The Proceedings of the Eighth International Conference on Creationism (2018)

with a normal value of thermal conductivity but with a uniform heat sink over a specified time. We have chosen an illustrative heat sink lifetime of 0.2 year (73 days), of a magnitude chosen to remove the same amount of heat as would be lost in total if the lithosphere cooled naturally down to steady state conditions. The spreading rate is taken as constant through this interval at 0.63 ms -1 , which is 10 9 times faster than present-day rates. The predicted surface heat flux after 73 days is 570 Wm -2 , falling to 3.8 Wm -2 after a further 4400 years to account for the post-Flood period. Figs. 5 and 6 show that, although the total heat loss in the GDH1 model is the same as in the long time scale calculation, most of it (>99.99%) is swallowed by the heat sink. In this case the predicted surface heat flux is much higher than in the long time scale calculation; even today it would be over 40 times higher than observed, and the depth profile is linear. Both predictions are contrary to observation. The depth profile could be modified by a different time dependence of the spreading rate, viz. by accelerating from a slow start, but this would not improve the surface heat flux prediction. 4. A heat sink suitably tailored in space and time The shortcomings of the uniform heat sink discussed in section 3 suggest how the postulated heat sink might be modified to give results closer to present day observation. First we note that the accumulated heat loss in each interval when the system reaches thermal equilibrium, characterized by the temperature distribution T ( z ) = T 0 + z ( T 1 - T 0 )/ L , is proportional to (1 - z / L ). This suggests a heat sink varying linearly with (1 - z / L ) . However given the same time scale as in section 3 this still produces a thermal boundary layer adjacent to the surface up to time t = 0.2 year, when the boundary layer and high surface heat flux disappear (see Figure 7). Most of the time there is a surface heat flux much larger than anything found on today’s ocean floors except at hot spots on mid- ocean ridges. With a constant spreading rate (0.63 ms -1 as for the uniform heat sink) the shrinkage and depth profiles are the same as for the case of a uniform heat sink, i.e. linear. In order to demonstrate the effect of the near-surface boundary layer we have increased the mesh resolution in this case to the finest available (Δ z =47.5 m) and reduced the heat sink lifetime to 0.025 year (9.13 days) without changing the spreading rate. The resulting depth and surface heat flux profiles are shown in Figure 8. The close link between shrinkage and heat flux is obvious. Our predicted surface heat flux is clearly far too high. Further reducing the heat sink lifetime would not improve the match with observation; it would merely worsen the discrepancy between predicted and observed bathymetry. This degree of mismatch between predicted and observed surface heat fluxes suggests a further modification of the shape of the postulated heat sink; it would seem that the heat sink must act much more strongly and quickly near the surface and at the earliest times. However a whole range of functional forms have been tried in our spreadsheets, and none have produced better fits to the data (i.e. the published heat flux and bathymetry curves in terms of uniformitarian time) than linear heat sink profiles of the form shown in equation (14); some forms (e.g. heat sink terms proportional to the square of the temperature disequilibrium) even produced heat flux curves with a minimum part way across the ocean basin. Thus our ‘final’ (best estimate) version of a spreadsheet calculation Worraker and Ward ◀ Ocean floor cooling ▶ 2018 ICC 679 Figure 5. Plot of ocean depth profile in the case of a uniform heat sink lasting for 0.2 years (73 days). In this case the GDH1 model shows a linear profile because almost all of the plate’s heat loss is due to the heat sink. The thermal conductivity value used here in the half space model is 10 9 times larger than its natural value in order to match the depth profile seen in Fig. 3 over the relevant (now very short) life of the heat sink. Figure 6. Temperature profiles in the GDH1 model with a uniform heat sink lasting for 0.2 years (73 days). These are essentially flat except in thin thermal boundary layers near the top and bottom of the plate. Consequently the heat flux at the surface is much higher than in the long time scale calculation, but overall most of the heat loss (>99.99%) is due to the heat sink. Figure 7. Temperature profiles in the case of a heat sink lasting for 0.2 year and varying linearly with depth, being zero at the bottom and maximum at the surface. Note the existence of a thermal boundary layer adjacent to the surface at all times prior to 0.2 year.