Emergent multiscale interdependence of land and ocean temperatures

Abstract. Land and ocean temperatures share external forcing but respond through markedly different thermal memories. Using uncertainty-aware empirical mode decomposition and recurrence-based dynamical indicators, we show that sea-surface-temperature variability is systematically stretched toward longer periods relative to land-air temperature. This scale dilation is consistent with the increase in the ocean's effective heat capacity as progressively slower forcing penetrates to greater depths. Against this separated hierarchy, modern warming reorganizes the joint dynamics: the effective dimension decreases, recurrence persistence increases, and land–ocean co-recurrence strengthens. Synchronization first appears at multidecadal scales and its lower boundary subsequently contracts toward decadal and intermittent interannual scales. A concurrent increase in ocean evaporation, absent over land, further identifies the hydrological cycle and latent-energy exchange as a plausible pathway for this growing interdependence. Together, these diagnostics describe a scale-dependent reorganization associated with the warming background: land and ocean increasingly revisit similar configurations together, while the joint trajectory exhibits lower local dimension and greater recurrence persistence. Enhanced co-recurrence extends toward shorter timescales and exceeds a surrogate expectation that preserves the two warming backgrounds, although changes in observational coverage and quality remain a possible contributor.