Icelandic Low and the Southern Oscillation Index was augmented with basin-wide Ekman drift over the Azores High. The addition of the wind is supported by a validation of the simpler two-layer Parsons-Veronis model of GS separation over the last 40 years. A multivariate analysis was carried out to compare 1-year-in-advance forecast correlations from four different models. The optimal predictors of the best performing model include: (a) the GSNW index from the previous year, (b) gyre-scale integrated Ekman Drift over the past 2 years, and (c) longitude of the Icelandic Low center lagged by 3 years. The forecast correlation over the 27 years (1994-2020) is 0.65, an improvement from the previous multi-parameter model's forecast correlation of 0.52. The improvement is attributed to the addition of the wind-drift component. The sensitivity of forecasting the GS path after extreme atmospheric years is quantified. Results indicate the possibility of better understanding and enhanced predictability of the dominant wind-driven variability of the Atlantic Meridional Overturning Circulation and of fisheries management models that use the GS path as a metric.

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.

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, ). The WCR formation over the whole region (75-55 degrees 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 degrees zones between 75 degrees W and 55 degrees 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 degrees 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 degrees 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.

Survival of Gulf Stream (GS) warm core rings (WCRs) was investigated using a census consisting of a total of 961 rings formed during the period 1980-2017. Kaplan-Meier survival probability and Cox hazard proportional models were used for the analysis. The survival analysis was performed for rings formed in four 5 degrees zones between 75 degrees W and 55 degrees W. The radius, latitude, and distance from the shelf-break of a WCR at formation all had a significant effect on the survival of WCRs. A pattern of higher survival was observed in WCRs formed in Zone 2 (70 degrees -65 degrees W) or Zone 3 (65 degrees -60 degrees W) and then demised in Zone 1 (75 degrees -70 degrees W). Survival probability of the WCRs increased to more than 70% for those formed within a latitude band from 39.5 degrees to 41.5 degrees N. Survival probability is reduced when the WCRs are formed near the New England Seamounts. Plain Language Summary The Gulf Stream produces warm core rings in the Western Atlantic Ocean due to its meandering nature. These warm core rings have physical, chemical, and biological impacts on shelf and slope sea regions of the Western North Atlantic. This region is one of the most highly productive fishing areas in the world, and there is a need to understand the Warm Core Ring influence on different food web systems. We use data from a 38-yearlong (1980-2017) warm core ring census to investigate the survival probability of these warm core rings. After using multiple survival analysis techniques (a popular analysis technique in the medical and health sciences), we observed a high survival probability in WCRs formed within the 7 degrees -65 degrees W longitudinal band. Also, the warm core rings which demised within the 75 degrees -70 degrees W longitudinal band exhibited higher survival. The effect of the New England Seamount Chain (NESC) on WCR survival probabilities was revealed through a Cox proportional hazard model which showed that the further east a ring was formed from the NESC, the higher the survival probability. These findings are very important as precursors to understand the effect of WCRs on shelf-slope processes in the Western North Atlantic. Key Points Survival of Gulf Stream warm core rings was analyzed using Kaplan-Meier and Cox Hazard proportional models Ring survival depends on the zone, season, latitude, and proximity to New England Seamount at formation A pattern of higher survival was observed for rings formed within 70 degrees -65 degrees W and then demised within 75 degrees -70 degrees W