In order to understand the difference between high temperature drop across the mantle's basal thermal boundary layer and much lower plume excess temperatures we evaluated computations with ASPECT. Some of them are published in the Ph.D. thesis of Poulami Roy, some others in previous work. Hence here we only include those models that are not published elsewhere. We also provide the routine to extract maximum and average plume temperatures versus depth. Our results show reduced excess temperatures, if plumes are more sheet-like, similar to 2-D models, or temperature at their source depth is less than at the CMB, for example if they are sourced on top of thermochemical piles. Excess temperatures are further reduced when averaged over the plume conduit or melting region.

We provide here the prm files and required input files for the Aspect 2-D cases shown in Figures 2 and 3, which are the only cases that are neither included in Steinberger et al. (2023) nor in the Ph.D. thesis of Poulami Roy (2024).

Figure 2 is computed with matteo_4.prm; in this case, the initial temperature is in initial_temp_ascii_2, prescribed (zero) surface velocitites are in vel-top-zero

Figure 3 is computed with matteo_14.prm; in this case, the initial temperature is in in initial_temp_ascii_4b.

In both cases, radial_visc_simple.txt is the radial viscosity structure corresponding to adiabatic temperatures, and the file temp-viscosity-prefactor.txt specifies the lateral viscosity variations due to temperature variations.
We also provide the Routine post_processing_matteo_10km.py for extracting plume temperatures versus depth, written by Matteo Jopke.

Furthermore, we provide csv files for all time steps listed in Tables B1 and B2 and shown in Figures 5-7 of the paper. These data have been used to compute plume temperatures and anomalous mass fluxes, in order to address the question posed in the title of the paper. Files are grouped according to model runs into tar files with the same name. The tables are also provided in the Appendix of this data description. The model files are grouped in .tar files according to the model types: single_plume.tar, 2_10.tar; 2.5_2_10.tar; no_slap.tar)