Search

Over the last 25 years, Canadian scientists have studied the permafrost environmental archives in the Klondike Goldfields south of Dawson City (e.g. Fraser and Burn, 1997; Kotler and Burn, 2010; Froese et al., 2009; Porter et al., 2016; Monteath et al., 2023). In 2023, a small Canadian-German team visiting this area to sample mining exposures in the Klondike area (Figure 1A). The goal was to conduct studies on ground ice (ice wedges and pore ice) and frozen sediments to reconstruct past landscape and climate conditions. Detailed profiles were sampled at three sites at Little Blanche Creek, Whitman Gulch and Bear Creek. Ice wedges were described in terms of their size, the color of ice, internal structure, existence and form of gas bubbles and were sampled by chain saw as blocks. The frozen sediment was cleaned, and ice, sediment and cryostructures were described, followed by sediment sampling with an axe and hammer. Separately, sediment cores were collected with a battery driven drill for biomarker studies. In our presentation, we present the first results of new field and laboratory studies. This concerns age determinations, sediment data, stable isotopes and hydrochemistry of the ground ice. The mean ice content measured was 38 ± 10 wt%. We expect new knowledge regarding the reconstruction of Late Quaternary environment of Central Yukon. References Fraser, T.A. and Burn, C.R. 1997: On the nature and origin of "muck" deposits in the Klondike area, Yukon Territory, Canadian Journal of Earth Sciences 34(10), 1333-1344, https://doi.org/10.1139/e17-106. Froese, D., Zazula, G., Westgate, J., Preece, S., Sanborn, P. A., Reyes, A., and Pearce, N. 2009: The Klondike goldfields and Pleistocene environments of Beringia, GSA Today, 19, 4-10, https://doi.org/10.1130/GSATG54A.1. Kotler, E. and Burn, C. R. 2000: Cryostratigraphy of the Klondike "muck" deposits, west-central Yukon Territory, Can. J. Earth Sci., 37, 849-861, https://doi.org/10.1139/e00-013. Monteath, A. J., Kuzmin

In the summer of 2023, three colleagues from the AWI Research Unit Potsdam worked together with two Canadian colleagues from the University of Toronto on permafrost outcrops in the vicinity of Dawson City. Dawson City is located in western Canada in the Yukon Territory near the Alaskan border at the mouth of the Klondike River into the Yukon and is known for its gold mining. During the Klondike Gold Rush at the end of the 19th century, tens of thousands of gold miners had spent several years in the Klondike Goldfields digging shafts in the permafrost with fires during the winter, driving tunnels horizontally and bringing the gold-bearing gravels to the surface. In the early 20th century through the 1960s, gold was washed out on a large scale in the main valleys with huge dredges, massively altering the landscape. Today, dozens of smaller and larger gold mines extract the gold placers and further alter the landscape. Huge sand and gravel mountains and long gravel walls with little vegetation cover can still be found on the valley floors today. The very continental climate in the study area leads to very cold winters (up to -50°C) and very warm summers. With temperatures up to 30°C and a very low mosquito density, we were able to sample the permafrost partly in T-shirts. Another consequence of the dry heat with only a few thundershowers were over 100 forest fires in the region, which, in addition to frequent smoke in Dawson City and the surrounding area, also led to evacuations of towns in the wider area and road closures. In the secondary valleys, the ice-rich permafrost overlying gold-bearing gravels is still being thawed with water cannons and removed with excavators. This created short-term opportunities for us to examine fresh permafrost walls. Our group examined and sampled both the long and wide ice wedges and the surrounding ice-rich sediment. Studies of ice chemistry and ice isotopy are planned. Different age determination methods will be carried out on the s

