The largest known cumulative logjam in the world spans 51 square meters and consists of trees that have fallen and floated over the rivers. As centuries passed, these trunks have accumulated throughout the delta. Now, this massive logjam has been seen to carry remarkable amounts of carbon.
Logjams and the Carbon Cycle
As per Science Alert, the logs altogether carry around 3.4 million tons of carbon. This shows a vital yet poor understanding of the carbon pool.
Such carbon amounts are equivalent to 2.5 million car emissions yearly. This just goes to show how sizable and significant these quantities are.
Findings regarding this logjam in the Arctic were detailed in the Geophysical Research Letters.
For several decades, scientists have known how driftwood moves in the Arctic. However, they are still generally unfamiliar with the carbon quantities that it stores and how much of a risk their loss would pose to climate concerns.
SciTechDaily reports that due to the icy and dry conditions in the Arctic, trees can stay preserved for tens of thousands of years. In fact, a tree from a thousand years ago may still appear as fresh as one that just recently fell.
Virginia Ruiz-Villanueva, a fluvial geomorphologist from the University of Lausanne who did not participate in the research efforts, explains how much efforts have focused on carbon fluxes in sediments and water. However, it was only recently that wood became an object of focus. The research field is young and fast-developing.
Ruiz-Villanueva adds that it is important to study wood not just for understanding the carbon cycle but also to know more about how these fluvial systems operate and how rivers distribute and mobilize such logs.
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Taking a Deeper Look at Logjams
To get an overview of the logs, the researchers specifically focused on the Mackenzie River, which is known to have huge deposits of wood and remarkably high-resolution imagery. Its delta is the world's third-largest in terms of land.
To map wood deposits, the researchers looked into 13,000 square kilometers of its delta. They were in the field for three weeks to measure driftwood, map logjams, and date the wood via radiocarbon dating.
After their work in the field, Alicia Sendrowski, a research engineer from Colorado State University and the study's leader, made use of remote imagery to pinpoint river-surface wood and project the logjam's aerial coverage. Based on measurements of the field, Sendrowski then estimated the wood volume inside the logjam and the carbon quantity being stored.
By doing so, Sendrowski discovered that the wood deposit, which consisted of over 400,000 miniature wood caches, kept roughly 3.4 million tons of carbon. Sendrowski further notes, however, that due to the logs kept under the soil, hidden from aerial view, and submerged in water, the total carbon amount could actually be double.
Sendrowski adds that the Mackenzie River Delta is a carbon storage "hotspot" due to its remarkably carbon-rich surfaces. She notes that it is important because as basin and climate changes take place, wood preservation may be reduced. Given the significant quantity of stored carbon, this would equate to a vital carbon storage loss.
Moreover, this is only one among the many basins across the Arctic. Collectively, all basins could be vital carbon pools that science has yet to dig deeper into.
The researchers also wanted to assess how long a tree in the Arctic could last. Carbon dating revealed that though some were from around or after the 1950s, some trees dated as far back as 700 CE.
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