Scaling Laws for Mixed Heated Convection With Pseudoplastic Rheology: Implications for the Bistability of Tectonic Mode.

Plate tectonics is a tectonic style thought to be the hallmark of habitable planets, and yet the inherent complexities of plate tectonic convection have clouded the establishment of simple scaling laws with which to model convective behavior and thermal evolution. We have recently developed a scaling approach for mixed heated convection, based upon several simple physical principles. Here, we generalize our scaling approach to mixed heated convection with pseudoplastic rheology, which gives rise to the plate tectonic mode of convection. We then apply our scaling results to the so‐called bistability of tectonic mode. By illustrating common pitfalls regarding heating mode and nondimensionalization, we demonstrate that tectonic mode is unique with respect to key planetary properties, and that a convective regime diagram for terrestrial planets is within reach. Plain Language Summary: Convection within planetary mantles (the rocky layer bounded by a thin crust and a metallic core) is driven by heating from within and from below, and it is largely dependent on rheology—how mantle rocks deform. We generalize convection scaling laws to the rheology and heating mode appropriate for planetary mantles. These scaling laws describe convective properties of plate tectonic convection, in which the surface layer of the mantle is weak enough to participate in convection, as well as stagnant lid convection, in which the surface layer is strong and immobile. We show that the state of the surface layer (the so‐called tectonic mode) is unique for a given rheological scenario. This restores confidence in the prospect of predicting tectonic mode from first‐order planetary properties, a crucial task given the connection between tectonic mode and habitability. Key Points: Mantle convection scaling laws are generalized for the heating mode and rheology appropriate for planetary mantlesConvective properties may be accurately predicted for both the plate tectonic and stagnant lid modes of convectionTectonic mode is unique for a given rheological scenario, despite the apparent bistability of numerical simulations [ABSTRACT FROM AUTHOR]