Eastern Beringia and beyond: Late Wisconsinan and Holocene landscape dynamics along the Yukon Coastal Plain, Canada

Terrestrial permafrost archives along the Yukon Coastal Plain (northwest Canada) have recorded landscape development and environmental change since the Late Wisconsinan at the interface of unglaciated Beringia (i.e. Komakuk Beach) and the northwestern limit of the Laurentide Ice Sheet (i.e. Herschel Island). The objective of this paper is to compare the late glacial and Holocene landscape development on both sides of the former ice margin based on permafrost sequences and ground ice. Analyses at these sites involved a multi-proxy approach including: sedimentology, cryostratigraphy, palaeoecology of ostracods, stable water isotopes in ground ice, hydrochemistry, and AMS radiocarbon and infrared stimulated luminescence (IRSL) dating. AMS and IRSL age determinations yielded full glacial ages at Komakuk Beach that is the northeastern limit of ice-free Beringia. Herschel Island to the east marks the Late Wisconsinan limit of the northwest Laurentide Ice Sheet and is composed of ice-thrust sediments containing plant detritus as young as 16.2 cal ka BP that might provide a maximum age on ice arrival. Late Wisconsinan ice wedges with sediment-rich fillings on Herschel Island are depleted in heavy oxygen isotopes (mean δ18O of −29.1‰); this, together with low dexcess values, indicates colder-than-modern winter temperatures and probably reduced snow depths. Grain-size distribution and fossil ostracod assemblages indicate that deglaciation of the Herschel Island icethrust moraine was accompanied by alluvial, proluvial, and eolian sedimentation on the adjacent unglaciated Yukon Coastal Plain until ~11 cal ka BP during a period of low glacio-eustatic sea level. The late glacial–Holocene transition was marked by higher-than-modern summer temperatures leading to permafrost degradation that began no later than 11.2 cal ka BP and caused a regional thaw unconformity. Cryostructures and ice wedges were truncated while organic matter was incorporated and soluble ions were leached in the thaw zone. Thermokarst activity led to the formation of ice-wedge casts and deposition of thermokarst lake sediments. These were subsequently covered by rapidly accumulating peat during the early Holocene Thermal Maximum. A rising permafrost table, reduced peat accumulation, and extensive ice-wedge growth resulted from climate cooling starting in the middle Holocene until the late 20th century. The reconstruction of palaeolandscape dynamics on the Yukon Coastal Plain and the eastern Beringian edge contributes to unraveling the linkages between ice sheet, ocean, and permafrost that have existed since the Late Wisconsinan

Permafrost and man

Permafrost, a thermal condition of the ground, has long been an understated phenomenon because it is not necessarily detectable by the human eye and because it is found in areas that had little economic relevance for mankind. Permafrost-man interactions are however many and manifold. Rising air temperatures in the Arctic, Antarctic and the high mountain regions and consequently rising permafrost temperatures have has resulted in great threats on infrastructure of the higher latitudes northern and mountain, even though man had learnt to build on permafrost since thousands of years in some cases. Accelerating rock glaciers, greater risk of natural hazard in mountain regions, stronger coastal erosion and the danger of gas hydrates thawing are all anthropogenic impacts to a certain extent. Mankind has however also learnt to use the permafrost regions and sought to exploit it early on for its freezing properties in summer to store goods, or recently on a larger scale to protect seeds, to store carbon dioxide or even to extract information from permafrost bacteria in genetic research. The growingåå number of economic activities in the Arctic, the Antarctic and mountain regions will create considerable challenges for the permafrost environment and prompts the need for comprehensive monitoring strategies of permafrost

Association of Polar Early Career Scientists - EGU 2008

The International Polar Year 2007–2008 (IPY) is advancing our fundamental understanding of the Polar Regions and the cryosphere as a whole. To ensure the legacy of these scientific advances, the next generation of polar scientists must be recruited, nurtured, educated, and mentored. To retain the current cohort of early career polar scientists and recruit the next generation of researchers, professional development and networking activities must be expanded to address difficulties in international and interdisciplinary collaborations, rapidly developing technologies, logistical requirements of field work, and the increasing need to disseminate science results to the public and policy makers. The Association of Polar Early Career Scientists (APECS), founded in 2006, is an international and interdisciplinary organization for undergraduate and graduate students, postdoctoral researchers, early faculty members and educators with interests in polar regions and the cryosphere. By providing networking and career development opportunities, APECS activities aim to raise the profile of polar research, develop effective leaders in education and outreach, and stimulate interdisciplinary and international research collaborations. APECS builds on extensive national and disciplinary networks to develop integrated research directions, meet career development needs, and communicate the urgencies of polar science to a worldwide audience. In addition to being a networking organization, APECS facilitates mentoring by and liaises with senior researchers. APECS’ primary objective is to assist young researchers in addressing the challenges of polar research as they progress through the early stages of their careers. Education and outreach is a high priority of APECS members for a number of reasons, including the stimulation and engagement of the next generation of polar scientists that will be needed to meet growing scientific challenges. APECS’ membership includes more than 700 early career researchers from every continent ranging from undergraduate and graduate students, postdoctoral fellows, and new faculty members. For more information, visit: http://arcticportal.org/apecs

