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Accurate digitization of synoptic ocean features is crucial for climate studies and the operational forecasting of ocean and coupled ocean-atmosphere systems. Today, for some North Atlantic operational regional models, skilled human experts visualize and extract the gulf stream and rings (warm and cold eddies) through an extensive and knowledge-based manual process. To automate this task, we develop a dynamics-inspired deep learning system that extracts the Gulf Stream and rings from concurrent satellite images of sea surface temperature (SST) and sea surface height (SSH). We pose the above problem as a multilabel semantic image segmentation problem. A novel deep convolutional neural network architecture named W-Net, with two parallel encoder-decoder branches, is developed to perform the segmentation. The W-Net's one branch is the SST branch (accepts SST image as input) and another is the SSH branch (accepts SSH as input), and the final output is a segmentation of gulf stream, warm rings, and cold rings. A dataset consisting of SST, SSH, and manual feature annotation (ground truth) from 2014 to 2018 is used for training. For gulf stream, we obtain 82.7% raw test accuracy and a low error of 4.39% in the detected path length. For the Rings, we obtain more than 71% raw eddy detection accuracy. A detailed ablation study and an examination of both SST and SSH parts of the network are presented to understand how the deep neural network learns to segment the gulf stream's meandering path and Rings accurately.

We report the initial results of an experimental investigation into the measurement of ocean surface currents with an ultrahigh frequency synthetic aperture radar (UHF SAR) that supports an along-track interferometric (ATI) mode. We compare results from two different approaches to the current measurement: analysis of wave dispersion in a time-sequence of subaperture images and standard ATI-SAR processing. We find that while both methods clearly show a surface velocity front over the north wall of the Gulf Stream, the change in velocity indicated by the dispersion method is significantly less than that indicated by ATI-SAR processing. We offer methodological and geophysical reasons for the observed differences.

The aim of this study was to investigate students’ understanding of the Gulf Stream as a geographical phenomenon and in relation to geospatial conceptualizations focusing on the geographical concep...

The Gulf Stream and Kuroshio regions feature strong sea surface temperature (SST) gradients that influence cyclone development and the storm track. Previous studies showed that smoothing the SSTs in either the North Atlantic or North Pacific yields a reduction in cyclone activity, surface heat fluxes, and precipitation, as well as a southward shift of the storm track and the upper-level jet. To what extent these changes are attributable to changes in individual cyclone behaviour, however, remains unclear. Comparing simulations with realistic and smoothed SSTs in the atmospheric general circulation model AFES, we find that the intensification of individual cyclones in the Gulf Stream or Kuroshio region is only marginally affected by reducing the SST gradient. In contrast, we observe considerable changes in the climatological mean state as well as a reduced cyclone activity in the North Atlantic and North Pacific storm tracks that are shifted equatorward in both basins. The upper-level jet in the Atlantic also shifts equatorward, while the jet in the Pacific strengthens in its climatological position and extends further east. Surface heat fluxes, specific humidity, and precipitation also respond strongly to the smoothing of the SST, with a considerable decrease in their mean values on the warm side of the SST front. This decrease is more pronounced in the Gulf Stream than in the Kuroshio region, due to the larger decrease in SST along the Gulf Stream SST front. Considering the differences of the different variables occurring within/outside of a 750 km radius of any cyclone over their entire lifetime, we find that cyclones play only a secondary role in explaining the differences in the mean state between the smoothed and realistic SST experiments.

Observations show that sea surface temperatures along the Gulf Stream and the Kuroshio Current tend to synchronize at decadal time scales. This synchronization, which we refer to as the boundary current synchronization (BCS), is reproduced in global climate models with high spatial resolution. Both in observations and model simulations, BCS is associated with meridional migrations of the atmospheric jet stream. Changes in the strength and path of the ocean currents associated with the jet shifts lead to the synchronicity of surface temperatures. Numerical simulations using a conceptual model and an atmospheric general circulation model are consistent with a notion that BCS is an interbasin air-sea coupled mode. Air temperature patterns similar to the one associated with BCS have been repeatedly observed, including in July of 1994 and 2018.

The Paleogene history of biogenic opal accumulation in the North Atlantic provides insight into both the evolution of deepwater circulation in the Atlantic basin and weathering responses to major climate shifts. However, existing records are compromised by low temporal resolution and/or stratigraphic discontinuities. In order to address this problem, we present a multi-site, high-resolution record of biogenic silica (bioSiO2) accumulation from Blake Nose (ODP Leg 171B, western North Atlantic) spanning the early Paleocene to late Eocene time interval (∼65–34 Ma). This record represents the longest single-locality history of marine bioSiO2 burial compiled to date and offers a unique perspective into changes in bioSiO2 fluxes through the early to middle Paleogene extreme greenhouse interval and the subsequent period of long-term cooling. Blake Nose bioSiO2 fluxes display prominent fluctuations that we attribute to variations in sub-thermocline nutrient supply via cyclonic eddies associated with the Gulf Stream. Following elevated and pulsed bioSiO2 accumulation through the Paleocene to early Eocene greenhouse interval, a prolonged interval of markedly elevated bioSiO2 flux in the middle Eocene between ∼46 and 42 Ma is proposed to reflect nutrient enrichment at Blake Nose due to invigorated overturning circulation following an early onset of Northern Component Water export from the Norwegian–Greenland Sea at ∼49 Ma. Reduced bioSiO2 flux in the North Atlantic, in combination with increased bioSiO2 flux documented in existing records from the equatorial Pacific between ∼42 and 38 Ma, is interpreted to indicate diminished nutrient supply and reduced biosiliceous productivity at Blake Nose in response to weakening of the overturning circulation. Subsequently, in the late Eocene, a deepwater circulation regime favoring limited bioSiO2 burial in the Atlantic and enhanced bioSiO2 burial in the Pacific was established after ∼38 Ma, likely in conjunction with re-invigoration of deepwater export from the North Atlantic. We also observe that Blake Nose bioSiO2 fluxes through the middle Eocene cooling interval (∼48 to 34 Ma) are similar to or higher than background fluxes throughout the late Paleocene–early Eocene interval (∼65 to 48 Ma) of intense greenhouse warmth. This observation is consistent with a temporally variable rather than constant silicate weathering feedback strength model for the Paleogene, which would instead predict that marine bioSiO2 burial should peak during periods of extreme warming.

