The climate secrets of the deepest part of the ocean, the Marianas Trench in the western Pacific Ocean, have been probed by scientists.

The international team used a submersible, designed to withstand immense pressures, to study the bottom of the 10.9km-deep underwater canyon.

Their early results reveal that ocean trenches are acting as carbon sinks.

This suggests that they play a larger role in regulating the Earth's chemistry and climate than was thought.

While this has been studied in other parts of the ocean, such as the abyssal plain - the large flat area of the ocean that lies between 4.6km and 5.5km of depth - the role deep sea trenches play in the carbon cycle has until now remained largely unknown.

"What it means is that we have carbon storage going on in these trenches that is higher than we thought before, and this really means that we have a carbon dioxide sink in the deep ocean that wasn't recognised before."

The next stage for the team is to quantify their results and work out exactly how much more carbon is stored in deep sea trenches compared with other parts of the sea, and how much carbon turnover by bacteria is being carried out