Please select your home edition
Edition
Protector 728x90

Natural Iron locks atmospheric carbon dioxide into the World's Oceans

by WHOI Media Relations on 23 Feb 2009
Biological productivity in large areas of the Southern Ocean is limited by the supply of iron, an important micronutrient for phytoplankton. The main sources of iron to the bloom area around the Crozet Islands in the Southern Ocean are the atmosphere, deep-sea upwelling (vertical), and the islands, themselves (horizontal). The image also shows the main circulation paths (green lines), topography and a composite SeaWIFS satelllite chlorophyll a image for the austral summer 2004-2005. (Planquette et al., 2007) Woods Hole Oceanographic Institution (WHOI) © http://www.whoi.edu/

An experiment to study the effects of naturally deposited iron in the Southern Ocean has filled in a key piece of the puzzle surrounding iron’s role in locking atmospheric carbon dioxide (CO2) in the ocean.

The research, conducted by an international team led by Raymond Pollard of the National Oceanography Centre, Southampton, and included Matthew Charette, a marine chemist at the Woods Hole Oceanographic Institution (WHOI), found that natural iron fertilization enhanced the export of carbon to the deep ocean. The research was published January 29, 2009, in the journal Nature.

Scientists have generally accepted the fact that biological productivity in large areas of the Southern Ocean is limited by the supply of iron, an important micronutrient for phytoplankton. However, downstream of ocean islands in this study area, massive phytoplankton blooms have been observed, leading to the idea that the islands themselves are somehow fertilizing the ocean with iron.

The team showed that this natural iron fertilization enhanced phytoplankton growth and productivity and the amount of carbon exported from the surface layer (100 meters) by two to three times. Moreover, they found that the amount of carbon stored at 3,000 meters and in the sediment was similarly two to three times higher beneath the natural fertilized region than for the nearby iron-poor region.

'This work demonstrated for the first time that Southern Ocean phytoplankton blooms fueled by natural sources of iron have the potential to sequester carbon in the deep ocean,' said Charette.

The team conducted their experiment in 2004-2005 on the seas around the Crozet Islands and Plateau at the northern boundary of the Southern Ocean, about 1,400 miles (2,200 kilometers) southeast of South Africa. These seas provided a natural laboratory, because each spring the waters north of Crozet experience an enormous bloom containing billions of individual phytoplankton and covering 120,000 square kilometers (the size of Ireland). In contrast, the area south of Crozet experiences only a small, short bloom later in the season.

'Our first question was, ‘where does the iron come from?’' said Charette. 'Airborne dust wasn’t the solution — there isn’t enough exposed soil on Crozet for winds to carry iron from the island to the deep water where the bloom occurs.

While other studies concluded that upwelling from the deep ocean was the main source of the iron, we wanted to test the hypothesis that the iron was coming from the island itself and the iron-rich sediments in the shallow water and the plateau area around it.'

Since the currents move from south to north over Crozet, the researchers reasoned that iron could be entrained in the water column as it flows over the plateau. First, they needed a way to understand how long it would take iron to travel from the island’s shore to the bloom site and if the rate of supply was enough to kick-start and sustain the bloom for several months.

Iron concentrations in the water wouldn’t tell them where it came from, so the team sampled waters around Crozet looking for naturally-occurring radium isotopes, which, like iron, originate in the sediments and can therefore be used to quantify the amount of iron that the islands and surrounding sediments can supply to the bloom area. The decaying isotopes provided a built-in clock for the investigators to determine how quickly the water moves over the plateau and into deeper water. The distribution of radium in the water column demonstrated that the source of the iron was the island and the sediments in the shallow water around it and the plateau.

A second question the team sought to answer was whether the differences in the blooms between the north and south sides of Crozet would result in greater amounts of carbon held in the deep ocean. Using sediment traps and sediment cores, the researchers uncovered the first evidence that carbon deposited at 3,000 meters and in the sediment was two to three times higher beneath the natural fertilized region than for the nearby iron-poor region. In addition, the sediment record shows that this has been so throughout the Holocene (about 10,000 years ago until present).

In recent years, schemes to fight global warming have included sequestering carbon in the deep ocean by fertilizing the ocean with iron to artificially induce plankton blooms.

As public interest in these ideas has increased, the authors point out that the amount of carbon sequestered in the deep ocean for a given input of iron falls far short of previous geoengineering estimates, 'with significant implications for proposals to mitigate the effects of climate change through purposeful addition of iron to the ocean,' wrote lead author Pollard.

