Remote Influences of Land Surface Temperature and their Implications for Sea Surface Temperature Patterns

Abstract

The spatial pattern of sea surface temperature (SST) plays a central role in shaping the climate system, yet the influence of land surface temperature (LST) remains poorly understood. Using a state-of-the-art coupled ocean--land--atmosphere model, we examine the model's response to regional LST perturbations imposed through LST nudging and idealized time-dependent ramp warming simulations. We find that LST warming over South America strengthens the tropical Pacific zonal SST gradient, yielding a more La Niña--like mean state. Enhanced LST increases the zonal contrast in diabatic heating and excites stationary Rossby wave responses, which reinforce alongshore winds and coastal upwelling in the eastern Pacific. This provides a dynamical pathway linking regional land warming to changes in the equatorial Pacific mean state. Similar responses are found for warming over North America, accompanied by North Pacific cooling, and for warming over Central Africa, coupled with tropical Atlantic cooling. In contrast, warming over the Maritime Continent or the Tibetan Plateau does not induce significant SST pattern changes. Historical simulations nudged toward observed LST exhibit cooling in the tropical southeast Pacific, with the tentative implication that uncertainty in LST may contribute to model-simulated SST biases during the historical period.

Figures (8)

• Figure 1: Ensemble-mean annual-mean surface skin temperature response from experiments that nudge land-surface temperatures over different regions, shown relative to the default piControl simulation (units: K).
• Figure 2: Same as Figure \ref{['fig:ts']} except the shading shows the annual-mean sea level pressure response (units: hPa) and the contours show the 925-hPa streamfunction response, computed using the library described in dawson2016windspharm.
• Figure 3: Same as Figure \ref{['fig:ts']}, except the shading shows the response of the annual-mean zonally asymmetric component of diabatic heating (eqn. \ref{['eqn-diabatic_forcing']}, units: $\mathrm{W\,m^{-2}}$).
• Figure 4: Same as Figure \ref{['fig:ts']} except the shading shows the annual-mean precipitation response (units: mm per day).
• Figure 5: Linear trend of surface skin temperature for ramp warming simulations of (a) 10 year, (b) 20 year, and (c) 30 year for linear ramp SA experiments. Panels d, e and f show the corresponding regional-mean surface temperature time series over the southeast Pacific and South America. Solid lines denote annual mean values, and dashed lines indicate the linear regression trends.