GHASS2

Type Oceanographic cruise
Ship Pourquoi pas ?
Ship owner Ifremer
Dates 16/08/2021 - 30/09/2021
Chief scientist(s) RIBOULOT Vincent , DUPRE Stéphanie ORCID, KER Stéphan ORCID, SULTAN Nabil ORCID

GEO-OCEAN - UMR 6538

Univ. Brest, CNRS, Ifremer, Univ. Bretagne Sud

Place Nicolas Copernic

29280 Plouzané

https://www.geo-ocean.fr/
DOI 10.17600/18001358
Objective

GHASS 2 cruise follows the GHASS cruise, which took place in September 2015 onboard the R/V Le Pourquoi pas?. The aims of this first cruise was to study the dynamics of the free gas/gas hydrate system and the factors triggering the sedimentary deformations and submarine instabilities previously suspected on both sides of the Danube Canyon. Following this exploration cruise where gas hydrates were sampled for the first time in this sector of the Black Sea, we demonstrated that the dynamics of gas hydrates, the geomorphology and sedimentary architecture control the location of the gas emissions detected in the water column (up to 450 m in height). Seismic data analyses (HR and SYSIF) have allowed us to partly characterize the gas hydrate system and the numerical modeling of the hydrate stability zone has allowed proposing various scenarios of destabilization of the hydrates in the past, as well as predicting their future evolution. With this comprehensive view of this fluid system, GHASS 2 has focussed on the north-eastern sector of the Danube Canyon and aims to get further insights in the characterization and quantification of the free gas/gas hydrate system. The objectives are threefold: (1) characterize the whole gas system, from the source to the hydrosphere via the migration paths, (2) quantify the gas fluxes at the water/sediment interface (methane and carbon balance) and (3) constrain the temporal evolution of the gas hydrate stability zone established by the numerical modeling, from the last glacial period (-20 kyr) to the present-day and the close future. This evolution may have triggered several sedimentary instabilities discovered during GHASS. The quantitative approaches considered for this cruise are multidisciplinary (geophysical, geotechnical, sedimentological, structural, bio-geochemical, microbiological) in order to understand the processes involved in the methane cycle and gas hydrate dissociation. Seismic reflection data are constrained by direct measurements with PENFELD penetrometer (with the 50 m length version). Acoustic data of the water column and the water/sediment interface (seabed and subsurface) are now constrained by in situ observations, sampling and measurements during NAUTILE dives as well as by water sampling from CTD Rosette and coring (Calypso, interface multicorer). Flow rates of free gas was measured with the NAUTILE instrumentation (PEGAZ).

Published data

Perret Tymea, Le Chenadec Gilles, Gaillot Arnaud, Ladroit Yoann, Dupré Stéphanie (2025). YOLO-WAL: Fluid emission detection by Water-column Acoustics and a deep Learning-approach. https://doi.org/10.17882/103478


Perret Tymea, Le Chenadec Gilles, Gaillot Arnaud, Ladroit Yoann, Dupré Stéphanie (2025). Target tracking in multibeam water-column images based on acoustic simulation of beam forming artifacts – video results. https://doi.org/10.17882/105583


Sultan Nabil, Riboulot Vincent, Dupré Stéphanie, Garziglia Sebastien, Ker Stephan (2024). Pore pressure and temperature data from the Black Sea collected using Ifremer piezometers (2021-2023). https://doi.org/10.17882/102536


Data managed by SISMER

Sampling operations

Dives

Missions

Bibliography

Publications

Perret Tymea, Le Chenadec Gilles, Gaillot Arnaud, Ladroit Yoann, Dupré StéphanieORCID (2025). Deep-learning-based detection of underwater fluids in multiple multibeam echosounder data. Frontiers In Remote Sensing, 6, 1532714 (20p.). Publisher's official version : https://doi.org/10.3389/frsen.2025.1532714 , Open Access version : https://archimer.ifremer.fr/doc/00939/105096/


Fabre Maud, Loncke Lies, Riboulot VincentORCID, Ker StephanORCID (2024). Did gas-hydrate dissociation promote slope instability in the western Black Sea after the end of the last glacial period? Marine And Petroleum Geology, 170, 107088 (25p.). Publisher's official version : https://doi.org/10.1016/j.marpetgeo.2024.107088 , Open Access version : https://archimer.ifremer.fr/doc/00908/101947/


Sultan NabilORCID, Riboulot VincentORCID, Dupré StéphanieORCID, Garziglia Sebastien, Ker StephanORCID (2024). The Role of Earth Tides in Reactivating Shallow Faults and Triggering Seafloor Methane Emissions. Journal Of Geophysical Research-solid Earth, 129(11), e2024JB030253 (25p.). https://doi.org/10.1029/2024JB030253


Fabre Maud, Riboulot VincentORCID, Loncke L., Ker StephanORCID, Ballas Gregory, Thomas Yannick, Ion G., Sultan NabilORCID (2024). Slow Dynamics of Hydrate Systems Revealed by a Double BSR. Geophysical Research Letters, 51(10), e2023GL106284 (10p.). Publisher's official version : https://doi.org/10.1029/2023GL106284 , Open Access version : https://archimer.ifremer.fr/doc/00891/100317/


Agnissan Constant Art-Clarie, Guimpier Charlène, Terzariol MarcoORCID, Fandino OliviaORCID, Chéron Sandrine, Riboulot VincentORCID, Desmedt Arnaud, Ruffine LivioORCID (2023). Influence of Clay-Containing Sediments on Methane Hydrate Formation: Impacts on Kinetic Behavior and Gas Storage Capacity. Journal Of Geophysical Research-solid Earth, 128(9), e2023JB027333 (22p.). Publisher's official version : https://doi.org/10.1029/2023JB027333 , Open Access version : https://archimer.ifremer.fr/doc/00849/96135/


References of Technical Reports

Thereau Estelle, Thomas Yannick (2023). GHASS2 – Traitement des données de sismique multitrace. Analyse de vitesse RMS et imagerie avec migration après sommation. REM/GEOOCEAN/ANTIPOD-21092023-01. https://archimer.ifremer.fr/doc/00854/96594/


Thomas Yannick, Ker StephanORCID, Thereau Estelle, Dupont Pauline (2021). MISSION GHASS2 LEG1 N/O Pourquoi pas ? 16 août au 3 septembre 2021, Mer Noire. Compte rendu d’acquisition sismique multi-trace. PDG/REM/GM/LAD-24112021-01.


Thereau Estelle (2021). MISSION GHASS2. N/O Pourquoi Pas?, 16 août au 1er octobre 2021, Mer Noire. Compte-rendu d'acquisition des données de sondeur de sédiment. PDG/REM/GM/LAD-22112021-01.


Thesis using campaign data

Panetier Aurélie (2023). Shipborne Global Navigation Satellite Systems for Offshore Atmospheric Water Vapor Monitoring. PhD Thesis, ENSTA Bretagne.


Colin FlorentORCID (2020). Caractérisation des systèmes gaz/hydrates de gaz de la Mer Noire par imagerie sismique haute résolution remorquée en fond de mer (SYSIF) / Characterisation of free gas/gas hydrate systems in the Black Sea based on deep-towed high-resolution multichannel seismic imaging (SYSIF). PhD Thesis, Université de Bretagne Occidentale. https://archimer.ifremer.fr/doc/00680/79246/