We investigate interannual coupling between the rotating elastic Earth and the ocean during the 1986--1987 El Ni¿o. We find the E-W component of the ground tilt at the Esashi Earth Tides Station up toward the east about 50 milliarc seconds (mas), a rise of sea level about 5 cm at Chichijima and Oshima in the northwestern Pacific Ocean, and an increase of ~1 cm in the very long baseline interferometry (VLBI) baseline distance between Kashima (Japan) and Kauai (Hawaiian Islands) as well as the residual length of day (LOD) changes of ~50 μs during the 1986--1987 El Ni¿o. The residual LOD is derived from elimination of changes in atmospheric angular momentum. Our discussions are based on the coupling between torsional motions of the elastic Earth and reflection of the eastward traveling equatorial Kelvin waves at the eastern boundary of the Pacific Ocean. These equatorial waves exchange the momentum and the axial and zonal component of vorticity with the elastic Earth. During the 1986--1987 El Ni¿o, reflection of the Kelvin wave is expected to excite torsional motions and to couple with differential zonal rotation in the elastic Earth and to generate anomalies of ~1.6 μs in LOD. The differential zonal rotation due to the torsional motion can produce the same order of the magnitude of changes in the VLBI baseline distance between Kashima and Kauai. Variations of the E-W component of the tilt cannot be explained by torsional motion. We infer that the midlatitude Rossby waves are generated in the central Pacific Ocean. This conclusion is consistent with sea level changes at Chichijima and Oshima and changes of the tilt at Esashi. ¿ 2000 American Geophysical Union