Spatiotemporal Variations in Surface Heat Loss Imply a Heterogeneous Mantle Cooling History

Abstract

Earth's thermal evolution is largely controlled by the rate of heat loss through the oceanic lithosphere. This cooling rate is time-dependent because changes in tectonic rates (e.g., rates of seafloor creation and consumption) affect the seafloor age distribution (e.g., Becker et al., 2009), and thus prescribe intervals of Earth history with greater or lesser oceanic heat loss. The rate of cooling is also highly variable spatially, with mantle beneath young seafloor cooling much more rapidly than its counterpart beneath large insulating continents (Figure 1a). These variations in mantle cooling rate change with time as the plate tectonic configuration evolves, potentially inducing large spatial and temporal variations in the heat content of the mantle (e.g., Lenardic et al., 2011). It is important to understand such variations in order to better constrain Earth's thermal evolution back in time. Over the past decades, the relationship between mantle heat flow and the age of the oceanic lithosphere has been continuously refined to fit geophysical data (e.g.

Determining Mid-Ocean Ridge Geography from Upper Mantle Temperature

“…Beyond recent (< 200 My) subduction history, the long-term convective and tectonic history, such as the presence of supercontinents, may also alter the thermal structure of the mantle under each basin. Karlsen et al (2021) argue that Rodinia, a longerlived ( 1.1-0.7 Ga) supercontinent, might have allowed more heat to accumulate under the Pacific mantle domain in contrast to the impact of the shorter-lived Pangea ( 300-180 Ma) on the African domain. The additional supercontinent insulation may be partially responsible for the present-day hemispherical temperature difference T P at depth (Figure 2a), despite faster cooling in the Pacific due to higher spreading rates after the breakup of Pangea (Karlsen et al, 2021).…”