Sea-Surface Variability
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H|0|elnino|El Nino|840|846|
G|0|ssh|sea-surface height|860|877|
    Sea surface variability refers to any change in sea level relative to some average sea level, usually a multiyear average. By comparing recorded sea levels to the established averages, scientists can observe the variability of the world's oceans from 10 day cycle to 10 day cycle, season to season, and year to year. 
    From the tropics to the poles, seasonal sea-level changes are dominated by the heating and cooling of the upper layer of the oceans. 
    Larger ocean masses tend to have more moderate seasonal changes. The southern hemisphere has less land mass, and more ocean mass than the northern hemisphere. As a result, the seasonal sea-level change in the south is about half as large as in the north. 
    Around the equator, sea-level changes can be observed in one of their more dramatic forms during an event known as El Nino. The higher sea-surface height shown in red and yellow reflects an excessive amount of unusually warm water in the upper ocean.
