Demons in the North Atlantic: Variability of Deep Ocean Ventilation

• Published in: Geophysical Research Letters
• Main Authors: Macgilchrist, G. A., Johnson, H. L., Lique, C., Marshall, D. P.
• 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 2021
• Subjects: dense water formation; Labrador Sea; Lagrangian; North Atlantic; ocean mixed layer; ocean ventilation; [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences
• Online Access: https://insu.hal.science/insu-03683267; https://insu.hal.science/insu-03683267/document; https://insu.hal.science/insu-03683267/file/83058.pdf; https://doi.org/10.1029/2020GL092340

International audience Translation of atmospheric forcing variability into the ocean interior via ocean ventilation is an important aspect of transient climate change. On a seasonal timescale in the subtropics, this translation is mediated by a so called "Demon" that prevents access to all except late winter mixed layer water. Here, we use an eddy permitting numerical circulation model to investigate a similar process operating on longer (interannual) timescales in the subpolar North Atlantic. We find that variations in atmospheric forcing are mediated in their translation to the ocean interior, with year to year changes in the late winter mixed layer depth being the critical factor. The signature of persistent strong atmospheric forcing driving deep mixed layers is preferentially ventilated to the interior when the forcing is ceased. Susceptibility to this effect depends on the location and density of subduction—with the rate at which newly ventilated water escapes its region of subduction being the crucial factor.