Life Cycles and Polycyclicity of Mega Retrogressive Thaw Slumps in Arctic Permafrost Revealed by 2D/3D Geophysics and Long‐Term Retreat Monitoring

Mega retrogressive thaw slumps (MRTS, >106 m3) are a major threat to Arctic infrastructure, alter regional biogeochemistry, and impact Arctic carbon budgets. However, processes initiating and reactivating MRTS are insufficiently understood. We hypothesize that MRTS preferentially develop a polycyclic behavior because the material is thermally and mechanically prepared for subsequent generation failure. In contrast to remote sensing, geophysical reconnaissance reveals the inner structure and relative thermal state of MRTS decameters beneath slump surfaces, potentially controlling polycyclicity. Based on their life cycle development, five (M)RTS were studied on Herschel Island, an MRTS hotspot on the Canadian Beaufort coast. We combine >2 km of electrical resistivity tomography (ERT), 500 m of ground-penetrating radar (GPR) and annual monitoring of headwall retreat from 2004 to 2013 to reveal the thermal state, internal structure, and volume loss of slumps. ERT data were calibrated with unfrozen-frozen transitions from frost probing of active layer thickness and shallow boreholes. In initial stage MRTS, ERT displays surficial thermal perturbations a few meters deep, coincident with recent mud pool and mud flow development. In early stage polycyclic MRTS, ERT shows decameter deep-reaching thermal perturbations persisting even 300 years after the last activation. In peak-stage polycyclic MRTS, 3D-ERT highlights actively extending deep-reaching thermal perturbations caused by gully incisions, mud slides and mud flows. GPR and headwall monitoring reveal structural disturbance by historical mud flows, ice-rich permafrost, and a decadal quantification of headwall retreat and slump floor erosion. We show that geophysical signatures identify long-lasting thermal and mechanical disturbances in MRTS predefining their susceptibility to polycyclic reactivation

Alkalinity generation from carbonate weathering in a silicate-dominated headwater catchment at Iskorasfjellet, northern Norway

The weathering rate of carbonate minerals is several orders of magnitude higher than for silicate minerals. Therefore, small amounts of carbonate minerals have the potential to control the dissolved weathering loads in silicate-dominated catchments. Both weathering processes produce alkalinity under the consumption of CO2. Given that only alkalinity generation from silicate weathering is thought to be a long-term sink for CO2, a misattributed weathering source could lead to incorrect conclusions about long- and short-term CO2 fixation. In this study, we aimed to identify the weathering sources responsible for alkalinity generation and CO2 fixation across watershed scales in a degrading permafrost landscape in northern Norway, 68.7–70.5∘ N, and on a temporal scale, in a subarctic headwater catchment on the mountainside of Iskorasfjellet, characterized by sporadic permafrost and underlain mainly by silicates as the alkalinity-bearing lithology. By analyzing total alkalinity (AT) and dissolved inorganic carbon (DIC) concentrations, as well as the stable isotope signature of the latter (δ13C-DIC), in conjunction with dissolved cation and anion loads, we found that AT was almost entirely derived from weathering of the sparse carbonate minerals. We propose that in the headwater catchment the riparian zone is a hotspot area of AT generation and release due to its enhanced hydrological connectivity and that the weathering load contribution from the uphill catchment is limited by insufficient contact time of weathering agents and weatherable materials. By using stable water isotopes, it was possible to explain temporal variations in AT concentrations following a precipitation event due to surface runoff. In addition to carbonic acid, sulfuric acid, probably originating from oxidation of pyrite or reduced sulfur in wetlands or from acid deposition, is shown to be a potential corrosive reactant. An increased proportion of sulfuric acid as a potential weathering agent may have resulted in a decrease in AT. Therefore, carbonate weathering in the studied area should be considered not only as a short-term CO2 sink but also as a potential CO2 source. Finally, we found that AT increased with decreasing permafrost probability, and attributed this relation to an increased water storage capacity associated with increasing contact of weathering agent and rock surfaces and enhanced microbial activity. As both soil respiration and permafrost thaw are expected to increase with climate change, increasing the availability of weathering agents in the form of CO2 and water storage capacity, respectively, we suggest that future weathering rates and alkalinity generation will increase concomitantly in the study area.</p

Ocean Colour remote sensing in the Southern Laptev Sea: evaluation and applications

