Fig. 13

Results of model calculations on ocean mass history. Regassing parameters (rate of regassing and duration of regassing pulse (τ₁)) are chosen to reproduce the inferred rapid sea-level drop (2–3 m/Myrs (in the last ~ 100 Myrs); Fig. 6). Degassing parameters include the area of cool regions with excess degassing (S_C) and the delay time (τ₂) for degassing since the beginning of excess regassing (and the plume upwelling velocity (~ 1 m/year)). a History of the water content in the MTZ (τ₁ = τ₂=100 Myrs). b Sea-level change corresponding to the model shown in (a) using a relation \( \Delta z\approx -\overline{z}\frac{M_{MTZ}\Delta {X}_{MTZ}}{W_{\mathrm{ocean}}} \) (Δz: sea-level change, \( \overline{z} \): average depth of the oceans (= 3730 m), M_MTZ: mass of the MTZ (= 4 × 10²³ kg)), ΔX_MTZ: change in the water content of the MTZ; W_ocean: mass of oceans (=1.4 × 10²¹ kg)). b Same as (a) except that τ₁=100 Myrs, and τ₂=200 Myrs. c Same as (b) except that τ₁=100 Myrs, and τ₂=200 Myrs. Observed sea-level changes (Fig. 7) can be explained with S_C=(3–10) × 10¹⁰ (m²) (i.e., a region with 200–350 km diameter)