The situation of global climate change has extended its claws into the Arctic region, where its effects are the most pronounced. Surface rates in the Arctic are predicted to be double the rates globally due to Arctic amplification (Meredith et al., 2019), resulting in a change in its physical environment ranging from the reduction in sea-ice extent to altered nutrient availability (Chetelat et al., 2022). These shifts will ultimately affect the cycling of mercury (Hg) in the arctic environment and its concentrations in water bodies.

Figure 1: Distribution of permafrost in the Northern Hemisphere (GRID, 2020)

Figure 2: Retrogressive Thaw Slumps (ESA, 2019)

Chetelat et al., (2022) identified that one of the potential contributors of Hg in arctic waters would be permafrost degradation, with a decline of 6% to 29% of permafrost with every 1℃ of warming. Surrounding the Arctic Ocean (Fig.1), this permafrost freezes and sequesters large amounts of deposited atmospheric mercury, which bonds with the soil organic matter (Zhang et al., 2020). The degradation of permafrost then leads to the occurrence of retrogressive thaw slumps (Fig.2), releasing large quantities of Hg laden and nutrient rich soils into lakes and streams of the Arctic drainage basin (Schaefer, 2020).

The estimates of mercury stored in permafrost is 1656 ± 962 Gg Hg in the top three meters of soil, where 793 ± 461 Gg Hg are frozen in permafrost (Schuster, 2018). Once in water bodies, the thawed permafrost enables the continued microbial decay and release of Hg from organic matter, which then undergoes further methylation to form methylmercury (Schaefer, 2020).  Campeau et al., (2021) noted that, out of all tributaries within the Arctic Ocean’s drainage basin, the increased summer permafrost slumping into the Peel River has contributed the highest mobilisation of ancient organic carbon and Hg stocks.

In conclusion, numerous sources have reflected the rise in permafrost disturbance across arctic rivers due to climate change and their potential in releasing ancient Hg stocks into water bodies. With the interconnected nature of water systems and the rate of climate change, it might be sooner rather than later when permafrost mercury becomes a pressing issue.

 

 

References:

Chételat, J., McKinney, M. A., Amyot, M., Dastoor, A., Douglas, T. A., Heimbürger-Boavida, L.-E., Kirk, J., Kahilainen, K. K., Outridge, P. M., Pelletier, N., Skov, H., St. Pierre, K., Vuorenmaa, J., & Wang, F. (2022). Climate change and mercury in the Arctic: Abiotic interactions. The Science of the Total Environment, 824, 153715–153715.

GRID. (2020). Permafrost in the Northern Hemisphere. GRID Arendal. Retrieved from: https://www.grida.no/resources/13519

ESA. (2019, May 17). Thaw slump. European Space Agency. Retrieved from: https://www.esa.int/ESA_Multimedia/Images/2019/05/Thaw_slump

Meredith, M., Sommerkorn, M., Cassotta, S., Derksen, C., Ekaykin, A., Hollowed, A., Kofinas, G., Mackintosh, A., Melbourne-Thomas, J., Muelbert, M.M.C., Ottersen, G., Pritchard, H., Shuur, E.A.G., 2019. Polar regions. In: Pörtner, H.-O., Roberts, D.C., Masson-Delmotte, V., Zhai, P., Tignor, M., Poloczanska, E., Mintenbeck, K., Alegría, A., Nicolai, M., Okem, A., Petzold, J., Rama, B., Weyer, N.M. (Eds.), IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Intergovernmental Panel on Climate Change (IPCC), pp. 203–320 (In Press).

Schaefer, K., Elshorbany, Y., Jafarov, E., Schuster, P. F., Striegl, R. G., Wickland, K. P., Sunderland, E. M., & Los Alamos National Lab. (LANL), N. M. (U. S., Los Alamos. (2020). Potential impacts of mercury released from thawing permafrost. Nature Communications, 11(1), 4650–4650.

Schuster, P. F., Schaefer, K. M., Aiken, G. R., Antweiler, R. C., Dewild, J. F., Gryziec, J. D., Gusmeroli, A., Hugelius, G., Jafarov, E., Krabbenhoft, D. P., Liu, L., Herman‐Mercer, N., Mu, C., Roth, D. A., Schaefer, T., Striegl, R. G., Wickland, K. P., Zhang, T., & Los Alamos National Lab. (LANL), N. M. (U. S., Los Alamos. (2018). Permafrost Stores a Globally Significant Amount of Mercury. Geophysical Research Letters, 45(3), 1463–1471.

Zhang, ZY., Li, G., Yang, L., Xin-Jun, W., & Guo-Xin, S. (2020). Mercury distribution in the surface soil of China is potentially driven by precipitation, vegetation cover and organic matter. In Environmental Sciences Europe.