Editing Sonar (section)

=== Gas leak detection from the seabed ===
Gas bubbles can leak from the seabed, or close to it, from multiple sources. These can be detected by both passive<ref name="Leighton+White_2012"/> and active sonar<ref name= "Westbrook_et_al_2009"/> (shown in schematic figure<ref name="Leighton+White_2012">{{cite journal|last1=Leighton, T.G. |author2=White, P.R. |title=Quantification of undersea gas leaks from carbon capture and storage facilities, from pipelines and from methane seeps, by their acoustic emissions|journal=Proceedings of the Royal Society A|url=http://resource.isvr.soton.ac.uk/staff/pubs/PubPDFs/2012_Leighton_White_(PRS)_Quantification_of_undersea_gas_leaks.pdf |year=2012|volume=468|issue=2138|pages=485–510|doi=10.1098/rspa.2011.0221|bibcode=2012RSPSA.468..485L|s2cid=108841954|doi-access=free}}</ref> by yellow and red systems respectively).
[[File:Seeps.png|thumb|upright=1.25|Active (red) and passive (yellow) sonar detection of bubbles from seabed (natural seeps and CCSF leaks) and gas pipelines, taken from ref.<ref name="Leighton+White_2012"/>]] Natural seeps of methane and carbon dioxide occur.<ref name= "Westbrook_et_al_2009"/> Gas pipelines can leak, and it is important to be able to detect whether leakage occurs from Carbon Capture and Storage Facilities (CCSFs; e.g. depleted oil wells into which extracted atmospheric carbon is stored).<ref name="BLackford_et_al_2014">{{cite journal|author1=Blackford, J. |author2=Stahl, H. |author3=Bull, J. |author4=Berges, B. |author5=Cevatoglu, M. |author6=Lichtschlag, A. |author7=Connelly, D. |author8=James, R. |author9=Kita, J. |author10=Long, D. |author11=Naylor, M. |author12=Shitashima, K. |author13=Smith, D. |author14=Taylor, P. |author15=Wright, I. |author16=Akhurst, M. |author17=Chen, B. |author18=Gernon, T. |author19=Hauton, C. |author20=Hayashi, M. |author21=Kaieda, H. |author22=Leighton, T. |author23=Sato, T. |author24=Sayer, M. |author25=Suzumura, M. |author26=Tait, K. |author27=Vardy, M. |author28=White, P. |author29=Widdicombe, S. |display-authors=3 |title=Detection and impacts of leakage from sub-seafloor deep geological carbon dioxide storage|journal=Nature Climate Change|date=28 September 2014|page=Published online|doi=10.1038/nclimate2381|volume=4|issue=11|url=https://eprints.soton.ac.uk/369551/1/Blackford%2520et%2520al%2520Nature%2520Climate%2520Change%2520QICS-postprint.pdf|bibcode=2014NatCC...4.1011B|s2cid=54825193 }}</ref><ref name="Berges_et_al_2015">{{cite journal |author1=Berges, B. J. P |author2=Leighton, T.G. |author3=White, P.R. |title=Passive acoustic quantification of gas fluxes during controlled gas release experiments |journal=International Journal of Greenhouse Gas Control |year=2015 |volume=38  |pages=64–79 |doi=  10.1016/j.ijggc.2015.02.008|bibcode=2015IJGGC..38...64B |url=http://eprints.soton.ac.uk/375114}}</ref><ref name= Hannis_et_al_2015>{{cite journal |author1=Hannis, S. |author2=Chadwick, A. |author3=Pearce, J. |author4=Jones, D. |author5=White, J. |author6=Wright, I. |author7=Connelly, D. |author8=Widdicombe, S. |author9=Blackford, J. |author10=White, P. |author11=Leighton, T. |display-authors=3 |title=Review of Offshore Monitoring for CCS Projects |journal= IEAGHG Technical Report 2015-02 (July 2015) |year=2015 | pages=Copyright 2016 IEAGHG |url= http://resource.isvr.soton.ac.uk/staff/pubs/PubPDFs/Pubs12721.pdf}}</ref><ref name= Hannis_et_al_2017>{{cite journal |author1=Hannis, S. |author2=Chadwick, A. |author3=Connelly, D. |author4=Blackford, J. |author5=Leighton, T. |author6=Jones, D. |author7=White, J. |author8=White, P.R. |author9=Wright, I. |author10=Widdicombe, S. |author11=Craig, J. |author12=Dixon, T. |display-authors=3 |title=Review of offshore CO2 storage monitoring: Operational and research experiences of meeting regulatory and technical requirements |journal= Energy Procedia |year=2017 |volume=114 |pages=5967–5980 |doi=10.1016/j.egypro.2017.03.1732 |doi-access=free }}</ref> Quantification of the amount of gas leaking is difficult, and although estimates can be made use active and passive sonar, it is important to question their accuracy because of the assumptions inherent in making such estimations from sonar data.<ref name="Leighton+White_2012"/><ref name="Ainslie+Leighton_2011">{{cite journal | last1 = Ainslie | first1 = M. A. | last2 = Leighton | first2 = T. G. | year = 2011 | title = Review of scattering and extinction cross-sections, damping factors, and resonance frequencies of a spherical gas bubble| url = http://resource.isvr.soton.ac.uk/staff/pubs/PubPDFs/Pub12667.pdf | journal = The Journal of the Acoustical Society of America | volume = 130 | issue = 5| pages = 3184–3208 | doi=10.1121/1.3628321| pmid = 22087992 | bibcode = 2011ASAJ..130.3184A }}</ref>