Evidence of freezing pressure in sea ice discrete brine inclusions and its impact on aqueous-gaseous equilibrium

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Crabeck, O., Galley, R., Mercury, Lionel, Delille, B., Tison, L., Rysgaard, S.
• Other Authors: Centre for Earth Observation Science Winnipeg, University of Manitoba Winnipeg, Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Milieux Poreux - UMR7327, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Unité d'Océanographie Chimique, Interfacultary Center for Marine Research (MARE), Université de Liège-Université de Liège, Laboratoire de Glaciologie Bruxelles, Université libre de Bruxelles (ULB), Greenland Climate Research Centre, Greenland Institute of Natural Resources (GINR), Arctic Research Centre Aarhus (ARC), Aarhus University Aarhus, ANR-10-LABX-0100,VOLTAIRE,Geofluids and Volatil elements – Earth, Atmosphere, Interfaces – Resources and Environment(2010), ANR-11-EQPX-0036,PLANEX,Planète Expérimentation: simulation et analyse in-situ en conditions extrêmes(2011), European Project: 730997,EUROCHAMP2020(2020)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU]Sciences of the Universe [physics]; Sea ice
• Online Access: https://insu.hal.science/insu-02005429; https://insu.hal.science/insu-02005429/document; https://insu.hal.science/insu-02005429/file/Crabeck_et_al-2019-Journal_of_Geophysical_Research__Oceans.pdf; https://doi.org/10.1029/2018JC014597

International audience Sea ice in part controls surface water properties and the ocean‐atmosphere exchange of greenhouse gases at high latitudes. In sea ice gas exists dissolved in brine and as air bubbles contained in liquid brine inclusions, or as bubbles trapped directly within the ice matrix. Current research on gas dynamics within the ocean‐sea ice‐atmosphere interface has been based on the premise that brine with dissolved air becomes supersaturated with respect to the atmosphere during ice growth. Based on Henry's Law, gas bubbles within brine should grow when brine reaches saturation during cooling, given that the total partial pressure of atmospheric gases is above the implicit pressure in brine of 1 atm. Using high‐resolution light microscopy time series imagery of gas bubble evolution inside discrete brine pockets, we observed bubbles shrinking during cooling events in response to the development of freezing pressure above 3 atm. During warming of discrete brine pockets, existing bubbles expand and new bubbles nucleate in response to depressurization. Pressure variation within these inclusions has direct impacts on aqueous‐gaseous equilibrium, indicating that Henry's Law at a constant pressure of 1 atm is inadequate to assess the partitioning between dissolved and gaseous fractions of gas in sea ice. This new evidence of pressure build‐up in discrete brine inclusions controlling the solubility of gas and nucleation of bubbles in these inclusions has the potential to affect the transport pathways of air bubbles and dissolved gases within sea ice‐ocean‐atmosphere interface and modifies brine biochemical properties.