Deep Yedoma permafrost: A synthesis of depositional characteristics and carbon vulnerability

Permafrost is a distinct feature of the terrestrial Arctic and is vulnerable to climate warming. Permafrost degrades in different ways, including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features. Pleistocene ice-rich permafrost with syngenetic ice-wedges, termed Yedoma deposits, are widespread in Siberia, Alaska, and Yukon, Canada and may be especially prone to rapid-thaw processes. Freeze-locked organic matter in such deposits can be re-mobilized on short time-scales and contribute to a carbon cycle climate feedback. Here we synthesize the characteristics and vulnerability of Yedoma deposits by synthesizing studies on the Yedoma origin and the associated organic carbon pool. We suggest that Yedoma deposits accumulated under periglacial weathering, transport, and deposition dynamics in non-glaciated regions during the late Pleistocene until the beginning of late glacial warming. The deposits formed due to a combination of aeolian, colluvial, nival, and alluvial deposition and simultaneous ground ice accumulation. We found up to 130 gigatons organic carbon in Yedoma, parts of which are well-preserved and available for fast decomposition after thaw. Based on incubation experiments, up to 10% of the Yedoma carbon is considered especially decomposable and may be released upon thaw. The substantial amount of ground ice in Yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo-erosion processes. Mobilization of permafrost carbon is expected to increase under future climate warming. Our synthesis results underline the need of accounting for Yedoma carbon stocks in next generation Earth-System-Models for a more complete representation of the permafrost-carbon feedback

Permafrost Deep Organic Matter: The IPA Yedoma Action Group

Die Action Group "The Yedoma Region: A Synthesis of Circum-Arctic Distribution and Thickness" der Internationalen Permafrost Assoziation (IPA) hat es zum Ziel die Verbreitung und Mächtigkeit von Yedoma Permafrost, einem spätpleitozänen sehr eisreichem Permafrost, zu quantifizieren. Yedoma ist durch Eisgehalte von bis zu 80vol% sehr anfällig gegenüber Erwärmung. Denn wenn das Bodeneis schmilzt und abgeführt wird sind Absenkungen der Bodenoberflächen von mehr als 30 Metern möglich, was deutliche Auswirkungen hat auf die Landschaft, samt Infrastruktur und menschlicher Landnutzung. Als Produkt dieses Projektes möchten wir hier eine circum-arktische Karte präsentieren. Diese Daten werden als Grundlage dazu dienen, den Kohlenstoffpool von Yedoma Ablagerungen realistisch in computergestützte Modelle zu implementieren und die zukünftigen Auswirkungen von Thermokarst und Thermoerosion auf die Treibhausgasemissionen abzuschätzen

Reconstructing Permafrost Sedimentological Characteristics and Post-depositional Processes of the Yedoma Stratotype Duvanny Yar, Siberia

Cryogenic weathering is a key driver of periglacial sediment composition and properties. Selective mineral-grain weathering caused by freeze-thaw cycles in permafrost environments has the ability to dominate this process, leading to silt-rich grain-size distributions. The cryogenic weathering index (CWI) is a promising tool to quantify cryogenic weathering and freezing conditions. It considers the low resistance of quartz to freeze-thaw cycles compared to feldspars. Using this approach, this study aims to decipher post-depositional weathering by reconstructing cryogenic late Pleistocene Yedoma origins of the Yedoma stratotype exposure Duvanny Yar. To estimate the recent environmental endmember and to determine the initial mineral composition of sediment until freezing, the distribution of CWI in the active layer was studied. In addition to CWI, we studied mineral composition, heavy mineral distribution, grain size distribution and grain morphology. We suggest that cryogenic weathering likely altered polygenetic deposits (fluvial, nival, colluvial, lacustrine, alluvial, and aeolian processes) during sediment and ground ice accumulation. Moreover, we found two CWI distribution peaks in the late Pleistocene - Holocene sediments at the boundaries between glacial and interglacial ages. In conclusion, we see that the Duvanny Yar sediment facies varied by CWI, but also with grain-size distribution, suggesting environmental changes during formation. Nevertheless, post-depositional processes like cryogenic weathering have influenced sediment characteristics and should be considered in paleoenvironmental reconstructions

Radiocarbon dating of Late Pleistocene and Holocene ice wedges in Mamontova Gora, Central Yakutia

Radiocarbon dating of the Late Pleistocene and Holocene syngenetic ice wedges, exposed at Mamontova Gora, are determined. The age of the ice wedges is shown to be younger than 20 ka, but older than 10 ka BP

Minimal, average, and maximum values of δ¹⁸O in ice wedge of the sections from Mamontova Gora and Syrdakh Lake, Central Yakutia