Enhanced permafrost warming and increased arctic river discharges have heightened concern about the input of terrigeneous matter into Arctic coastal waters. We used optical operational satellite data from the Ocean Colour sensor MERIS onboard the ENVISAT satellite mission for synoptic monitoring of the pathways of terrigeneous matter in the southern Laptev Sea. MERIS satellite data from 2006 on to 2011 were processed using the Case2Regional Processor, C2R, installed in the open-source software ESA BEAM-VISAT. Since optical remote sensing using Ocean Colour satellite data has seen little application in Siberian Arctic coastal and shelf waters, we assess the applicability of the calculated MERIS parameters with surface water sampling data from the Russian-German ship expeditions LENA2010 and TRANSDRIFT-XVII taking place in August and September 2010 in the southern Laptev Sea. The surface waters of the southern Laptev Sea are characterized by low transparencies, due to turbid river water input, terrestrial input by coastal erosion, resuspension events and, therefore, high background concentrations of Suspended Particulate Matter, SPM, and coloured Dissolved Organic Matter, cDOM. The mapped calculated optical water parameters, such as the first attenuation depth, Z90, the attenuation coefficient, k, and Suspended Particulate Matter, SPM, visualize resuspension events that occur in shallow coastal and shelf waters indicating vertical mixing events. The mapped optical water parameters also visualize that the hydrography of the Laptev Sea is dominated by frontal meanders with amplitudes up to 30 km and eddies and filaments with diameters up to 100 km that prevail throughout the ice-free season. The meander crests, filaments and eddy-like structures that become visible through the mapped MERIS C2R parameters indicate enhanced vertical and horizontal transport energy for the transport of terrigenous and living biological matter in the surface waters during the ice-free season

Dynamics of Arctic Permafrost Coasts in the 21st Century

Climate warming is particularly pronounced in the Arctic with temperatures rising twice as much as in the rest of the world. It seems natural that this warming has profound effects on the speed of erosion of Arctic coasts, since the majority consists of permafrost, composed of unlithified material and hold together by ice. Permafrost stores approximately 1307 Gt of carbon, which is almost 60 % more than currently being contained in the atmosphere. Understanding the main drivers and dynamics of permafrost coastal erosion is of global relevance, especially since floods and erosion are both projected to intensify. However, the assessment of the impacts of climate warming on Arctic coasts is impaired by little data availability. We reviewed relevant scientific literature on changing dynamics of Arctic coast, potential drivers of these changes and the impacts on the human and natural environment. We provide a comprehensive overview over the state of the art and share our thoughts on how we envision potential pathways of future Arctic coastal research. We found that the overwhelming majority of all studied Arctic coasts is erosive and that in most cases erosion rates per year are increasing, threatening coastal settlements, infrastructure, cultural sites and archaeological remains. The impacts on the natural environment are also manifold and reach from changing sediment fluxes which limit light availability in the water column to a higher input of carbon and nutrients into the nearshore zone with the potential to influence food chains

Rapid retreat of permafrost coastline observed with aerial drone photogrammetry

Permafrost landscapes are changing around the Arctic in response to climate warming, with coastal erosion being one of the most prominent and hazardous features. Using drone platforms, satellite images, and historic aerial photographs, we observed the rapid retreat of a permafrost coastline on Qikiqtaruk – Herschel Island, Yukon Territory, in the Canadian Beaufort Sea. This coastline is adjacent to a gravel spit accommodating several culturally significant sites and is the logistical base for the Qikiqtaruk – Herschel Island Territorial Park operations. In this study we sought to (i) assess short-term coastal erosion dynamics over fine temporal resolution, (ii) evaluate short-term shoreline change in the context of long-term observations, and (iii) demonstrate the potential of low-cost lightweight unmanned aerial vehicles (“drones”) to inform coastline studies and management decisions. We resurveyed a 500&thinsp;m permafrost coastal reach at high temporal frequency (seven surveys over 40&thinsp;d in 2017). Intra-seasonal shoreline changes were related to meteorological and oceanographic variables to understand controls on intra-seasonal erosion patterns. To put our short-term observations into historical context, we combined our analysis of shoreline positions in 2016 and 2017 with historical observations from 1952, 1970, 2000, and 2011. In just the summer of 2017, we observed coastal retreat of 14.5&thinsp;m, more than 6 times faster than the long-term average rate of 2.2±0.1&thinsp;m&thinsp;a−1 (1952–2017). Coastline retreat rates exceeded 1.0±0.1&thinsp;m&thinsp;d−1 over a single 4&thinsp;d period. Over 40&thinsp;d, we estimated removal of ca. 0.96&thinsp;m3&thinsp;m−1&thinsp;d−1. These findings highlight the episodic nature of shoreline change and the important role of storm events, which are poorly understood along permafrost coastlines. We found drone surveys combined with image-based modelling yield fine spatial resolution and accurately geolocated observations that are highly suitable to observe intra-seasonal erosion dynamics in rapidly changing Arctic landscapes.</p