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- Chuvilin, E., et al.
(author)
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In-situ temperatures and thermal properties of the East Siberian Arctic shelf sediments : Key input for understanding the dynamics of subsea permafrost
- 2022
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In: Marine and Petroleum Geology. - : Elsevier BV. - 0264-8172 .- 1873-4073. ; 138
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Journal article (peer-reviewed)abstract
- Significant reserves of methane (CH4) are held in the Arctic shelf, but the release of CH4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years. Our studies demonstrate progressive degradation of subsea permafrost which controls the scales of CH4 release from the sediment into the water-atmospheric system. Thus, new knowledge about the thermal state of subsea permafrost is crucial for better understanding of the permafrost -hydrate system and associated CH4 release from the East Siberian Arctic Shelf (ESAS) – the broadest and shallowest shelf in the World Ocean, which contains about 80% of subsea permafrost and giant pools of hydrates. Meanwhile, the ESAS, still presents large knowledge gaps in many aspects, especially with respect to subsea permafrost distribution and physical properties of bottom sediments. New field data show that the ESAS has an unfrozen (ice-free) upper sediment layer, which in-situ temperature is −1.0 to −1.8 °C and 0.6оС above the freezing point. On one hand, these cold temperature patterns may be related to the presence of subsea permafrost, which currently primarily occurs in the part of the ESAS that is shallower than 100 m, while ice-bearing sediments may also exist locally under deeper water in the Laptev Sea. On the other hand, the negative bottom sediment temperatures of −1.8 °C measured on the Laptev Sea continental slope sediments underlying water columns as deep as down to 330 m may result from dissociation of gas hydrates or possibly from dense water cascading down from the shelf. In contrast, data collected on recent expeditions in the northern Laptev shelf, zones of warmer bottom temperatures are coinciding with methane seeps, likely induced by seismic and tectonic activity in the area. These warm temperatures are not seen in the East Siberian Sea area, not even in areas of methane seeps, yet with little seismic activity.The thermal conductivity and heat capacity of bottom sediments recorded in the database of thermal parameters for the ESAS areas mainly depend on their lithification degree (density or porosity), moisture content, and particle size distribution. The thermal conductivity and heat capacity average about 1.0 W/(m·K) and 2900 kJ/(m3·K), with ±20% and ±10% variance, respectively, in all sampled Arctic sediments to a sub-bottom interval of 0–0.5 m.
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- Wechsler, A, et al.
(author)
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Generation of viable cholesterol-free mice
- 2003
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In: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 302:5653, s. 2087-2087
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Journal article (peer-reviewed)
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- Charkin, Alexander N., et al.
(author)
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Discovery and characterization of submarine groundwater discharge in the Siberian Arctic seas : a case study in the Buor-Khaya Gulf, Laptev Sea
- 2017
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In: The Cryosphere. - : Copernicus GmbH. - 1994-0416 .- 1994-0424. ; 11:5, s. 2305-2327
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Journal article (peer-reviewed)abstract
- It has been suggested that increasing terrestrial water discharge to the Arctic Ocean may partly occur as submarine groundwater discharge (SGD), yet there are no direct observations of this phenomenon in the Arctic shelf seas. This study tests the hypothesis that SGD does exist in the Siberian Arctic Shelf seas, but its dynamics may be largely controlled by complicated geocryological conditions such as permafrost. The field-observational approach in the southeastern Laptev Sea used a combination of hydrological (temperature, salinity), geological (bottom sediment drilling, geoelectric surveys), and geochemical (Ra-224, Ra-223, Ra-228, and Ra-226) techniques. Active SGD was documented in the vicinity of the Lena River delta with two different operational modes. In the first system, groundwater discharges through tectonogenic permafrost talik zones was registered in both winter and summer. The second SGD mechanism was cryogenic squeezing out of brine and water-soluble salts detected on the periphery of ice hummocks in the winter. The proposed mechanisms of groundwater transport and discharge in the Arctic land-shelf system is elaborated. Through salinity vs. Ra-224 and Ra-224/Ra-223 diagrams, the three main SGD-influenced water masses were identified and their end-member composition was constrained. Based on simple mass-balance box models, discharge rates at sites in the submarine permafrost talik zone were 1.7 x 10(6) m(3) d(-1) or 19.9 m(3) s(-1), which is much higher than the April discharge of the Yana River. Further studies should apply these techniques on a broader scale with the objective of elucidating the relative importance of the SGD transport vector relative to surface freshwater discharge for both water balance and aquatic components such as dissolved organic carbon, carbon dioxide, methane, and nutrients.
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- Nazarewicz, Julia, et al.
(author)
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Assessing risk among women who perpetrate intimate partner abuse
- 2024
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In: Psychology, Crime and Law. - : Routledge. - 1068-316X .- 1477-2744.
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Journal article (peer-reviewed)abstract
- This paper presents a prospective evaluation of the predictive validity of three risk assessment instruments in a sample of Australian women identified by police as intimate partner abuse (IPA) perpetrators. Using a subsample from Spivak et al. (2020), 410 female IPA perpetrators were screened using the Victoria Police Screening Assessment for Family Violence Risk (VP-SAFvR) and evaluated alongside two samples of 60 and 229 female IPA perpetrators assessed using the Brief Spousal Assault Form for the Evaluation of Risk (B-SAFER) and a modified version of the Lethality Screen respectively. Of the three instruments, the VP-SAFvR possessed indicators of effective discrimination (i.e. sensitivity, specificity, area under the curve) and predictive validity (i.e. positive predictive value, negative predictive value) on general IPA recidivism and its intended outcome of family or intimate partner abuse. The B-SAFER risk judgement similarly predicted its intended outcome of physical IPA recidivism, with notable indicators of discrimination and predictive validity. The results of the Modified Lethality Screen were conversely mixed on measures of discrimination and prediction for its intended outcome of severe IPA. The current findings suggest that these instruments function consistently for women and men who are identified by police as perpetrating family or intimate partner abuse.
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