The oxygen isotope composition of the Late Pleistocene and Holocene syngenetic ice wedges, exposed at Mamontova Gora and Syrdakh Lake, is determined. In the area of Mamontova Gora, δ¹⁸O is in the range of –24.7 to –30.9‰ for the Late Pleistocene ice wedges, and of –23.2 to –25.9‰ for the Holocene ice wedges. In the area of Syrdakh Lake, δ18O ranges from –29.2 to –32.5‰. Obtained isotope data allowed to reconstruct the average winter air temperatures

Cobalt(II) Complexes Based on Benzylmalonate Anions Exhibiting Field-Induced Single-Ion Magnet Slow Relaxation Behavior

The reaction of (NBu4)2Bzmal (where Bzmal2− is benzylmalonate dianion) with Co(OAc)2∙4H2O gives the [Co(Bzmal)(EtOH)(H2O)]n 2D-polymer (1). The addition of 2,2′-bipyridine (bpy) to the starting system results in the [Co(Bzmal)(bpy)2]·H2O·EtOH molecular complex (2). Their molecular and crystal structures were analyzed by single-crystal X-ray crystallography. An analysis of the static magnetic data supported by the SA-CASSCF/NEVPT2 calculations revealed the presence of easy-plane magnetic anisotropy in both complexes. The AC susceptibility data confirm that both complexes show a slow field-induced (HDC = 1000 Oe) magnetic relaxation behavior

Geochemical, lithological, and geochronological characteristics of sediment samples from Yedoma and thermokarst deposits in Siberia and Alaska 1998-2016

This dataset merges data from the yedoma domain in Northern Siberia (RU) and Alaska (US). It includes numerous fieldwork campaigns, which take place since 1998 . In total 224 samples from drained Thermokarst, basins and 736 Yedoma samples are included from 27 sites (17 Siberia, 10 Alaska). The laboratory methods are the following: Total organic carbon (TOC) samples were measured with a carbon-nitrogen-sulphur analyser (Elementar Vario EL III) or a TOC analyser (Elementar Vario Max C). For ice content measurement needed for bulk density calculation (bulkdens), samples were weighed in wet and ovendry state during field expeditions or dried in the lab using a freeze dryer. BD was then calculated using its inverse relationship with porosity (see Strauss et al 2013 for details)). Because pore volume is assumed to be ice saturated, the pore volume can be directly inferred from the segregated ice content. Ice content was determined by dying in the file already or with an freeze dryer in the lab. 14C dates were compiled from different sources given with locations in Table S1 in the supplement of Strauss et al 2017. Areal estimation of yedoma and degraded sites were done with literature estimates including general estimates in Strauss et al 2013. Data from local- and regional-scale analyses of Yedoma deposit versus thermokarst-affected areas (summarised in Strauss et al 2013) indicate that ~70% of the Yedoma region area is affected by degradation. The remaining Yedoma deposit extent is ~416,000 km². We further estimate that ~10% of the Yedoma region is covered with lakes and rivers and thus underlain by unfrozen deposits (150,000 km²) and ~4% is covered with other deposits including deltaic and fluvial sediments (50,000 km²), leaving ~56% (775,000 km²) of the Yedoma region covered by frozen thermokarst deposits in drained thermokarst lakes. Detailed information about the methods can be found in Strauss et al 2013 and 2017 and the supplements (https://doi.org/doi:10.1002/2013GL058088, https://doi.org/10.1016/j.earscirev.2017.07.007)

Two decades of active layer thickness monitoring in northeastern Asia

This study summarizes seasonal thawing data collected in different permafrost regions of northeast Asia over the 1995–2018 period. Empirical observations were undertaken under the Circumpolar Active Layer Monitoring (CALM) program at a range of sites across the permafrost landscapes of the Yana-Indigirka and Kolyma lowlands and the Chukotka Peninsula, and supplemented with 10 years of observations from volcanic mountainous areas of the Kamchatka Peninsula. Thaw depth observations, taken using mechanical probing at the end of the thawing season, and ground temperature measurements, were analyzed with respect to air temperatures trends. The data from 24 sites (16 in the Indigirka-Kolyma region, 5 in Chukotka and 3 in Kamchatka) reveal different reactions of the active layer thickness (ALT) to recent changes in atmospheric climate. In general, there is a positive relation between ALT and summer air temperatures. Since the early 2000s positive ALT anomalies (compared with mean data from all sites) prevail in the Kolyma and Chukotka area, with only one alas site showing a negative ALT trend. The only active site in the Kamchatka Mountains shows no significant thaw depth changes over the period of observation. Two other Kamchatka sites were affected during a volcanic eruption in 2012