March 15, 2021 Chief Researcher, Head of the Laboratory of Hydrological Processes of the P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences, DSc, ex-president of the International Association for Physical Ocean Sciences (IAPSO) Evgeny Morozov is 75 years old. E.G. Morozov is a prominent scientist and organizer of world-class science in the field of studying the temporal and spatial variability of hydrological processes and internal waves in a wide range of scales. He was the first to build a map of the amplitudes of tidal internal waves of the World Ocean. His monograph “Oceanic Internal Waves” published in 1985 in Russian, as well as his article “Semidiurnal internal wave global field”, published in the Deep Sea Research in 1995, are among the most cited on the problem of internal tidal waves. Unique results were obtained by E.G. Morozov in the study of internal waves in the Arctic, including under the ice and near the front of glaciers sliding into the ocean on Spitsbergen. He made a significant contribution to the study of various currents: the Gulf Stream, the Kuroshio and their rings, the Antarctic Circumpolar Current, the California Current, the Falkland Current, the Lomonosov and Tareev subsurface equatorial currents. Since 1999 he has been a member of the Executive Committee of the International Association for the Physical Sciences of the Ocean (IAPSO) and since 2011 he has been elected President of the IAPSO, represented the IAPSO in this capacity on the Executive Committee of the International Geodetic and Geophysical Union (IUGG) and on the Executive Committee of the Scientific Committee on Oceanic research (SCOR). E.G. Morozov is the chairman of the Ocean Physical Sciences Section of the National Geophysical Committee of the Russian Academy of Sciences.

The euphausiid genus Stylocheiron includes species with biogeographical distributions spanning multiple ocean basins. Despite their circumglobal distributions, the species show low levels of genetic diversity and little or no evidence of population structure based on the mitochondrial cytochrome oxidase I (COI) barcode region, with the exception of a possible cryptic species within Stylocheiron affine. Stylocheiron elongatum showed

The Loop Current evolves in the Gulf of Mexico as a continuation of the Yucatan Current and its upstream Caribbean Current, entering through the Yucatan Channel from the Northwestern Caribbean Sea. The Loop Current system contains the associated rich eddy field and together with the Florida Current controls the exit of the Gulf Stream toward the Atlantic Ocean and its downstream evolution along the US coasts. We examine the consequences of this natural connectivity, focusing on the dynamical synergy of mesoscale circulation processes downstream (north) of the Yucatan Channel (Gulf interior, dominated by Loop Current variability) and upstream (south) of the Yucatan Channel (Northwestern Caribbean Sea). We focus on Caribbean Anticyclones, their characteristics and evolution as they feed into the Loop Current system. We employ observational (satellite altimetry and drifters) and simulated (ocean numerical model) data for a 9-year period (2010–2018). Several metrics related to the Loop Current (maximum latitude, axis), Yucatan Current (zonal position), and Caribbean Sea mesoscale circulation (vorticity) are used to quantify how the accurate representation of Caribbean eddies can improve the prediction of the Loop Current. The numerical results, the altimetry observational fields, and the respective drifter trajectories show a strong relationship between the Caribbean Anticyclones and the Loop Current variability, both at the base of the Loop Current (position of the Yucatan Current) and within the Gulf interior (northern Loop Current position and orientation). During retracted Loop Current periods, the evolution of anticyclones in the Yucatan Channel plays a role on the eastward tilt of the Loop Current axis and the zonal shift of the Yucatan Current close to the island of Cuba. Lagrangian analyses confirmed that coherent anticyclonic flux across the Yucatan Channel usually evolves closer to Cuba and is associated with retracted Loop Current phases. A lag of 5 to 10 days between the anticyclonic vorticity in the northwestern Caribbean and the Loop Current variability was identified. The evolution of Caribbean Anticyclones crossing the Yucatan Channel is thus an influencing factor on the interior dynamics of the Gulf of Mexico and the connectivity processes with the Caribbean Sea.

The bulk sea surface temperature (SST) simulated by COAMPS/NCOM [Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) and the Navy Coastal Ocean Model (NCOM)] compares reasonably well with the bulk SST measured on the North Carolina shelf during the October of 2015 field campaign of the CASPER Project (Wang et al. in Bull Amer Met Soc 99:1449–1471, 2018). The model slightly overestimates the field data by about 0.15 °C; a linear regression is strong with a coefficient of determination r2 > 0.9. In deep waters of the Gulf Stream core, COAMPS/NCOM typically underestimates the measured SST by less than 1 °C except in the cold lens or meander where the temperature gradients were smoothed by the model. It is evident that sub-mesoscale features like frontal eddies, meanders and filaments, require a resolution higher than the 3 km grid spacing adopted for modeling.

Daniel Williams, “Transatlantic Climate and Gulf Stream Aesthetics” (pp. 57–91) The Gulf Stream gained scientific prominence in the nineteenth century as a test case for theories about the dynamics of ocean currents and the equilibrium of transatlantic climate. Discourse about the current supplied descriptions, analogies, and myths that persist into the present. Triangulating oceanic, ecological, and transatlantic approaches to literary study, this essay argues that the nineteenth-century discourse of the Gulf Stream included a significant aesthetic dimension organized by a dialectic between stability and variability. First, the essay traces the Gulf Stream’s presence in eighteenth- and nineteenth-century scientific writing and print culture, showing how memorable figures and vivid illustrations accentuated the risk of climate variability even as they charted an apparently stable oceanic system. Next, it considers the work of two poets separated by the ocean, Gerard Manley Hopkins and Sidney Lanier. While ostensibly using the Gulf Stream motif to reflect on geographic identity and cultural belonging, Hopkins and Lanier use formal and figurative techniques that register the threat of climate instability, offering a deeper sense of climate disquiet than the scientific materials on which they drew. Finally, the essay looks at the poetry of Derek Walcott, sketching the afterlife of the Gulf Stream discourse, extending its formal and figurative lineage, and renewing the present ecological urgency of thinking with an Earth-system process as a motif of climatic connection and obligation.

Global sea level reconstruction (RecSL) for 1900–2015 was used to estimate the variations in oceanic kinetic energy (OKE) and compare OKE with changes in wind patterns and wind kinetic energy (WKE); the comparison was done for each latitude and for 5 western boundary currents (WBCs). Two contributors to variability in sea level were analyzed: gravitational, rotational and deformational effects (GRD) related to changes in water masses (barystatic sea level change), and changes in the sterodynamic sea level (SDSL), associated with changes in wind, steric sea level and ocean circulation. GRD changes were responsible for latitudinal multidecadal variations with time scale of ~ 60 to 80 years, while SDSL changes were responsible for interannual and decadal variability, and together with the Greenland ice melt, to sea level acceleration since the 1960s. Regional changes near WBCs show a coherent upward trend in OKE (+ 24% ± 3 increase per century), while trends in WKE over the same regions changed widely from -11% (decrease) over the Gulf Stream region to + 28% (increase) over the Brazil Current region. Low frequency oscillations of wind and oceanic kinetic energy are correlated in some WBCs (e.g., R = 0.5 in the Kuroshio region) but not in others (e.g., R = -0.05 in the Gulf Stream region). The study suggests that several forcing mechanisms contribute to the increased OKE, they include an increased wind-stress curl over subtropical gyres, local changes in wind patterns that impact some WBCs, and large uneven warming near WBCs that increased sea level gradients and thus intensified OKE.

