Terrestrial hydroclimate change projections in full-complexity climate models are characterized by a patchwork of regional drying and wetting responses for most variables, even as temperatures warm and evaporative demand increases. Yet, certain geologic proxies suggest that during warm climates of the deep past, the continents were very wet. Recent studies also find that climate models do not reproduce the observed enhancement of tropical precipitation by the presence of land.
Motivated by this gap in understanding, we explore continental hydroclimates and their responses to global warming in an atmospheric model over several different idealized land-ocean configurations, with ocean heat transport turned on and off. We find that the presence and width of Mediterranean-like subtropical seaways play key roles in wetting the continents, and that the cooling of the tropical ocean by heat transport further wets the tropical continent(s) in a thermally direct response. Critically, configurations with drier (wetter) tropical continents tend to further dry (wet) them with global warming, and these responses are strongly concave-down nonlinear. We also briefly test the roles of land parameters, astronomical choices, and topography.