Fig. 4

Short title: 1-D conductivity profiles Detailed legend: Left column (a+c): the best-fit conductivity profiles derived using tippers at the GAN observatory (a) and the TDC observatory (c) are shown by black solid lines along with 95 % confidence intervals (black dashed lines). For reference, the conductivity profiles for old Pacific lithosphere (red line, Baba et al. 2010), for Tristan da Cunha (turqouise line, Baba et al. 2016), and hydrous and dry olivine (blue and brown lines, Katsura and Yoshino 2015) are shown. Additionally, best-fit homogeneous Earth models are shown by dashed gray lines. Right column (b+d): the observed tippers are indicated by circles, the tippers predicted from the 1-D models are indicated by solid lines, and the tippers predicted from the homogeneous Earth models are indicated by dashed lines. Additionally, induction coil data for GAN are shown by crosses