Featured Research

from universities, journals, and other organizations

Geochemistry survey at Chatham Rise reveals absence of modern day greenhouse gas emissions

Date:
May 29, 2013
Source:
Naval Research Laboratory
Summary:
Geochemistry analysis of fossil sediment injection structures off the New Zealand coast in February and March reveal no presence of modern day expulsions of methane gas, a potential contributor to global 'greenhouse effect' warming.

Three dimensional seabed map of Chatham Rise displays two pockmark features, each approximately 10 kilometers in diameter, on the southern flank of the Chatham Rise seafloor. Water depth, in meters, is indicated in the legend on left.
Credit: Courtesy Research Expedition SO226-2, 2013

Geochemistry analysis conducted by the U.S. Naval Research Laboratory of fossil sediment injection structures off the New Zealand coast in February and March reveal no presence of modern day expulsions of methane gas, a potential contributor to global 'greenhouse effect' warming.

The main focus of this most recent expedition was to investigate the geological origin of seafloor anomalies discovered during a 2007 marine-life survey on the Chatham Rise.

During the 2007 survey scientists discovered several large seafloor craters, or pockmarks, including a giant 11 kilometers by 6 kilometers pockmark in water depths of about 1,000 meters, considered immense compared with pockmarks observed elsewhere in the world.

Scientists from Germany, New Zealand, and United States used the two-leg voyage aboard the German research vessel, R/V Sonne, to map and investigate giant seabed features and subsurface structures characteristic of large scale gas-rich fluid migration about 500 kilometers east of Christchurch, South Island, New Zealand.

While the gas and related sediment chemistry results demonstrate this system is no longer geochemically active, these very large pockmarks -- 11 kilometers by 6 kilometers in diameter and 100 meters deep -- are part of a much larger field of many thousands of smaller pockmarks that extends eastward along the Chatham Rise. Covering approximately 20,000 kilometers of seafloor, these pockmarks suggest sporadic gas escape may be occurring, possibly only during glacial intervals that occur approximately every 20,000 years.

"Geochemical analyses of the seafloor craters taken during the second leg of the voyage displayed no indication of a vertical methane flux through the sediment as indicated by the first part of the voyage," said Richard Coffin, chief scientist, NRL Chemistry Division. "This result suggests that gas-charged fluid escape leading to the pockmark formation may have occurred in the past, but seafloor gas seeps are not currently active."

The first leg of the survey was to map the seabed and undertake a high-resolution three-dimensional (3D) seismic survey over some of the pockmarks to image the sub-seafloor. During the second leg of the expedition, Coffin led geochemical investigations at four distinct Chatham Rise locations based on data from the seismic surveys. Piston and multi coring was conducted for geochemical evaluation of sediment and pore water to assess current and past day vertical fluid and gas fluxes.

"The apparent absence of methane in the shallow sediment and water column at the giant pockmark area was a surprise given the first leg results," Coffin said. "Onboard analysis showed no current day flux of deep sediment thermogenic or biogenic methane to the shallow sediment."

Scientists believe the latest results indicate the pockmarks are formed by gas escape that has come from rocks buried deep beneath the rise. Methane may have escaped during vigorous ancient degassing from under the seafloor into the ocean with significant implications for climate change and ocean acidification.

Ongoing seismic interpretation and pore water chemistry studies, to be undertaken by the international team of investigators, is expected to clarify the history of the enigmatic giant pockmarks and underlying sedimentary structures.


Story Source:

The above story is based on materials provided by Naval Research Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

Naval Research Laboratory. "Geochemistry survey at Chatham Rise reveals absence of modern day greenhouse gas emissions." ScienceDaily. ScienceDaily, 29 May 2013. <www.sciencedaily.com/releases/2013/05/130529101621.htm>.
Naval Research Laboratory. (2013, May 29). Geochemistry survey at Chatham Rise reveals absence of modern day greenhouse gas emissions. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2013/05/130529101621.htm
Naval Research Laboratory. "Geochemistry survey at Chatham Rise reveals absence of modern day greenhouse gas emissions." ScienceDaily. www.sciencedaily.com/releases/2013/05/130529101621.htm (accessed September 18, 2014).

Share This



More Earth & Climate News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Researchers Explore Shipwrecks Off Calif. Coast

Researchers Explore Shipwrecks Off Calif. Coast

AP (Sep. 16, 2014) Federal researchers are exploring more than a dozen underwater sites where they believe ships sank in the treacherous waters west of San Francisco in the decades following the Gold Rush. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Isolated N. Korea Asks For International Help With Volcano

Isolated N. Korea Asks For International Help With Volcano

Newsy (Sep. 16, 2014) Mount Paektu volcano in North Korea is showing signs of life and there's not much known about it. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins