El Niño/La Niña Watch & PDO

What is sea-surface height?

The height (or "relief") of the sea surface is caused by both gravity (which doesn't change much over 100's of years), and the active (always changing) ocean circulation. The normal slow, regular circulation (ocean current) patterns of sea-surface height move up and down (warming and cooling and wind forcing) with the normal progression of the seasons ... winter to spring to summer to fall.

Using theory of ocean dynamics, sea-surface heights measured by satellites such as Jason-3 can be used to calculate how much heat is stored in the ocean below. The year-to-year and, even, decade-to-decade changes in the ocean that indicate climate events such as the El Niño, La Niña and Pacific Decadal Oscillation are dramatically visualized by these data. Sea-surface height is the most modern and powerful tool for taking the "pulse" of the global ocean.

What are we looking at?

These images show sea surface height anomalies with the seasonal cycle (the effects of summer, fall, winter, and spring) removed. The differences between what we see and what is normal for different times and regions are called anomalies, or residuals. When oceanographers and climatologists view these "anomalies" they can identify unusual patterns and can tell us how heat is being stored in the ocean to influence future planetary climate events. Each image is a 10-day average of data, centered on the date indicated.

For additional information visit:

• PO.DAAC - to order data
• NASA HQ's Oceanography Program
• Earth Observatory - for additional data sets
• NOAA's home page - for additional information on AVHRR and SST satellites.