@article {Bornstein2013,
	title = {{Direct temperature and salinity acoustic full waveform inversion}},
	journal = {Geophysical Research Letters},
	volume = {40},
	number = {16},
	year = {2013},
	month = {aug},
	pages = {4344{\textendash}4348},
	abstract = {Recent work has shown that Full Waveform Inversion could be suitable to extract physical properties such as sound speed (c), density ($\rho$), temperature (T), and salinity (S) from the weak impedance contrasts associated with the ocean{\textquoteright}s thermohaline fine structure.The seismic inversion approaches proposed so far are based on the iterative inversion of c from multichannel seismic data, while the rest of parameters (T,S, and $\rho$) are determined in a second step using two equations of state and a local T-S empirical relationship. In this work, we present an alternative to this approach. Using 1-D synthetic seismic data, we demonstrate that the direct full waveform inversion of T and S using adjoint methods is feasible without the use of any local T-S relationship and that the models of physical properties obtained with this approach are far more accurate than those inferred from c. Key Points T and S can be inverted simultaneously from ocean acoustic data using FWI Local T-S empirical relationships are not required for the inversion Our T and S results have a potential density error of 0.01 kg/m3. {\textcopyright} 2013. American Geophysical Union. All Rights Reserved.},
	keywords = {acoustic oceanography, adjoint method, full waveform inversion, thermohaline fine structure},
	issn = {00948276},
	doi = {10.1002/grl.50844},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84882307211\&partnerID=tZOtx3y1},
	author = {Bornstein, G. and Biescas, B. and Sallar{\`e}s, V. and Mojica, J. F.}
}
@article {Kormann2011,
	title = {{Application of acoustic full waveform inversion to retrieve high-resolution temperature and salinity profiles from synthetic seismic data}},
	journal = {Journal of Geophysical Research},
	volume = {116},
	number = {C11},
	year = {2011},
	month = {nov},
	pages = {C11039},
	abstract = {Recent works show that multichannel seismic (MCS) systems are able to provide detailed information on the oceans{\textquoteright} fine structure. The aim of this paper is to analyze whether 1-D full waveform inversion algorithms are suitable to recover the extremely weak acoustic impedance contrasts associated to the oceans{\textquoteright} fine structure, as well as their potential to image meso-scale objects such as meddies. We limited our analysis to synthetic, noise-free data, in order to identify some methodological issues related to this approach under idealistic conditions (e.g., 1-D wave propagation, noise-free data, known source wavelet). We first discuss the influence of the starting model in the context of the multi-scale strategy that we have implemented. Then we show that it is possible to retrieve not only sound speed but also salinity and temperature contrasts within reasonable bounds from the seismic data using Neural Network relationships trained with regional oceanographic data sets. Potentially, the vertical resolution of the obtained models, which depends on the maximum frequency inverted, is of the order of 5-10 m, whereas the root mean square error of the inverted properties is shown to be \~{}0.5 m/s for sound speed, 0.1C for temperature, and 0.06 for salinity. To conclude this study, we have inverted synthetic data simulated along an oceanographic transect acquired during the EU-funded Geophysical Oceanography (GO) project. The results demonstrate the applicability of the method for synthetic data, as well as its potential to define oceanographic features along 2-D transects at full ocean depth with excellent lateral resolution. Copyright 2011 by the American Geophysical Union.},
	issn = {0148-0227},
	doi = {10.1029/2011JC007216},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-82355181440\&partnerID=tZOtx3y1},
	author = {Kormann, J. and Biescas, B. and Korta, N. and De La Puente, J. and Sallar{\`e}s, V.}
}
@article {Buffett2010,
	title = {{Stochastic heterogeneity mapping around a mediterranean salt lens}},
	journal = {Ocean Science},
	volume = {6},
	number = {1},
	year = {2010},
	pages = {423{\textendash}429},
	abstract = {We present the first application of Stochastic Heterogeneity Mapping based on the band-limited von K{\'a}rm{\'a}n function to a seismic reflection stack of a Mediterranean water eddy (meddy), a large salt lens of Mediterranean water. This process extracts two stochastic parameters directly from the reflectivity field of the seismic data: the Hurst number, which ranges from 0 to 1, and the correlation length (scale length). Lower Hurst numbers represent a richer range of high wavenumbers and correspond to a broader range of heterogeneity in reflection events. The Hurst number estimate for the top of the meddy (0.39) compares well with recent theoretical work, which required values between 0.25 and 0.5 to model internal wave surfaces in open ocean conditions based on simulating a Garrett-Munk spectrum (GM76) slope of \&-2. The scale lengths obtained do not fit as well to seismic reflection events as those used in other studies to model internal waves. We suggest two explanations for this discrepancy: (1) due to the fact that the stochastic parameters are derived from the reflectivity field rather than the impedance field the estimated scale lengths may be underestimated, as has been reported; and (2) because the meddy seismic image is a two-dimensional slice of a complex and dynamic three-dimensional object, the derived scale lengths are biased to the direction of flow. Nonetheless, varying stochastic parameters, which correspond to different spectral slopes in the Garrett-Munk spectrum (horizontal wavenumber spectrum), can provide an estimate of different internal wave scales from seismic data alone. We hence introduce Stochastic Heterogeneity Mapping as a novel tool in physical oceanography.},
	issn = {18120784},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-77950468840\&partnerID=tZOtx3y1},
