Continuous measurements of atmospheric dimethylsulfide (DMS) have been performed over a 10-year period (1990--1999) at Amsterdam Island in the southern Indian Ocean. Atmospheric DMS ranges from 5 to 1930 parts per trillion by volume (pptv) and shows a clear seasonal variation with a factor of 20 in amplitude between its maximum in January (austral summer) and minimum in July-August (austral winter). Important deviations from the 10-year monthly mean as high as 100% have been detected, which could not be explained by changes in meteorology and/or oxidation capacity of the atmosphere. Comparison with a three dimensional (3-D) chemistry/transport model revealed that changes in the source strength of DMS as high as a factor of 2 were required to account for such DMS interannual variations. In addition, DMS variability was found to be closely related to sea surface temperature anomalies, clearly indicating a link between DMS and climate changes. ¿ 2000 American Geophysical Union