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  • 1
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    Data assimilative modeling investigation of Gulf Stream Warm Core Ring interaction with continental shelf and slope circulation (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2014. 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 119 (2014): 5968–5991, doi:10.1002/2014JC009898.
    Description: A data assimilative ocean circulation model is used to hindcast the interaction between a large Gulf Stream Warm Core Ring (WCR) with the Mid-Atlantic Bight (MAB) shelf and slope circulation. Using the recently developed Incremental Strong constraint 4D Variational (I4D-Var) data assimilation algorithm, the model assimilates mapped satellite sea surface height (SSH), sea surface temperature (SST), in situ temperature, and salinity profiles measured by expendable bathythermograph, Argo floats, shipboard CTD casts, and glider transects. Model validations against independent hydrographic data show 60% and 57% error reductions in temperature and salinity, respectively. The WCR significantly changed MAB continental slope and shelf circulation. The mean cross-shelf transport induced by the WCR is estimated to be 0.28 Sv offshore, balancing the mean along-shelf transport by the shelfbreak jet. Large heat/salt fluxes with peak values of 8900 W m−2/4 × 10−4 kg m−2 s−1 are found when the WCR was impinging upon the shelfbreak. Vorticity analysis reveals the nonlinear advection term, as well as the residual of joint effect of baroclinicity and bottom relief (JEBAR) and advection of potential vorticity (APV) play important roles in controlling the variability of the eddy vorticity.
    Description: Research support provided through ONR grants N00014-06-1-0739, N00014-10-1-0367, and NSF grant OCE-0927470 is much appreciated. B. Powell was supported by ONR grant N00014-09-10939. K. Chen was supported by the Woods Hole Oceanographic Institution Postdoctoral Scholar Program.
    Description: 2015-03-12
    Keywords: Gulf Stream ; Warm Core Ring ; Shelf circulation ; Data assimilation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Interannual variability of winter-spring temperature in the Middle Atlantic Bight : relative contributions of atmospheric and oceanic processes (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. 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 121 (2016): 4209–4227, doi:10.1002/2016JC011646.
    Description: Relative contributions between the local atmospheric and oceanic processes on the interannual variability of winter-spring shelf temperature in the Middle Atlantic Bight (MAB) are investigated based on a regional ocean model. The model demonstrates sufficient capability to realistically simulate the interannual temperature changes during 2003–2014. On interannual time scales, the mean winter/spring temperature in the MAB is determined by the combination of the initial temperature at the beginning of the season and the mean cumulative air-sea flux, while the mean cumulative ocean advective flux plays a secondary role. In spite of the overall importance of air-sea flux in determining the winter and spring temperature, the relative contributions between air-sea flux and ocean advective flux on the evolution of the temperature anomaly in each individual year varies. The predictability of spring (April–June) temperature based on winter (January–March) temperature is weak because the temporal decorrelation time scale changes significantly from year to year. Both the highly variable shelf temperature and its decorrelation time scale are affected by the changes in the relative contributions between the air-sea flux and ocean advective flux.
    Description: National Science Foundation Grant Number: OCE-1435602
    Description: 2016-12-18
    Keywords: Interannual variability ; Winter-spring temperature ; Air-sea flux ; Ocean advective flux ; Decorrelation time scale ; Predictability
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    The interannual variability of the breakdown of fall stratification on the New Jersey Shelf (2018)
    John Wiley & Sons
    Details
    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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  • 4
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    The role of atmospheric forcing versus ocean advection during the extreme warming of the Northeast U.S. continental shelf in 2012 (2015)
    John Wiley & Sons
    Details
    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): 4324–4339, doi:10.1002/2014JC010547.
    Description: In the coastal ocean off the Northeast U.S., the sea surface temperature (SST) in the first half of 2012 was the highest on the record for the past roughly 150 years of recorded observations. The underlying dynamical processes responsible for this extreme event are examined using a numerical model, and the relative contributions of air-sea heat flux versus lateral ocean advective heat flux are quantified. The model accurately reproduces the observed vertical structure and the spatiotemporal characteristics of the thermohaline condition of the Gulf of Maine and the Middle Atlantic Bight waters during the anomalous warming period. Analysis of the model results show that the warming event was primarily driven by the anomalous air-sea heat flux, while the smaller contribution by the ocean advection worked against this flux by acting to cool the shelf. The anomalous air-sea heat flux exhibited a shelf-wide coherence, consistent with the shelf-wide warming pattern, while the ocean advective heat flux was dominated by localized, relatively smaller-scale processes. The anomalous cooling due to advection primarily resulted from the along-shelf heat flux divergence in the Gulf of Maine, while in the Middle Atlantic Bight the advective contribution from the along-shelf and cross-shelf heat flux divergences was comparable. The modeling results confirm the conclusion of the recent analysis of in situ data by Chen et al. (2014a) that the changes in the large-scale atmospheric circulation in the winter of 2011–2012 primarily caused the extreme warm anomaly in the spring of 2012. The effect of along-shelf or cross-shelf ocean advection on the warm anomalies from either the Scotian Shelf or adjacent continental slope was secondary.
    Description: K.C. was supported by the Woods Hole Oceanographic Institution Postdoctoral Scholar program, the Coastal Ocean Institute, and the National Science Foundation (NSF) under grant OCE-1435602. G.G.G. was supported by NSF grants OCE-1435602 and OCE-1129125. Y.-O.K. was supported by the NSF grant OCE-1435602. W.G.Z. was supported by the NSF grant OCE-1129125.
