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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. 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 123 (2018): 6503-6520, doi:10.1029/2018JC014049.
    Description: During the seasonal evolution of stratification on the New Jersey shelf in the fall, strong thermal stratification that was established in the preceding summer is broken down through wind‐driven processes and surface cooling. Ten years of output from a Regional Ocean Modeling Systems run and a one‐dimensional mixed layer model is used here to examine the interannual variability in the strength of the stratification and in the processes that reduce stratification in fall. Our analysis shows that the strength of the stratification at the end of the summer is not correlated with the timing of shelf destratification. This indicates that processes that occur within the fall are more important for the timing of stratification breakdown than are the initial fall conditions. Furthermore, wind‐driven processes reduce a greater fraction of the stratification in each year than does the surface cooling during the fall. Winds affect the density gradients on the shelf through both changes to the temperature and salinity fields. Processes associated with the downwelling‐favorable winds are more effective than those during upwelling‐favorable winds in breaking down the vertical density gradients. In the first process, cross‐shelf advective fluxes during storms act to decrease stratification during downwelling‐favorable winds and increase stratification during upwelling‐favorable winds. Second, there is also enhanced velocity shear during downwelling‐favorable winds, which allows for more shear instabilities that break down stratification via mixing. Observational data and model output from Tropical Storm Ernesto compare favorably and suggest that downwelling‐favorable winds act through the mechanisms identified from the Regional Ocean Modeling Systems results.
    Description: DOC | National Oceanic and Atmospheric Administration (NOAA) Grant Number: NA13OAR4830233; NSF | GEO | Division of Ocean Sciences (OCE) Grant Number: 1558960
    Description: 2019-03-12
    Keywords: Middle Atlantic Bight ; Fall stratification ; Ekman buoyancy flux ; ROMS ; Interannual variability ; Storms
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. 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 120 (2015): 2370-2384, doi:10.1002/2014JC010516.
    Description: Expendable bathythermographs (XBTs) have been launched along a repeat track from New Jersey to Bermuda from the CMV Oleander through the NOAA/NEFSC Ship of Opportunity Program about 14 times per year since 1977. The XBT temperatures on the Middle Atlantic Bight shelf are binned with 10 km horizontal and 5 m vertical resolution to produce monthly, seasonally, and annually averaged cross-shelf temperature sections. The depth-averaged shelf temperature, Ts, calculated from annually averaged sections that are spatially averaged across the shelf, increases at 0.026 ± 0.001°C yr−1 from 1977 to 2013, with the recent trend substantially larger than the overall 37 year trend (0.11 ± 0.02°C yr−1 since 2002). The Oleander temperature sections suggest that the recent acceleration in warming on the shelf is not confined to the surface, but occurs throughout the water column with some contribution from interactions between the shelf and the adjacent Slope Sea reflected in cross-shelf motions of the shelfbreak front. The local warming on the shelf cannot explain the region's amplified rate of sea level rise relative to the global mean. Additionally, Ts exhibits significant interannual variability with the warmest anomalies increasing in intensity over the 37 year record even as the cold anomalies remain relatively uniform throughout the record. Ts anomalies are not correlated with annually averaged coastal sea level anomalies at zero lag. However, positive correlation is found between 2 year lagged Ts anomalies and coastal sea level anomalies, suggesting that the region's sea level anomalies may serve as a predictor of shelf temperature.
    Description: J.F. was supported as a Woods Hole Oceanographic Institution Summer Student Fellow by the National Science Foundation's Research Experiences for Undergraduates through OCE-0649139. M.A. received support through OCE-1332667 and G.G. through OCE-1435602.
    Description: 2015-09-27
    Keywords: Oleander ; Ocean heat content ; Expendable bathythermograph ; Shelfbreak front ; Sea level ; Middle Atlantic Bight
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-10-20
    Description: 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 February 2021.