Over the last 25 years, Canadian scientists have studied the permafrost environmental archives in the Klondike Goldfields south of Dawson City. In 2023, a small Canadian-German team visiting this area to sample mining exposures in the Klondike area. The goal was to conduct studies on ground ice (ice wedges and pore ice) and frozen sediments to reconstruct past landscape and climate conditions. Detailed profiles were sampled at three sites at Little Blanche Creek, Whitman Gulch and Bear Creek. Ice wedges were described in terms of their size, the color of ice, internal structure, existence and form of gas bubbles and were sampled by chain saw as blocks. The frozen sediment was cleaned, and ice, sediment and cryostructures were described, followed by sediment sampling with an axe and hammer. Separately, sediment cores were collected with a battery driven drill for biomarker studies. In our presentation, we present the first results of new field and laboratory studies. This concerns age determinations, sediment data, stable isotopes and hydrochemistry of the ground ice. We expect new knowledge regarding the reconstruction of Late Quaternary environment of Central Yukon.

This contribution provides a short summary of three permafrost-related contributions to the upcoming 3rd volume of the Encyclopaedia of Quaternary Science. There are 24 chapters on ‘Permafrost and Periglacial Features’, and three of those are led by authors from the D-A-CH Permafrost Community. Specifically, these are ‘Ancient and past permafrost’, ‘Yedoma: Late Pleistocene ice-rich syngenetic permafrost of Beringia’ and ‘Organic matter storage and vulnerability in the permafrost domain’. With this presentation, we aim to give you a short introduction and show the key figures out of these three encyclopaedia chapters already now. In more detail, the broader perspective on ancient permafrost dynamics examines its formation, stability, and degradation in response to climate variations over the Quaternary. This encyclopaedia contribution distinguishes between ancient permafrost persisting since the Pleistocene and past permafrost, no longer existing at a specific locality. Recent research challenges traditional associations between permafrost and glacial periods, highlighting the complexity of permafrost responses to climate change. The Yedoma segment delves into the unique depositional processes of late Pleistocene Beringia, where a cold, dry climate fostered Yedoma formation due to periglacial weathering and syngenetic ice wedge growth. Yedoma hills in Siberia and foothill regions in Alaska, as well as valley fillings in mountain regions in Siberia and Alaska and in the Yukon Territory of western Canada are remnants of this feature, offering insight into paleoenvironmental, cryolithological, sedimentological and large carbon stock characteristics. The permafrost regions soil organic matter chapter synthesizes recent data and shows that this warming-susceptible region holds a staggering ~1500 Gt of organic carbon on land, with an additional ~2800 Gt in subsea permafrost. As permafrost degrades, it releases carbon, affecting ecosystems and greenhouse gas emissions. Pro

Organic carbon (OC) in permafrost interacts with the mineral fraction of soil and sediments, representing < 1% to ~80% of the total OC pool. Quantifying the nature and controls of mineral-OC interactions is therefore crucial for realistic assessments of permafrost-carbon-climate feedbacks, especially in ice-rich regions facing rapid thaw and the development of thermo-erosion landforms. Here, we analyzed sediment samples from the Batagay megaslump in East Siberia, and we present total element concentrations , mineralogy, and mineral-OC interactions in its different stratigraphic units. Our findings indicate that up to 34 ± 8% of the OC pool interacts with mineral surfaces or elements. Interglacial deposits exhibit enhanced OC-mineral interactions, where OC has undergone greater microbial transformation and has likely low degradability. We provide a first-order estimate of ~12,000 tons of OC mobilized annually downslope of the headwall (i.e., the approximate mass of 30 large aircrafts), with a maximum of 38% interacting with OC via complexation with metals or associations to poorly crystalline iron oxides. These data imply that over one-third of the OC exposed by the slump is not readily available for mineralization, potentially leading to prolonged OC residence time in soil and sediments under stable physicochemical conditions.

