Gyre-scale deep convection in the subpolar North Atlantic Ocean during winter 2014-2015

• Published in: Geophysical Research Letters
• Main Authors: Piron, A., Thierry, V., Mercier, H., Caniaux, G.
• 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), ANR-10-EQPX-0040,NAOS,Observations de l'océan global pour l'étude et la prévision de l'océan et du climat: préparation de la nouvelle décennie d'Argo(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: North Atlantic ocean; deep convection; Argo; air-sea forcing; mixed layer depth; preconditioning; [SDU]Sciences of the Universe [physics]; Irminger Sea; Labrador Sea; North Atlantic
• Online Access: https://insu.hal.science/insu-03682755; https://insu.hal.science/insu-03682755/document; https://insu.hal.science/insu-03682755/file/Geophysical%20Research%20Letters%20-%202017%20-%20Piron%20-%20Gyre%25u2010scale%20deep%20convection%20in%20the%20subpolar%20North%20Atlantic%20Ocean%20during%20winter.pdf; https://doi.org/10.1002/2016GL071895

International audience Using Argo floats, we show that a major deep convective activity occurred simultaneously in the Labrador Sea (LAB), south of Cape Farewell (SCF), and the Irminger Sea (IRM) during winter 2014-2015. Convection was driven by exceptional heat loss to the atmosphere (up to 50% higher than the climatological mean). This is the first observation of deep convection over such a widespread area. Mixed layer depths exceptionally reached 1700 m in SCF and 1400 m in IRM. The deep thermocline density gradient limited the mixed layer deepening in the Labrador Sea to 1800 m. Potential densities of deep waters were similar in the three basins (27.73-27.74 kg m -3 ) but warmer by 0.3°C and saltier by 0.04 in IRM than in LAB and SCF, meaning that each basin formed locally its own deep water. The cold anomaly that developed recently in the North Atlantic Ocean favored and was enhanced by this exceptional convection.