The dramatic, glacier-carved inlets called fjords capture and store carbon better than open-water marine systems, report researchers.
“Carbon sequestration is the big buzzword, but we’re still getting a handle on how it works,” says Thomas Bianchi, a geochemist at the University of Florida. In order to make informed land-use decisions and accurate climate predictions, “finding and understanding these hot spots is critical,” he says.
Although fjords represent a tiny fraction of the seas, they store 11 percent of the carbon buried in the oceans—an estimated 18 million metric tons a year, according to the study in Nature Geosciences.
Locking that carbon away prevents it from converting to carbon dioxide, one of the greenhouse gases that contributes to a warming atmosphere. Fjords’ efficiency at storing carbon comes from their deep, narrow V shape, which allows carbon to sink into low-oxygen zones where it is less likely to be consumed by aerobic bacteria and re-enter the atmosphere as a greenhouse gas.
Scientists have known for years that fjords were coastal environments with high carbon storage, but because they make up just a tenth of a percent of the world’s oceans, no one realized just how important they were, Bianchi says.
“Most of the focus has been on the big river deltas, because they drain so much more surface area in their large watersheds,” he says.
The team studied samples of core and surface sediment from fjords in New Zealand, then compared their results with previous data from the Arctic, sub-Arctic Canada, British Columbia, Norway, Sweden, Scotland, Greenland, Svalbard, Alaska, Chile, and Antarctica.
Their results reveal fjords to be five times more efficient at sequestration than continental shelves, another key area for carbon burial. Averaged by area, fjords buried carbon at a rate double that of the oceans overall.
Bianchi hopes the findings will draw attention to fjords’ importance for better-informed conservation decisions.
“It’s amazing that systems that are so small can have such a huge global impact,” he says. “It sends the message that fjords are not only beautiful, they’re providing a very important service.”
Bianchi’s former doctoral student Richard Smith, now a postdoctoral fellow at the University of Connecticut, led the team, which included researchers from New Zealand, South Africa, Tulane University in New Orleans, and the Woods Hole Oceanographic Institution in Massachusetts.
Source: University of Florida