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March 2011 Issue

Scientists Find Deep-Sea Vents In Waters of Southern Ocean
Scientists aboard the research ship James Cook have discovered a new set of deep-sea volcanic vents in the waters of the Southern Ocean. The discovery, announced in February, is the fourth made by the research team in three years, suggesting that deep-sea vents may be more common in the oceans than previously thought.

Using an underwater camera system, the researchers saw slender mineral spires three meters tall, with shimmering hot water gushing from their peaks and gossamer-like white mats of bacteria coating their sides. The vents are at a depth of 520 meters in a newly discovered crater close to the South Sandwich Islands, a remote group of islands about 500 kilometers southeast of South Georgia.

In the three decades since scientists first encountered vents in the Pacific, around 250 have been discovered worldwide. Most have been found on mid-ocean ridges, however, and very few are known in the Antarctic.

“We’re finding deep-sea vents more rapidly than ever before,” said expedition leader Paul Tyler, a professor at the University of Southampton’s School of Ocean and Earth Science. “And we’re finding some in places other than at mid-ocean ridges, where most have been seen before.”

The team hopes to understand more about the distribution and evolution of life in the deep ocean, the role that deep-sea vents play in controlling the chemistry of the oceans and the diversity of microbes that thrive in different conditions beneath the waves.

The researchers were exploring Adventure Caldera, a crater-like hole in the seafloor three kilometers across and 750 meters deep at its deepest.


Scientists Find Part of New Zealand’s “Pink Terraces”
They were called the eighth wonder of the world. Until the late 19th century, New Zealand’s Pink and White Terraces along Lake Rotomahana attracted tourists from around the world interested in seeing formations created by a large geothermal system. But the eruption of Mount Tarawera in 1886 buried the terraces in sediment and caused the lake basin to enlarge, engulfing the land where the terraces stood. No one knew if they survived.

In February, scientists from New Zealand’s GNS Science, in collaboration with engineers and scientists from Woods Hole Oceanographic Institution and colleagues from Lamont-Doherty Earth Observatory and NOAA’s Pacific Marine Environmental Laboratory, located portions of the long-lost Pink Terraces.

The research team, using autonomous underwater vehicles (AUVs) to map the bottom of Lake Rotomahana, said they are certain they have found the lower portions of the Pink Terraces on the lake floor. Project leader Cornel de Ronde, of GNS Science, said the team was elated by the discovery.

“The first side scan sonar image gave a hint of a terraced structure so we scanned the area twice more and we are now 95 percent certain we are seeing the bottom two tiers of the Pink Terraces,” de Ronde said.

Side scan sonar and bathymetric data collected by two Hydroid Inc. (Pocasset, Massachusetts) REMUS 100 AUVs clearly show crescent-shaped terraced structures in about 60 meters of water. They are covered by a brownish lake sediment. After detecting areas of interest with the AUV’s sonar systems, the team used the underwater camera system, developed with funds from the National Science Foundation, to capture images of the lake floor, where they were able to photograph some of the stepped terrace edges.

de Ronde said the rest of the Pink Terraces were either destroyed or are still concealed under thick sediment not able to be penetrated by high-frequency sonars.

The scientists found no sign of the larger White Terraces in the part of the lake that matched their location prior to 1886. The two terraces, part of a very large on-land geothermal system, were separated by several hundred meters prior to the eruption.

There are few examples of large land-based geothermal systems torn apart by an eruption and becoming inundated in this way. Scientists hope this study will help them better understand how geothermal systems respond to disruptions of this kind.


USGS Studies Underwater Ridge Impact On Circulation, Climate
Discoveries on how underwater ridges impact the ocean’s circulation system will help improve climate projections, U.S. Geological Survey (USGS) scientists said last month.

An underwater ridge can trap the flow of cold, dense water at the bottom of the ocean. Without the ridge, deepwater can flow freely and speed up the ocean circulation pattern, which generally increases the flow of warm surface water. Warm water on the surface makes the formation of sea ice difficult, and with less ice present to reflect the sun, surface water will absorb more sunlight and continue to warm.

USGS scientists looked back three million years, to the mid-Pliocene warm period, and studied the influence of the Greenland-Scotland Ridge on surface water temperature.

“Sea-surface temperatures in the North Atlantic and Arctic Oceans were much warmer during the mid-Pliocene warm period than they are today, but climate models so far have been unable to fully understand and account for the cause of this large scale of warming,” said USGS scientist Marci Robinson. “Our research suggests that a lower height of the Greenland-Scotland Ridge during this geologic age was a contributor to the increase of poleward heat transport.

“This is the first time the impact of a North Atlantic underwater ridge on the ocean circulation system was tested in a mid-Pliocene experiment. Understanding this process allows for more accurate predictions of factors such as ocean temperature and ice volume changes.”

The USGS said research was conducted on the mid-Pliocene because it is the most recent interval in the Earth’s history in which global temperatures reached and remained at levels similar to those projected for the 21st century. Therefore, it may be one of the closest analogs in helping to understand the Earth’s current and future conditions.

The article was published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.


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