    Description: Observations of hydrographic and dynamical properties on the Middle Atlantic Bight shelf document strong variability at time scales spanning events that last a few days to century long trends. This thesis studies individual processes which impact shelf temperature and velocity structure, and quantifies the mean velocity conditions at the shelf break. Chapter 2 uses model output to study the dynamics that lead to the breakdown of summertime thermal stratification, and how the processes which reduce stratification vary from year to year. In summer, the atmosphere heats the surface of the ocean, leading to strong thermal stratification with warm water overlying cool water. During fall, strong storm events with downwelling-favorable winds are found to be the primary process by which stratification is reduced. The timing of these events and the associated destratification varies from year to year. In Chapter 3, the velocity structure of the New Jersey shelf break is examine, with a focus on the Shelfbreak Jet. Using 25 years of velocity measurements, mean velocity sections of the Shelfbreak Jet are created in both Eulerian and stream coordinate frameworks. The jet exhibits strong seasonal variability, with maximum velocities observed in spring and minimum velocities in summer. Evidence is found that Warm Core Rings, originating from the Gulf Stream and passing through the Slope Sea adjacent to the New Jersey shelf, tend to shift the Shelfbreak Jet onshore of its mean position or entirely shutdown the Shelfbreak Jet’s flow. At interannual timescales, variability in the Shelfbreak Jet velocity is correlated with the temperature on the New Jersey Shelf, with temperature lagging by about 2 months. Chapter 4 focuses on the impact of Warm Core Rings on the velocity and temperature structure on the New Jersey shelf. Warm Core Rings that have higher azimuthal velocities and whose cores approach closer to the shelf are found to exert greater influence on the shelf’s along-shelf velocities, with the fastest and closest rings reversing the direction of flow at the shelf break. Warm Core Rings are also observed to exert long-lasting impacts on the shelf temperature, with faster rings cooling the shelf and slower rings warming the shelf. Seasonal changes in thermal stratification strongly affect how rings alter the shelf temperature. Rings in summer tend to cool the shelf, and rings throughout the rest of the year generally warm the shelf.
    Description: This research was funded under WHOI Academic Programs Endowed Funds, NSF #OCE-1634094, and NSF #OCE-1924041.
    Keywords: Temperature variability ; Velocity variability ; Middle Atlantic Bight
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 4
    Publication Date: 2022-06-13
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Forsyth, J., Gawarkiewicz, G., & Andres, M. The impact of Warm Core Rings on Middle Atlantic Bight shelf temperature and shelf break velocity. Journal of Geophysical Research: Oceans, 127, (2022): e2021JC017759, https://doi.org/10.1029/2021jc017759.
    Description: Warm Core Rings (WCRs) are known to disrupt the shelf flow as well as drive strong heat transport onto the Middle Atlantic Bight shelf. We examine 27 rings sampled by the container ship Oleander, 16 rings which have in-situ velocity data and 11 rings identified from satellite sea surface height but with in-situ temperature data, to study the variability in rings' impact on shelf break velocities and on the temperature of the adjacent shelf. WCRs that have higher rotational velocities and are closer to the shelf are found to exert greater influence on the along-shelf velocities, with the fastest and closest rings reversing the direction of flow at the shelf break. As rings approach the study site, the Shelfbreak Jet is faster than when the rings are about to exit the study site, likely due to first steepening then flattening of the isopycnals at the Shelfbreak Front. Rings also have lasting impacts on the shelf temperature: rings with faster rotational velocities cool the shelf and rings with slower rotational velocities warm the shelf. The evolution of temperature on the shelf as a ring passes is strongly tied to the season. During warmer seasons, when temperature stratification on the shelf is strong, a ring cools the shelf; during periods of weak thermal stratification, rings tend to warm the shelf. Rings which cool the shelf are additionally associated with increased upwelling as they pass the study site.
    Description: J. Forsyth and M. Andres were supported by OCE-1924041. J. Forsyth and G. Gawarkiewicz were supported by ONR N00014-19-1-2646. G. Gawarkiewicz was also supported by NSF under grant OCE-1851261.
