Estimated Seasonal Cycle of North Atlantic Eighteen Degree Water Volume.

• Published in: Journal of Physical Oceanography
• Main Authors: Forget, Gaël, Maze, Guillaume, Buckley, Martha, Marshall, John
• Other Authors: Massachusetts Institute of Technology (MIT), Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: Seasonal cycle; North Atlantic; Water masses; Airndashsea interaction; Heat budgets; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
• Online Access: https://hal.science/hal-00588851; https://doi.org/10.1175/2010JPO4257.1

International audience The seasonal cycle in the volume and formation rate of Eighteen Degree Water (EDW) in the North Atlantic is quantified over the 3-yr period from 2004 to 2006. The EDW layer is defined as all waters that have a temperature between 17° and 19°C. The study is facilitated by a synthesis of various observations--principally Argo profiles of temperature and salinity, sea surface temperature, and altimetry--using a general circulation model as an interpolation tool. The winter increase in EDW volume is most pronounced in February, peaking at about 8.6 Svy, where 1 Svy ≈ 3.15 × 1013 m3 corresponding to a 1 Sv (Sv ≡ 106 m3 s−1) flow sustained for one year. This largely reflects winter EDW formation due to air-sea heat fluxes. Over the remainder of the year, newly created EDW is consumed by air-sea heat fluxes and ocean mixing, which roughly contribute ⅔ and ⅓, respectively. The authors estimate a net annual volume increase of 1.4 Svy, averaged over the 3-yr period. It is small compared to the amplitude of the seasonal cycle (8.6 Svy) and annual formation due to air-sea fluxes (4.6 Svy). The overall EDW layer volume thus appears to fluctuate around a stable point during the study period. An estimate of the full EDW volume budget is provided along with an uncertainty estimate of 1.8 Svy, and largely resolves apparent conflicts between previous estimates.