“Carbon sequestration is the big buzzword, but we’re still getting a handle on how it works,” said Thomas Bianchi, a University of Florida geochemist. “Finding and understanding these hot spots is critical.”

Scientists have focused on the oceans as they look for where the carbon dioxide is going. It makes sense. Oceans cover 70% of the Earth and observing them with satellites is easy.

It turns out there’s one feature that does an outstanding job capturing and storing carbon dioxide. Fjords. According to a new study, fjords make up just 0.3% of Earth’s surface area – yet they sequester 18 million tons of carbon per year. That is 11% of the total carbon dioxide absorbed by marine sediment.

Fjord in Norway

Credit: Odda Kommune/Flickr

Bianchi says fjords have always been known for their high carbon storage, but they were dismissed because of how small they are – relative to the world’s oceans. Plus, monitoring fjords can be tough. Satellites don’t do the trick.

“Many have no roads leading to them, so you can only get to them by helicopter,” Irina Overeem, a sediment geologist at the University of Colorado Boulder, tells Nature. “You can’t take samples when there is ice — and for some places, like Greenland, that is about nine months of the year.”

The group of scientists collected samples from fjords in New Zealand. These samples, along with samples from the Arctic, sub-Arctic Canada, British Columbia, Norway, Sweden, Scotland, Greenland, Svalbard, Alaska, Chile and Antarctica, showed fjords were five times more efficient at capturing and storing carbon than continental shelves.

What makes fjords so good at capturing and storing carbon?

The deep, low-oxygen water is key. Carbon can sink quickly without being consumed by bacteria. This prevents the carbon from reentering the atmosphere.

Scientists don’t have all the answers though. For instance, fjords in Alaska capture carbon better than other locations. Researchers aren’t sure why.

It’s amazing that systems that are so small can have such a huge global impact,” Bianchi said. “It sends the message that fjords are not only beautiful, they’re providing a very important service.”

One of the deepest fjords on Earth.

Meet Sognefjord. This is the fjord you imagine when you think of one. It stretches for nearly 130 miles and hits a depth of 4,291 feet.

fjord Norway

Credit: Scandinavian Travel

Sognefjord is a popular tourist destination. It’s home to several national parks and two UNESCO sites.

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