Abstract: The meridional Ekman heat transport in the Southern Ocean plays an important role in regulating the global thermohaline circulation and water-mass transformation. Using reanalysis products together with empirical orthogonal function (EOF) analysis and correlation analysis, this study systematically examines the interannual variability of the upper-ocean meridional Ekman heat transport in the Southern Ocean and its responses to major climate modes. The results show the mean meridional Ekman heat transport is broadly separated by 55°S, with northward transport occurring north of this latitude and southward transport south of it. In the Indian and Atlantic Oceans (50°-60°S) and the Pacific Ocean (60°-70°S), the interannual variability of the meridional Ekman heat transport is primarily driven by sea surface temperature variability, which explains 40%-70% of the total variance. In contrast, in other regions, wind-stress variability is the dominant factor, accounting for over 80% of the variance. The leading mode of interannual variability exhibits a zonally banded spatial structure and is mainly regulated by the Southern Annular Mode (SAM). During the positive phases of SAM, the meridional Ekman heat transport anomalies are positive between 50°S and 60°S, while negative anomalies occur north of 50°S and south of 60°S. The anomaly center of the second mode is primarily located north of 55°S in the Pacific, potentially serving as a precursor signal for El Niño-Southern Oscillation (ENSO) events. Negative Ekman heat transport anomalies in this region tend to precede El Niño events in the tropical Pacific, whereas positive anomalies may favor the development of La Niña events. The anomalies associated with the third mode are primarily distributed north of 55°S, with alternating positive and negative patterns from west to east, forming a dipole-like structure between the western-eastern basins in each of the three oceans. This mode is primarily regulated by ENSO and may be associated with the wind-evaporation-sea surface temperature positive feedback mechanism. Overall, this study advances our understanding of the critical role of wind forcing and sea surface temperature variations in the Southern Ocean in the global heat balance.