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Modulation of near-inertial motions on the Mississippi-Alabama Shelf

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Abstract

In this study, we diagnose the time variability and vertical structure of the high- and low-frequency motions on the Mississippi-Alabama Shelf as observed with a bottom-mounted ADCP (Acoustic Doppler Current Profiler) and CTD (Conductivity-Temperature-Depth). The mooring was deployed about 20 km offshore of Mobile Bay for a period from May 17 to August 23, 2018. At this latitude, the diurnal land and sea breeze has the same frequency as the local inertial frequency. Similar to the wind, the observed high-frequency baroclinic velocities (> 30 cm/s) have a broadband diurnal peak and more energy in the clockwise motions. About 60% of the variance in these motions is due to mode 1, which resembles a two-layer structure with surface and bottom velocities that are 180∘ out of phase. These are all characteristics of wind-driven motions that interact with the coastal wall. The month of June features the best conditions for energetic near-inertial motions: upwelling, consistent sea breeze, and a more continuous instead of a two-layer stratification. This causes near-inertial energy to be also projected on a baroclinic mode 2, featuring a subsurface maximum. This maximum may be attributed to the downward propagation of near-inertial internal wave energy. The observed alongshore low-frequency flows and the up- and downwelling are mostly driven by low-frequency winds. About 83% of the variance in the alongshore low-frequency flows is due to mode 1, which eigenfunction resembles a vertically sheared flow. We find that the amplitude of the near-inertial motions is modulated by the up- and downwelling. During downwelling, the near-inertial baroclinic kinetic energy is greatly reduced because of a reduction in stratification and weaker diurnal winds.

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References

  • Alford MH (2001) Fine-structure contamination: observations and a model of a simple two-wave case. J Phys Oceanogr 31:2645–2649

    Article  Google Scholar 

  • Alford MH, MacKinnon JA, Simmons HL, Nash JD (2016) Near-inertial internal gravity waves in the ocean. Ann Rev Mar Sci 8:95–123

    Article  Google Scholar 

  • Buijsman MC, Stephenson GR, Ansong JK, Arbic B, Green M, Shriver JGRJ, Vic C, Wallcraft A, Zhao Z (2020) On the interplay between horizontal resolution and wave drag and their effect on tidal baroclinic mode waves in realistic global ocean simulations. Ocean Model 152(101656). https://doi.org/10.1016/j.ocemod.2020.101656https://doi.org/10.1016/j.ocemod.2020.101656

  • Chant RJ (2001) Evolution of near-inertial waves during an upwelling event on the new jersey inner shelf. J Phys Oceanogr 31:746–764

    Article  Google Scholar 

  • Chen C, **e L (1997) A numerical study of wind-induced, near-inertial oscillations over the texas-louisiana shelf. J Geophys Res: Oceans 102(C7):15583–15593

    Article  Google Scholar 

  • Chen C, Reid RO, Jr WDN (1996) Near-inertial oscillations over the texas-louisiana shelf. J Geophys Res: Oceans 101(C2):3509–3524

    Article  Google Scholar 

  • Coogan J, Dzwonkowski B, Lehrter J (2019) Effects of coastal upwelling and downwelling on hydrographic variability and dissolved oxygen in mobile bay. J Geophys Res: Oceans 124(2):791–806

    Article  Google Scholar 

  • D’Asaro EA (1989) The decay of wind-forced mixed layer inertial oscillations due to the β effect. J Geophys Res: Oceans 94:2045–2056. https://doi.org/10.1029/JC094iC02p02045

    Article  Google Scholar 

  • DiMarco SF, Howard MK, Reid RO (2000) Seasonal variation of wind-driven diurnal current cycling on the texas-louisiana continental shelf. Geophys Res Lett 27(7):1017–1020

    Article  Google Scholar 

  • Dzwonkowski B, Park K (2012) Subtidal circulation on the alabama shelf during the deepwater horizon oil spill. J Geophys Res: Oceans 117(C3)

  • Dzwonkowski B, Park K, Ha HK, Graham WM, Hernandez FJ, Powers SP (2011) Hydrographic variability on a coastal shelf directly influenced by estuarine outflow. Cont Shelf Res 31:939–950

    Article  Google Scholar 

  • Dzwonkowski B, Fournier S, Park K, Dykstra SL, Reager JT (2018) Water column stability and the role of velocity shear on a seasonally stratified shelf, mississippi bight, northern gulf of mexico. J Geophys Res Oceans 123(8):5777–5796

    Article  Google Scholar 

  • Gerkema T, Zimmerman JTF (2008) An introduction to internal waves. Lecture Notes, Royal Netherlands Institute for Sea Research

  • Gonella J (1972) A rotary-component method for analysing meteorological and oceanographic vector time series. In: Deep sea research and oceanographic abstracts, vol 19. Elsevier, pp 833–846

  • Gough MK, Reniers AJHM, MacMahan JH, Howden SD (2016) Resonant near-surface inertial oscillations in the northeastern gulf of mexico. J Geophys Res Oceans 121(4):2163–2182

    Article  Google Scholar 

  • Halle C, Pinkel R (2003) Internal wave variability in the beaufort sea during the winter of 1993/1994. J Geophys Res Oceans 108(C7)

  • Hopkins JE, Stephenson GR, Green JAM, Inall ME, Palmer MR (2014) Storms modify baroclinic energy fluxes in a seasonally stratified shelf sea: Inertial-tidal interaction. J Geophys Res Oceans 119 (10):6863–6883

    Article  Google Scholar 

  • Hsu SA, Meindl EA, Gilhousen DB (1994) Determining the power-law wind-profile exponent under near-neutral stability conditions at sea. J Appl Meteorol Climatol 33:757–765

