Preliminary paleoenvironmental analysis of permafrost deposits at Batagaika megaslump, Yana Uplands, northeast Siberia

Pollard

2019

Environ. Res. Lett.

104

An increase in retrogressive thaw slump (RTS) activity has been observed in the Arctic in recent decades. However, a gap exists between observations in high Arctic polar desert regions where mean annual ground temperatures are as cold as −16.5°C and vegetation coverage is sparse. In this study, we present a ∼30 year record of annual RTS observations (frequency and distribution) from 1989 to 2018 within the Eureka Sound Lowlands, Ellesmere and Axel Heiberg Islands. Record summer warmth in 2011 and 2012 promoted rapid RTS initialization, increasing active slumps from 100 in a given year or less to over 200 regionally and promoting RTS initiation in previously unaffected terrain. Differential GPS and remote sensing observations of 12 RTSs initiated during this period (2011-2018) provided a mean headwall retreat rate for all RTSs of 6.2 m yr −1 and for specific RTSs up to 26.7 m yr −1 . To better understand the dynamics of climate and terrain factors controlling RTS headwall retreat rates we explored RTS interactions by correlating headwall retreat with climate factors (thawing degree days, annual rainfall and annual snowfall) and terrain factors (aspect and slope). Our findings indicate a sensitivity of cold permafrost in the high Arctic to climate-driven thermokarst initiation, but the decoupling of RTS dynamics from climate appears to occur over time for individual RTS as terrain factors take on a greater role controlling headwall retreat. Detailed observations of thermokarst development in a high Arctic polar desert permafrost setting are important as it demonstrates the sensitivity of this system to changes in summer temperatures and highlight differences to changes occurring in other Arctic permafrost regions.

Section: Rts Occurrence and Retreat Ratessupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Rapid initialization of retrogressive thaw slumps in the Canadian high Arctic and their response to climate and terrain factors

Pollard

2019

Environ. Res. Lett.

104

“…Mean d values at the coastal sites are higher (compared to MIS 3), between 4 ‰ and 12 ‰ (e.g. Opel et al, 2011;Meyer et al, 2002b;Wetterich et al, 2008. In contrast, in the Yana Highlands, the Late Holocene mean d value of 6 ‰ is lower compared to MIS 3, whereas Late Holocene d values in central Yakutia (between 6 ‰ and 11 ‰) are rather similar to MIS 3 values (Popp et al, 2006).…”

Section: Holocenementioning

confidence: 90%

Past climate and continentality inferred from ice wedges at Batagay megaslump in the Northern Hemisphere's most continental region, Yana Highlands, interior Yakutia

et al. 2019

Self Cite

Abstract. Ice wedges in the Yana Highlands of interior Yakutia – the most continental region of the Northern Hemisphere – were investigated to elucidate changes in winter climate and continentality that have taken place since the Middle Pleistocene. The Batagay megaslump exposes ice wedges and composite wedges that were sampled from three cryostratigraphic units: the lower ice complex of likely pre-Marine Isotope Stage (MIS) 6 age, the upper ice complex (Yedoma) and the upper sand unit (both MIS 3 to 2). A terrace of the nearby Adycha River provides a Late Holocene (MIS 1) ice wedge that serves as a modern reference for interpretation. The stable-isotope composition of ice wedges in the MIS 3 upper ice complex at Batagay is more depleted (mean δ18O about −35 ‰) than those from 17 other ice-wedge study sites across coastal and central Yakutia. This observation points to lower winter temperatures and therefore higher continentality in the Yana Highlands during MIS 3. Likewise, more depleted isotope values are found in Holocene wedge ice (mean δ18O about −29 ‰) compared to other sites in Yakutia. Ice-wedge isotopic signatures of the lower ice complex (mean δ18O about −33 ‰) and of the MIS 3–2 upper sand unit (mean δ18O from about −33 ‰ to −30 ‰) are less distinctive regionally. The latter unit preserves traces of fast formation in rapidly accumulating sand sheets and of post-depositional isotopic fractionation.

“…One of the most conspicuous manifestations of thermokarst is the retrogressive thaw slump (RTS; Fig. 1), which develops as a result of mass wasting in ice-rich glacial deposits across northwestern Canada, Alaska, and western Siberia (Kokelj et al, 2017a) and in Yedoma regions of Alaska and Siberia (Murton et al, 2017). Thaw slumps are widespread throughout glaciated terrain in the western Canadian Arctic (Kokelj et al, 2017a;, including on the Peel Plateau .…”

Section: Introductionmentioning

confidence: 99%

Retrogressive thaw slumps temper dissolved organic carbon delivery to streams of the Peel Plateau, NWT, Canada

2017

Abstract. In Siberia and Alaska, permafrost thaw has been associated with significant increases in the delivery of dissolved organic carbon (DOC) to recipient stream ecosystems. Here, we examine the effect of retrogressive thaw slumps (RTSs) on DOC concentration and transport, using data from eight RTS features on the Peel Plateau, NWT, Canada. Like extensive regions of northwestern Canada, the Peel Plateau is comprised of thick, ice-rich tills that were deposited at the margins of the Laurentide Ice Sheet. RTS features are now widespread in this region, with headwall exposures up to 30 m high and total disturbed areas often exceeding 20 ha. We find that intensive slumping on the Peel Plateau is universally associated with decreasing DOC concentrations downstream of slumps, even though the composition of slump-derived dissolved organic matter (DOM; assessed using specific UV absorbance and slope ratios) is similar to permafrost-derived DOM from other regions. Comparisons of upstream and downstream DOC flux relative to fluxes of total suspended solids suggest that the substantial fine-grained sediments released by RTS features may sequester DOC. Runoff obtained directly from slump rill water, above entry into recipient streams, indicates that the deepest RTS features, which thaw the greatest extent of buried, Pleistocene-aged glacial tills, release low-concentration DOC when compared to paired upstream, undisturbed locations, while shallower features, with exposures that are more limited to a relict Holocene active layer, have within-slump DOC concentrations more similar to upstream sites. Finally, fine-scale work at a single RTS site indicates that temperature and precipitation serve as primary environmental controls on above-slump and below-slump DOC flux, but it also shows that the relationship between climatic parameters and DOC flux is complex for these dynamic thermokarst features. These results demonstrate that we should expect clear variation in thermokarst-associated DOC mobilization across Arctic regions. However, they also show that within-region variation in thermokarst intensity and landscape composition is critical for determining the biogeochemical response. Geological and climate legacy shape the physical and chemical composition of permafrost and thermokarst potential. As such, these factors must be considered in predictions of land-to-water carbon mobilization in a warming Arctic.