The thawing and erosion of the arctic permafrost coasts has increased so drastically in the past that more than 20 metres of land is consumed by the sea every year at some locations. The earth masses that get removed in the process increasingly blur the shallow water areas, and release nutrients and pollutants. However, the consequences of such processes on life in the coastal zone and on traditional fishing areas are unknown.
In a paper in the January issue of Nature Climate Change, the scientists at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) are calling for more attention to be focussed on the ecological consequences of coastal erosion. According to them, an interdisciplinary research programme involving policy-makers and inhabitants of the Arctic coasts is required.
Indeed, the difference could not have been greater. During winter, when the Beaufort Sea freezes around the Canadian permafrost island of Herschel Island, the seawater in the sample bottles appear crystal clear. Then, in the summer, when the ice floes are melted, and the sun and waves wear away the cliff, the seawater sample becomes a cloudy broth.
“Herschel Island loses up to 22 metres of coast each year. The thawed permafrost slides down into the sea in the form of mudslides and blurs the surrounding shallow water areas so much that the brownish-grey sediment plumes reach many kilometres into the sea,” said AWI researcher Dr Michael Fritz.
His observations of Herschel Island can now be applied to large parts of the Arctic. Permaforst coasts now make up 34 percent of the coasts worldwide. Particularly in the Arctic, its soil contains a lot of frozen water, which keep the sediments together, much like cement. However, if the permafrost thaws, the binding effect fails, releasing the sediments which are then washed away by waves.
In the process, greenhouse gases like methane and carbon dioxide are released, thus leading to even more global warming. Many nutrients and pollutants like nitrogen, phosphorous or mercury are found within the eroded material. As these substances enter the ocean, they are further transported, degraded or accumulated, permanently altering the food chain. “We can until now only guess the implications for the food chain. To date, almost no research has been carried out on the link between the biogeochemistry of the coastal zone and increasing erosion, and what consequences this has on ecosystems, on traditional fishing grounds, and thus also on the people of the Arctic,” said Dr Fritz.
As such, he, together with Dutch permafrost expert Jorien Vonk and AWI researcher Hugues Lantuit, is calling on the polar research community to systematically investigate the consequences of coastal erosion for the arctic shallow water areas. “The processes in the arctic coastal zone play an outstanding role for four reasons. Firstly, the thawed organic material is decomposed by microorganisms, producing greenhouse gases. Secondly, released nutrients stimulate the growth of algae, which can lead to the formation of low-oxygen zones. Thirdly, the addition of organic carbon increases the acidification of the sea, and fourth, the sediments are deposited on the seabed or are transported to the open ocean. This has direct consequences for the biology of the sea,” they said.
Link to the study: www.nature.com/nclimate/journal/v7/n1/full/nclimate3188.html