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In High Arctic northern Greenland, future responses to climatic changes are poorly understood on a landscape scale. Here, we present a study of the geomorphology and cryostratigraphy in the Zackenberg Valley in NE Greenland (74°N) containing a geomorphological map and a simplified geocryological map, combined with analyses of 13 permafrost cores and two exposures. Cores from a solifluction sheet, alluvial fans, and an emerged delta were studied with regards to cryostructures, ice and total carbon contents, grain size distribution, and pore water electrical conductivity; and the samples were AMS 14C dated. The near-surface permafrost on slopes and alluvial fans is ice rich, as opposed to the ice-poor epigenetic permafrost in the emerged delta. Ground ice and carbon distribution are closely linked to sediment transport processes, which largely depend on lithology and topography. Holocene alluvial fans on the lowermost hillslopes, covering 12% of the study area, represent paleoenvironmental archives. During the contrasting climates of the Holocene, the alluvial fans continued to aggrade – through the warmer early Holocene Optimum, the colder late Holocene, and the following climate warming – and by 0.45 mm a− 1, on average. This is caused by three factors: sedimentation, ground ice aggradation, and vegetation growth and is reflected by AMS 14C dating and continuously alternating cryostructures. Highly variable sedimentation rates in space and time at the alluvial fans have been detected. This is also reflected by alternating lenticular and microlenticular cryostructures indicating syngenetic permafrost aggradation during sedimentation with suspended and organic-matrix cryostructures indicating quasi-syngenetic permafrost aggradation in response to vegetation growth in periods with reduced or no sedimentation. Over time, this causes organic matter to become buried, indicating that alluvial fans represent effective carbon sinks that have previously been overlooked.

This paper presents the history and cryostratigraphy of the upper permafrost in the High-Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents, and grain-size distribution, and were 14C- and OSL-dated. Spatial variability in ice and carbon contents is closely related to the sedimentary history and mode of permafrost aggradation. In the valley bottom, saline epigenetic permafrost with pore ice down to depths of 10.7 m depth formed in deltaic sediments since the mid-Holocene; cryopegs were encountered below 6 m. In the top 1 to 5 m, syngenetic and quasi-syngenetic permafrost with microlenticular, lenticular, suspended and organic-matrix cryostructures developed due to loess and alluvial sedimentation since the colder late Holocene, which resulted in the burial of organic material. At the transition between deltaic sediments and loess, massive ice bodies occurred. A pingo developed where the deltaic sediments reached the surface. On hillslopes, suspended cryostructure on solifluction sheets indicates quasi-syngenetic permafrost aggradation; lobes, in contrast, were ice-poor. Suspended cryostructure in eluvial deposits reflects epigenetic or quasi-syngenetic permafrost formation on a weathered bedrock plateau. Landform-scale spatial variations in ground ice and carbon relate to variations in slope, sedimentation rate, moisture conditions and stratigraphy. Although the study reveals close links between Holocene landscape evolution and permafrost history, our results emphasize a large uncertainty in using terrain surface indicators to infer ground-ice contents and upscale from core to landform scale in mountainous permafrost landscapes.

This study examines soil physical and environmental conditions controlling patterned-ground variability on an alluvial fan in a continuous permafrost landscape, at Adventdalen, Svalbard. On-site monitoring of ground temperature, soil moisture and snow depth, laboratory analyses of soil physical properties and principal component analysis indicate that the distribution of patterned ground depends primarily on soil texture, soil moisture and the winter ground thermal regime associated with snow cover. Mudboils and composite patterns (mudboils surrounded by small polygons) occupy well-drained areas composed of clay-rich aeolian sediments. Compared to mudboils, composite patterns show a sharper contrast in soil texture between barren centres and vegetated rims. Hummocks filled with organic materials develop on poorly drained lowlands associated with a shallow water table. Ice-wedge polygons are dominant on sandy loess-covered areas where the local wind regime minimises snow cover, enhancing ground cooling that promotes thermal contraction cracking. Copyright © 2016 John Wiley & Sons, Ltd.

