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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2007. 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 112 (2007): C06014, doi:10.1029/2006JC003947.
    Description: In aerial surveys conducted during the Tropical Ocean–Global Atmosphere Coupled Ocean-Atmosphere Response Experiment and the low-wind component of the Coupled Boundary Layer Air-Sea Transfer (CBLAST-Low) oceanographic field programs, sea surface temperature (SST) variability at relatively short spatial scales (O(50 m) to O(1 km)) was observed to increase with decreasing wind speed. A unique set of coincident surface and subsurface oceanic temperature measurements from CBLAST-Low is used to investigate the subsurface expression of this spatially organized SST variability, and the SST variability is linked to internal waves. The data are used to test two previously hypothesized mechanisms for SST signatures of oceanic internal waves: a modulation of the cool-skin effect and a modulation of vertical mixing within the diurnal warm layer. Under conditions of weak winds and strong insolation (which favor formation of a diurnal warm layer), the data reveal a link between the spatially periodic SST fluctuations and subsurface temperature and velocity fluctuations associated with oceanic internal waves, suggesting that some mechanism involving the diurnal warm layer is responsible for the observed signal. Internal-wave signals in skin temperature very closely resemble temperature signals measured at a depth of about 20 cm, indicating that the observed internal-wave SST signal is not a result of modulation of the cool-skin effect. Numerical experiments using a one-dimensional upper ocean model support the notion that internal-wave heaving of the warm-layer base can produce alternating bands of relatively warm and cool SST through the combined effects of surface heating and modulation of wind-driven vertical shear.
    Description: We gratefully acknowledge funding for this research from the Office of Naval Research through the CBLAST Departmental Research Initiative (grants N00014-01-1-0029, N00014-05-10090, N00014-01-1-0081, N00014-04-1-0110, N00014-05-1-0036, N00014-01-1-0080) and the Secretary of the Navy/Chief of Naval Operations Chair (grant N00014-99-1-0090).
    Keywords: Internal waves ; Upper-ocean processes
    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, 2007. 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 112 (2007): C03011, doi:10.1029/2007JC004135.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2004. 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 31 (2004): L20308, doi:10.1029/2004GL021192.
    Description: Satellite remote sensing provides diverse and useful ocean surface observations. It is of interest to determine if such surface observations can be used to infer information about the vertical structure of the ocean's interior, like that of temperature profiles. Earlier studies used either sea surface temperature or dynamic height/sea surface height to infer the subsurface temperature profiles. In this study we have used neural network approach to estimate the temperature structure from sea surface temperature, sea surface height, wind stress, net radiation, and net heat flux, available from an Arabian Sea mooring from October 1994 to October 1995, deployed by the Woods Hole Oceanographic Institution. On the average, 50% of the estimations are within an error of ±0.5°C and 90% within ±1.0°C. The average RMS error between the estimated temperature profiles and in situ observations is 0.584°C with a depth-wise average correlation coefficient of 0.92.
    Description: This work is carried out as a part of the Department of Ocean Development project.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2005. 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 110 (2005): C03020, doi:10.1029/2004JC002377.
    Description: During July–August 2001, oceanographic variability on the New England inner continental shelf was investigated with an emphasis on temporal scales shorter than tidal periods. Mooring and ship survey data showed that subtidal variation of inner shelf stratification was in response to regional Ekman upwelling and downwelling wind driven dynamics. High-frequency variability in the vertical structure of the water column at an offshore mooring site was linked to the baroclinic internal tide and the onshore propagation of nonlinear solitary waves of depression. Temperature, salinity, and velocity data measured at an inshore mooring detected a bottom bore that formed on the flood phase of the tide. During the ebb tide, a second bottom discontinuity and series of nonlinear internal waves of elevation (IWOE) formed when the water column became for a time under hydraulic control. A surface manifestation of these internal wave crests was also observed in aircraft remote sensing imagery. The coupling of IWOE formation to the offshore solitary waves packets was investigated through internal wave breaking criterion derived in earlier laboratory studies. Results suggested that the offshore solitons shoaled on the sloping shelf, and transformed from waves of depression to waves of elevation. The coupling of inshore bore formation to the offshore solitary waves and the possible impact of these periodic features on mixing on the inner shelf region are discussed.
    Description: This work was funded by the Office of Naval Research under grant N00014-99-1-0029 and Secretary of the Navy/CNO Chair grant N00014-99-1-0090 to R. A. W.
    Keywords: Internal waves ; Internal waves of elevation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2004. 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 109 (2004): C08016, doi:10.1029/2003JC002024.