Continental shelf regions in the ocean play an important role in the global cycling of carbon and nutrients, but their responses to global change are understudied. Global Earth system models (ESMs), as essential tools for building understanding of ocean biogeochemistry, are used extensively and routinely for projections of future climate states; however, their relatively coarse spatial resolution is likely not appropriate for accurately representing the complex patterns of circulation and elemental fluxes on the shelves along ocean margins. Here, we compared 29 ESMs used in the Intergovernmental Panel on Climate Change (IPCC)'s Assessment Reports (ARs) 5 and 6 and a regional biogeochemical model for the northwest North Atlantic (NWA) shelf to assess their ability to reproduce surface observations of temperature, salinity, nitrate and chlorophyll. The NWA region is biologically productive, influenced by the large-scale Gulf Stream and Labrador Current systems and particularly sensitive to climatically induced changes in large-scale circulation. Most ESMs compare relatively poorly to observed surface nitrate and chlorophyll and show differences with observed surface temperature and salinity that suggest spatial mismatches in their large-scale current systems. Model-simulated nitrate and chlorophyll compare better with available observations in AR6 than in AR5, but none of the models perform equally well for all four parameters. The ensemble means of all ESMs, and of the five best-performing ESMs, strongly underestimate observed chlorophyll and nitrate. The regional model has a much higher spatial resolution and reproduces the observations significantly better than any of the ESMs. It also simulates reasonably well vertically resolved observations from gliders and bi-monthly ship-based monitoring observations. A ranking of the ESMs indicates that only one ESM has good and consistent performance for all variables. An additional evaluation of the ESMs along the regional model boundaries shows larger variability but is generally consistent with the ranking on the shelf. Overall, 11 ESMs were deemed satisfactory for use in the NWA, either directly or for regional downscaling.

The North Atlantic north of 50 ∘ N is one of the most intense ocean sink areas for atmospheric CO 2 considering the flux per unit area, 0.27 Pg-C yr −1 , equivalent to −2.5 mol C m −2 yr −1 . The northwest Atlantic Ocean is a region with high anthropogenic carbon inventories. This is on account of processes which sustain CO 2 air–sea fluxes, in particular strong seasonal winds, ocean heat loss, deep convective mixing, and CO 2 drawdown by primary production. The region is in the northern limb of the global thermohaline circulation, a path for the long-term deep-sea sequestration of carbon dioxide. The surface water masses in the North Atlantic are of contrasting origins and character, with the northward-flowing North Atlantic Drift, a Gulf Stream offspring, on the one hand and on the other hand the cold southward-moving low-salinity Polar and Arctic waters with signatures from Arctic freshwater sources. We have studied by observation the CO 2 air–sea flux of the relevant water masses in the vicinity of Iceland in all seasons and in different years. Here we show that the highest ocean CO 2 influx is to the Arctic and Polar waters, respectively, - 3.8 ± 0.4 and - 4.4 ± 0.3 mol C m −2 yr −1 . These waters are CO 2 undersaturated in all seasons. The Atlantic Water is a weak or neutral sink, near CO 2 saturation, after poleward drift from subtropical latitudes. These characteristics of the three water masses are confirmed by data from observations covering 30 years. We relate the Polar Water and Arctic Water persistent undersaturation and CO 2 influx to the excess alkalinity derived from Arctic sources. Carbonate chemistry equilibrium calculations clearly indicate that the excess alkalinity may support at least 0.058 Pg-C yr −1 , a significant portion of the North Atlantic CO 2 sink. The Arctic contribution to the North Atlantic CO 2 sink which we reveal was previously unrecognized. However, we point out that there are gaps and conflicts in the knowledge about the Arctic alkalinity and carbonate budgets and that future trends in the North Atlantic CO 2 sink are connected to developments in the rapidly warming and changing Arctic. The results we present need to be taken into consideration for the following question: will the North Atlantic continue to absorb CO 2 in the future as it has in the past?

The new gravity field models of gravity field and steady-state ocean circulation explorer (GOCE), TIM_R6 and DIR_R6, were released by the European Space Agency (ESA) in June 2019. The sixth generation of gravity models have the highest possible signal and lowest error levels compared with other GOCE-only gravity models, and the accuracy is significantly improved. This is an opportunity to build high precision geostrophic currents. The mean dynamic topography and geostrophic currents have been calculated by the 5th (TIM_R5 and DIR_R5), 6th (TIM_R6 and DIR_R6) release of GOCE gravity field models and ITSG-Grace2018 of GRACE gravity field model in this study. By comparison with the drifter results, the optimal filtering lengths of them have been obtained (for DIR_R5, DIR_R6, TIM_R5 and TIM_R6 models are 1° and for ITSG-Grace2018 model is 1.1°). The filtered results show that the geostrophic currents obtained by the GOCE gravity field models can better reflect detailed characteristics of ocean currents. The total geostrophic speed based on the TIM_R6 model is similar to the result of the DIR_R6 model with standard deviation (STD) of 0.320 m/s and 0.321 m/s, respectively. The STD of the total velocities are 0.333 m/s and 0.325 m/s for DIR_R5 and TIM_R5. When compared with ITSG-Grace2018 results, the STD (0.344 m/s) of total geostrophic speeds is larger than GOCE results, and the accuracy of geostrophic currents obtained by ITSG-Grace2018 is lower. And the absolute errors are mainly distributed in the areas with faster speeds, such as the Antarctic circumpolar circulation, equatorial region, Kuroshio and Gulf Stream areas. After the remove-restore technique was applied to TIM_R6 MDT, the STD of total geostrophic speeds dropped to 0.162 m/s.