	author = {Buffett, G. G. and Hurich, C. A. and Vsemirnova, E. A. and Hobbs, R. W. and Sallar{\`e}s, V. and Carbonell, R. and Klaeschen, D. and Biescas, B.}
}
@article {Sallares2009,
	title = {{Relative contribution of temperature and salinity to ocean acoustic reflectivity}},
	journal = {Geophysical Research Letters},
	volume = {36},
	number = {20},
	year = {2009},
	month = {oct},
	pages = {L00D06},
	abstract = {Marine seismic data display laterally coherent reflectivity from the water column that is attributed to fine-scale oceanic layering. The amplitude of the different reflections is the expression of acoustic impedance contrasts. between neighbouring water masses, and therefore water reflectivity maps the ocean{\textquoteright}s vertical sound speed and density (i.e., temperature and salinity) variations. Here we determine the relative contribution of each parameter by computing the temperature and salinity partial derivatives of sound speed and density, and using them to estimate reflection coefficients from a real oceanographic dataset. The results show that the mean contribution of density variations is 5-10\%, while 90-95\% is due to sound speed variations. On average, 80\% of reflectivity comes from temperature contrasts. Salinity contribution averages 20\%, but it is highly variable and reaches up to 40\% in regions prone to diffusive convection such as the top of the Mediterranean Undercurrent in the Gulf of Cadiz. Copyright 2009 by the American Geophysical Union.},
	issn = {0094-8276},
	doi = {10.1029/2009GL040187},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-72149084920\&partnerID=tZOtx3y1},
	author = {Sallar{\`e}s, V. and Biescas, B. and Buffett, G. and Carbonell, R. and Danobeitia, J. J. and Pelegr{\'\i}, J. L.}
}
@article {Buffett2009,
	title = {{Seismic reflection along the path of the Mediterranean Undercurrent}},
	journal = {Continental Shelf Research},
	volume = {29},
	number = {15},
	year = {2009},
	month = {aug},
	pages = {1848{\textendash}1860},
	abstract = {Seismic reflection profiling is applied to the study of large scale physical oceanographic processes in the Gulf of C{\'a}diz and western Iberian coast, coinciding with the path of the Mediterranean Undercurrent. The multi-channel seismic reflection method provides clear images of thermohaline fine structure with a horizontal resolution approximately two orders of magnitude higher than CTD casting. The seismic data are compared with co-located historical oceanographic data. Three seismic reflectivity zones are identified: North Atlantic Central Water, Mediterranean Water and North Atlantic Deep Water. Seismic evidence for the path of the Mediterranean Undercurrent is found in the near-slope reflectivity patterns, with rising reflectors between about 500 and 1500 m. However, the core of the undercurrent is largely transparent. Seismic images show that central and, particularly, intermediate Mediterranean Waters have fine structure coherent over horizontal distances of several tens of kilometers. However, the intensity of the reflectors, and their horizontal coherence, decreases downstream. This change in seismic reflectivity is probably the result of diminished vertical thermohaline contrasts between adjacent water masses, so that double-diffusion processes become unable to sustain temperature and salinity staircases. Comparison of root-mean-square seismic amplitudes with temperature and salinity differences between the Mediterranean Undercurrent and the overlying central waters suggests a causal relationship between observed thermohaline fine structure and true seismic amplitudes. We estimate that, within this intermediate water stratum, impedance contrasts are mainly controlled by sound speed contrasts (a factor between 3.5 and 10 times larger than density contrasts), which are mainly controlled by temperature contrasts (a factor between 1.5 and 5 times larger than salinity contrasts). {\textcopyright} 2009 Elsevier Ltd. All rights reserved.},
	keywords = {Amplitude, Entrainment, Mediterranean Undercurrent, Mixing, Salinity, Seismic oceanography, Temperature, thermohaline fine structure},
	issn = {02784343},
	doi = {10.1016/j.csr.2009.05.017},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-69249209739\&partnerID=tZOtx3y1},
	author = {Buffett, G.G. and Biescas, B. and Pelegr{\'\i}, J.L. and Mach{\'\i}n, F. and Sallar{\`e}s, V. and Carbonell, R. and Klaeschen, D. and Hobbs, R.}
}
@article {Biescas2008,
	title = {{Imaging meddy finestructure using multichannel seismic reflection data}},
	journal = {Geophysical Research Letters},
	volume = {35},
	number = {11},
	year = {2008},
	month = {jun},
	pages = {L11609},
	abstract = {This work illustrates the great potential of multichannel seismic reflection data to extract information from the finestructure of meddies with exceptional lateral resolution (10-15 m). We present seismic images of three meddies acquired in the Gulf of Cadiz (SW Iberian Peninsula), which consist of concentric reflectors forming oval shapes that sharply contrast with the background oceanic structure. The seismic images reveal the presence of different regions within the meddies that are consistent with those observed in historical temperature (T) and salinity (S) data. The core region, characterized by smooth T and S variations, is weakly reflective. The double-diffusive upper and lower boundaries and the lateral-interleaving outer edges, characterized by stronger T and S contrasts, display strong reflectivity bands. These new observations clearly show differences between layers developed at the upper and lower boundaries that can contribute to th knowledge of mixing processes and layering formation in oceans. Copyright 2008 by the American Geophysical Union.},
	issn = {0094-8276},
	doi = {10.1029/2008GL033971},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-49849096389\&partnerID=tZOtx3y1},
	author = {Biescas, B. and Sallar{\`e}s, V. and Pelegr{\'\i}, J. L. and Mach{\'\i}n, F. and Carbonell, R. and Buffett, G. and Danobeitia, J. J. and Calahorrano, A.}
}
