The genesis of Yedoma Ice Complex permafrost – grain-size endmember modeling analysis from Siberia and Alaska

Abstract

Abstract. The late Pleistocene Yedoma Ice Complex is an ice-rich and organic-bearing type of permafrost deposit widely distributed across Beringia and is assumed to be especially prone to deep degradation with warming temperature, which is a potential tipping point of the climate system. To better understand Yedoma formation, its local characteristics, and its regional sedimentological composition, we compiled the grain-size distributions (GSDs) of 771 samples from 23 Yedoma locations across the Arctic; samples from sites located close together were pooled to form 17 study sites. In addition, we studied 160 samples from three non-Yedoma ice-wedge polygon and floodplain sites for the comparison of Yedoma samples with Holocene depositional environments. The multimodal GSDs indicate that a variety of sediment production, transport, and depositional processes were involved in Yedoma formation. To disentangle these processes, a robust endmember modeling analysis (rEMMA) was performed. Nine robust grain-size endmembers (rEMs) characterize Yedoma deposits across Beringia. The study sites of Yedoma deposits were finally classified using cluster analysis. The resulting four clusters consisted of two to five sites that are distributed randomly across northeastern Siberia and Alaska, suggesting that the differences are associated with rather local conditions. In contrast to prior studies suggesting a largely aeolian contribution to Yedoma sedimentation, the wide range of rEMs indicates that aeolian sedimentation processes cannot explain the entire variability found in GSDs of Yedoma deposits. Instead, Yedoma sedimentation is controlled by local conditions such as source rocks and weathering processes, nearby paleotopography, and diverse sediment transport processes. Our findings support the hypothesis of a polygenetic Yedoma origin involving alluvial, fluvial, and niveo-aeolian transport; accumulation in ponding waters; and in situ frost weathering as well as postdepositional processes of solifluction, cryoturbation, and pedogenesis. The characteristic rEM composition of the Yedoma clusters will help to improve how grain-size-dependent parameters in permafrost models and soil carbon budgets are considered. Our results show the characteristic properties of ice-rich Yedoma deposits in the terrestrial Arctic. Characterizing and quantifying site-specific past depositional processes is crucial for elucidating and understanding the trajectories of this unique kind of ice-rich permafrost in a warmer future.

The cryostratigraphy of the Yedoma cliff of Sobo-Sise Island (Lena delta) reveals permafrost dynamics in the central Laptev Sea coastal region during the last 52 kyr

“…Nevertheless, several studies (e.g. Mackay, 1983;Murton and French, 1994;Kotler and Burn, 2000;Schwamborn et al, 2006;Fritz et al, 2012) have shown that δ 18 O and δD isotopes in intra-sedimental ice can still reflect environmental and climatic changes when considered with caution and/or focused on pore ice Porter and Opel, 2020). Higher δ 18 O and δD but lower d values are found in MIS 3 compared to MIS 2 (Figs.…”

“…Cryostructures of intra-sedimental ice as well as its stablewater-isotope composition host information of past freezing conditions (e.g. Dereviagin et al, 2013;Schwamborn et al, 2006). The stable-isotope composition of wedge ice is more often used in palaeoclimate studies and serves as a proxy for winter climate conditions and moisture sources because the wedge ice derives mainly from winter precipitation (e.g.…”

Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

“…Nevertheless, modern ice-scouring process can hardly affect the outer shelf sediments at >200 m depth. Furthermore, coarse-grained sediments can be exported from eroding Siberian Yedoma Ice Complex coastlines [66][67][68] or rather transported via lateral brine injections produced by bottom dense-water eddies [69].…”

Retrogressive Thaw Slumps on Ice‐Rich Permafrost Under Degradation: Results From a Large‐Scale Laboratory Simulation

“…Amphitheater‐shaped slump hollows are 30–50 m wide and are characterized by (1) their concave profile of collapsed banks and (2) highly degraded conical polygons (Figure 1) with wide troughs referred to as “baydjarakhs” (Soloviev, 1973). This ice‐rich permafrost is characterized by its medium and/or fine sand ( D 50 200–300 µm) and silty material ( D 50 18–30 µm) of Quaternary lacustrine or aeolian (loessic) origin (Schirrmeister et al., 2020; Soloviev, 1973). These sediments contain ∼30%–40% of ice by volume, in addition to large syngenetic ice wedges (Strauss et al., 2017; Ulrich et al., 2014).…”