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Fjords regulating worldwide climate change: New Zealand research

Xinhua, May 5, 2015 Adjust font size:

The scenic fjords of Norway, New Zealand and other parts of the world are major carbon sinks that play an important role in regulating the Earth's climate, New Zealand scientists said Tuesday.

University of Otago researchers analyzed sediment data from fjord systems worldwide and estimated that about 18 million tons of organic carbon was buried in fjords each year, equivalent to 11 percent of annual marine carbon burial globally.

Per unit area, fjord organic carbon burial rates were twice as large as the ocean average.

"Therefore, even though they account for only 0.1 percent of the surface area of oceans globally, fjords act as hotspots for organic carbon burial," researcher Dr Candida Savage said in a statement.

Fjords are long, deep and narrow estuaries formed at high latitudes during glacial periods as advancing glaciers cut major valleys near the coast.

They are found in northwest Europe, Greenland, North America, New Zealand, and Antarctica.

As deep and often low oxygen marine environments, fjords provided stable sites for carbon-rich sediments to accumulate, Savage said.

Carbon burial was an important natural process that provided the largest carbon sink on the planet and influenced atmospheric carbon dioxide (CO2) levels at multi-thousand-year time scales.

The researchers suggested that fjords could play an especially important role as a driver of atmospheric CO2 levels during times when ice sheets were advancing or retreating.

During glacial retreats, which last occurred about 11,700 years ago, fjords would trap and prevent large volumes of organic carbon flowing out to the continental shelf, where chemical processes would have caused CO2 to be produced, said Savage.

Once glaciers started advancing again this material would likely then be pushed out onto the shelf and CO2 production would increase.

"In essence, fjords appear to act as a major temporary storage site for organic carbon in between glacial periods. This finding has important implications for improving our understanding of global carbon cycling and climate change," she said. Endi