The genesis of Yedoma Ice Complex permafrost – grain-size endmember modeling analysis from Siberia and Alaska
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.
AWI Organizations > Climate Sciences > Atmospheric Physics
AWI Organizations > Geosciences > Terrestrial Environmental Systems
Helmholtz Research Programs > PACES II (2014-2020) > TOPIC 1: Changes and regional feedbacks in Arctic and Antarctic > WP 1.3: Degrading permafrost landscapes; carbon, energy and water fluxes
Helmholtz Research Programs > PACES II (2014-2020) > TOPIC 3: The earth system from a polar perspective > WP 3.1: Circumpolar climate variability and global teleconnections at seasonal to orbital time scales
Arctic Land Expeditions > AK-Land_2006_Fairbanks_Barrow
Arctic Land Expeditions > RU-Land_2012_Lena_BuorKhaya
Arctic Land Expeditions > RU-Land_2012_Kytalyk_Kolyma
Arctic Land Expeditions > RU-Land_2011_Kytalyk
Arctic Land Expeditions > RU-Land_2005_Lena
Arctic Land Expeditions > RU-Land_2007_Lena
Arctic Land Expeditions > RU-Land_2010_Lena
Arctic Land Expeditions > RU-Land_1998_Lena
Arctic Land Expeditions > RU-Land_1999_Lena
Arctic Land Expeditions > RU-Land_2000_Lena
Arctic Land Expeditions > RU-Land_2003_Lena_Anabar
Arctic Land Expeditions > RU-Land_2008_Kolyma
Arctic Land Expeditions > RU-Land_2013_Yakutia