Biogeochemical and geocryological characteristics of wedge and thermokarst‐cave ice in the CRREL permafrost tunnel, Alaska

Douglas, Thomas A.; Fortier, Daniel; Shur, Y.; Kanevskiy, Mikhail; Guo, Laodong; Cai, Yihua; Bray, Matthew T.

doi:10.1002/ppp.709

Cited by 47 publications

(53 citation statements)

References 28 publications

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“…Because of their wide spatial distribution in Arctic lowlands and the measured DOC concentrations, we conclude that, of massive groundice types, ice wedges hold the greatest potential for DOC storage with a maximum of 28.6 mg L −1 . This is in good agreement with DOC measurements in a so-far limited number of ice wedges by Douglas et al (2011) in Alaska and Vonk et al (2013b) in east Siberia, who showed DOC concentrations of 18.4-68.5 mg L −1 (n = 5) and 8.8-15 mg L −1 (n = 3), respectively. Ulrich et al (2014) have calculated maximum wedgeice volumes (WIVs), which range from 31.4 to 63.2 vol % for late Pleistocene Yedoma deposits and from 6.6 to 13.2 vol % for Holocene thermokarst deposits in east Siberia and Alaska.…”

Section: Doc Stocks In Ground Ice and Relevance To Carbon Cyclingsupporting

confidence: 90%

Dissolved organic carbon (DOC) in Arctic ground ice

et al. 2015

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Abstract. Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L −1 (mean: 9.6 mg L −1 ). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg 2+ and K + . DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km 2 . This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

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Section: Doc Stocks In Ground Ice and Relevance To Carbon Cyclingsupporting

confidence: 90%

Dissolved organic carbon (DOC) in Arctic ground ice

et al. 2015

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“…Given the opportunity to function, these proteins should be capable of efficiently dealing with DNA damage as it appears. Survival in ancient permafrost and the capacity to grow and metabolize at subzero temperatures (14,24,25) were thus the primary rationales for using P. arcticus as a model for examining if bacteria can repair their DNA under conditions physicochemically similar to those found in situ, i.e., low temperature and organic carbon concentrations (total of ϳ10 mg C liter Ϫ1 ) similar to values reported for permafrost (29,30).…”

Section: Discussionmentioning

confidence: 99%

DNA Double-Strand Break Repair at −15°C

Dieser

Battista

Christner

2013

Appl Environ Microbiol

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The survival of microorganisms in ancient glacial ice and permafrost has been ascribed to their ability to persist in a dormant, metabolically inert state. An alternative possibility, supported by experimental data, is that microorganisms in frozen matrices are able to sustain a level of metabolic function that is sufficient for cellular repair and maintenance. To examine this experimentally, frozen populations of Psychrobacter arcticus 273-4 were exposed to ionizing radiation (IR) to simulate the damage incurred from natural background IR sources in the permafrost environment from over ϳ225 kiloyears (ky). High-molecularweight DNA was fragmented by exposure to 450 Gy of IR, which introduced an average of 16 double-strand breaks (DSBs) per chromosome. During incubation at ؊15°C for 505 days, P. arcticus repaired DNA DSBs in the absence of net growth. Based on the time frame for the assembly of genomic fragments by P. arcticus, the rate of DNA DSB repair was estimated at 7 to 10 DSBs year ؊1 under the conditions tested. Our results provide direct evidence for the repair of DNA lesions, extending the range of complex biochemical reactions known to occur in bacteria at frozen temperatures. Provided that sufficient energy and nutrient sources are available, a functional DNA repair mechanism would allow cells to maintain genome integrity and augment microbial survival in icy terrestrial or extraterrestrial environments. The results from decades of studying the stability of DNA in bacteria may be summarized in two uncomplicated axioms. First, genomic DNA is not inert; the genetic material will degrade with time, and damage will accumulate unless that degradation is repaired. And second, if this degradation is not reversed, the cell will die. The repair processes that cope with DNA damage are integral to life, and it is assumed that all species express means of maintaining genetic integrity.The importance of DNA repair to cell viability motivated extensive study of the biochemistry and molecular biology of these repair processes in model organisms such as Escherichia coli (1). Although the advantages of using this species for such studies are well documented, there is a question as to whether detailed knowledge of DNA repair in E. coli as observed under standard laboratory conditions adequately represents the full spectrum of bacterial responses to DNA damage. For instance, DNA repair is an energy-intensive activity (2, 3), but microbial species in nature rarely experience optimal conditions for growth or have access to nutrient excess. Without a generous supply of energy, cells may need to generate a more measured response, rationing available resources in a manner that prioritizes the most important tasks for survival. Moreover, viability in the absence of cellular reproduction is sustained only by cells that do not accumulate a level of damage (e.g., to DNA) that exceeds a threshold beyond which effective repair is no longer possible.Genomic DNA and viable bacteria are preserved in ancient ice and permafrost for hun...