International audience; The input of mechanical power to the ocean due to the surface wind-stress, in regions which correspond to different regimes of ocean dynamics, is considered using data from satellites observations. Its dependence on the coarse-graining range of the atmospheric and oceanic velocity in space from 0.5 o to 10 o and time from 6h to 40 days is determined. In the area of the Gulf Stream and the Kuroshio extensions the dependence of the power-input on space-time coarse-graining varies over tenfold for the coarse-graining considered. It decreases over twofold for the Gulf Stream extension and threefold for the Kuroshio extension, when the coarse-graining length-scale passes from a few degrees to 0.5 o at a temporal coarse-graining scale of a few days. It increases over threefold in the Gulf Stream and the Kuroshio extensions when the coarse-graining passes from several days to 6h at a spatial coarse-graining of a few degrees. The power input is found to increase monotonically with shorter coarse-graining in time. Its variation with coarse-graining in space has no definite sign. Results show that including the dynamics at scales below a few degrees reduces considerably the power input by air-sea interaction in regions of strongly non-linear ocean currents. When the ocean velocities are not considered in the shear calculation the power-input is considerably (up to threefold) increased. The dependence of the power input on coarse-graining in space and time is close to being multiplicatively separable in all regions and for most of the coarse-graining domain considered.

The present study examined the relationship between turbulent surface heat flux (SHF) and sea surface temperature (SST) variations using daily observational data. The SHF and SST relationship displays notable differences between winter and summer and prominent time-scale dependence in both seasons. In the mid-latitude SST frontal regions, SST has a larger role in driving SHF in winter than in summer. In the subtropical gyre regions, SHF plays a larger role in the SST change in summer than in winter. In winter, SHF has a larger effect on the SST change in the South China Sea than in the Arabian Sea and Bay of Bengal. In summer, the SST effect on SHF is dominant in the Arabian Sea, whereas the SHF impact on SST is dominant in the Philippine Sea. In the Gulf Stream, Kuroshio Extension and Agulhas Return Current, the SST effect extends up to 90-day time scales in winter, the SHF impact is limited to time scales below 20 days and the SST effect is dominant on time scales above 20 days in summer. In winter, the SHF effect extends up to 90-day time scales in the Bay of Bengal, South China Sea, and Philippine Sea, but is limited to time scales below 40 days in the Arabian Sea. In summer, the SST effect extends up to 90-day time scales in the Arabian Sea, whereas the SHF and SST effect is large on time scales shorter and longer than 40 days, respectively, in the Philippine Sea.

Recent research suggests the widespread existence of the signal-to-noise paradox in seasonal-to-decadal climate predictions. The essence of the paradox is that the signal-to-noise ratio in models can be unrealistically small and models may make better predictions of the observations than they predict themselves. The paradox highlights a potentially serious issue with model predictions as previous studies may underestimate the limit of predictability. The focus of this paper is two-fold: the first objective is to re-examine decadal predictability from the lens of the signal-to-noise paradox in the context of CMIP5 models. We demonstrate that decadal predictability is generally underestimated in CMIP5 models possibly due to the existence of the signal-to-noise paradox. Models underestimate decadal predictability in regions where it is likely for the paradox to exist, especially over the Tropical Atlantic Ocean and Tropical Indian Ocean and eddy-rich regions, including the Gulf Stream, Kuroshio Current, and Southern Ocean. The second objective follows from the results of the first, attempting to determine if this underestimate of decadal predictability is, at least partially, due to missing ocean mesoscale processes and features in CMIP5 models. A suite of coupled model experiments is performed with eddying and eddy-parameterized ocean component. Compared with eddy-parameterized models, the paradox is less likely to exist in eddying models, particularly over eddy-rich regions. These also happen to be regions where increased decadal predictability is identified. We hypothesize that this enhanced predictability is due to the enhanced vertical connectivity in the ocean. The presence of mesoscale ocean features and associated vertical connectivity significantly influence decadal variability, predictability, and the signal-to-noise paradox.

Using buoy observations from 2004 to 2010 and newly released atmospheric reanalysis and satellite altimetry-derived geostrophic currents from 1993 to 2017, the quantitative contribution of daily mean surface currents to air–sea turbulent heat flux and wind stress uncertainties in the Gulf Stream (GS) region is investigated based on bulk formulas. At four buoy stations, the daily mean latent (sensible) heat flux difference between the estimates with and without surface currents range from −18 (−4) to 20 (4) W m−2, while the daily mean wind stress difference ranges from −0.04 to 0.02 N m−2. The positive values indicate higher estimates with opposite directions between surface currents and absolute winds. The transition between positive and negative differences is significantly associated with synoptic-scale weather variations. The uncertainties based on buoy observations are approximately 7% and 3% for wind stress and turbulent heat fluxes, respectively. The new reanalysis and satellite geostrophic currents confirm the uncertainties identified by buoy observations with acceptable discrepancies and provide a spatial view of the uncertainty fields. The mean geostrophic currents are aligned with the surface wind along the GS; therefore, the turbulent heat fluxes and wind stress will be “underestimated” with surface currents included. However, on both sides of the GS, the surface flow can be upwind due to possible mechanisms of eddy–mean flow interactions and recirculations, resulting in higher turbulent heat flux estimations. The wind stress and turbulent heat flux uncertainties experience significant seasonal variations and show long-term trends.

The ichthyological studies carried out at the shelf of North-Eastern Greenland in 2002–2017 new regions of dwelling of beaked redfish Sebastes mentella were discovered. It is shown that the distribution of underyearlings is not limited to the European shelf, but extends much further to the west, to the deep-water part of the Fram Strait. Juvenile individuals of beaked redfish constantly occur off North-Eastern Greenland, where the branches of the Gulf Stream reach its shelf, and further south to the area of the formation of a circular current in the eastern part of the Greenland Sea and western the Norwegian Sea. It is likely, that this cyclonic system and the cold Greenland Current are an integral part of the feeding and migratory path of larvae, juvenile specimens and adult beaked redfish to the area of its reproduction on the European shelf, as well as in the Irminger Sea.

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 a local anticyclonic 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.

High-resolution satellite observations and numerical experiments have revealed local enhancement of time-mean surface wind convergence along the axes of warm western boundary currents and divergence slightly poleward. A recent study has suggested that frequent occurrence of persistent atmospheric fronts and sea level pressure (SLP) troughs along a sea surface temperature (SST) front are responsible for shaping the frontal-scale wind convergence and divergence contrast as seen in the wintertime climatology near the Kuroshio Extension (KE). These events tend to induce surface wind convergence with moderate magnitude. Through atmospheric reanalysis with high-resolution SST, the present study reveals that, as in the vicinity of the KE, surface wind convergence with moderate magnitude and divergence with moderate-to-extreme magnitude are found to play a primary role in shaping the climatological-mean wind convergence–divergence contrasts across the SST fronts near the Gulf Stream (GS) and Agulhas Return Current (ARC) in winter. In contrast, strong-to-extreme convergence events associated with synoptic-scale atmospheric disturbances are found to yield horizontally uniform time-mean wind convergence. Furthermore, cluster analysis and case studies suggest that persistent atmospheric fronts and SLP troughs are responsible for inducing moderate wind convergence also near the GS and ARC. Thus, these features are consistent with their counterpart near the KE, but the impacts of the ARC tend to be substantially weaker, probably due to its cooler SST among other potential factors.

