Alaskan fjords have been revealed as a major player in helping rid the atmosphere of excess carbon -- temporarily, at least. A team of geochemists from the US, New Zealand and South Africa collected and analysed 573 sediment samples and 124 sediment cores from every fjord system across the globe, and found that those in Alaska and the Antarctic are working harder than the open ocean to capture and store carbon before it can become carbon dioxide.
As the team points out in Nature Geosciences, it had already been supposed that fjords are "hotspots of organic carbon burial, because they receive high rates of organic material fluxes from the watershed". However, experts who spoke to Nature said the potential of fjords as carbon sinks has not been properly investigated until now, because it's difficult to map their small surface area. They're also physically harder to traverse when collecting samples. This latest study finally proves the hypothesis, and shows that fjords are in fact massive CO2 hoarders, capturing 18 million metric tons every year, totalling 11 percent of the carbon buried in the ocean. It's an impressive percentage, when we remember that fjords make up only 0.1 percent of the world's oceans.
Fjords cross the planet, with the deep, ancient estuaries found in Scotland, Sweden, Norway, Canada, Greenland, Svalbard, Chile, Alaska, Antarctica and the Arctic. Samples were taken from the bottom of each, and they were found to bury five times as much carbon as sediment in continental shelves -- regions already known to be efficient carbon buriers.
The team suggests that when glaciers melt, the fjords capture vast amounts of carbon contained in the surrounding bedrock, as it is pulled down. It may reemerge as CO2 when the glaciers return, however, making fjords only a temporary storage solution.
Fjords have definitely "been under-recognised as a significant mechanism of carbon storage in the deeper marine realm," professor of carbon capture and storage at the University of Edinburgh, Stuart Haszeldine, told WIRED.co.uk. However, he notes the levels involved -- we are still only tagging ten percent on to estimates of carbon storage in the deep sea -- are not enough to make a dent in climate change.
Because so little is know about how fjords capture and store carbon, the team behind the study still does not understand why the Alaskan fjords act more efficiently than their cousins around the globe. Finding the answer, will help push forward research in more than one way.
Haszeldine points out that understanding carbon capture in fjords will help us create better models and predictions to understand climate change. We could also learn a lot from the capture and storage techniques and use them in enhanced ways.
"There may be speculative ideas on how to enhance the storage of organic carbon in these fjord sites, for example by deliberate disposal of biomass into these deep stagnant waters, so that acts as a reduction of atmospheric CO2 after the biomass has recaptured CO2 from the atmosphere," he tells WIRED.co.uk. "However, any such engineered disposal action will require much more work and understanding of the deep seabed ecosystem impacts, and will require national legislation to be enacted."
"Even if it's not forever, extra carbon storage is very useful right now to reduce human impacts on the world in the crucial decades to 2100."
Carbon sequestration -- the capture and storage of CO2 -- has been the buzzword of late in climate change discussions, having been deemed vital to help reduce the impact of the industrialised world on our atmosphere. It's been estimated that billions of tonnes of CO2 need to be removed in this way from power plants over the next few decades, and manmade projects are ongoing to help kickstart this mission. In October 2014, a massive coal power plant in Saskatchewan, Canada, was retrofitted for carbon capture. In this instance, the captured CO2 at Boundary Dam is being used to help the plant extract more oil from the ground. Meanwhile in Mississippi in the US, a $5.6 billion, 582-megawatt coal plant is due to open this month.
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