Kremeur A. S. auteur aut IRD Levy M. auteur aut IRD Aumont Olivier auteur aut IRD Reverdin G. auteur aut IRD text journalArticle eng text/pdf reformatted digital access An idealized biophysical model of the North Atlantic was designed to investigate the setting and variability of the subtropical mode water (STMW) biogeochemical properties and its impact on surface primary production in the North Atlantic. The model solution first emphasizes that the exact timing of STMW formation versus the timing of the spring bloom is of primary importance for setting the STMW biogeochemical properties. The surface primary production reaches its maximum in March in the STMW formation region just before its subduction. Thus the spring bloom consumes nitrate at the surface before STMW subducts, and STMW leaves the upper layers depleted in nutrients and fueled in organic matter. This spring consumption explains the low nutrient content of STMW observed near its source region by J.B. Palter et al. (2005). Furthermore, the model suggests that STMW plays a key role in exporting dissolved organic matter (DOM) at subsurface. The spring bloom produces a significant amount of DOM sequestrated in the mode waters after its subduction. This large pool of DOM is then remineralized with time along the transit of STMW through the subtropical gyre. Consequently, the nutrient content of STMW increases as it moves away from its source region. Finally, the model shows also that STMW is very important in controlling primary production in the western boundary current (WBC) region. Indeed, STMW remains isolated from the surface along its trajectory within the subtropical gyre. It joins the mixed layer by obduction in the WBC region only. This nutrient-rich old STMW irrigates and fertilizes the euphotic zone primarily in the WBC and then spreads along the boundary between the two gyres by advection. specialized ATLANTIQUE 034 032 114 C07019 2009 0148-0227 https://www.documentation.ird.fr/hor/fdi:010081439 10.1029/2008jc005161 0148-0227 [F B010081439] https://www.documentation.ird.fr/hor/fdi:010081439 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2022-02/010081439.pdf IRD - Base Horizon / Pleins textes 2009-09-01 2022-02-04 fdi:010081439 fre