The filtering procedure is usually mandatory for modeling mean dynamic topography (MDT) when a geodetic approach based on the Mean Sea Surface (MSS) and the Global Geopotential Model (GGM) is used. This is due to the inconsistent spectral contents between MSS and GGM. However, traditional isotropic filtering algorithms (e.g., Gaussian filter) consider neither the MDT locations nor their azimuth when smoothing the signal within the filtering radius. Hence, the isotropic filtering will attenuate the MDT signal near the current and filter the current signal into the surrounding ocean, which may lead to signal contamination and distortion. In this study, we set up a least squares-based (LS) approach to model MDT signal from the altimeter-derived MSS and geoid height using spherical harmonics from GGMs, where MDT is parameterized by Lagrange Basis Functions (LBFs). The design matrix is segmentally established, considering the error information of GGM in various spectral bands. Numerical experiments in the Gulf Stream show that applications of full error variance-covariance matrix or only diagonal error variance of GGM may have marginal effects on the MDT modeling. The MDT computed from this LS-based approach using the latest releases of Gravity Field and Steady-state Ocean Circulation Explorer (GOCE) geoid models, i.e., GO_CONS_GCF_2_DIR_R6 and Gravity Observation Combination 06s model (GOCO06s), have the best agreement with the comparison data, especially near the current region. Deduced geostrophic velocities based on the MDT solutions show that the LS-based approach recovers the current signal better than the Gaussian filtering by 1.8 cm/s. Estimated error map illustrates that errors are more concentrated near the coastal region.

Cape Hatteras is a major topographic feature on the continental shelf of the U.S. eastern seaboard that changes the dynamics of nearshore large ocean currents, including the Labrador Current and Gulf Stream. Cape Hatteras constricts shelf habitat and restricts the migratory corridors of highly migratory species through this area. Our objective was to describe the seasonal patterns of presence for three species—the Spiny Dogfish Squalus acanthias, Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus, and Sandbar Shark Carcharhinus plumbeus—and analyze environmental conditions associated with fish presence near this feature. These species are managed under the Magnuson–Stevens Act, and two of them are also listed as species of concern under the Endangered Species Act. Transmitter detections from tagged fish recorded by the Cape Hatteras acoustic array, which was deployed just south of the cape, indicated that these species are present year‐round. The greatest number of detections occurred from November through April. This simple baseline of seasonal presence can provide insights for regional offshore development activities, which have the potential to affect movement patterns of migratory species through the Cape Hatteras constriction. Our results show the value of strategically placed acoustic arrays for observing fish habitat use and provide presence/absence data to enhance our understanding of species ecology and distribution.

In winter, the warm water of the Gulf Stream anchors a salient precipitation band. Previous studies suggested a close relationship between the sea surface temperature (SST) front and the precipitation band through sea level pressure (SLP) adjustment. This study uses 17 years of high-resolution precipitation observations to reveal that the variation in wintertime precipitation over the Gulf Stream is related to the North Atlantic Oscillation (NAO) at the interannual time scale. The moisture budget analysis shows that the climatological precipitation band is supported by the large evaporation from the Florida Current, mean flow, and synoptic moisture convergence within the boundary layer, with a negative contribution from mean-flow moisture advection by the prevailing northwesterlies. For interannual variability, by contrast, the negative contribution of mean-flow moisture advection significantly decreases due to anomalous southeasterlies west of the intensified Azores high at the positive NAO phase. The contributions from mean-flow moisture advection and mean and synoptic convergence vary greatly along the Gulf Stream. In addition, mean-flow and synoptic moisture convergences positively contribute to the precipitation band both in climatology and at the interannual time scale, indicative of a positive feedback between precipitation and boundary layer convergence. Our analysis suggests that the SLP adjustment mechanism across the SST front is still at work in interannual variability, and the variation of synoptic activities over the Gulf Stream plays an important role in modulating the frontal precipitation. By relating the frontal precipitation to the NAO, this study bridges small-scale air–sea interaction and large-scale atmospheric circulation.

The Gulf Stream affects global climate by transporting water and heat poleward. The current’s volume transport increases markedly along the U.S. East Coast. An extensive observing program using autonomous underwater gliders provides finescale, subsurface observations of hydrography and velocity spanning more than 15° of latitude along the path of the Gulf Stream, thereby filling a 1500-km-long gap between long-term transport measurements in the Florida Strait and downstream of Cape Hatteras. Here, the glider-based observations are combined with shipboard measurements along Line W near 68°W to provide a detailed picture of the along-stream transport increase. To account for the influences of Gulf Stream curvature and adjacent circulation (e.g., corotating eddies) on transport estimates, upper- and lower-bound transports are constructed for each cross–Gulf Stream transect. The upper-bound estimate for time-averaged volume transport above 1000 m is 32.9 ± 1.2 Sv (1 Sv ≡ 106 m3 s−1) in the Florida Strait, 57.3 ± 1.9 Sv at Cape Hatteras, and 75.6 ± 4.7 Sv at Line W. Corresponding lower-bound estimates are 32.3 ± 1.1 Sv in the Florida Strait, 54.5 ± 1.7 Sv at Cape Hatteras, and 69.9 ± 4.2 Sv at Line W. Using the temperature and salinity observations from gliders and Line W, waters are divided into seven classes to investigate the properties of waters that are transported by and entrained into the Gulf Stream. Most of the increase in overall Gulf Stream volume transport above 1000 m stems from the entrainment of subthermocline waters, including upper Labrador Sea Water and Eighteen Degree Water.

For 30+ years, submarine cable voltage measurements have been a critical measurement system used to produce a highly valuable time series of daily Florida Current volume transport at 27°N in the Fl...