    Keywords: Warm Core Rings ; Middle Atlantic Bight ; CMV Oleander ; Shelfbreak processes
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rossby, T., Flagg, C. N., Donohue, K., Fontana, S., Curry, R., Andres, M., & Forsyth, J. Oleander is more than a flower twenty-five years of oceanography aboard a merchant vessel. Oceanography, 32(3), (2019): 126-137, doi:10.5670/oceanog.2019.319.
    Description: Since late fall 1992, CMV Oleander III has been measuring upper ocean currents during its weekly trips between Bermuda and Port Elizabeth, New Jersey, by means of an acoustic Doppler current profiler installed in its hull. The overarching objective of this effort has been to monitor transport in the Gulf Stream and surrounding waters. With 25 years of observation in hand, we note that the Gulf Stream exhibits significant year-to-year variations but no evident long-term trend in transport. We show how these data have enabled studies of oceanic variability over a very wide range of scales, from a few kilometers to the full 1,000 km length of its route. We report that the large interannual variations in temperature on the continental shelf are negatively correlated with flow from the Labrador Sea, but that variability in the strength of this flow cannot account for a longer-term warming trend observed on the shelf. Acoustic backscatter data offer a rich trove of information on biomass activities over a wide range of spatial and temporal scales. A peek at the future illustrates how the new and newly equipped Oleander will be able to profile currents to greater depths and thereby contribute to monitoring the strength of the meridional overturning circulation.
    Description: First and foremost we extend our heartfelt thanks to the Bermuda Container Line/Neptune Group Management Ltd for permission to operate an acoustic Doppler current profiler on board CMV Oleander III, a 150 kHz ADCP between 1992 and 2004, and a 75 kHz ADCP between 2005 and 2018. Their interest and support is gratefully acknowledged. Cor Teeuwen, our initial contact in Holland while the ship was still under construction, played an important role in facilitating the original ADCP installation. His evident interest to make this concept work has stimulated similar activities on other commercial vessels. The interest and willingness of the shipping industry to be supportive of science has been a very positive experience for all of us who have ventured in this direction. Initial funding came from NOAA and the Office of Naval Research. Since 1999, the National Science Foundation has supported the project through funding to the University of Rhode Island and Stony Brook University, and now also to the Bermuda Institute of Ocean Sciences (BIOS), which will be taking over the Oleander operation. NSF is also funding the current transition to the new CMV Oleander. In the early years, G. Schwartze and E. Gottlieb were very helpful with technical support for the project. This included frequent visits to the ship before we had the capability to transfer the data through the Ethernet. We thank Jules Hummon and Eric Firing for adapting the UNOLS-wide UHDAS ADCP operating system to the merchant marine environment. We thank E. Williams and P. Ortner at the Rosenstiel School of Marine and Atmospheric Science, University of Miami, for making the 38 kHz ADCP data from Explorer of the Seas available to us. We also want to thank the NOAA Ship Of Opportunity Program for continued interest in and support of XBT operations along the Oleander section. That support started over 40 years ago and is now stronger than ever. All ADCP data from 1992 through 2018 have been archived at the Joint Archive for Shipboard ADCP (JASADCP), established at the University of Hawaii by NOAA’s National Centers for Environmental Information (NCEI). Averaged yearly data sets can be downloaded in ASCII text or NetCDF formats (http://ilikai.soest.hawaii.edu/​sadcp/main_inv.html). We thank Patrick Caldwell, JASADCP’s manager, for his assistance. All ADCP and XBT data can be obtained at the Stony Brook website: http://po.msrc.sunysb.edu/Oleander/. The URL to the project website is http://oleander.bios.edu—an updated data portal and products will soon be accessible here. An ERDDAP server for Oleander data (in the process of being configured) is at this address: http://erddap.​oleander.​bios.edu:​8080/​erddap/. The following link to BIOS lists over 40 publications that have used the ADCP data one way or another: http://oleander.bios.edu/publications/. We thank the two reviewers for their many interesting and helpful comments and suggestions.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gawarkiewicz, G., Chen, K., Forsyth, J., Bahr, F., Mercer, A. M., Ellertson, A., Fratantoni, P., Seim, H., Haines, S., & Han, L. Characteristics of an advective Marine Heatwave in the Middle Atlantic Bight in early 2017. Frontiers in Marine Science, 6, (2019): 712, doi: 10.3389/fmars.2019.00712.
