Featured Images

Text Size

Animation of Pacific Ocean Sea Surface Heights Showing El Nino and La Nina Events 1993 to 2011
04.28.11
 

This animation depicts year-to-year variability in sea surface height, and chronicles two decades of El Nino and La Nina events. It was created using NASA ocean altimetry data from 1993 to 2011, as measured by several NASA spacecraft.

This remarkable video chronicles the almost 19 years of sea-surface height measurements collected from the precise and continuous TOPEX/Poseidon, Jason-1 and Jason-2 altimetric satellites. These ocean viewing spacecraft use radar altimetry to collect sea surface height data of all the world's oceans.

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 (due to 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, TOPEX/Poseidon and Jason sea-surface heights 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 oceans.

In this video the ocean height measurements are processed to highlight the interannual ocean signals of sea surface height. An example of “interannual’ variability is the 3 to 5 year flipping of the climate from El Nino to La Nina, and back to La Nina. The blue areas represent a drop in ocean height where cooler than normal water (and more dense) is located. The La Nina event is identified by a pool of colder than normal water in the eastern Pacific Ocean. The red areas represent a rise in ocean height where sea surface temperatures are warmer than normal. El Nino is identified by a pool of warmer than normal sea surface temperatures in the eastern Pacific Ocean.

Below the Pacific Basin animation is shown the growth (from 1992 to 2011) of the globally averaged sea surface height. To simplify this presentation, the seasonal signal (annual heating during summer and cooling during winter) has been removed. What is seen is the gradual, steady rise in sea level during these two decades. The average worldwide rise in sea level is almost 60 mm (2.4 inches), about 3 mm/year (1/8 inch/year). This rise is due to the warming of the global oceans and an increase in mass (new water) from the observed melting of terrestrial glaciers and polar icecaps.

This animation of images shows 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.

Text Credit:
Alan Buis/NASA's Jet Propulsion Laboratory
Rob Gutro/NASA's Goddard Space Flight Center