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They are some of the most dramatic landscapes on the planet, but fjords could also play a far greater role in climate change than was previously believed.

Researchers have found that the huge glacier-shaped ocean inlets can absorb far more carbon from the atmosphere compared to the rest of the ocean.

They estimate 18 million tonnes of carbon become locked in the sediment that sits at the bottom of fjords every year – the equivalent of 11 per cent of the total amount absorbed the world's seas.

Fjords, like Doubtful Sound in New Zealand pictured above, can trap 18 million tonnes of carbon a year in the sediment on their sea floor - accounting for 11% of the carbon taken up by the oceans, a new study has found

The scientists also found that fjords, which only account for 0.1 per cent of the world's oceans, also bury carbon at twice the rate of the sea as a whole.

It raises the prospect that fjord dotted coastlines like in Norway, Greenland, Canada and Alaska could provide a way of helping to combat global warming due to rising carbon dioxide levels.

By providing a way of rapidly trapping carbon in the sediment on the seafloor, they may help to reduce levels of the greenhouse gas.

Dr Thomas Bianchi, a geochemist at the University of Florida who was involved in the study, said: 'It's amazing that systems that are so small can have such a huge global impact.

'It sends the message that fjords are not only beautiful, they're providing a very important service.

'Carbon sequestration is the big buzzword, but we're still getting a handle on how it works.'

He added that finding hot spots like these could help scientists to make better climate change predictions.

The role of fjords in the global carbon cycle has been largely overlooked by scientists in the past because they make up such a small amount of the world's oceans.

Instead they have concentrated on large river systems and continental shelves.

The fjord's ability to store carbon comes from their shape. Carbon dioxide is absorbed by plants on land that create soil and sediment which is swept down to the coast by rivers and streams.

As fjords tend to be unusually deep – carved out by the movement of glaciers – the sediment is quickly locked away in an environment that is extremely low in oxygen.

This prevents bacteria from breaking down the sediment and releasing the carbon back into the atmosphere.

Researchers Dr Richard Smith, a marine biologist with Global Marine Research, and his colleagues, measured the carbon concentrations from 573 sediment samples and 124 core samples from fjords around the world.

Carved by glaciers during the ice ages, fjords provide dramatic landscapes but they are also sinks for huge amounts of carbon packed sediment that is eroded from the mountains and washined into the sea

Writing in the journal Nature Geoscience, they said: 'The deposition and long-term burial of organic carbon in marine sediments has played a key role in controlling atmospheric O2 and CO2 concentrations over the past 500 million years .

'Marine carbon burial represents the dominant natural mechanism of long-term organic carbon sequestration.

'Per unit area, fjord organic carbon burial rates are twice as large as the global ocean average, and fjord sediments contain twice as much organic carbon as biogenous sediments underlying the upwelling regions of the ocean.

'We conclude that fjords may play an important role in climate regulation on glacial–interglacial timescales.'

The researchers also found that Alaskan fjords appear to be particularly efficient at trapping carbon and may account for up to half of the carbon buried by fjords.

The graph above shows the organic carbon concentrations in fjords from sites around the world (shown on the inset map). The figure above each bar shows the organic carbon content of sediments washed into the fjords

The use of land around fjords could play an important role in how carbon is stored in them in the future and there may be ways to increase the amount they take up. 

Richard Keil, an oceanographer at the University of Washington in Seattle, who was not involved in the study, added that there may be other carbon burial hotspots around the world.

He said: 'Sediments underlying the ocean's oxygen depleted zones, which lie along continental margins, also contain abnormally high organic carbon contents.

'We still lack a full understanding of organic carbon burial. Terrestrial and marine-based budgets need to be merged, other regions of high organic carbon sequestration need to be identified, and definitions of long-term for carbon burial and sequestration need to be forged.

'Only then will we be able to address the large issues we face in the Anthropocene.'