ATLAS Deliverable 1.3: Recent AMOC and N Atlantic gyre properties and dynamics

One of the goals of ATLAS is to examine how changing circulation in the North Atlantic has affected deep-sea marine ecosystems. Strong motivation for this comes from recent instrumental-based data showing a weakening of the large-scale overturning circulation of the Atlantic from 2004 onwards (Srokosz & Bryden, 2015). As part of WP1 Objective 1, ATLAS has undertaken analysis of high resolution proxy archives of circulation over multi-decadal to centennial timescales, providing longer term context for currently observed variability. There are two dominant large-scale features of ocean circulation in the North Atlantic that potentially influence the case study sites of ATLAS:
(1) The Atlantic Meridional overturning Circulation (AMOC)
(2) The Subpolar Gyre (SPG) circulation.
The AMOC is comprised of northward transport of warm surface and thermocline waters, and their deep southward return flow as dense waters that formed by cooling processes and sinking at high latitudes (Fig. 1). As well as the vertically overturning of the North Atlantic, there is also horizontal circulation linked to surface ocean currents. An anti-clockwise circulation of surface currents in the northern North Atlantic forms the SPG. ATLAS work led by UCL has helped constrain the recent behaviour of these two large-scale circulation systems (Thornalley et al., 2018 & in prep.; Spooner et al., in prep).