ALBERT

Description: Arctic river deltas are sensitive polar landscapes at the land-ocean interface. In contrast to lower latitude deltas, Arctic deltas are characterized by low temperatures, a strong seasonality and the presence of permafrost. Seasonal freezing conditions and underlying permafrost hinders runoff for most of the year and leads to typical land forms such as ice wedge polygons, frost mounds and thermokarst lakes. However, compared to other permafrost dominated landscapes, Arctic deltas are more dynamic. The surface morphology is changing constantly due to river ice break up and subsequent spring flooding, coastal and shoreline erosion, thaw slumping, and degradation of ice rich deposits. Deltaic sediments also tend to be highly susceptible to ground-ice aggradation, making them more ice-rich than adjacent nondeltaic landscapes. In addition, Arctic deltas will be severely affected by global climate change through sea level rise, lengthened thaw season, changing river discharge, storm surge flooding and thawing permafrost. We are therefore at risk, to face reactivation of millennia-old soil carbon and nitrogen deposits by the degradation of previously permanently frozen river delta deposits. However, there is a lack of studies on Arctic deltas and only very coarse estimates on Arctic delta carbon and nitrogen stocks exist. Here we present a new data-set of 140 soil cores, including more than 1400 samples from 17 different deltas spread across the Arctic. We combine new and legacy soil core data to estimate for the first time pan-Arctic deltaic carbon and nitrogen stocks and close a knowledge gap for deep permafrost stock estimations. We found that Arctic deltas present a significant pool for organic carbon and nitrogen, thus their change poses risks far beyond the Arctic. Permafrost thaw in such dynamic landscapes will increase nutrient transport from land to ocean with implications on Arctic near-shore zones (e.g. affecting foodwebs and biogeochemical processes) as well as increased greenhouse gas release due to large amounts of carbon and nitrogen becoming available from previously frozen ground. Our study highlights the need to better understand dynamic processes in Arctic deltas, since these vulnerable carbon and nitrogen rich deposits will be severely affected by the effects of global climate change.

Description: The Lena River Delta is underlain by permafrost. Thus, it is highly vulnerable to climate warming and may degrade in different ways, by shoreline erosion, land surface subsidence, deepening of the seasonal thawing front, and development of rapid thaw features such as lakes, gullies and landslides.

Description: Perennially frozen ground and sea ice are key constituents of permafrost coastal systems, and their presence is the primary difference between temperate and high-latitude coastal processes. These systems are some of the most rapidly changing landscapes on Earth and, in the Arctic, are representative of the challenges being faced at the intersection between natural and anthropogenic systems. Permafrost thaw, in combination with increasing sea level and decreasing sea-ice cover, exposes arctic coastal and nearshore areas to rapid environmental and social changes. Based on decadal timescales, observations in the Arctic indicate an increase in permafrost coastal bluff erosion and storm surge flooding of low-lying ice-rich permafrost terrain. However, circum-arctic observations remain limited and the factors responsible for the apparent increase in arctic coastal dynamics are poorly constrained. A better understanding of permafrost coastal systems and how they are responding to changes in the Arctic is important since a high proportion of Arctic residents live on or near coastlines, and many derive their livelihood from terrestrial and nearshore marine resources. An expanding industrial, scientific, and commercial presence in the Arctic Ocean will also require advanced knowledge about permafrost coastlines as terrestrial access points. Since the issues involved span political, cultural, geographical, and disciplinary borders, an international network focused on permafrost coastal systems in transition is needed. An integrative network focused on permafrost coastal systems is required to realize and address the scale and complexity of the processes, dynamics, and responses of this system to physical, ecological, and social change. A primary focus of such an effort would be guided by the fact that the issues and impacts associated with permafrost coastal systems in transition are far greater than any single institution or discipline is capable of addressing alone. Future permafrost coastal system dynamics will challenge conventional wisdom as the system enters a new state impacting human decision making and adaptation planning, cultural heritage resources and ecosystems, and likely resulting in unforeseen challenges across the Arctic.

Description: Permafrost thaw is associated with impacts on climate, land surface and coastal and river bank structures. Thermokarst and thermoerosion, for example, are thaw processes that lead to ground subsidence. Two main factors of surface subsidence vulnerability are the sedimentological composition, including ground ice content, and the temperature state of permafrost. This surface destabilization is getting relevant because of a potential positive feedback of deep thaw to the global climate system through the release of greenhouse gases trapped beneath or in the permafrost, as well as through the release of so far freeze-locked old carbon by microbial decomposition. With these facts in mind the overarching aims of our drilling campaigns were to retrieve deep (〉 50m) frozen and unfrozen sediment cores including sediments, ice, and organic components.