These images show that the central and eastern Pacific Ocean was unusually cold in December 2010, a tell-tale sign of La Niña. The associated rainfall map shows that La Niña was impacting weather in parts of the globe.
La Niña is an occurrence of unusually cold water temperatures in the Pacific Ocean along the equator (the precise area affected is outlined in black in the image above). La Niña and its opposite, El Niño, are linked to seesaw variations in air pressure over the tropical Pacific and affect weather patterns across the globe. NASA monitors developing El Ni&ntidle;o and La Niña events by observing sea surface temperatures. This image compares the water temperatures observed in late January 2006 to long-term average conditions for that time of year. The recent data were collected by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). Red shows where sea surface temperatures are warmer than normal and blue where they are colder than normal.
With its own forms of underwater weather, the ocean has fronts and circulation patterns that move heat and nutrients around its basins. Changes near the surface often start with changes in the depths.
A strip of cold water hugging the equator in the eastern tropical Pacific Ocean in mid-June may foreshadow a transition from El Niño to La Niña conditions
A trio of globes of sea surface height anomalies shows a deep pulse of warm water—a Kelvin wave—crossing the Pacific Ocean in February 2010. Kelvin waves strengthen and maintain El Niño episodes.