Equilibrium temperature vs. ﹩T_{\mathrm{deep}\,}﹩. The temperature of the deep isotherm ﹩T_{\mathrm{deep}\,}﹩ is expected to be strongly correlated with the equilibrium temperature ﹩T_{\mathrm{eq}\,}﹩, giving a line sloping up to the right. Bracketed lines give constraints on ﹩T_{\mathrm{deep}\,}﹩, while arrows pointing downward represent upper limits.