Drivers of Interannual Salinity Variability in the Arctic Ocean

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Hochet, Antoine, Lique, Camille, Sévellec, Florian, Llovel, William
• Other Authors: Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2024
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Arctic; Arctic Ocean; East Siberian Shelf; Sea ice
• Online Access: https://hal.science/hal-04603954; https://hal.science/hal-04603954/document; https://hal.science/hal-04603954/file/JGR%20Oceans%20-%202024%20-%20Hochet%20-%20Drivers%20of%20Interannual%20Salinity%20Variability%20in%20the%20Arctic%20Ocean.pdf; https://doi.org/10.1029/2023JC020852

International audience Accurate projections and attribution of Arctic Ocean changes in climate models require a good understanding of the mechanisms underlying interannual salinity variability in the region. Although some mechanisms have been extensively studied in idealized setting, in particular for the dynamics of the Beaufort gyre (BG), it remains unclear how applicable they are to more complex systems. This study introduces a new diagnostic based on salinity variance budget to robustly assess the mechanisms of salinity variations. The diagnostic is then applied to the "Estimating the Circulation and Climate of the Ocean" state estimate. Results indicate that the advection of salinity anomaly in the direction of the mean salinity gradient made by velocity anomalies is the primary source of interannual salinity variability. These velocities are primarily attributed to fluctuating winds via Ekman transports. Fluctuating surface freshwater fluxes from the atmosphere and sea ice are the second most important source of variability and cannot be neglected. The two sinks of interannual salinity variance are associated with the erosion of large scale gradients of the mean circulation by eddies and to a lesser extent to the diffusive terms. Over continental shelves, particularly over the East Siberian Shelf (ESS), ocean surface freshwater fluxes and diffusion play a more important role than in the deep basins. We also report a strong intensification of all sources and sinks of interannual salinity variability in the BG and an opposite weakening in the ESS in the second decade of the analysis (2004-2014) with respect to the first (1993-2003).A clear understanding of the mechanisms of the slow salinity variations in the Arctic could help improving their representation in climate models and provide directions on where new in-situ observing systems should be positioned. Most of the past studies of the mechanisms have used simple models in which several important realistic characteristics, such as the true bathymetry, ...