The meandering of the Gulf Stream through the Straits of Florida is associated with eddy activity to the north (along the Florida Keys) and the south (along the Cuban coast). This study focuses on recently identified processes along the Cuban coast, namely anticyclonic eddies (Cuban ANticyclones: CubANs) and cyclonic activity characterized by cold-core eddies (cyclones) and coastal upwelling that enhances them. It is shown that these processes are an important factor for the evolution of the Loop Current/Florida Current (LC/FC) system. In particular, the Gulf Stream meandering inside the Straits (that is manifested as the position of the FC branch) is strongly related to CubANs either inside the retracted (closer to the Cuban coast) LC branch (CubAN “A”) or outside the LC as independent eddies (CubAN “B”). There are also mixed cases that both types of CubANs can be present, sharing a common place of origin, but evolving differently. These anticyclones are found to be strongly related to cyclonic activity and resulting temperature gradients along Cuba, characterized by cold-core cyclonic eddies and additional pools of cold waters that have upwelled under wind influence. These processes are shown to influence Gulf Stream meandering and also largely control the offshore export of upwelled, generally cooler and more productive, coastal waters. High-resolution simulations, in tandem with a variety of observational data, are used during a period of 8 years (2010–2017) to describe the evolution of CubANs and their contribution to Gulf Stream variability and associated coastal to offshore interactions. These findings are important for connectivity pathways between US and Cuban marine protected areas and between US coasts and the main Cuban area of oil exploration.

The relationship between age and oxygen is one that is often assumed in oceanography to be relatively simple. Because oxygen utilization rates are difficult to directly measure in the ocean, it is commonly assumed that the apparent oxygen utilization divided by the water age is a good representation of respiration. Likewise, because of limited transient tracer observations and difficulties constraining water age, it has been suggested that oxygen could be a useful proxy for age. In this paper, we explore the relationship between age and oxygen using observations from Line W, a repeat hydrography cruise track which crosses the Gulf Stream, extending from Cape Cod to Bermuda, and an Earth System Model simulation. In both the observations and the model, the assumed positive linear relationship between apparent oxygen utilization (AOU) and mean age is not found within and directly below the ventilated thermocline at the end of Line W. In the Earth System Model decoupling of age and AOU is found in gyre centers, in some coastal upwelling zones, and downstream of mode water formation regions that show large variability in isopycnal depth. In all three regions, differences in the spatial distribution of sources of age and AOU become critically important, producing offset maxima in the gyre centers, and different time variability of sources in the other two areas.

Of the more than 150 ctenophore species, the oceanic ctenophore Eurhamphaea vexilligera is notable for its bright orange-yellow ink, secreted from numerous small vesicles that line its substomodeal comb rows. To date, in situ observations by scuba divers have proved the most fruitful method of observing these animals' natural behavior. We present the results of one such contemporary scuba-based observation of E. vexilligera, conducted in the Gulf Stream waters off the coast of Florida, using high-resolution photography and video. Utilizing underwater camera systems purpose built for filming gelatinous zooplankton, we observed E. vexilligera ink release and swimming behavior in situ. From these data, we describe the timeline and mechanics of E. vexilligera ink release in detail, as well as the animal's different swimming behaviors and resulting ink dispersal patterns. We also describe a rolling swimming behavior, accompanied and possibly facilitated by a characteristic change in overall body shape. These observations provide further insight into the behavioral ecology of this distinctive ctenophore and may serve as the foundation for future kinematic studies.

This study suggests that the Gulf Stream influence on the wintertime North Atlantic troposphere is most pronounced when the eddy-driven jet (EDJ) is farthest south and better collocated with the Gulf Stream. Using the reanalysis dataset NCEP-CFSR for December–February 1979–2009, the daily EDJ latitude is separated into three regimes (northern, central, and southern). It is found that the average trajectory of atmospheric fronts covaries with EDJ latitude. In the southern EDJ regime (~19% of the time), the frequency of near-surface atmospheric fronts that pass across the Gulf Stream is maximized. Analysis suggests that this leads to significant strengthening in near-surface atmospheric frontal convergence resulting from strong air–sea sensible heat flux gradients (due to strong temperature gradients in the atmosphere and ocean). In recent studies, it was shown that the pronounced band of time-mean near-surface wind convergence across the Gulf Stream is set by atmospheric fronts. Here, it is shown that an even smaller subset of atmospheric fronts—those associated with a southern EDJ—primarily sets the time mean, due to enhanced Gulf Stream air–sea interaction. Furthermore, statistically significant anomalies in vertical velocity extending well above the boundary layer are identified in association with changes in EDJ latitude. These anomalies are particularly strong for a southern EDJ and are spatially consistent with increases in near-surface atmospheric frontal convergence over the Gulf Stream. These results imply that much of the Gulf Stream influence on the time-mean atmosphere is modulated on synoptic time scales, and enhanced when the EDJ is farthest south.

The Gulf Stream (GS) transports a massive amount of heat northward to high latitudes and releases sensible and latent heat to the atmosphere, playing an important role in the North Atlantic and European climate change. The change trends of the GS transport and pathway are still uncertain to date. Our analyses of altimeter observations from 1993 to 2016 indicate that the linear trends in surface maximum speed, transport, and latitudinal location of the GS are significant east of 61° W at the 95% level while they are small and not significant between 72° W and 61° W. The weakening trend of the GS during the period from 1993 to 2016 is accompanied with a southward-shifting path, which is associated with the decline of the North Atlantic Oscillation (NAO) and possibly reduction in the Atlantic meridional overturning circulation (AMOC).

An unusual double-thermostad warm-core ring of the Gulf Stream was discovered in the Slope Sea, south of Georges Bank, during the R/V Endeavor cruise 578 in May 2016. The ring’s stratification was peculiar as it included two thermostads at, respectively, 100–200 m (core T = 18.14°C, S = 36.52) and 250–500 m (core T = 16.70°C, S = 36.35). Extensive use of satellite data (SST imagery and SSH maps) allowed the life history of this ring to be reconstructed, with independent SST and SSH data mutually corroborating each other. The double-thermostad ring was formed by vertical alignment of two preexisting warm-core anticyclonic rings of the Gulf Stream. The first ring spawned by the Gulf Stream in February has cooled by ~2°C before merging in April with the second ring spawned by the Gulf Stream in March. During vertical alignment of these rings, the warmer ring overrode the colder ring, thereby forming the double-thermostad ring surveyed in May 2016. From ADCP sections through the ring, the upper and lower thermostads had different core relative vorticities of −0.65f and −0.77f, respectively, where f is the local Coriolis parameter. An in-depth literature survey has confirmed that this is the first report of a double-thermostad warm-core ring of the Gulf Stream and one of the best-documented cases of vertical alignment of two eddies ever observed in the World Ocean.

