“We can go whenever you want,” said Edmo Campos, a researcher from the Oceanographic Institute of the University of São Paulo (IO-USP) to Captain José Helvécio Moraes de Rezende at 2:10 in the afternoon on Saturday, December 1, on the bridge of the Alpha-Crucis, an oceanographic research vessel anchored in the port of Santos. While Rezende, in a navy blue uniform with his name printed on the collar, conducted the final map and equipment checks, Campos, in a cap and Bermuda shorts, his cabin key and a pen drive tethered to his chest by a blue ribbon, had time to examine the tower with the equipment that Cristina Schultz (on her third ocean expedition in 2012) and Pablo Oliveira (on his first shipboard expedition) had installed on the edge of the stern to measure carbon dioxide flux and humidity. These instruments would be used in one of the experiments to be conducted during their two-week voyage.
The Alpha-Crucis, recently purchased for use by São Paulo state universities with FAPESP funding, departed at three o’clock in the afternoon on its first international cruise, headed southwest, with an expected return date of December 17 (see map). On board were 20 researchers including eight Brazilians, as well as six undergraduate and graduate students, three from Argentina and three from the United States, their leader Campos, and 19 crew members. The voyage is part of a thematic project coordinated by Campos and an international program called SAMOC (South Atlantic Meridional Overturning Circulation), whose principal purpose is to develop and implement a system for monitoring changes in the meridional transport of mass and heat—and climate changes in general—in the South Atlantic.
“We want to understand the present-day processes and monitor what happens in the next few decades in the South Atlantic,” Campos said. “Even the slightest change in the amount of heat in the ocean has a major effect on the Earth’s climate.” Campos explains that ocean currents in the South Atlantic transport heat to the Northern hemisphere at a power of about 1.5 petawatts, or 1.5 × 1015 joules per second. This is equivalent to 100,000 times the energy generated by the Itaipu dam, whose 20 generating units have 14 gigawatts of installed capacity (1 petawatt = 1 × 1015 watts; 1 gigawatt = 109 watts).
“The South Atlantic is the only ocean that transports heat towards the Equator, which results in a net heat transport to the North Atlantic. This transfer of heat to the North Atlantic is one of the mechanisms that govern global climate,” commented Argentine researcher Silvia Garzoli. She is the former Director of the Physical Oceanography Division and current Chief Scientist of the Atlantic Oceanographic and Meteorological Laboratory (AOML) of the U.S. National Oceanographic and Atmospheric Administration (NOAA). Based in the United States since 1980—initially at Columbia University in New York and since 1996 at NOAA-AOML—Garzoli is a leading researcher on ocean currents in the South Atlantic.
“We are finally going to measure current variability—in a project financed by Brazil, Argentina and the United States—using a suitable ship,” she noted. As the most experienced researcher in the group, Garzoli observed that it is also the first voyage undertaken by the Alpha-Crucis to collect water samples and take temperature measurements in deep water, up to six kilometers below the surface.
SAMOC includes research groups from France, Brazil, the United States, South Africa, Argentina, Russia and Germany. The plan calls for Brazil to provide some of the observation instruments, participate in voyages to install, maintain and recover the equipment, and work with France to develop a common strategy for regional climate models that can assess the influence of ocean circulation on climate and its impact on South America and Africa.
Groups from Brazil, Argentina and the United States will work in areas close to South America, and the groups from France, Germany and South Africa will work near southern Africa. “Without detracting from the previous initiatives, this is one of the few Brazilian projects with real international participation that will look at phenomena in the South Atlantic that are not just local, but global in scope and interest,” Campos said.
On the afternoon of December 4—the day before arriving at the point where they would complete the first station, or data collection point—two culinarily gifted researchers, Osmar Moller of the Federal University of Rio Grande (FURG), Brazil, and Alberto Piola of the University of Buenos Aires, Argentina, made churrasco on the upper deck as the ship moved along in good weather, preparing the group for the hard work ahead. After arriving at the first station, the researchers worked 12-hour shifts followed by 12 hours of rest.