Tropospheric reactive bromine (Bry) influences the oxidation capacity of the atmosphere by acting as a sink for ozone and nitrogen oxides. Aerosol acidity plays a crucial role in Bry abundances through acid-catalyzed debromination from sea-salt-aerosol, the largest global source. Bromine concentrations in a Russian Arctic ice-core, Akademii Nauk, show a 3.5-fold increase from pre-industrial (PI) to the 1970s (peak acidity, PA), and decreased by half to 1999 (present day, PD). Ice-core acidity mirrors this trend, showing robust correlation with bromine, especially after 1940 (r = 0.9). Model simulations considering anthropogenic emission changes alone show that atmospheric acidity is the main driver of Bry changes, consistent with the observed relationship between acidity and bromine. The influence of atmospheric acidity on Bry should be considered in interpretation of ice-core bromine trends.

Snowpack emissions are recognized as an important source of gas-phase reactive bromine in the Arctic and are necessary to explain ozone depletion events in spring caused by the catalytic destruction of ozone by halogen radicals. Quantifying bromine emissions from snowpack is essential for interpretation of ice-core bromine. We present ice-core bromine records since the pre-industrial (1750 CE) from six Arctic locations and examine potential post-depositional loss of snowpack bromine using a global chemical transport model. Trend analysis of the ice-core records shows that only the high-latitude coastal Akademii Nauk (AN) ice core from the Russian Arctic preserves significant trends since pre-industrial times that are consistent with trends in sea ice extent and anthropogenic emissions from source regions. Model simulations suggest that recycling of reactive bromine on the snow skin layer (top 1 mm) results in 9–17% loss of deposited bromine across all six ice-core locations. Reactive bromine production from below the snow skin layer and within the snow photic zone is potentially more important, but the magnitude of this source is uncertain. Model simulations suggest that the AN core is most likely to preserve an atmospheric signal compared to five Greenland ice cores due to its high latitude location combined with a relatively high snow accumulation rate. Understanding the sources and amount of photochemically reactive snow bromide in the snow photic zone throughout the sunlit period in the high Arctic is essential for interpreting ice-core bromine, and warrants further lab studies and field observations at inland locations.

Mineral-organic carbon (OC) interactions account for 30 – 80 % of the total permafrost OC pool. Quantifying the nature and controls of mineral-OC interactions is necessary to better assess permafrost-carbon-climate feedbacks. This is particularly true for ice-rich environments that are impacted by rapid thaw and the development of thermokarst landforms. Retrogressive thaw slumps are amongst the most dynamic forms of slope thermokarst and they expand through the years due to the ablation of an ice-rich headwall. These phenomena are important to consider in the permafrost carbon budget since they expose deep OC sometimes tens of thousands of years old that would not have re-entered the modern carbon cycle if these disturbances had not occurred. Here, we analyzed sediment samples collected from the headwall of the Batagay megaslump, East Siberia, locally reaching 55 m high. The series of discontinuous deposits comprises also older sediment up to ~650 ka old. We present total element concentrations, mineralogy, and mineral-OC interactions in the different stratigraphic units. The mineralogy in the deposits is very similar across the sedimentary series. Our data show that up to 34 ± 8 % of the total OC pool is stabilized by mineral-OC interactions. For most of the analyzed samples, associations to poorly crystalline iron oxides do not have a significant role in OC stabilization. Hypothesizing a retreat rate of 26000 m²/yr and constant thickness of stratigraphic units within the headwall, we provide a first order estimate of ~2 × 10^7 kg of OC is exported annually downslope of the headwall, with ~ 38 % being geochemically stabilized by complexation with metals or associations to poorly crystalline iron oxides. These data support that more than one third of the organic carbon exposed by this massive thaw slump is not directly available for mineralization, but rather stabilized geochemically.