Characterizing deep-sea coral biodiversity is essential to evaluate the current state of deep-sea ecosystems and to assess vulnerability to anthropogenic threats such as offshore drilling and ocean acidification. Thousands of deep-sea coral records from the past 6 decades are compiled in the publicly accessible NOAA database, but few large-scale analyses of deep-sea coral biodiversity through time have been conducted. This study provides the longest temporal analysis of deep-sea coral generic biodiversity (58 yr), and the first such study for US waters. To mitigate missing temporal and spatial data, a machine learning model was employed to simulate deep-sea coral occurrences. Patterns of deep-sea coral generic biodiversity were calculated for observed and simulated data from 1960 to 2018 in the US marine ecoregions of the Gulf Stream Slope, Carolinian Atlantic Shelf and Slope, South Florida/Bahamian Atlantic Shelf and Slope, and Northern Gulf of Mexico (NGOM) Shelf and Slope. There were statistically significant decreases in deep-sea coral generic biodiversity for all ecoregion/depth pairs in simulated data and most ecoregion/depth pairs in observed data. There was relative stability in biodiversity from 1960 to the mid-2000s, followed by generally rapid decreases between 2007 and 2011. Biodiversity stabilized after 2011, though it remains at the lowest average level in the past 58 yr. Most ecoregions and depths show the lowest generic richness during the most recent time interval (2010–2018) compared to the preceding 5 decades. The most persistent deep-sea coral genera from 1960 to 2018 vary based on ecoregion and depth. Rapid decreases in biodiversity support previous work showing deep-sea corals can undergo biodiversity loss in less than 4 yr, which is alarming given their slow growth and decadal recovery times. This analysis provides a robust temporal framework for future researchers to evaluate casual mechanisms affecting deep-sea coral biodiversity and inform on conservation strategies.

Based on average monthly data of the ORAS4 ocean reanalysis, the spatial distribution and values of anomalies of the ocean surface temperature and the velocity of surface currents occurring in the North Atlantic at the meridional displacements of the north wall of the Gulf Stream in January–February are determined. Gulf Stream North Wall Index data are used as data on Gulf Stream movements. The spatial distributions of anomalies corresponding to the northern and southern positions of the North Wall are based on averaging the fields of ocean surface temperature and the velocity of currents corresponding to each phase of the Gulf Stream North Wall index. It has been revealed that for meridional displacements of the North Wall of the Gulf Stream, statistically significant anomalies of the modulus of current velocity (0.03 m/s) and ocean surface temperature (1°C) are not only in the area of the Wall, but also along the entire northern boundary of the Gulf Stream. Here the value of the correlation coefficient of velocity time series with the Gulf Stream North Wall index is 0.56. As for temperature, the same coefficient is 0.50. Significant temperature anomalies (0.3°C) are found off the coast of the Iberian Peninsula and in the central part of the subtropical gyre. The values of the correlation coefficients of time series of the surface temperature and the index of the Gulf Stream in these areas are 0.48 and 0.53 respectively.

This paper presents a hierarchical control framework for a kite-based marine hydrokinetic (MHK) system that executes power-augmenting cross-current flight, along with simulation results based on a high-fidelity turbulent flow model that is representative of flow conditions in the Gulf Stream. The hierarchical controller is used to robustly regulate both the kite’s flight path and the intra-cycle spooling behavior, which is ultimately used to realize net positive energy production at a base station motor/generator system. Two configurations are examined in this paper: one in which the kite is suspended from a surface-mounted platform, and another in which the kite is deployed from the seabed. To evaluate the robustness of this control framework in a realistic ocean environment, we present simulation results whereby we superimpose low-frequency data from the Mid Atlantic Bight South Atlantic Bight Regional Ocean Modeling System and acoustic Doppler current profiler measurements with a high-frequency turbulence model, resulting in a high-fidelity 3D spatiotemporal flow field that is presented to the kite system. Based on this simulation framework, we demonstrate the effectiveness of the control system both in terms of robust flight and power generation.

This is the first report of the Barents Sea Ice Edge (BIE) project. The BIE position has varied between latitude 76°N and above 82°N during the last 440 years. During the period 10,000 to 6000 years ago, Arctic climate was significantly warmer than today. We review various oceanic and atmospheric factors that may have an effect on the BIE position. The Gulf Stream beat with respect to alternations in flow intensity and N-S distribution plays a central role for the changes in climate and BIE position during the last millennium. This occurred in combination with external forcing from total solar irradiation, Earth’s shielding strength, Earth’s geomagnetic field intensity, Earth’s rotation, jet stream changes; all factors of which are ultimately driven by the planetary beat on the Sun, the Earth and the Earth-Moon system. During the last 20 years, we see signs of changes and shifts that may signal the end of the late 20th century warm period. The BIE position is likely to start advancing southward in next decade.

To anyone who had the temerity to press a nose against the picture, to sniff at or try to smell it, he gave a clear message. . . . Just below his signature and the painting’s date, Homer wrote in light-colored script, as if it were flotsam from a wreck: “At 12 feet from this picture/you can see it.”

Sea level rise (SLR) is causing acceleration in the frequency and duration of minor tidal flooding (often called “sunny-day” or “nuisance” flooding) along the U.S. East Coast. Those floods have a seasonal pattern that often follows the monthly mean sea level anomaly which peaks in September–October for stations between New York and south Florida. However, there are large differences between coasts: for example, over 75% of the minor floods occur during the fall in Florida, but during the spring and winter in Boston. Various data and forcing, such as tide gauge records, surface temperatures, winds, long-term tidal cycles, and the Gulf Stream flow, were analyzed to examine potential drivers and mechanisms that can contribute to the seasonal pattern of floods. The seasonal water temperature cycle, with maximum temperatures in August, could not by itself explain the seasonal sea level pattern, but two mechanisms that significantly correlate with the seasonal sea level and flooding patterns are the annual and semi-annual tidal cycles (correlation of ~ 0.97) and changes in the Gulf Stream (GS) flow (correlation of − 0.6; the GS shows a maximum decline in September–October during the period of peak flooding). The combination of the seasonal pattern of tropical storms and high coastal sea level can explain the high frequency of fall flooding along the Southeastern U.S. coasts, while winter storms have more influence on the northeastern coasts. In recent decades however, the seasonal pattern seemed to have shifted so that increased flooding is seen on the northeastern coasts during spring and summer, while in the Mid-Atlantic and southeastern coasts, a dramatic increase in flooding is seen almost exclusively during the fall. A long-term change in the mean zonal wind pattern along the coast can contribute to the recent shift in the seasonal flooding pattern. The study can help regional adaptation and resilience planning for flood-prone coastal cities and communities.

