Scientists say data from satellites have allowed them to create one of the most detailed maps of the globe's ocean currents, along with their movements, ever produced.
The view of the currents and their speeds comes from observations by a number of satellites, but most particularly from data gathered by the European Space Agency's Gravity and Ocean Circulation Explorer (GOCE) spacecraft, which made precise measurements of Earth's gravity from 2009 to 2013.
The role of gravity, as measured by the GOCE satellite, is significant in driving ocean circulation. Knowledge of ocean currents is important to climate modelers because those currents help move around 30 percent of the Earth's heat around the globe.
They also help regulate Earth's climate by carrying heat in surface waters from low to high latitudes, then after they've cooled at those high latitudes they sink and create a cooler flow that returns back toward the equator.
The researchers, presenting the results of their work at a GOCE conference in Paris, described how the satellite's ultra-precise gravity measurements helped them create a simulation of the Earth's oceans at rest, allowing observation of the effects of gravity on ocean currents.
Earth's gravity varies just slightly from location to location as a result of the uneven distribution of our planet's mass in its interior.
GOCE, in measuring these variations, helped scientists create a map of the mean dynamic topography of the ocean surface, showing higher- and lower-than-average water levels.
Gravity causes ocean water to "pile up" in some areas, then run "downhill" to create moving currents.
"GOCE has really made a breakthrough for the estimation of ocean currents," says Marie-Helene Rio from the Italian National Research Council's Institute of Atmospheric Sciences and Climate.
The data on ocean currents, combined with recorded sea temperatures, will allow scientists to calculate how much energy they move around the planet.
"The accurate estimate of ocean surface currents, as provided today by the combination of GOCE and altimetry data, is crucial for the better understanding of the ocean dynamics," Rio says. "In particular, the assimilation of this information into operational ocean monitoring and forecasting systems will provide highly valuable new insight into the present and future state of the ocean."
During its operational period, the GOCE satellite was the lowest-orbiting scientific spacecraft above the Earth, gathering data from a distance of just 140 miles.
That required periodic use of an onboard thruster to keep it in its orbit, and when the engine's fuel was exhausted GOCE fell victim to the very force it was measuring and plummeted back to Earth, breaking up and falling into the South Atlantic ocean -- and its currents.
