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  • Gulf Stream  (8)
  • American Geophysical Union  (6)
  • Massachusetts Institute of Technology and Woods Hole Oceanographic Institution  (2)
  • American Institute of Physics (AIP)
  • PANGAEA
  • Springer Nature
  • Wiley
  • Wiley-Blackwell
  • 2020-2023  (8)
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  • 1
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    The Gulf Stream: along-stream evolution of volume transport and water properties observed by underwater gliders (2022)
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Details
    Publikationsdatum: 2022-10-20
    Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2021.
    Beschreibung: The Gulf Stream, the western boundary current of the subtropical North Atlantic, plays a key role in the Earth’s climate system with its poleward volume and heat transports being major components of the upper limb of the Atlantic Meridional Overturning Circulation. Extensive observations collected using Spray autonomous underwater gliders from 2004 through 2020 fill a 1500-km-long gap in longer-term sustained subsurface measurements of the Gulf Stream. The gliders provide concurrent, high-resolution measurements of Gulf Stream hydrography and velocity over more than 15 degrees of latitude between Florida and New England. These observations are used to characterize the along-stream evolution of Gulf Stream volume transport; its long-known poleward increase is shown to result primarily from entrainment of subthermocline waters. Antarctic Intermediate Water, which makes up the deepest waters within the Gulf Stream in the Florida Strait, is eroded through both vertical mixing and lateral stirring as it flows downstream. Satellite-based observations of sea surface height coincident with the glider observations are used to evaluate the efficacy of inferring Gulf Stream transport from remotely sensed measurements. The detailed analyses of Gulf Stream transport and water property evolution herein provide targets for regional and global circulation models to replicate.
    Beschreibung: We gratefully acknowledge funding from the National Science Foundation (OCE-0220769, OCE-1633911, OCE-1923362, OCE-1558521), NOAA’s Global Ocean Monitoring and Observing Program (NA14OAR4320158, NA19OAR4320074), the Office of Naval Research (N000141713040), WHOI’s Oceans and Climate Change Institute, Eastman Chemical Company, and the W. Van Alan Clark, Jr. Chair for Excellence in Oceanography at WHOI (awarded to Breck Owens).
    Schlagwort(e): Gulf Stream ; Autonomous underwater gliders ; Volume transport
    Repository-Name: Woods Hole Open Access Server
    Materialart: Thesis
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  • 2
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    A survival analysis of the gulf stream warm core rings (2021)
    American Geophysical Union
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    Publikationsdatum: 2022-10-26
    Beschreibung: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(10),(2020): e2020JC016507, https://doi.org/10.1029/2020JC016507.
    Beschreibung: 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° zones between 75° W and 55° 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°–65° W) or Zone 3 (65°–60° W) and then demised in Zone 1 (75°–70° W). Survival probability of the WCRs increased to more than 70% for those formed within a latitude band from 39.5° to 41.5° N. Survival probability is reduced when the WCRs are formed near the New England Seamounts.
    Beschreibung: We are grateful for financial supports from NOAA (NA11NOS0120038), NSF (OCE‐1851242), SMAST, and UMass Dartmouth. G. G. was supported by NSF under grant OCE‐1851261.
    Beschreibung: 2021-04-14
    Schlagwort(e): Gulf Stream ; Warm core rings ; Survival analysis
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 3
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    On assessing ERA5 and MERRA2 representations of cold-air outbreaks across the Gulf Stream (2021)
    American Geophysical Union
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    Publikationsdatum: 2022-10-20
    Beschreibung: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 48(19), (2021): e2021GL094364, https://doi.org/10.1029/2021GL094364.
    Beschreibung: 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.
    Beschreibung: This work was supported by NASA grant 80NSSC19K0390 to ACTIVATE, a NASA Earth Venture Suborbital-3 (EVS-3) investigation funded by NASA's Earth Science Division and managed through the Earth System Science Pathfinder Program Office. The Pacific Northwest National Laboratory (PNNL) is operated for the US Department of Energy (DOE) by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830.
    Beschreibung: 2022-03-08
    Schlagwort(e): Cold-air outbreaks ; Surface fluxes ; Gulf Stream ; ACTIVATE ; ERA5 ; MERRA2
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 4
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    Characterizing the impact of underwater glider observations on the Navy Coastal Ocean Model (NCOM) in the Gulf Stream Region (2021)
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Details
    Publikationsdatum: 2022-10-20
    Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2021.
    Beschreibung: 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.
    Beschreibung: This research was funded via the United States Navy’s Civilian Institution Program with the Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program (MIT/WHOI JP). Glider observations and analyses have been generously supported by the National Science Foundation (OCE-0220769, OCE-1558521, OCE-1633911, OCE-1923362), NOAA’s Global Ocean Monitoring and Observing Program (NA14OAR4320158, NA19OAR4320074), the Office of Naval Research (N000141713040), Eastman Chemical Corporation, WHOI’s Oceans and Climate Change Institute, and the W. Van Alan Clark, Jr. Chair for Excellence in Oceanography at WHOI (awarded to Breck Owens).
    Schlagwort(e): Model ; Glider ; Gulf Stream
    Repository-Name: Woods Hole Open Access Server
    Materialart: Thesis
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  • 5
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    Spatial and temporal variability of the Gulf Stream near Cape Hatteras (2021)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Andres, M. Spatil and temporal variability of the Gulf Stream near Cape Hatteras. Journal of Geophysical Research: Oceans, 126(9), (2021): e2021JC017579, https://doi.org/10.1029/2021JC017579.