    Description: Mixed layer depth (MLD) over the north Indian Ocean (30°S to 30°N and 40°E to 110°E) is computed using the simple one-dimensional model of Price et al. [1986] forced by satellite-derived parameters (winds and chlorophyll). Seasonal chlorophyll observations obtained from the Coastal Zone Color Scanner allow us to examine how biology interacts with physics in the upper ocean by changing the absorption of light and thus the heating by penetrative solar radiation, an effect we refer to as biological heating. Our analysis focus mainly on two aspects: the importance of varying biology in the model simulations relative to runs with constant biology and secondly, the contribution of biology to the seasonal variability of the MLD. The model results are compared with observations from a surface mooring deployed for 1 year (October 1994 to October 1995) in the central Arabian Sea and also with available conductivity-temperature-depth (CTD) observations from the Arabian Sea during the period 1994–1995. The effect of biological heating on the upper ocean thermal structure in central Arabian Sea is found to be greatest in August. In other months it is either the wind, which is the controlling factor in mixed layer variations, or the density variations due to winter cooling and internal dynamics. A large number of CTD observations collected under the Joint Global Ocean Flux study and World Ocean Circulation Experiment have been used to validate model results. We find an overall improvement by approximately 2–3 m in root-mean-square error in MLD estimates when seasonally varying chlorophyll observations are used in the model.
    Description: U.S. Navy Office of Naval Research (grant N00014-94-1-0161)
    Keywords: Biological heating ; ERS scatterometer wind ; Extinction depth ; 1-D mixed layer model ; Mixed layer depth variations
    Repository Name: Woods Hole Open Access Server
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  • 6
    Publication Date: 2022-10-20
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Davis, S. R., Farrar, J. T., Weller, R. A., Jiang, H., & Pratt, L. J. The land-sea breeze of the Red Sea: observations, simulations, and relationships to regional moisture transport. Journal of Geophysical Research-Atmospheres, 124, (2019): 13803-13825, doi: 10.1029/2019JD031007.
    Description: Unique in situ observations of atmospheric conditions over the Red Sea and the coastal Arabian Peninsula are examined to study the dynamics and regional impacts of the local land‐sea breeze cycle (LSBC). During a 26‐month data record spanning 2008–2011, observed LSBC events occurred year‐round, frequently exhibiting cross‐shore wind velocities in excess of 8 m/s. Observed onshore and offshore features of both the land‐ and sea‐breeze phases of the cycle are presented, and their seasonal modulation is considered. Weather Research and Forecasting climate downscaling simulations and satellite measurements are used to extend the analysis. In the model, the amplitude of the LSBC is significantly larger in the vicinity of the steeper terrain elements encircling the basin, suggesting an enhancement by the associated slope winds. Observed and simulated conditions also reflected distinct gravity‐current characteristics of the intrinsic moist marine air mass during both phases of the LSBC. Specifically, the advance and retreat of marine air mass was directly tied to the development of internal boundary layers onshore and offshore throughout the period of study. Convergence in the lateral moisture flux resulting from this air mass ascending the coastal topography (sea‐breeze phase) as well as colliding with air masses from the opposing coastline (land‐breeze phase) further resulted in cumulous cloud formation and precipitation.
    Description: This study was supported by National Science Foundation (NSF) Grant OCE‐1435665 and National Aeronautics and Space Administration (NASA) Grants 80NSSC18K1494 and NNX14AM71G. Further support for Lawrence Pratt was provided by NSF Grant OCE‐1154641. The authors wish to thank Sarah Gille for insightful conversations related to this work. GLDAS data used in this study were acquired as part of the mission of NASA's Earth Science Division and archived and distributed by the Goddard Earth Sciences (GES) Data and Information Services Center (DISC). We further acknowledge the use of data and imagery from LANCE FIRMS operated by the NASA/GSFC/Earth Science Data and Information System (ESDIS) with funding provided by NASA/HQ. The in situ data from the WHOI/KAUST mooring is available at a WHOI repository (http://uop.whoi.edu/projects/kaust/form.php) for academic and research purposes. The mooring data collected during the WHOI‐KAUST collaboration was made possible by awards USA00001, USA00002, and KSA00011 to WHOI by the KAUST in the Kingdom of Saudi Arabia. The buoy and tower data collection was a result of the work of the WHOI Upper Ocean Processes Group and staff at KAUST; John Kemp, Jason Smith, Paul Bouchard, Sean Whelan, Yasser Abualnaja, Yasser Kattan, and Abdulaziz Al‐Suwailem all made major contributions.
