“Millions of Submerged Trees in Mackenzie River Delta Store Underestimated Carbon Quantity”

Until now, the quantity of carbon stored by these submerged tree trunks has been underestimated.

Scientists have turned their eyes to the great Mackenzie River, which runs through the Northwest Territories. At the end of its 1,738 km, the longest river in Canada flows into the Arctic Ocean, forming a wide delta where the trunks of trees washed away by the water accumulate. Millions of trunks lie under the water and on the banks.

Stretching over 51 km², this gigantic driftwood jam alone would store 3.1 million tonnes of carbon, the equivalent of the emissions of 2.5 million cars over one year. These results were recently published in Geophysical Research Letters.

A team of American and British scientists arrived at this result by combining data from satellite images with those taken on the ground. The jam is actually made up of 400,000 smaller piles of wood.

While the scientific community has long studied the carbon cycle with water and sediment, less is known about what happens with the logs floating and moving in the Arctic, says Alicia Sendrowski, lead author of the study. The researcher, who was completing her doctorate at Michigan Technological University at the time of this study, said she was surprised by the amount observed. “We knew there was wood because we could see it on the satellite images. But once there, we realized there were a lot more than expected. In the field, the team took the opportunity to measure the many tree deposits along the river, count the quantity of wood piled up, determine its porosity, and so on. These data made it possible to know the volume occupied by the trees and to convert it into the quantity of stored carbon.

These trees that are partially or completely submerged in water have accumulated over a long period of time to form this gigantic ice jam. “With erosion, trees that grow near a floodplain or riverbank fall into rivers. Ice and snowmelt can also bring the trunks into the rivers, ”explains Alicia Sendrowski in a telephone interview. She points out that the Mackenzie River crosses a vast territory and thus collects all the tree trunks which then end up in the delta.