The Oceanographic Modeling and Observation Network (REMO) focuses on scientific and technological development of operational oceanography in Brazil considering both numerical forecasting and observational systems. A key component of the forecasting system is the recently constructed REMO Ocean Data Assimilation System (RODAS) into the HYbrid Coordinate Ocean Model (HYCOM). Here, RODAS is presented for the first time with its full capability. RODAS employs a multivariate ensemble optimal interpolation scheme that is able to assimilate Argo temperature (T) and salinity (S) profiles, sea surface temperature (SST) analyses, and satellite along-track or gridded sea-level anomaly (SLA) data. RODAS is presented together with a series of Observing System Experiments (OSEs), in which components of the Global Ocean Observing System (GOOS) were systematically withheld from 3-year assimilation runs over the Atlantic Ocean. Using the same initial condition from a full assimilation run, OSEs were performed from 1 January 2010 to 31 December 2012 withholding (i) only Argo data; (ii) only UK MetOffice OSTIA SST analyses; (iii) only satellite along-track altimetry data; and (iv) all observation types. These runs were also compared with the full assimilation run and the model free run to evaluate the impact of different observations into the model state. The results show that each observation type brings complementary information into the analyses. Assimilation of SST is needed to better constrain the mixed layer temperature, while assimilation of SLA mainly improves the representation of circulation by adding mesoscale-like features, such as those found in the Gulf Stream and the Brazil-Malvinas Confluence. In the subsurface, only Argo observations are able to constrain the thermohaline state. When Argo data are withheld, the quality of S is seriously compromised and becomes worse than the free run in the upper ocean. Additionally, the run withholding all observation types shows that the model state in the surface almost reaches the free run state by the end of the third year. However, below 300 m, the memory of the Argo data assimilation is longer and the quality of T and S is only degraded by 35% in comparison with the full assimilation run.

Hurricanes interact with the Gulf Stream in the South Atlantic Bight (SAB) through a wide variety of processes, which are crucial to understand for prediction of open-ocean and coastal hazards during storms. However, it remains unclear how waves are modified by large-scale ocean currents under storm conditions, when waves are aligned with the storm-driven circulation and tightly coupled to the overlying wind field. Hurricane Matthew (2016) impacted the U.S. Southeast coast, causing extensive coastal change due to large waves and elevated water levels. The hurricane traveled on the continental shelf parallel to the SAB coastline, with the right side of the hurricane directly over the Gulf Stream. Using the Coupled Ocean–Atmosphere–Wave–Sediment Transport modeling system, we investigate wave–current interaction between Hurricane Matthew and the Gulf Stream. The model simulates ocean currents and waves over a grid encompassing the U.S. East Coast, with varied coupling of the hydrodynamic and wave components to isolate the effect of the currents on the waves, and the effect of the Gulf Stream relative to storm-driven circulation. The Gulf Stream modifies the direction of the storm-driven currents beneath the right side of the hurricane. Waves transitioned from following currents that result in wave lengthening, through negative current gradients that result in wave steepening and dissipation. Wave–current interaction over the Gulf Stream modified maximum coastal total water levels and changed incident wave directions at the coast by up to 20°, with strong implications for the morphodynamic response and stability of the coast to the hurricane.

The warm Gulf Stream sea surface temperatures strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 reanalyses, affecting the turbulent surface fluxes. Known problems within the ERA5 boundary layer (too-dry and too-cool with too strong westerlies), ascertained primarily from ACTIVATE 2020 campaign aircraft dropsondes and secondarily from older buoy measurements, reinforce surface flux biases. In contrast, MERRA2 winter surface winds and air-sea temperature/humidity differences are slightly too weak, producing surface fluxes that are too low. Reanalyses boundary layer heights in the strongly forced winter cold-air-outbreak regime are realistic, whereas late-summer quiescent stable boundary layers are too shallow. Nevertheless, the reanalysis biases are small, and reanalyses adequately support their use for initializing higher-resolution cloud process modeling studies of cold-air outbreaks.

Bycatch in fisheries is a major threat to many seabird species. Understanding and predicting spatiotemporal changes in seabird bycatch from fisheries might be the key to mitigation. Inter-annual spatiotemporal patterns are evident in seabird bycatch of the U.S. Atlantic pelagic longline fishery monitored by the National Marine Fisheries Service Pelagic Observer Program (POP) since 1992. A newly developed fast computing Bayesian approximation method provided the opportunity to use POP data to understand spatiotemporal patterns, including temporal changes in location of seabird bycatch hotspots. A Bayesian model was developed to capture the inherent spatiotemporal structure in seabird bycatch and reduce the bias caused by physical barriers such as coastlines. The model was applied to the logbook data to estimate seabird bycatch for each longline set, and the mid-Atlantic bight and northeast coast were the fishing areas with the highest fleet bycatch estimate. Inter-annual changes in predicted bycatch hotspots were correlated with Gulf Stream meanders, suggesting that predictable patterns in Gulf Stream meanders could enable advanced planning of fishing fleet schedules and areas of operation. The greater the Gulf Stream North Wall index, the more northerly the seabird bycatch hotspot two years later. A simulation study suggested that switching fishing fleets from the hindcasted actual bycatch hotspot to neighboring areas and/or different periods could be an efficient strategy to decrease seabird bycatch while largely maintaining fishers’ benefit.

The mid-latitude jet stream ties together the two major western boundary currents

The relationship between Gulf Stream (GS) transport and coastal sea level is investigated using monthly GS transport between 1993–2019 at Florida Straits and ten altimeter tracks. The results show ...

As the western boundary current of the North Atlantic, the Gulf Stream is a well established area of interest for the United States Navy, predominately due to its proximity to the continental shelf and the associated challenges of acoustic propagation across large property gradients. Autonomous underwater gliders conduct routine, high-resolution surveys along the U.S. East Coast, including within the Gulf Stream. These observations are assimilated into the operational Navy Coastal Ocean Model (NCOM). An investigation of the forecast-to-nowcast changes in the model for 2017 demonstrates the impact of the observations on the model. The magnitude of model change as a function of distance from nearest new observation reveals relatively large impact of glider observations within a radius of 𝒪(100) km. Glider observations are associated with larger local impact than Argo data, likely due to glider sampling focusing on large spatial gradients. Due to the advective nature of the Gulf Stream system, the impact of glider observations in the model is anisotropic with larger impacts extending downstream from observation locations. Forecast-to-nowcast changes in modeled temperature, salinity, and density result in improved agreement between observed and modeled ocean structure within the upper 200 m over the 24 hours between successive model runs.

The Gulf Stream is expected to slow and shift poleward over the next century due to climate change. We investigate whether such changes are already observable in the altimetric record (1993–2018) u...