The reconstruction of past sea-ice distribution in the Southern Ocean is crucial for an improved understanding of ice-ocean-Atmosphere feedbacks and the evaluation of Earth system and Antarctic ice sheet models. The Antarctic Peninsula (AP) has been experiencing a warming since the start of regular monitoring of the atmospheric temperature in the 1950s. The associated decrease in sea-ice cover contrasts the trend of growing sea-ice extent in East Antarctica. To reveal the long-Term sea-ice history at the northern Antarctic Peninsula (NAP) under changing climate conditions, we examined a marine sediment core from the eastern basin of the Bransfield Strait covering the last Deglacial and the Holocene. For sea-ice reconstructions, we focused on the specific sea-ice biomarker lipid IPSO25, a highly branched isoprenoid (HBI), and sea-ice diatoms, whereas a phytoplankton-derived HBI triene (C25:3) and warmer open-ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraethers (GDGTs) and diatom assemblages and compare our sea-ice and temperature records with published marine sediment and ice core data. A maximum ice cover is observed during the Antarctic Cold Reversal 13ĝ€¯800-13ĝ€¯000 years before present (13.8-13ĝ€¯ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3ĝ€¯ka. An overall decreasing sea-ice trend throughout the Middle Holocene coincides with summer ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by highly variable winter sea-ice concentrations and a sustained decline in the duration and/or concentration of spring sea ice. Overall diverging trends in GDGT-based TEX86L and RI-OH' subsurface ocean temperatures (SOTs) are found to be linked to opposing spring and summer insolation trends, respectively.

Pronounced glacial and interglacial climate cycles characterized northern ecosystems during the Pleistocene. Our understanding of the resultant community transformations and past ecological interactions strongly depends on the taxa found in fossil assemblages. Here, we present a shotgun metagenomic analysis of sedimentary ancient DNA (sedaDNA) to infer past ecosystem-wide biotic composition (from viruses to megaherbivores) from the Middle and Late Pleistocene at the Batagay megaslump, East Siberia. The shotgun DNA records of past vegetation composition largely agree with pollen and plant metabarcoding data from the same samples. Interglacial ecosystems at Batagay attributed to Marine Isotope Stage (MIS) 17 and MIS 7 were characterized by forested vegetation (Pinus, Betula, Alnus) and open grassland. The microbial and fungal communities indicate strong activity related to soil decomposition, especially during MIS17. The local landscape likely featured more open, herb-dominated areas, and the vegetation mosaic supported birds and small omnivorous mammals. Parts of the area were intermittently/partially flooded as suggested by the presence of water-dependent taxa. During MIS 3, the sampled ecosystems are identified as cold-temperate, periodically flooded grassland. Diverse megafauna (Mammuthus, Equus, Coelodonta) coexisted with small mammals (rodents). The MIS 2 ecosystems existed under harsher conditions, as suggested by the presence of cold-adapted herbaceous taxa. Typical Pleistocene megafauna still inhabited the area. The new approach, in which shotgun sequencing is supported by metabarcoding and pollen data, enables the investigation of community composition changes across a broad range of taxonomic groups and inferences about trophic interactions and aspects of soil microbial ecology.

The High Arctic is assumed to be the last reserve of a stable cryosphere. Recent publications from the Canadian High Arctic indicate, however, that changes are currently happening much faster than expected, and the future trajectory is unknown. The rate and magnitude of recent climate warming has implications for the stability of ice, especially in the far north. Moreover, air temperatures at unprecedently high levels lead to drastic retreat in sea ice extent, larger and longer ice-free shelf seas, which now may act as a “new Arctic” moisture source with clear impact on the regional hydrological and cryospheric processes. Terrestrial ice (glaciers and ice caps, ice fraction in permafrost) in the high Russian Arctic is expected to change. This terrestrial ice is a freshwater inventory on land or that has been preserved in a stable state for hundreds of years. It contains unique information about past and present climate changes which is stored in the terrestrial ice to be studied, i.e. with stable isotope methods. In this presentation, we focus on the stable hydrogen and oxygen isotopes as a unifying proxy employed for addressing cryospheric, atmospheric, marine and terrestrial research questions In the framework of the Arctic Century 2021 expedition, we addressed the hydroclimate situation of High Arctic Islands, by studying firn/ice cores from three visited ice caps. Here, Windy Ice Dome (WD, Franz-Josef-Land) and Akademii Nauk ice cap (AN, Severnaya Zemlya) have been revisited and cored after more than 20 years, now complementing earlier longer ice cores. The University ice cap (UN, Severnaya Zemlya) has been cored for the first time. Key observations were intensive near-surface melt processes inducing the percolation of meltwater, numerous thick melt layers (reaching up to 80 cm), as well as liquid water in the borehole at AN and UN ice caps complicated drilling. The ice-coring program (5 cores, 27.2 m of core) has been accompanied by snow sampling (N=126) and an