    Beschreibung: In situ observations from a 19-month deployment of current- and pressure-sensor equipped inverted echo sounders (CPIESs) along and across the Gulf Stream near Cape Hatteras capture spatial and temporal variability where this western boundary current separates from the continental margin. Regional hydrographic casts and two temperature cross-sections spanning the Gulf Stream southeast of Cape Hatteras are used with the CPIESs' records of acoustic travel time to infer changes in thermocline depth DT and Gulf Stream position. Wave-like Gulf Stream meanders are observed where the Stream approaches the separation location with periods less than 15 days, wavelengths less than 500-km, and phase speeds between 40 and 70 km d−1. Though meander amplitudes typically decrease by ∼30% on the final approach to Cape Hatteras, some signals are still coherent across the Gulf Stream separation location. Temporal variability in meander intensity may be related to the Loop Current ∼1,400 km upstream. Mesoscale variability is strongest downstream of the separation location where Gulf Stream position is no longer constrained by the steep continental slope. Low frequency transport changes in the Florida Straits are correlated with sea-surface height gradients along the entire South Atlantic Bight (SAB) and with DT inferred at the CPIES sites. The correlations with DT are likely due to coherent transport anomalies in the Gulf Stream approaching the separation location, which then drive Gulf Stream position changes downstream of the separation location. The patterns of coherent transport anomalies may reflect large-scale atmospheric forcing patterns or rapid equatorward propagation of barotropic signals along the SAB.
    Beschreibung: This research was supported by the National Science Foundation through grant OCE-1558521.
    Schlagwort(e): Altimetry ; Cape Hatteras ; CPIES ; Gulf Stream ; Meanders
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 6
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    Forecasting the Gulf Stream path using buoyancy and wind forcing over the North Atlantic (2021)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-05-27
    Beschreibung: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(8), (2021): e2021JC017614, https://doi.org/10.1029/2021JC017614.
    Beschreibung: 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°W and 65°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.
    Beschreibung: The authors are grateful for financial supports from NSF (OCE-1851242), SMAST, and UMass Dartmouth. GG was supported by NSF under grants OCE-1657853 and OCE-1558521.
    Beschreibung: 2022-01-28
    Schlagwort(e): Gulf Stream ; Azores high ; Icelandic low ; forecasting ; AMOC ; North Atlantic
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 7
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    Variability of deep water in Jordan Basin of the Gulf of Maine: influence of Gulf Stream warm core rings and the Nova Scotia Current (2021)
    American Geophysical Union
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    Publikationsdatum: 2022-05-27
    Beschreibung: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(5), (2021): e2020JC017136, https://doi.org/10.1029/2020JC017136.
    Beschreibung: As the nutrient-rich subsurface slope water intruding into the deep basin of the Gulf of Maine (GoM) supports the high biological productivity in the semi-enclosed gulf, it is important to understand the process and time scale of such slope water intrusion. This study focuses on variations of the GoM deep water on seasonal to interannual time scales and the influences of open ocean processes on the temporal variation of the deep water properties. Based on long-term monitoring data, it is found that the deep water at Jordan Basin (one of three major basins in the GoM) is persistently warmer in winter than in summer, which is distinctly different from the seasonality of surface water in the basin and the deep water on neighboring shelf seas. The unique seasonality in the deep GoM reflects a time-lagged response to shoreward intrusion of the subsurface slope water off the GoM. Both observation-based lag-correlation analyses and numerical simulations confirm a timescale of approximately 3 months for the intruding subsurface slope water to flow from Northeast Channel to Jordan Basin. Properties of the intruding slope water at the Northeast Channel were significantly correlated with the Gulf Stream position and dramatically impacted by episodic warm-core rings shed from Gulf Stream. Inside the deep GoM, the intruding slope water was also indirectly affected by the fresher water input from Nova Scotia Current. Spreading of the fresher water inside the gulf strengthens near-surface stratification, suppresses deep convection, and preserves heat and salt in the deep GoM during the wintertime.
    Beschreibung: This study is supported by the National Science Foundation through grant OCE 1634965.
    Beschreibung: 2021-11-06
    Schlagwort(e): Gulf of Maine deep water ; Gulf Stream ; mooring data ; numerical simulation ; remote sensing data ; warm-core ring
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 8
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    A census of the warm-core rings of the Gulf Stream: 1980-2017 (2020)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2019JC016033, doi:10.1029/2019JC016033.
    Beschreibung: 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, https://doi.org/10.1038/s41598-019-48661-9). The WCR formation over the whole region (75–55°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° zones between 75°W and 55°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°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°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.
    Beschreibung: The authors acknowledge financial support from NOAA (NA11NOS0120038), NSF (OCE‐0815679 and OCE‐1851242), and SMAST and UMass Dartmouth. G. G. was supported by NSF under Grant OCE‐1657853 as well as a Senior Scientist Chair from WHOI. We have benefitted from many discussions on Gulf Stream and WCR with Magdalena Andres, Andre Schmidt, Paula Fratantoni, Jon Hare, Wendell Brown, Kathy Donohue, Tom Rossby, Peter Cornillon, and Randy Watts.
    Beschreibung: 2020-12-29
    Schlagwort(e): Gulf Stream ; Warm Core Rings ; Regime‐Shift ; Lifespan of rings ; size of rings ; Ring Census
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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