    Keywords: Sea‐breeze ; Land‐breeze ; Red Sea ; African coast ; Air‐sea ; Observations and modelling
    Repository Name: Woods Hole Open Access Server
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  • 7
    Publication Date: 2022-10-26
    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 Geophysical Research Letters 46(1), (2018): 293-302, doi:10.1029/2018GL080956.
    Description: Ground‐breaking measurements from the ocean observatories initiative Irminger Sea surface mooring (60°N, 39°30′W) are presented that provide the first in situ characterization of multiwinter surface heat exchange at a high latitude North Atlantic site. They reveal strong variability (December 2014 net heat loss nearly 50% greater than December 2015) due primarily to variations in frequency of intense short timescale (1–3 days) forcing. Combining the observations with the new high resolution European Centre for Medium Range Weather Forecasts Reanalysis 5 (ERA5) atmospheric reanalysis, the main source of multiwinter variability is shown to be changes in the frequency of Greenland tip jets (present on 15 days in December 2014 and 3 days in December 2015) that can result in hourly mean heat loss exceeding 800 W/m2. Furthermore, a new picture for atmospheric mode influence on Irminger Sea heat loss is developed whereby strongly positive North Atlantic Oscillation conditions favor increased losses only when not outweighed by the East Atlantic Pattern.
    Description: We are grateful to Meric Srokosz and the two reviewers for helpful comments on this work. S. J. acknowledges the U.K. Natural Environment Research Council ACSIS programme funding (Ref. NE/N018044/1). M. O. acknowledges support from EU Horizon 2020 projects AtlantOS (grant 633211) and Blue Action (grant 727852). G. W. K. M. acknowledges support from the Natural Sciences and Engineering Research Council of Canada. Support for the Irminger Sea array of the ocean observatories initiative (OOI) came from the U.S. National Science Foundation. Thanks to the WHOI team and ships' officers and crew for the field deployments and to Nan Galbraith for processing the data and computing the air‐sea fluxes. Support for this processing, and making available and sharing the OOI data, came from the National Science Foundation under a Collaborative Research: Science Across Virtual Institutes grant (82164000) to R. A. W. Data used are available from the following sites: NOAA Climate Prediction Center NAO and EAP indices ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/tele_index.nh, ECMWF Reanalysis 5 (ERA5) https://www.ecmwf.int/en/forecasts/datasets/archive‐datasets/reanalysis/datasets/era5, and ocean observatories initiative Irminger Mooring https://ooinet.oceanobservatories.org/.
    Description: 2019-06-18
    Keywords: Irminger Sea ; Air-sea interaction ; Surface heat flux ; Atmospheric modes ; Surface flux mooring ; Atmospheric reanalysis
    Repository Name: Woods Hole Open Access Server
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  • 8
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2006. 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 111 (2006): C05015, doi:10.1029/2005JC002989.
    Description: New in situ observations from 10°N, 125°W during 1997–1998 show strong intraseasonal variability in meridional velocity and sea surface temperature. The 50- to 100-day oscillations in sea surface height (SSH) have long been recognized as a prominent aspect of oceanic variability in the region of 9–13°N in the eastern Pacific Ocean. We use in situ and satellite data to more fully characterize this variability. The oscillations have zonal wavelengths of 550–1650 km and propagate westward in a manner consistent with the dispersion relation for first baroclinic mode, free Rossby waves in the presence of a mean westward flow. Analysis of 9 years of altimetry data shows that the amplitude of the 50- to 100-day SSH variability at 10°N is largest on 90–115°W, with peak amplitudes occurring around April. Some eddies traveling westward at 10–13°N emanate from near the gulfs of Tehuantepec and Papagayo, but eddies sometimes also appear to intensify well away from the coast while in the North Equatorial Current (NEC). The hypothesis that the intraseasonal variability and its annual cycle are associated with baroclinic instability of the NEC is supported by a spatiotemporal correlation between the amplitude of 50- to 100-day variability and the occurrence of westward zonal flows meeting an approximate necessary condition for baroclinic instability. The notion that baroclinic instability may be involved is further corroborated by the tendency of the NEC to weaken while the eddies intensify, even as the wind works to strengthen the current.
    Description: The authors gratefully acknowledge support for the fieldwork under the NOAA Office of Global Programs Pan American Climate Studies program (grants NA66GPO130 and NA96GPO428) and for analysis and publication (grants NA87RJ0445 and NA17RJ1223).
    Repository Name: Woods Hole Open Access Server
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  • 9
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2012. 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 117 (2012): C03017, doi:10.1029/2011JC007267.