    Article  Google Scholar 

  • Jarosz E, Hallock ZR, Teague WJ (2007) Near-inertial currents in the desoto canyon region. Cont Shelf Res 27:2407–2426

    Article  Google Scholar 

  • Jochum M, Briegleb BP, Danabasoglu G, Large WG, Norton NJ, Jayne SR, Alford MH, Bryan FO (2013) The impact of oceanic near-inertial waves on climate. J Climate 26(9):2833–2844

    Article  Google Scholar 

  • Johnston TMS, Chaudhuri D, Mathur M, Rudnick DL, Sengupta D, Simmons HL, Tandon A, Venkatesan R (2016) Decay mechanisms of near-inertial mixed layer oscillations in the bay of bengal. Oceanography 29(2):180–191

    Article  Google Scholar 

  • Kelly SM (2019) Coastally generated near-inertial waves. J Phys Oceanogr 49(11):2979–2995

    Article  Google Scholar 

  • Kim SY, Kurapov AL, Kosro PM (2015) Influence of varying upper ocean stratification on coastal near-inertial currents. J Geophys Res Oceans 120(12):8504–8527

    Article  Google Scholar 

  • Kunze E (1985) Near-inertial wave propagation in geostrophic shear. J Phys Oceanogr 15 (5):544–565

    Article  Google Scholar 

  • Large WG, Pond S (1981) Open ocean momentum flux measurements in moderate to strong winds. J Phys Oceanography 11(3):324–336

    Article  Google Scholar 

  • Lucas AJ, Pitcher GC, Probyn TA, Kudela RM (2014) The influence of diurnal winds on phytoplankton dynamics in a coastal upwelling system off southwestern africa. Deep-Sea Res II Top Stud Oceanogr 101:50–62

    Article  Google Scholar 

  • Nam S, Send U (2013) Resonant diurnal oscillations and mean alongshore flows driven by sea/land breeze forcing in the coastal southern california bight. J Phys Oceanography 43:616–630

    Article  Google Scholar 

  • Noble MA, Ramp SR (2000) Subtidal currents over the central california slope: evidence for offshore veering of the undercurrent and for direct, wind-driven slope currents. Deep-Sea Res II Top Stud Oceanogr 47 (5-6):871–906

    Article  Google Scholar 

  • Pettigrew NR (1980) The dynamics and kinematics of the coastal boundary layer off long island. PhD thesis, Massachusetts Institute of Technology. https://doi.org/10.1575/1912/3727

  • Qu L, Thomas LN, Hetland RD (2021) Near-inertial-wave critical layers over slo** bathymetry. J Phys Oceanogr 51(6):1737–1756. https://doi.org/10.1175/JPO-D-20-0221.1

    Article  Google Scholar 

  • Rippeth TP (2005) Mixing in seasonally stratified shelf seas: a shifting paradigm. Philosophical Trans Royal Soc A: Math Phys Eng Sci 363(1837):2837–2854

    Article  Google Scholar 

  • Rudnick D (1998) Wavelet transform (wvlt). http://chowder.ucsd.edu/Rudnick/SIO_221B.html

  • Shearman RK (2005) Observations of near-inertial current variability on the new england shelf. J Geophys Res Oceans 110(C2)

  • Simpson J, Hyder P, Rippeth T, Lucas I (2002) Forced oscillations near the critical latitude for diurnal-inertial resonance. J Phys Oceanogr 32:177–187

    Article  Google Scholar 

  • Teague WJ, Wijesekera HW, Jarosz E, Lugo-Fernández A, Hallock ZR (2014) Wavelet analysis of near-inertial currents at the east flower garden bank. Cont Shelf Res 88:47–60. https://doi.org/10.1016/j.csr.2014.06.013

    Article  Google Scholar 

  • Zhang X, DiMarco SF, IV DCS, Howard MK, Jochens AE, Hetland RD (2009) Near-resonant ocean response to sea breeze on a stratified continental shelf. J Phys Oceanogr 39:2137–2155

    Article  Google Scholar 

  • Zhang X, Smith DC, DiMarco SF, Hetland RD (2010) A numerical study of sea-breeze-driven ocean poincare wave propagation and mixing near the critical latitude. J Phys Oceanogr 40(1):48–66

    Article  Google Scholar 

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Acknowledgements

We thank Brian Dzwonkowski for sharing the Dauphin Island Sea Lab mooring CTD data and for providing comments and suggestions on an earlier version of this article. We appreciate Captain Daniel Meek of the M/V Sweet Sue and Davin Wallace and his students Clayton Dike, Rob Hollis, and Nina Gal for their help in deploying and retrieving the USM mooring. Davin Wallace also reviewed an earlier version of this manuscript. Finally, we would like to thank the reviewers for their useful comments and suggestions.

Funding

Maarten Buijsman and Jordan Earls are funded by the Office of Naval Research (ONR) grant N00014-15-1-2288 and the National Science Foundation (NSF) grant OCE1537449. Maarten Buijsman and Helen Weierbach are funded by the National Aeronautic Space Administration (NASA) grant 80NSSC18K0771.

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Authors and Affiliations

  1. School of Ocean Science and Engineering, University of Southern Mississippi, 1020 Balch Blvd, Stennis Space Center, MS, 39529, USA

    Maarten C. Buijsman, Jordan Earls & Helen Weierbach

  2. Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

    Helen Weierbach

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  1. Maarten C. Buijsman
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Correspondence to Maarten C. Buijsman.

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Buijsman, M.C., Earls, J. & Weierbach, H. Modulation of near-inertial motions on the Mississippi-Alabama Shelf. Ocean Dynamics 71, 1087–1103 (2021). https://doi.org/10.1007/s10236-021-01483-8

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