Ocean Seasons

Ocean seasons are measured by comparing seasonal variations in sea level to the yearly average. The highest sea level -- shown as the large areas of red in the fall image -- is caused by summer heating of the upper ocean in the northern hemisphere. The lowest sea level -- seen as blue and purple -- occurs off the east coast of landmasses during spring in the northern hemisphere. This is the result of winter winds blowing off the continents and removing large amounts of ocean heat.

In the tropics, the sea level is primary controlled by wind. The seasonal sea-level change in the Indian Ocean, greatest of the three oceans, is controlled by seasonal monsoon winds.

TOPEX/Poseidon data show how heat storage changes from season-to-season. We discovered that the average seasonal sea-level change is about twice as large in the norther hemisphere as in the southern hemisphere -- partly the result of the larger oceanic areas in the southern hemisphere, which moderate seasonal changes.

NASA/JPL/Caltech
JPL Identification #: P-44074