Pulses of South Atlantic water into the tropical North Atlantic since 1825 from coral isotopes

Decadal and multidecadal changes in the meridional overturning circulation may originate from either the subpolar North Atlantic or the Southern Hemisphere (Fig.1).

Figure 1: *Location of coral (diamond) and scleroponge (circle) samples used in this study and schematic view of the tropical and subtropical currents.*

New records of carbon and oxygen isotopes from an eastern Martinique Island (Lesser Antilles) coral (1 in Fig.1) reveal irregular, decadal, double-step events of low ∆14C and enhanced vertical mixing, high δ18O and high δ13C values starting in 1885 (Fig.2).

Figure 2: *Variations of carbon and oxygen isotopes and vertical mixing W as a function of time (year) in the Martinique coral bands.*

Comparison of the new and published ∆14C records indicates that the last event (1956–1969) coincides with a widespread, double-step ∆14C low of South Atlantic origin from 32°N to 18°S, associated with a major slowdown of the Caribbean Current transport between 1963 and 1969 (Fig. 3).

Figure 3: *Post-1940 variations of the surface water properties from oxygen and carbon isotopes and of Orinoco and Amazon rivers runoffs.*

This event and the past Martinique ∆14C lows are attributed to pulses of northward advection of low ∆14C Sub-Antarctic Mode Waters into the tropical Atlantic. They are coeval with changes of the tropical freshwater budget and likely driven by meridional overturning circulation changes.

Reference: Martine Paterne, Ellen R.M. Druffel, Thomas P. Guilderson, Dominique Blamart, Christophe Moreau, Jennifer Weil-Accardo, Nathalie Feuillet. Pulses of South Atlantic water into the tropical North Atlantic since 1825 from coral isotopes. Sci. Adv., 2023, XXX, 10.1126/sciadv.adi1687