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Hello ocean seeding, goodbye

A couple of news items from the ocean fertilization front:

The Indo-German LOHAFEX experiment in the Southern Ocean, suspended two weeks ago, can be conducted as planned. Independent reviews sought by the German science ministry concluded that the experiment is in agreement with environmental standards and international law. On Tuesday, the team on board the German Polarstern started dumping its cargo of 20 tonnes of iron sulphate. The ship will stay around the area for around six weeks, giving the scientists’ enough time to observe the growth and decay of an ‘artificial’ algal bloom.


Picture: RV Polarstern (Alfred Wegener Institute)

It’ll be interesting how their observations, in particular concerning the rate and efficiency of carbon export to the deep ocean, will relate with data reported in a Nature paper this week on natural iron fertilization.

The CROZEX study was conducted in 2004 and 2005 near the Crozet archipelago at the northern boundary of the Southern Ocean. Raymond Pollard of the National Oceanography Centre Southampton and his team found that natural iron fertilization, by dust supplied from the Crozet Islands, increases biological production and the amount of organic carbon taken down into the deep ocean.

That’s not particularly surprising. But what’s amazing is this: The amount of carbon sequestered to 200 metres depth, while 18 times greater than that during an artificially induced bloom (like LOHAFEX), was a stunning 77 times smaller than the amount that had previously been determined during a natural bloom in the nearby Kerguelen region. What’s more, carbon flux at 3,000 metres, where carbon dioxide sucked up at the surface would be safely locked away for centuries, was just 3% of that at 100 metres. Check out this week’s Nature podcast and the paper here (subscription)

“CROZEX carbon sequestration for a given iron supply (…) falls 15-20 times short of some geo-engineering estimates,” the authors conclude. This, you’ve guessed it, has “significant implications for proposals to mitigate the effects of climate change through purposeful addition of iron the ocean.”

It has indeed. The Nature news story here makes the point that the findings, if they hold up, could actually be the final blow to such proposals. The notion that putting a little iron into the oceans here and there will suck up most of the surplus atmospheric carbon dioxide is pretty much dead, so it seems. Alas, it was just too good to be true.

Quirin Schiermeier


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    Peter McEvoy said:

    It will definitely be interesting to see how this one plays out. We shouldn’t need questionable measures like this on, but unfortunately more and more it looks like we will. Let’s hope it doesn’t turn into a disaster.

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    Chris Tobias said:

    Hi, great article and good to know this is one of the last times we’re going to see ocean seeding taking place.


    Chris Tobias


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