Deep-Sea Research I 51 (2004) 665–699 The large-scale context for oceanic subduction in the Northeast Atlantic R.A. Weller a, *, P.W. Furey a , M.A. Spall a , R.E. Davis b a Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA b Scripps Institution of Oceanography, La Jolla, CA 92037, USA Received 11 April 2003; received in revised form 29 October 2003; accepted 3 January 2004 Abstract The large-scale context for oceanic subduction is examined in the region bounded by 10  N and 40  N and 10  W and 40  W using data collected from June 1991 to June 1993. In contrast to climatology, it was found that over the entire region the ocean gained heat, ranging from 10–30Wm –2 to the north to 40–50Wm –2 to the south. Steady tradewinds dominated the southeastern half of the region. To the northwest of the axis of these tradewinds was a broad region of downward Ekman pumping with a 2-yr mean of about 50m yr –1 . Wind-driven surface currents and a seasonal cycle in mixed layer temperature and depth were found that reflected the influence of local forcing. The interior circulation was consistent with the clockwise circulation of the eastern end of the subtropical gyre, though eddy variability dominated the northern part of the region. Due to Ekman convergence the winter mixed layer in the central and southwestern parts of the region was as deep as to the north; however, it was also warm. This deep, warm mixed layer in the center of the region aided the subduction of water from the northeast by providing a protective cap; isopycnals that outcropped to the north passed well below the base of this mixed layer. r 2004 Elsevier Ltd. All rights reserved. Keywords: Atlantic; Circulation; Upper ocean; Subduction; Water mass; Air–sea coupling 1. Introduction Oceanic subduction refers to the processes by which mixed layer waters are incorporated into the main thermocline (Stommel, 1979; Luyten et al., 1983). Ekman pumping contributes to water being isolated from the mixed layer as does lateral induction (Marshall et al., 1993). The seasonal cycle of the upper ocean plays, in particular, an important role in subduction (Woods, 1985; Qiu and Huang, 1995; Paillet and Ahran, 1996) with spring restratification capping over the deep mixed layer formed during the previous winter, as evidenced by the match between the T/S properties of the thermocline in the Northeast Atlantic (Montgomery, 1938) and those of the late winter mixed layer. It is probable that the loss of water from the mixed layer is also spatially modulated. Fronts, for example, are thought to be a site of active subduction (Rudnick and Luyten, 1996; Rudnick, 1996; Pollard and Regier, 1992). However, a perspective on subduction that dates from Montgomery (1938) and Iselin (1939) is that large-scale spatial gradients and the seasonal cycle ARTICLE IN PRESS *Corresponding author. Tel.: +1-508-289-2508; fax: +1- 508-457-2163. E-mail address: rweller@whoi.edu (R.A. Weller). 0967-0637/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr.2004.01.003