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“…In addition 0.5-to-2-m thick and 6-m-wide saucer-shaped ice bodies exist which were interpreted as frozen thaw ponds by Hamilton et al (1988) and as thermokarst-cave ice by Shur et al (2004). Ice wedges and cave ice were also studied by Douglas et al (2011) and Lachniet et al (2012) for biogeochemical and radiocarbon analyses, respectively. The permafrost sequence of the Fox Tunnel is finished by Holocene alluvial deposits, radiocarbon-dated between 8.5 and 2.5 ka BP.…”

Section: Study Areamentioning

confidence: 99%

Late Quaternary paleoenvironmental records from the Chatanika River valley near Fairbanks (Alaska)

Schirrmeister

Meyer

Andreev

et al. 2016

Quaternary Science Reviews

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a b s t r a c tPerennially-frozen deposits are considered as excellent paleoenvironmental archives similar to lacustrine, deep marine, and glacier records because of the long-term and good preservation of fossil records under stable permafrost conditions. A permafrost tunnel in the Vault Creek Valley (Chatanika River Valley, near Fairbanks) exposes a sequence of frozen deposits and ground ice that provides a comprehensive set of proxies to reconstruct the late Quaternary environmental history of Interior Alaska. The multi-proxy approach includes different dating techniques (radiocarbon-accelerator mass spectrometry [AMS 14 The studied sequence consists of 36-m-thick late Quaternary deposits above schistose bedrock. Main portions of the sequence accumulated during the early and middle Wisconsin periods. The lowermost unit A consists of about 9-m-thick ice-bonded fluvial gravels with sand and peat lenses. A late Sangamon (MIS 5a) age of unit A is assumed. Spruce forest with birch, larch, and some shrubby alder dominated the vegetation. High presence of Sphagnum spores and Cyperaceae pollen points to mires in the Vault Creek Valley. The overlying unit B consists of 10-m-thick alternating fluvial gravels, loess-like silt, and sand layers, penetrated by small ice wedges. OSL dates support a stadial early Wisconsin (MIS 4) age of unit B. Pollen and plant macrofossil data point to spruce forests with some birch interspersed with wetlands around the site. The following unit C is composed of 15-m-thick ice-rich loess-like and organic-rich silt with fossil bones and large ice wedges. Unit C formed during the interstadial mid-Wisconsin (MIS 3) and stadial late Wisconsin (MIS 2) as indicated by radiocarbon ages. Post-depositional slope processes significantly deformed both, ground ice and sediments of unit C. Pollen data show that spruce forests and wetlands dominated the area. The macrofossil remains of Picea, Larix, and Alnus incana ssp. tenuifolia also prove the existence of boreal coniferous forests during the mid-Wisconsin interstadial, which were replaced by treeless tundra-steppe vegetation during the late Wisconsin stadial. Unit C is discordantly overlain by the 2-m-thick late Holocene deposits of unit D. The pollen record of unit D indicates boreal forest vegetation similar to the modern one.The permafrost record from the Vault Creek tunnel reflects more than 90 ka of periglacial landscape dynamics triggered by fluvial and eolian accumulation, and formation of ice-wedge polygons and postdepositional deformation by slope processes. The record represents a typical Wisconsin valley-bottom facies in Central Alaska.

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Biogeochemical and geocryological characteristics of wedge and thermokarst‐cave ice in the CRREL permafrost tunnel, Alaska

Cited by 47 publications

References 28 publications

Dissolved organic carbon (DOC) in Arctic ground ice

Dissolved organic carbon (DOC) in Arctic ground ice

DNA Double-Strand Break Repair at −15°C

Late Quaternary paleoenvironmental records from the Chatanika River valley near Fairbanks (Alaska)

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