Support for this project came from the Natural Environment Research Council and the National Science Foundation.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment.

http://www.whoi.edu
Protector - 660 x 82North Technology - Southern SparsZhik ZKG 660x82

Related Articles

America's Cup - Japanese launch new Challenger in Bermuda
A historic day today at the Dockyards in Bermuda as SoftBank Team Japan unveiled their brand new AC50 A historic day today at the Dockyards in Bermuda as SoftBank Team Japan unveiled their brand new America’s Cup Class race boat, Hikari, the next-generation boat designed to win the first ever America’s Cup for a Japanese flagged challenger. Hikari, meaning “flash of light”, was selected from over 430 names submitted by fans in Japan through a nationwide contest held by SoftBank Corp. in the le
Posted today at 2:11 am
Cool drone footage of Dongfeng Race Team on the water
Dongfeng is back in the water and training is well underway for the returning Chinese campaign. Dongfeng is back in the water and training is well underway for the returning Chinese campaign. Stunning drone footage of the re-fitted Volvo Ocean 65 has been released as the team hit the water off the coast of Lisbon.
Posted on 25 Feb
America's Cup - Oracle Team USA loses crew overboard - Video
OTUSA video of crew member Graeme Spence when he fell off the front cross beam of the team's new AC50 Oracle Team USA came close to having a serious injury to crew member Graeme Spence when he fell off the front cross beam of the team's new AC50 - a situation that has been feared as he passed between the foils, while the new America's Cup Defender was sailing at speed.
Posted on 23 Feb
Volvo Ocean Race - 10 young sailors who made an impact on race history
Age is just a number, right? Well, yes – according to some of the sailors who've tackled the world's toughest ocean test Age is just a number, right? Well, yes – according to some of the sailors who've tackled the world's toughest ocean test. They say 'if you're good enough, you're old enough', and this lot certainly proved that. Here, we look back at some of the most iconic young sailors in the Volvo Ocean Race and its predecessor, the Whitbread Round the World Race's four-and-a-half decade history.
Posted on 23 Feb
America's Cup - Artemis Racing launches their AC50 in Bermuda
Artemis Racing's new race yacht, “Magic Blue”, was christened today by Torbjörn Törnqvist's wife, Natalia, at a special Artemis Racing's new race yacht, “Magic Blue”, was christened today by Torbjörn Törnqvist's wife, Natalia, at a special celebration in Bermuda. The launch sees the culmination of more than three years of intense design and development work, which began almost immediately after the finish of the 34th America’s Cup in San Francisco.
Posted on 22 Feb
Volvo Ocean Race – Pablo Arrarte joins MAPFRE as watch captain
With just 242 days to go until the start of the 2017-18 edition on October 22, preparations are already well underway. Arrarte, who raced onboard Brunel in 2014-15, will also assume the role of deputy to Olympic gold medallist Xabi Fernández, who was named as skipper on Friday.
Posted on 22 Feb
Gladwell's Line - AC50 Roll Call shows several late or absent
The AC50 unveiling/launch/sailing call-sheet has had a few additions since Land Rover BAR were the first to launch The AC50 unveiling/launch/sailing call-sheet has had a few additions since Land Rover BAR were the first to launch on February 6 - the earliest day permitted under the 28-day voluntary Blackout amendment to the Protocol governing the current event.
Posted on 21 Feb
Emirates Team NZ and Southern Spars launching into the America’s Cup
Built by Southern Spars, Emirates Team New Zealand’s newest America’s Cup yacht has been launched. Built by Southern Spars, Emirates Team New Zealand’s newest America’s Cup yacht has been launched. The Auckland-based mast builder demonstrated its standing as one of the world’s top carbon fibre manufacturers. Southern delivered Emirates Team NZ’s most technically advanced yacht ever, meeting the extremely strict budget, construction, weight and timing requirements.
Posted on 20 Feb
America's Cup - Emirates Team NZ's bike team in training - Video
Emirates Team New Zealand have released a short video of four of their grinding team in training Emirates Team New Zealand have released a short video of four of their grinding team in training - including two Olympic class sailors and an Olympic Gold medalist rower.
Posted on 20 Feb
America's Cup - Oracle Team USA sails AC50 for first time in Bermuda
Oracle Team USA took to the Great Sound on Monday, sailing its newly launched America's Cup Class boat, '17' Oracle Team USA took to the Great Sound on Monday, sailing its newly launched America's Cup Class boat, '17', for the first time. 'We had a successful day,' said skipper Jimmy Spithill dockside after the training session. 'First impressions were great. The boat went really well, so everyone is happy.'
Posted on 20 Feb