Permafrost is vulnerable to rapid changes in climate, and increasing air temperatures have recently resulted in the increase of active layer thickness, thaw subsidence and warming of the underlying permafrost. Such changes have important implications for geotechnical properties and the stability of infrastructures in permafrost-affected areas. Many studies focus on the sensitivity of the active layer with respect to changes in climate conditions, but few assess the sensitivity of active layer thermal properties in relation to sediment types and soil water contents, and the importance of direct measurements of thermal property sensitivity with respect to soil water content compared to default physical relationships incorporated in process-based models. In this study, we use on-site data and samples to measure thermal conductivity (TC) at different gravimetric water/ice contents (GWC) in frozen and thawed permafrost. The samples, obtained from an emerged delta and an alluvial fan in the Zackenberg Valley, NE Greenland, are characterized by contrasting grain-size distribution and mineralogy. We calibrated a coupled heat and water transfer model, the “CoupModel”, to simulate permafrost temperatures at two sites on the delta. The sites have different snow depth characteristics and were simulated using both observed and default values of TC, and observed liquid soil water content. The results show that depth- and sediment type-specific TC values are crucial for a successful model simulation, and that transfer function derived values of TC are useful for modeling permafrost temperatures as long as site- and depth-specific grain size distribution and ice contents are defined. A thicker snow pack increased ground surface temperatures and resulted in a 1 °C higher annual mean ground temperature at the depth of zero annual amplitude. Permafrost temperatures increased by 1.5 °C and 3.5 °C at the depth of 18 m with 3 °C and 6 °C ground surface warming, but warming combined with increased soil water content had no important additional effect on the thermal regime when ground surface temperatures were prescribed as upper boundary conditions. Precipitation in the form of snow, however, may have a larger effect on ground temperatures directly, due to the surface temperature changes, than will the subsequent changes in thermal properties following increase in soil water content.

This study aims to improve the previous soil organic carbon (SOC) and total nitrogen (TN) storage estimates for the Zackenberg area (NE Greenland) that were based on a land cover classification (LCC) approach, by using geomorphological upscaling. In addition, novel SOC estimates for deeper deposits (down to 300 cm depth) are presented. We hypothesize that landforms will better represent the long-term slope and depositional processes that result in deep SOC burial in this type of mountain permafrost environments. The updated mean SOC storage for the 0–100 cm soil depth is 4.8 kg C m−2, which is 42 % lower than the previous estimate of 8.3 kg C m−2 based on land cover upscaling. Similarly, the mean soil TN storage in the 0–100 cm depth decreased with 44 % from 0.50 kg (±0.1 CI) to 0.28 (±0.1 CI) kg TN m−2. We ascribe the difference to a previous areal overestimate of SOC and TN-rich vegetated land cover classes. The landform-based approach more correctly constrains the depositional areas in alluvial fans and deltas with high SOC and TN storage. These are also areas of deep carbon storage with an additional 2.4 kg C m−2 in the 100–300 cm depth interval. This research emphasizes the need to consider geomorphology when assessing SOC pools in mountain permafrost landscapes.

The Zackenberg Delta is located in Northeast Greenland (74°30'N, 20°30'E) at the outlet of the Zackenberg Valley. The deltaic fill at the mouth of the valley consists of a series of terraces (ca. 2 km2) formed during a fall in relative sea level. The modern Zackenberg River has incised through the paleo-deltaic deposits creating exposures (up to 22 m in height) along the rivers banks. In addition, coastal processes have exposed sediments in 4 m – 20 m high coastal cliffs. In 2012, two 20 m long ice-bonded sediment cores were retrieved from within the deltaic deposits. The combination of river and coastal exposures with the analysis of ground ice in these cores permitted the reconstruction of the valley-fill succession and evaluation of the timing and nature of permafrost aggradation. Permafrost in the palaeo-deltaic deposits is predominantly epigenetic and aggraded following the subaerial exposure of the delta plain (beginning ca. 11 ka). The exposed deposits in the Zackenberg Valley provide a unique opportunity to investigate the relationship between depositional environments and processes, grain-size properties and cryostratigraphy in epigenetic lowland permafrost environments.