tokens: location of the continent, especially for the fast-rotating case; for P = 5 days, this transport can increase from 7 gigatons per second (Gt s −1 ) in an aquaplanet to 14 Gt s −1 when the continent is located to both the northeast and northwest of the substellar point (not shown). This transport brings along with it the ozone and water vapor; it is unclear how the change of this transport will affect the ozone of the dayside. Therefore, AOGCMs are required to fully understand the ozone distribution on these exoplanets when a continent is present. 5. Conclusion We investigate the climate impact of a relatively small terrestrial continent on a synchronously rotating exoplanet by using an AOGCM. It is found that the climate is highly sensitive to the location of the continent, mainly because of the existence of a strong equatorial westerly jet in the ocean on such exoplanets. This jet is responsible for ∼90% of the heat transport from dayside to nightside, and the strength of this jet largely determines the global climate. When a continent blocks the equatorial westerly at the equator, the climate cools. The strongest cooling effect is obtained when it lies slightly to the west of the substellar point. On the other hand, the westerly jet strengthens and the climate warms when a continent obstructs the poleward branch of the oceanic gyre circulation. Enhanced oceanic heat transport to the nightside reduces the sea ice coverage there, and thereby reduces the sea-ice input from nightside to dayside. This reduces the planetary albedo and raises the GMST. The GMST can vary by more than 20° C simply by varying the location of a small continent. The outer edge of the HZ around an M-dwarf defined by stellar constant can change by 15% when a small continent is located at different places. Because the atmospheric circulation, atmospheric water vapor, and ocean upwelling all change with the location of the continent, the atmospheric chemistry and biosignatures may also change. Although major topographic features tend to align with the star-planet axis for synchronously rotating exoplanets (Wieczorek 2007 ; Turbet et al. 2016 ; Salazar et al. 2020 ), small continents or island arc chains may exist everywhere. Our results demonstrate that these small features can still change the global climate of a synchronously rotating exoplanet by as much as that of a round continent. We also demonstrate that it is possible to engineer the climate on such exoplanets by building a dam at appropriate locations. Appendix Model and Experimental Design A.1. Climate Model The simulations presented in this work were done with the fully coupled AOGCM CCSM3 (Collins et al. 2006 ). The model is the same as that used by Yang et al. ( 2019 ). The atmosphere and land share the same Gaussian grid, and the ocean and sea ice share the same grid. The resolution of the CCSM3 model is set to “T31_gx3v5.” In this setting, the horizontal grid spacing is approximately 3.75° by 3.75° for the
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