Holocene pore‐ice δ 18 O and δ 2 H records from drained thermokarst lake basins in the Old Crow Flats, Yukon, Canada

Ice wedges in the Holocene deposits of alases and floodplains have been studied in the Kolyma Lowland region. Most ice wedges have been found within alases dated to between 11 and 4.2 cal kyr BP, corresponding to the Greenlandian and Northgrippian stages of the Holocene. This study confirms that the greatest intensity of ice wedge growth occurred during $10.5-6 cal kyr BP. A decrease in their growth was mainly caused by alas draining and reduced sedimentation. In the last 4-4.5 cal kyr BP (defined as the Meghalayan stage of the Holocene), ice wedges continued to grow in old alases, sometimes as a younger generation, as well as within young alases and floodplains of the Kolyma River and its tributaries. Mean January air temperatures were quite stable during the Holocene and varied usually approximately between À33 and À41 C, with a slight cooling during the Meghalayan stage. Minor variations in mean January air temperature may indicate a stability of winter climate of northern Yakutia, probably as a result of the stable influence of the Siberian anticyclone.

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confidence: 79%

Holocene ice wedges of the Kolyma Lowland and January paleotemperature reconstructions based on oxygen isotope records

Vasil'chuk

Budantseva

2021

“…The same positive climate trend was established for the Old Crow region (Yukon, Canada) where maximum warming was dated to 10-9 cal ka BP. 87,88 After the apparent warming stage during the first half of the Holocene recorded in most Arctic regions, further winter climatic trends were ambiguous.…”

Section: Summer Thermal Optimum During Greenlandian-northgrippian Sta...mentioning

confidence: 99%

“…However, it should be noted that these data were obtained rather for summer air temperatures, since paleotemperature reconstructions were performed on pore ice from frozen sediments. 87,88 Stable isotope records for glacial ice cores for Vavilov ice cap and Academy of Sciences ice dome, Severnaya Zemlya archipelago, 89 demonstrate a pronounced positive shift at the transition to the early Holocene thermal optimum (from 1.5 to 3.5‰ on the δ 18 O profiles), but no noticeable variations of δ 18 O values are recorded on the isotope profiles dated to the "after-optimal" period (the range of δ 18 O values did not exceed 1-2‰), indicating rather stable climate conditions.…”

Section: Comparison Of Holocene Climate Trends In the Arctic Permafro...mentioning

confidence: 99%

Holocene January paleotemperature of northwestern Siberia reconstructed based on stable isotope ratio of ice wedges

Vasil'chuk

Budantseva

2022

Ice wedges are considered as a paleoarchive of winter air temperatures as their stable isotope composition has been widely used to reconstruct winter climatic conditions in the Arctic regions. Ice wedge stable isotope records, obtained in recent decades for many Arctic permafrost areas of Russia and North America, demonstrate a clear shift from lower to higher values between the Late Pleistocene and Holocene (by 5-10‰ for δ 18 O values in some regions of the Russian Arctic), which is widely accepted as evidence of winter air temperature increase. However, the evolution of winter air temperatures during the Holocene is less clear and, according to proxy reconstructions, winter climate trends are not synchronous and may significantly vary throughout the Arctic. In this study, we investigate the stable isotope composition of Holocene syngenetic ice wedges and modern ice veinlets of northwestern Siberia.Radiocarbon dating of enclosing sediments and a few dates of organic material from ice wedges demonstrate that ice wedges grew constantly within the study area during the Holocene though early-mid-Holocene in northwestern Siberia is often considered as a thermal optimum. In fact, many proxy records indicate an increase of summer air temperatures followed by thermokarst activity, peatland formation, and northward advance of the treeline. According to our data, winter climate conditions in terms of mean air temperature of the coldest winter month (January) did not change significantly during the key Holocene stages, and during the Greenlandian and most of the Northgrippian stages (between 11.4 and 6 cal ka BP) mean January air temperature (T mJ ) varied between À21 and À30 C, and from the end of the Northgrippian, during the Meghalayan stages of Holocene (5.2-0.9 cal ka BP), T mJ varied between À24 to À28 C. Mean January air temperature during the Holocene was generally 1-2 C lower than the modern one, meanwhile the submeridional direction of T mJ isotherms and eastward decrease of T mJ values in Holocene are similar to the modern pattern.

“…Former lake basins tend to be poorly‐drained, and on centennial to millennial timescales, these conditions facilitate organic soil accumulation and the development of polygonal peatlands and wetland complexes 48,49 . These features are stable components of the landscape and can comprise a significant portion of the terrestrial environment 26,39,50–54 . As such, rapidly‐drained lake basins provide excellent systems to explore the factors influencing permafrost aggradation in a warming climate and the evolution and resilience of permafrost in emergent landscapes across continuous and extensive discontinuous permafrost zones.…”

Section: Introductionmentioning

confidence: 99%

“…48,49 These features are stable components of the landscape and can comprise a significant portion of the terrestrial environment. 26,39,[50][51][52][53][54] As such, rapidly-drained lake basins provide excellent systems to explore the factors influencing permafrost aggradation in a warming climate and the evolution and resilience of permafrost in emergent landscapes across continuous and extensive discontinuous permafrost zones. In this study, we describe the surface conditions (soil, vegetation, snow, and ground temperature) at six lake basins that drained between 20 and $100 years prior to our fieldwork.…”

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confidence: 99%

Impacts of ecological succession and climate warming on permafrost aggradation in drained lake basins of the Tuktoyaktuk Coastlands, Northwest Territories, Canada

Lantz

Kokelj

2022

Rapidly increasing air temperatures will alter permafrost conditions across the Arctic, but variation in soils, vegetation, snow conditions, and their effects on ground thermal regime complicate prediction across spatial and temporal scales. Processes that result in the emergence of new surfaces (lake drainage, channel migration, isostatic uplift, etc.) provide an opportunity to assess the factors influencing permafrost aggradation and terrain evolution under a warming climate. In this study we describe ground temperatures, vegetation, and snow and soil conditions at six drained lake basins (DLBs) that have exposed new terrain in the Tuktoyaktuk Coastlands in the last 20-100 years. We also use one-dimensional thermal modeling to assess the impact of ecological succession and future climate scenarios on permafrost conditions in historical and future DLBs. Our field observations show that deep snow pack and shallow organic layers at shrub-dominated DLBs promote increased thaw depth and ground temperatures compared to a sedge-dominated DLB and two ancient DLB reference sites. Modeling of past and future drainages shows that climate warming projected under RCP 8.5 will reduce rates of permafrost aggradation and thickness, and drive top-down thaw that could degrade permafrost in shrub-dominated DLBs by the end of the century. Permafrost at sedge-dominated sites was more resilient to warming under RCP 8.5, with the onset of top-down thaw delayed until about 2080.Together, this indicates that the effects of ecological succession on organic soil development and snow drifting will strongly influence the aggradation and resilience of permafrost in DLBs. Our analysis suggests that DLBs and other emergent landscapes will be the first permafrost-free environments to develop under a warming climate in the continuous permafrost zone. K E Y W O R D S climate change, drained lake, permafrost, tundra 1 | INTRODUCTION Air temperatures in northern Canada have increased at more than double the average global rate. 1,2 Accelerated warming has increased permafrost temperatures and active-layer thickness at sites across theThe data used in this study will be made available through a Northwest Territories Geological Survey Open Data Report.