In addition to preparation of the instruments and team training sessions, one of the tasks planned for the first four days of the voyage was to do simultaneous launches of expendable bathythermographs (XBTs) and radiosonde balloons to obtain data on temperature variation in the atmosphere and in the first 700 meters of the water column, while the ship continued to the farthest point, about 1,400 kilometers off the coast. The sampling with XBTs and radiosondes continued after work began on the stations.
After they reached the easternmost point, with the ship’s bow facing the coast, the researchers began working with the Seabird 911-Plus conductivity-temperature-depth (CTD) profiling system, which records the conductivity, temperature and depth of the ocean. (Conductivity is used to calculate salinity.) The CTD was mounted on a rosette or carousel with 24 five-liter Niskin bottles, which collect samples of water for chemical and biological analysis in depths up to 6,000 meters. According to the reports that Campos sent during the trip, the first CTD launch was made on December 5, and the researchers worked for four and a half hours on this operation, collecting samples from as deep as 10 meters from the ocean floor. The depth at that point was 4,750 meters.
Ana Paula CamposAlso at that station, the first of the four Pressure Inverted Echo Sounders (PIES) that NOAA deployed in 2009 was also recovered and launched back into the ocean. According to Campos, the echo sounders can operate autonomously on the seabed for up to five years, sampling and internally recording data on an hourly basis. “The data can be recovered, downloaded, or it might be better to say uploaded, by acoustic telemetry,” he explained. “On this cruise, in addition to NOAA’s four PIES, we also deployed three new sensors acquired with FAPESP’s support.”
These new sensors are equipped with a current meter, so they are called CPIES. The researchers plan to take one cruise each year to recover the stored data. After four years, the PIES/CPIES are recovered and swapped with new ones.
“The operation involved recovering the instrument and launching another one, with enough batteries for up to another five years,” Campos said. The task took five and a half hours and, at that point, “the ship had to be completely adrift, with the machinery shut down so that the noise from the engines would not interfere with acoustic communication with the echo sounder.”
Ana Paula CamposOn Saturday afternoon, December 8, the weather changed ahead of a huge storm. “For around 15 hours we had waves as high as three meters, which prevented us from completing the CTD station planned for 46.75W, 34.5S,” Campos reported. “Under such adverse conditions, we decided to navigate to the next station, where, on the morning of December 9, the second CPIES was launched with minor difficulty. Since it was again impossible to launch the CTD, we opted to continue launching XBTs and weather balloons. At that station, though, the wind was so strong that three attempts to launch radiosondes failed.”
By the end of the afternoon, with five-meter waves and strong, gusty winds, Campos and Captain Rezende decided to change course and head for what would be the last station, near the Albardão lighthouse off the coast of the state of Rio Grande do Sul. “The decision to navigate on a western course was wise, since the storm was moving from west to east. After an extremely rough night, late on the afternoon of December 9 we arrived at the station off Albardão. There, the seas were much calmer, and we immediately initiated the coastal station sequence, navigating in the opposite direction, west to east. At about nine a.m. on December 11, we arrived at 50.31W, 30.5S, the location for deploying the third and last CPIES. Launch completed most successfully, despite somewhat rough seas.” The Alpha-Crucis continued heading east, and some of the tasks that had been canceled due to weather were able to be completed. At the end of the day on December 12, the ship began its return to the port of Santos, where it arrived on the morning of December 16.
1. Impact of the Southern Atlantic on the global overturning circulation (MOC) and climate (SAMOC) (nº 11/50552-4); Grant mechanism Thematic project; Coordinator Edmo José Dias Campos (IO-USP); Investment R$ 1,406,307.62 (FAPESP)
2. Impact of the Southwestern Atlantic Ocean on South American climate for the 20th and 21st centuries (nº 2008/58101-9); Grant mechanism Thematic project; Coordinator Tercio Ambrizzi (IAG-USP); Investment R$ 3,061,048.47 (FAPESP).