Arctic is warming close to four times faster than the global average and, as a direct outcome, permafrost temperatures have increased by up to 0.39 ± 0.15 °C in the years 2007-2016. This increased warming is expected to generate a permafrost carbon feedback on the climate by promoting permafrost thaw and by emitting additional volumes of greenhouse gases into the atmosphere. Still, it is estimated that between 30% and 80% of soil organic carbon (OC) in permafrost is stabilized by geochemical interactions with mineral elements such as iron and thus less likely to be emitted as greenhouse gases. Quantifying the nature and controls of mineral-OC interactions is necessary to better frame permafrost-carbon-climate feedbacks, particularly in ice-rich environments that result in rapid thawing and the development of thermokarst landforms. Thaw slumps are amongst the most dynamic forms of slope thermokarst and expand through the years due to the ablation of an ice-rich headwall each summer. These phenomena are important to consider in the permafrost carbon budget since they expose a deep OC pool that may reach tens of thousands of years old and that would not have re-entered the modern carbon cycle if these disturbances had not occurred. Here, we collected samples from the Batagaika crater, Siberia, on a headwall reaching locally 55 m high - every half a meter for the upper 10 m of the headwall and then every meter. We present total element concentrations, mineralogy, and mineral-organic carbon interactions in the different stratigraphic units, i.e., from the top to the bottom, i) the organic surface layer, ii) the Holocene cover, iii) the upper ice complex, also called Yedoma, which is dominated by large ice wedges, iv) the woody debris layer which consists of macroscopic terrestrial plant remains, v) the lower sand unit of pore-ice-cemented aeolian-sourced fine sand, and vi) the lower ice complex which reveals ice-rich deposits of ice-wedges and provides access to ancient

The Batagay megaslump, a permafrost thaw feature in north-eastern Siberia, provides access to ancient permafrost up to ∼650 kyr old. We aimed to assess the permafrost-locked organic matter (OM) quality and to deduce palaeo-environmental information on glacial–interglacial timescales. We sampled five stratigraphic units exposed on the 55 m high slump headwall and analysed lipid biomarkers (alkanes, fatty acids and alcohols). Our findings revealed similar biogeochemical signatures for the glacial periods: the lower ice complex (Marine Isotope Stage (MIS) 16 or earlier), the lower sand unit (sometime between MIS 16–6) and the upper ice complex (MIS 4–2). The OM in these units has a terrestrial character, and microbial activity was likely limited. Contrarily, the n-alkane and fatty acid distributions differed for the units from interglacial periods: the woody layer (MIS 5), separating the lower sand unit and the upper ice complex, and the Holocene cover (MIS 1), on top of the upper ice complex. The woody layer, marking a permafrost degradation disconformity, contained markers of terrestrial origin (sterols) and high microbial decomposition (iso- and anteiso-fatty acids). In the Holocene cover, biomarkers pointed to wet depositional conditions and we identified branched and cyclic alkanes, which are likely of microbial origin. Higher OM decomposition characterised the interglacial periods. As climate warming will continue permafrost degradation in the Batagay megaslump and in other areas, large amounts of deeply buried ancient OM with variable composition and degradability are mobilised, likely significantly enhancing greenhouse gas emissions from permafrost regions.