Acronyms Site Map

This data visualizer on NASA's Ocean Motion website gives access to the following global ocean surface current behaviors between 1992 and 2011: current speed, current direction, current convergence, and current vorticity as well as the anomaly values for each. An anomaly is the difference between a measurement made on a specific date and the mean value of that same measurement over many years. A non-zero anomaly indicates a difference from the normal behavior

Current speed measures how far the water surface moves in one second. The current direction tells the direction of flow (shown as black arrows). Current convergence measures how strongly the current flows towards or flows away from a location. A positive convergence of water indicates flow inwards to a location and is evidence of downwelling (surface water forced to lower depths). A negative convergence indicates flow outwards and is evidence of upwelling (deeper water rising to the surface).

Current vorticity measures how strongly water swirls around on the surface. Positive (negative) vorticity indicates counterclockwise (clockwise) rotation of water. Vortices in flow indicate turbulence and they are important because it causes mixing of water.