Comparing the Dynamics of Free Subduction in Cartesian and Spherical Domains

Abstract

Subduction is the process where oceanic lithosphere descends into the underlying mantle at a convergent plate boundary, providing the major buoyancy force that drives plate tectonics and mantle convection (e.g., Forsyth

The Role of Slab Remnants in Modulating Free Subduction Dynamics: A 3‐D Spherical Numerical Study

“…Our models are a simplified representation of Earth's subduction systems, but they provide fundamental insight into the first‐order effects that slab remnants have on active subduction zones, and vice‐versa. They are executed in a 3‐D spherical shell domain, which is important for simulating Earth's subduction systems, particularly those that exceed 2,400 km in width (F. Chen et al., 2022a). They also better capture the mechanical properties of subducting slabs than previous global models of mantle convection that incorporate slab remnants (e.g., Becker & Faccenna, 2011; Bunge et al., 2002; D. R. Davies et al., 2012, 2015; Lowman, 2011; Yanagisawa et al., 2010).…”

“…Simulations are undertaken using Fluidity (e.g., D. R. Davies et al., 2011, 2016; Kramer et al., 2012; Kramer, Davies, & Wilson, 2021; Le Voci et al., 2014), an adaptive, anisotropic, unstructured‐mesh finite element and control volume computational modeling framework, capable of efficiently simulating multi‐material whole‐mantle visco‐plastic (Tosi et al., 2015) subduction in spherical shell geometries (F. Chen et al., 2022a, 2022b). Fluidity's adaptive mesh capabilities allow our simulations to achieve a local resolution of ∼3 km in regions of dynamical significance (i.e., in regions of high solution curvature within and adjacent to the subducting slab, the remnant and at the interface between upper and lower mantle), with coarser resolution of up to ∼300 km elsewhere.…”

“…The importance of sphericity in simulating the dynamics of subduction, particularly for wider subduction systems, has been demonstrated by F. Chen et al. (2022a), who identify two key limitations of Cartesian compared to spherical models: (a) the presence of sidewall boundaries in Cartesian models, which modify the flow regime; and (b) the reduction of space with depth in spherical shells, alongside the radial gravity direction, which cannot be captured in Cartesian domains. This motivates the use of spherical models herein.…”

“…The configuration of our reference models without remnants (cases with full widths‐W‐ of W2400 and W4800) follows the setup of F. Chen et al. (2022a) for a subducting plate with plate buoyancy and thickness in the mid‐range for natural subduction (cases S_W2400 and S_W4800, respectively). Simulations are undertaken in a hemispherical shell domain (thus exploiting the symmetry of the system to halve the computational domain's extent) with outer and inner radii that correspond to Earth's surface and CMB (Figure 2a).…”

“…Despite this, a systematic study into how the dynamics of subduction are influenced by slab remnants (and vice versa) has not yet been undertaken. Furthermore, the effects of a 3‐D spherical shell domain, which constrains the space available for mantle flow (F. Chen et al., 2022a), on slab‐remnant interaction, have not previously been considered.…”