Researchers Find Hydrothermal Vent Fields In Far North

26 September 2005 | 02:25 Code : 5882 Geoscience events
Scientists from the University of Bergen and Oregon State University have discovered the northernmost hydrothermal
Scientists from the University of Bergen and Oregon State University have discovered the northernmost hydrothermal vents in the world along the Mohns Ridge in the Arctic Ocean.

"I've seen a lot of hydrothermal systems all over the world's oceans," said Adam Schultz, a geophysicist from OSU's College of Oceanic and Atmospheric Sciences, "and these Arctic fields are spectacular."

The three-week expedition was led by marine geologist Rolf Pedersen of the University of Bergen, who has been exploring the Arctic Ridge system from Iceland to Spitzbergen Island since 1999. The scientists, who were aboard the G.O. Sars research vessel, used a remotely operated vehicle to explore the vent fields, which they discovered around latitude 71 degrees, north of Iceland.

Much of the Arctic Ridge system is unexplored, and a vent field on the shelf of Iceland is the only one that scientists have seen in the northern latitudes. Unlike that Icelandic field, however, the newly discovered vent fields are full of life, according to Pedersen.

"There were huge numbers of chimneys - 30, 40, 50 or more," Pedersen said. Shrimp, anemones and bacterial mats dominated the animal life at the site. The researchers also found a type of tubeworm on the vent structures and in the outlying area - an important discovery, they say, because tubeworms had previously only been observed in Pacific Ocean vent fields.

Schultz used a temperature and flow sensor, called an isosampler, to help document the characteristics of the new vent fields.

"We found two large high-temperature fields and as we explored them, we would come upon a large mound of chimneys with superheated water jetting out of them," Schultz said. "Then in the distance, we'd see another mound and then beyond that, another one, and so on."

Temperatures in one field reached as high as 260 degrees C, and the scientists believe they may have approached 300 degrees C in the second field, although they were unable to measure them.

The OSU scientist said there also is a vast low-temperature field in the region that supports a diverse community of life, including large sea-lilies that "sit atop mineral/bacterial chimney-like structures that look at the world like pineapples."

"That is a particularly strange form of vent," Schultz said, "because the fluids coming out of these vents come out at temperatures only a fraction of a degree above the temperature of the background seawater and that is very cold - below zero Celsius - which is only possible in the Arctic.

"I'm not sure if we can even call these 'hydrothermal' vents," he added. "Perhaps they are 'hydrocryo' vents, meaning vents that emit cold water."

Schultz's team carried out measurements of the water flowing out of the vents at both the high-temperature and low-temperature fields. His team included Phil Taylor, an oceanic engineer who has a dual faculty appointment with OSU and Cardiff University in the United Kingdom.

They used the isosampler to determine that the fluids flowing from the vents had undergone "phase separation," which means they had been superheated sufficiently to have boiled - even at the enormous pressures of the deep seafloor. This process produces pure water vapor, Schultz says, as well as heated seawater and a heated briny fluid.

"This is typical of seawater that has encountered hot magma at depth beneath the seafloor, then vents out through smoker chimneys," Schultz pointed out. The vent fields were discovered at depths of 500 to 700 meters.

Pedersen said the researchers ironically had come close to discovering the vents on a previous voyage, when they were within about 500 meters from the spot the fields were located. Gales and rough seas complicated those previous efforts, he added.

This time, the researchers were able to locate the fields, which are about 100 to 200 meters in size. Yet they still had logistical problems.

"The chimneys were so dense that it was difficult in some areas to get the ROV (remotely operated vehicle) in there," Pedersen said. "In fact, we got the ROV cable stuck on one of them. It almost melted."

The researchers plan to return next year to more precisely identify the animals discovered at the vents, sample the microbes, and perform more detailed studies of the water column above the fields.

The scientists also believe there are additional vents fields to discover.

The study was part of the BioDeep project supported by the Norwegian Research Council. The project, which includes researchers in Norway, the United States and Sweden, investigates microbial life in the ocean's floor. OSU and the University of Bergen are collaborating on these deep biosphere studies. In addition to Schultz and Taylor, OSU oceanographer Martin Fisk is a key scientist in that collaboration


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