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Thawing permafrost affects Arctic warming

13 September 2023
One effect of climate change is the thawing of permafrost, the 'permanently' frozen soil. Climate scientist Dirk Jong's PhD research examined the journey of the organic carbon from permafrost from the source to the sediment. And which part is broken down or captured again. Even though the research shows that some of the material is stored again in the sediment, the majority breaks down into CO2 and only further strengthens the process of climate change.

Self-reinforcing effect
Climate change is hitting the Arctic disproportionately hard. In some places the coastline is collapsing into the sea at a rate of more than ten meters per year. The so-called thaw craters, where the permafrost landscape thaws and collapses like a child's ice cream in the hot sun, are also growing rapidly in size and number. As a result, villages and communities in the Arctic region are being hit hard. Permafrost is full of organic carbon: plant remains that have been frozen in the soil since the last ice age. Thawing of the permafrost allows this material to break down into greenhouse gases CO2 and methane, which could have a self-reinforcing effect on Arctic warming.

Erosion of coastline and riverbanks
Especially along rivers and the coast of the Arctic Ocean, the thawing of permafrost is accelerating due to erosion of the coastline and river banks. Some of the organic carbon released is broken down, but some also ends up in river deposits and the sediment of the seabed, which store the organic carbon for a longer period of time. Recent research in Canada and Siberia shows that all types of organic carbon must be investigated in an integrated manner. The part that is dissolved in the water, the part that floats as particles in the water and the part that is in the sediment. His research shows that each part responds differently to transport from land to sea, is processed differently along the way and that a specific research approach is needed.

Crucial role transition zones
The researchers also see that two 'transition zones' en route from land to sea - from frozen material to thawed, and from freshwater system to sea - play a crucial role in the breakdown of organic carbon from permafrost. Furthermore, Jong discovered that a combination of methods is necessary if samples from different places need to be compared - a sediment sample from the seabed cannot be compared one-to-one with a riverbank sample, a permafrost sample, or a water sample. Jong further developed these methods and recommends the use of similar methods.

Fieldwork in Canada and Siberia
Jong conducted his research in Canada and Siberia where he took samples from the entire transport system of permafrost-derived material; from the still frozen permafrost, the thawed mud plains and mud flows, streams and rivers, river deltas and coastal areas and the open ocean. He filtered water samples to separate dissolved material from floating material and took sediment samples from the rivers and seabed. In the lab he carried out geochemical and sedimentological analyses to characterize the organic material in the water, on filters and in the sediment to see what part comes from permafrost and what part is modern plant and algae remains, or to measure different ' biomarkers' to see how fresh the organic material still is. These analyses showed that part of the organic carbon from the permafrost is indeed stored again on the seabed, but also that most of it is lost along the way.