    Description: 2015-12-15
    Keywords: Extreme temperature ; Heat budget ; Northeast U.S. coastal ocean ; Numerical modeling ; Air-sea interaction ; Climate change
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Does Pacific variability influence the Northwest Atlantic shelf temperature? (2018)
    John Wiley & Sons
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    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): 4110–4131, doi:10.1029/2017JC013414.
    Description: The relationship between North Pacific variability and sea surface temperature (SST) of the Northwest Atlantic continental shelf is examined over interannual time scale in 1982–2014. Statistically significant negative correlations exist between Pacific Decadal Oscillation (PDO) index and SST in the Gulf of Maine (GoM) in spring and summer. Cross‐correlation analysis further suggests significant negative lead‐lag correlations, with the spring PDO leading the GoM SST by 0–3 months while the summer PDO lags by 1–3 months. These correlations are dominated by the interannual component of the PDO. Statistical relationships are placed in context by further investigating the physical processes controlling the upper ocean mixed layer temperature budget in the GoM. The results reveal contrasting roles between the atmosphere and the ocean in spring and summer, respectively. Local atmospheric forcings, in particular the radiative air‐sea fluxes, are the dominant driver for the interannual variability of springtime SST over the Northwest Atlantic shelf. In contrast, oceanic terms are important in controlling the interannual variability of summertime SST. As a result, reconstructed SST using atmospheric forcings successfully reproduces the statistical relationship with PDO in spring, but not in summer. Furthermore, it is shown that the SST anomalies in the central and eastern North Pacific play a key role in these relationships.
    Description: National Science Foundation Ocean Science Division Grant Numbers: OCE‐1435602 , OCE‐1558960 , OCE‐1634094; National Oceanic and Atmospheric Administration Climate Program Office MAPP program Grant Number: NA170AR4310111
    Description: 2018-12-28
    Keywords: Continental shelf temperature variability ; Atmosphere‐ocean interaction ; Mixed layer temperature ; Coastal to large‐scale connections ; Pacific Decadal Oscillation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Variational data assimilative modeling of the Gulf of Maine in spring and summer 2010 (2015)
    John Wiley & Sons
    Details
    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): 3522–3541, doi:10.1002/2014JC010492.
    Description: A data assimilative ocean circulation model is used to hindcast the Gulf of Maine [GOM) circulation in spring and summer 2010. Using the recently developed incremental strong constraint 4D Variational data assimilation algorithm, the model assimilates satellite sea surface temperature and in situ temperature and salinity profiles measured by expendable bathythermograph, Argo floats, and shipboard CTD casts. Validation against independent observations shows that the model skill is significantly improved after data assimilation. The data-assimilative model hindcast reproduces the temporal and spatial evolution of the ocean state, showing that a sea level depression southwest of the Scotian Shelf played a critical role in shaping the gulf-wide circulation. Heat budget analysis further demonstrates that both advection and surface heat flux contribute to temperature variability. The estimated time scale for coastal water to travel from the Scotian Shelf to the Jordan Basin is around 60 days, which is consistent with previous estimates based on in situ observations. Our study highlights the importance of resolving upstream and offshore forcing conditions in predicting the coastal circulation in the GOM.
    Description: Research support was provided by National Oceanic and Atmospheric Administration (NOAA) grant NA06NOS4780245 for the Gulf of Maine Toxicity (GOMTOX) program. RH and DJM were also supported by NOAA grant NA11NOS4780023 under the PCMHAB program. YL was partly supported by Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the George D. Grice Postdoctoral Scholarship.
    Description: 2015-11-19
    Keywords: Gulf of Maine ; Circulation modeling ; Data assimilation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Diagnosing the warming of the Northeastern U.S. Coastal Ocean in 2012 : a linkage between the atmospheric jet stream variability and ocean response (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2014. 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 119 (2014): 218–227, doi:10.1002/2013JC009393.
    Description: The temperature in the coastal ocean off the northeastern U.S. during the first half of 2012 was anomalously warm, and this resulted in major impacts on the marine ecosystem and commercial fisheries. Understanding the spatiotemporal characteristics of the warming and its underlying dynamical processes is important for improving ecosystem management. Here, we show that the warming in the first half of 2012 was systematic from the Gulf of Maine to Cape Hatteras. Moreover, the warm anomalies extended through the water column, and the local temperature change of shelf water in the Middle Atlantic Bight was largely balanced by the atmospheric heat flux. The anomalous atmospheric jet stream position induced smaller heat loss from the ocean and caused a much slower cooling rate in late autumn and early winter of 2011–2012. Strong jet stream intraseasonal oscillations in the first half of 2012 systematically increased the warm anomalies over the continental shelf. Despite the importance of advection in prior northeastern U.S. continental shelf interannual temperature anomalies, our analyses show that much of the 2012 warming event was attributed to local warming from the atmosphere.
    Description: K.C. was supported by the Woods Hole Oceanographic Institution Postdoctoral Scholarship, with funding provided by the Cooperative Institute for North Atlantic Region. G.G.G. was supported by grant N00014-11-1-0160 from the Office of Naval Research. S.J.L. was supported by the National Science Foundation under grant OCE-1154575.
    Description: 2014-07-13
    Keywords: 2012 warming ; Warm anomaly ; Northeastern U.S. Coastal Ocean ; Jet stream
    Repository Name: Woods Hole Open Access Server
    Type: Article
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