Density Staircases Are Disappearing in the Canada Basin of the Arctic Ocean

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Ménesguen, Claire, Lique, Camille, Caspar‐cohen, Zoé
• Other Authors: Océan Dynamique Observations Analyse (ODYSSEY), Université de Rennes (UR)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom Paris (IMT)-Institut Mines-Télécom Paris (IMT), 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 2022
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Arctic Ocean; Canada; canada basin; Sea ice
• Online Access: https://hal.science/hal-03910680; https://hal.science/hal-03910680/document; https://hal.science/hal-03910680/file/JGR%20Oceans%20-%202022%20-%20M%20nesguen%20-%20Density%20Staircases%20Are%20Disappearing%20in%20the%20Canada%20Basin%20of%20the%20Arctic%20Ocean.pdf; https://doi.org/10.1029/2022JC018877

International audience In the Canada Basin of the Arctic Ocean, warm and salty Atlantic-origin Water (AW) lies in the intermediate layer (250–800 m) below a colder and fresher surface layer. It results in a depth range where vertical thermohaline gradients are propitious to double-diffusion. Indeed, thermohaline staircases are commonly observed and associated with double-diffusive processes. Using observations from the Beaufort Gyre Exploration Project large database and Ice-Tethered Profilers, we document the presence of density staircases in the 300–700 m depth range with a striking strong spatial and temporal coherence. However, since 2007, a progressive smoothing of these staircases has occurred, beginning from the western half of the basin. Quantifying this evolution, we find that a general pattern is a clear evolution over time from numerous thicksteps (≃40 m) with sharp interfaces to fewer and thinner steps (≃30 m) with smoother interfaces. After 2014, marked density staircases have almost disappeared in most of the Canada Basin. The vanishing of staircases occurs over a few years and coincides with modifications of the large scale circulation and thermohaline large scale horizontal gradients. As the small scale thermohaline structures are thought to play an important role for the vertical and horizontal exchanges of heat within the Canada Basin, the disappearance of the steps may impact the heat distribution at depth, with potential consequences for the evolution of the sea ice cover.