    Description: There has been wide interest in Marine Heatwaves and their ecological consequences in recent years. Most analyses have focused on remotely sensed sea surface temperature data due to the temporal and spatial coverage it provides in order to establish the presence and duration of Heatwaves. Using hydrographic data from a variety of sources, we show that an advective Marine Heatwave was initiated by an event in late December of 2016 south of New England, with temperature anomalies measuring up to 6°C and salinity anomalies exceeding 1 PSU. Similar features were observed off of New Jersey in February 2017, and are associated with the Shelfbreak Front migrating from its normal position to mid-shelf or further onshore. Shelf water of 34 PSU was observed just north of Cape Hatteras at the 30 m isobath and across the continental shelf in late April 2017. These observations reveal that the 2017 Marine Heatwave was associated with a strong positive salinity anomaly, that its total duration was approximately 4 months, and its advective path extended roughly 850 km along the length of the continental shelf in the Middle Atlantic Bight. The southward advective velocity implied by the arrival north of Cape Hatteras is consistent with previous estimates of alongshelf velocity for the region. The origin of this Marine Heatwave is likely related to cross-shelf advection driven by the presence of a Warm Core Ring adjacent to the shelfbreak south of New England.
    Description: GG was supported by the van Beuren Charitable Foundation, the National Science Foundation under grants OCE-1657853 and OCE-1558521 as well as a Senior Scientist Chair from the Woods Hole Oceanographic Institution. KC was supported by the National Science Foundation under grants OCE-1558960 and OCE-1634094. JF was supported by the National Science Foundation OCE-1634094. AM and AE were supported by the van Beuren Charitable Foundation. HS, SH, and LH were supported by the National Science Foundation OCE-1558920.
    Keywords: Heatwave ; Middle Atlantic Bight ; Shelfbreak front ; Warm core ring ; Coastal ocean circulation
    Repository Name: Woods Hole Open Access Server
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  • 7
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Forsyth, J., Andres, M., & Gawarkiewicz, G. . Shelfreak jet structure and variability off New Jersey using ship of opportunity data from the CMV Oleander. Journal of Geophysical Research: Oceans, 125(9), (2020): e2020JC016455. doi:10.1029/2020JC016455.
    Description: Repeat measurements of velocity and temperature profiles from the Container Motor Vessel (CMV) Oleander provide an unprecedented look into the variability on the New Jersey Shelf and upper continental slope. Here 1362 acoustic Doppler current profiler (ADCP) velocity sections collected between 1994 and 2018 are analyzed in both Eulerian and stream coordinate reference frames to characterize the mean structure of the Shelfbreak Jet, as well as its seasonal to decadal variability. The Eulerian mean Shelfbreak Jet has a maximum jet velocity of 0.12 m s−1. The maximum jet velocity peaks in April and May and reaches its minimum in July and August. In a stream coordinate framework, the jet is only identified in 61% of transects, and the mean stream coordinate Shelfbreak Jet has a maximum jet velocity of 0.32 m s−1. Evidence is found that Warm Core Rings, originating from the Gulf Stream arriving in the Slope Sea adjacent to the New Jersey Shelf, shift the Shelfbreak Jet onshore of its mean position or entirely shutdown the Shelfbreak Jet's flow. At interannual timescales, variability in the Shelfbreak Jet velocity is correlated with the temperature on the New Jersey Shelf 2 months later. When considered in a stream coordinate framework, Shelfbreak Jet have decreased over the time period considered in the study.
    Description: J. F. and M. A. were supported by NSF OCE‐1634094 and OCE‐1924041. G. G was supported by NSF OCE‐1851261.
    Keywords: Shelfbreak Jet ; Middle Atlantic Bight ; Ship of opportunity ; Continental shelf processes ; Western Boundary Currents
    Repository Name: Woods Hole Open Access Server
    Type: Article
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