Global warming along the 24th parallel

The band of ocean between the Canary Isands and Florida is where the greatest northward transfer of heat takes place in the Atlantic. "It's one pentawatt per year, equivalent to half a million power plants annually," says the oceanographer Eugenio Fraile. Natural, then, that this latitude of the Atlantic has been of great interest to scientists for some time. In half a century at least six campaigns have been conducted, measuring various aquatic parameters - temperature, salinity, currents, and so forth. Global warming has made it all the more urgent to know what is going on in the Atlantic and, by its influence, in all the oceans.

The seventh campaign in this band of the Atlantic, along the 24-degree North parallel, has now begun aboard the Spanish oceanographic ship Sarmiento de Gamboa (of the state research agency CSIC) as part of the Malaspina project of circumnavigation, along with another oceanographic ship, the Hespérides. The northward flow of heat directly affects the European climate, making winters in Lisbon, for example, milder than in New York, even at the same latitude," explains Alonso Hernández, scientific chief of the campaign. And any variation in this transfer of heat will also affect the whole Earth.

"Between the 1957 and 1998 campaigns an increase in temperature at 24 degrees north was found that works out to one degree Celsius per century, and that's a great deal," says Fraile. "But from 1998 to 2004 the temperature fell by 0.15 degrees, and we want to know if these are just fluctuations, and if there is a trend to warming," adds the researcher from the Spanish Oceanographic Institute (IEO).

"In the 1992 campaign along 24 North, it was seen for the first time that global change affected the deep ocean," notes Eduardo Balguerías, director of the IEO. The Sarmiento de Gamboa carries Fraile and 20 other researchers, plus five specialists from the CSIC's Marine Technology Unit (UTM), who attend to the instruments, besides a crew of 16. They are due to reach Santo Domingo in March.

"We measure water temperature, salinity, pressure, fluorescence, carbon dioxide concentration, currents, phytoplankton, zooplankton and other parameters, in soundings that go right down to the ocean floor, taking 24 registers per second," Fraile explains. For this they use what is called a CTD unit, with all the necessary sensors and water sample bottles, which descends to the ocean floor, at depths of up to 6,500 meters. Buoys are also released, with temperature, salinity and pressure sensors, which will function adrift for three and a half years, descending to 2,000 meters and emerging periodically to send data by satellite.

In operation since 2008, the Sarmiento de Gamboa is an advanced ship with 28 campaigns already completed. "It has the best of equipment, and there is a waiting list two years long to do research projects in it," says Mario Martínez, head of the UTM team.