Extended Data Figure 3: Indian seafloor and radiocarbon distributions.

a, d, g, j, Zonally summed seafloor areas as a function of latitude and depth. b, e, h, k, Zonally summed incrop areas as a function of latitude and pseudo-depth. c, f, i, l, Along-density zonal mean radiocarbon content (Δ¹⁴C) as a function of latitude and pseudo-depth. Note that the colour scales differ from those in Fig. 3. Panels with a pseudo-depth y axis have density contoured in black every 0.1 kg m⁻³ for γ ≥ 27.5 kg m⁻³. White curves in all panels except g–i depict the local northward–southward and diabatic–adiabatic transition levels inferred from the incrop area distribution, as in Fig. 3. In the Central Indian Basin (g–i), whose abyss is not fed from the south but instead through gaps in the Ninety East Ridge, the white curves correspond to the peak and weak incrop density surfaces based on the total sub-basin incrop profile. Sub-basin masks are shown in Extended Data Fig. 1b.