    Description: Frequency spectra from deep-ocean near-bottom acoustic measurements obtained contemporaneously with wind, wave, and seismic data are described and used to determine the correlations among these data and to discuss possible causal relationships. Microseism energy appears to originate in four distinct regions relative to the hydrophone: wind waves above the sensors contribute microseism energy observed on the ocean floor; a fraction of this local wave energy propagates as seismic waves laterally, and provides a spatially integrated contribution to microseisms observed both in the ocean and on land; waves in storms generate microseism energy in deep water that travels as seismic waves to the sensor; and waves reflected from shorelines provide opposing waves that add to the microseism energy. Correlations of local wind speed with acoustic and seismic spectral time series suggest that the local Longuet-Higgins mechanism is visible in the acoustic spectrum from about 0.4 Hz to 80 Hz. Wind speed and acoustic levels at the hydrophone are poorly correlated below 0.4 Hz, implying that the microseism energy below 0.4 Hz is not typically generated by local winds. Correlation of ocean floor acoustic energy with seismic spectra from Oahu and with wave spectra near Oahu imply that wave reflections from Hawaiian coasts, wave interactions in the deep ocean near Hawaii, and storms far from Hawaii contribute energy to the seismic and acoustic spectra below 0.4 Hz. Wavefield directionality strongly influences the acoustic spectrum at frequencies below about 2 Hz, above which the acoustic levels imply near-isotropic surface wave directionality.
    Description: Funding for the ALOHA Cabled Observatory was provided by the National Science Foundation and the State of Hawaii through the School of Ocean and Earth Sciences and Technology at the University of Hawaii-Manoa (F. Duennebier, PI). Donations from AT&T and TYCOM and the cooperation of the U.S. Navy made this project possible. The WHOI-Hawaii Ocean Time series Station (WHOTS) mooring is maintained by Woods Hole Oceanographic Institution (PIs R. Weller and A. Plueddemann) with funding from the NOAA Climate Program Office/Climate Observation Division. NSF grant OCE- 0926766 supported R. Lukas (co-PI) to augment and collaborate on the maintenance of WHOTS. Lukas was also supported during this analysis by The National Ocean Partnership Program “Advanced Coupled Atmosphere-Wave-Ocean Modeling for Improving Tropical Cyclone Prediction Models” under contract N00014-10-1-0154 to the University of Rhode Island (I. Ginis, PI).
    Description: 2012-09-10
    Keywords: Air-sea interaction ; Marine acoustics ; Ocean observatories ; Ocean waves ; Wave spectra
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. 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, 46(8), (2019):4346-4355, doi:10.1029/2018GL081577.
    Description: A yearlong record from moored current, temperature, conductivity, and four mixing meters (χpods) in the northernmost international waters of the Bay of Bengal quantifies upper‐ocean turbulent diffusivity of heat (Kt) and its response to the Indian monsoon. Data indicate (1) pronounced intermittency in turbulence at semidiurnal, diurnal, and near‐inertial timescales, (2) strong turbulence above 25‐m depth during the SW (summer) and NE (winter) monsoon relative to the transition periods (compare Kt 〉 10−4 m2/s to Kt  ∼ 10−5 m2/s, and (3) persistent suppression of turbulence (Kt 〈 10−5 m2/s) for 3 to 5 months in the latter half of the SW monsoon coincident with enhanced near‐surface stratification postarrival of low‐salinity water from the Brahmaputra‐Ganga‐Meghna delta and monsoonal precipitation. This suppression promotes maintenance of the low‐salinity surface waters within the interior of the bay preconditioning the upper northern Indian Ocean for the next year's monsoon.
    Description: This work was supported by the U.S. Office of Naval Research (ONR) Grants N00014‐14‐1‐0236 and N00014‐17‐1‐2472, and the Ocean Mixing and Monsoon program of the Indian Ministry of Earth Sciences. The deployment of the Woods Hole Oceanographic Institution mooring and RW and JTF were supported by ONR Grant N00014‐13‐1‐0453. The deployment and recovery of the mooring were carried out by RV Sagar Nidhi and RV Sagar Kanya, respectively, with the help of the crew and science parties. Thanks to National Institute of Ocean Technology (India) for buoy support. The authors acknowledge invaluable discussions with Johannes Becherer, Deepak Cherian, and Sally Warner at CEOAS, OSU, and Dipanjan Chaudhuri, J Sree Lekha, and Debasis Sengupta at CAOS, IISc. The authors thank two anonymous reviewers for their detailed reviews, which have helped sharpen many aspects of this paper. Data can be accessed as described in section S2.
    Description: 2019-10-08
    Keywords: Ocean turbulence ; Turbulence suppression ; Indian Monsoon ; Bay of Bengal ; Turbulent Mixing ; Chipod
    Repository Name: Woods Hole Open Access Server
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