Taylor D. Sullivan, A. Parsekian, Jane Sharp, P. Hanke, F. Thalasso, M. Shapley, M. Engram, K. W. Walter Anthony
The occurrence and magnitude of natural fossil methane (CH4) emissions in the Arctic are poorly known. Emission of geologic CH4, a potent greenhouse gas, originating beneath permafrost is of particular interest due to the potential for positive feedback to climate warming, whereby accelerated permafrost thaw releases permafrost‐trapped CH4 in a future warmer climate. The development of through‐going taliks in Arctic lakes overlying hydrocarbon reservoirs is one mechanism of releasing geologically sourced, subpermafrost CH4. Here we use novel gas flux measurements, geophysical observations of the subsurface, shallow sediment coring, high‐resolution bathymetry measurements, and lake water chemistry measurements to produce a synoptic survey of the gas vent system in Esieh Lake, a northwest Alaska lake with exceedingly large geologic CH4 seep emissions. We find that microbially produced fossil CH4 is being vented though a narrow thaw conduit below Esieh Lake through pockmarks on the lake bottom. This is one of the highest flux geologic CH4 seep fields known in the terrestrial environment and potentially the highest flux single methane seep. The poleward retreat of continuous permafrost may have implications for more subcap CH4 release with increased permafrost thaw.
{"title":"Influence of permafrost thaw on an extreme geologic methane seep","authors":"Taylor D. Sullivan, A. Parsekian, Jane Sharp, P. Hanke, F. Thalasso, M. Shapley, M. Engram, K. W. Walter Anthony","doi":"10.1002/ppp.2114","DOIUrl":"https://doi.org/10.1002/ppp.2114","url":null,"abstract":"The occurrence and magnitude of natural fossil methane (CH4) emissions in the Arctic are poorly known. Emission of geologic CH4, a potent greenhouse gas, originating beneath permafrost is of particular interest due to the potential for positive feedback to climate warming, whereby accelerated permafrost thaw releases permafrost‐trapped CH4 in a future warmer climate. The development of through‐going taliks in Arctic lakes overlying hydrocarbon reservoirs is one mechanism of releasing geologically sourced, subpermafrost CH4. Here we use novel gas flux measurements, geophysical observations of the subsurface, shallow sediment coring, high‐resolution bathymetry measurements, and lake water chemistry measurements to produce a synoptic survey of the gas vent system in Esieh Lake, a northwest Alaska lake with exceedingly large geologic CH4 seep emissions. We find that microbially produced fossil CH4 is being vented though a narrow thaw conduit below Esieh Lake through pockmarks on the lake bottom. This is one of the highest flux geologic CH4 seep fields known in the terrestrial environment and potentially the highest flux single methane seep. The poleward retreat of continuous permafrost may have implications for more subcap CH4 release with increased permafrost thaw.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"484 - 502"},"PeriodicalIF":5.0,"publicationDate":"2021-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2114","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42250882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The processes of freezing–thawing and hydration–dissociation change the content of liquid water that coexists with ice or hydrate in porous media, such as frozen soils and hydrate‐bearing sediments, changing their physicomechanical properties. In this study, a generalized phase equilibrium equation is presented for both frozen soils and hydrate‐bearing sediments by considering the capillary and osmotic pressures. The liquid water content is related to temperature depression, plotted as the soil freezing characteristic curve (SFCC) or the soil hydration characteristic curve (SHCC), by combining the generalized phase equilibrium equation and the soil‐water characteristic curve (SWCC). From the SFCC or the SHCC, the phase equilibrium surface can be calculated in the space of temperature, pressure, and liquid water content. The proposed generalized phase equilibrium equation and the model of SFCC and SHCC can help to estimate the physicomechanical properties that depend on the fraction of the liquid or solid phase in porous media. Finally, the SHCC is employed to analyze the dissociation of hydrate‐bearing sediments using various methods.
{"title":"Comparison of freezing and hydration characteristics for porous media","authors":"Jiazuo Zhou, Wenpeng Liang, Xiangchuan Meng, Changfu Wei","doi":"10.1002/ppp.2116","DOIUrl":"https://doi.org/10.1002/ppp.2116","url":null,"abstract":"The processes of freezing–thawing and hydration–dissociation change the content of liquid water that coexists with ice or hydrate in porous media, such as frozen soils and hydrate‐bearing sediments, changing their physicomechanical properties. In this study, a generalized phase equilibrium equation is presented for both frozen soils and hydrate‐bearing sediments by considering the capillary and osmotic pressures. The liquid water content is related to temperature depression, plotted as the soil freezing characteristic curve (SFCC) or the soil hydration characteristic curve (SHCC), by combining the generalized phase equilibrium equation and the soil‐water characteristic curve (SWCC). From the SFCC or the SHCC, the phase equilibrium surface can be calculated in the space of temperature, pressure, and liquid water content. The proposed generalized phase equilibrium equation and the model of SFCC and SHCC can help to estimate the physicomechanical properties that depend on the fraction of the liquid or solid phase in porous media. Finally, the SHCC is employed to analyze the dissociation of hydrate‐bearing sediments using various methods.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"702 - 713"},"PeriodicalIF":5.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2116","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48232414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Simulations with a one‐dimensional heat transfer model (TONE) were performed to reproduce the near surface ground temperature regime in the four main types of soil profiles found in Narsajuaq River Valley (Nunavik, Canada) for the period 1990–2100. The permafrost thermal regime was simulated using climate data from a reanalysis (1948–2002), climate stations (1989–1991, 2002–2019) and simulations based on climate warming scenarios RCP4.5 and RCP8.5 (2019–2100). The model was calibrated based on extensive field measurements made between 1989 and 2019. The results were used to estimate when soil thermal contraction cracking will eventually stop and to forecast the melting of ice wedges due to active‐layer thickening. For the period 1990–2019, all soil profiles experienced cracking every year until 2006, when cracking became intermittent during a warm period before completely stopping in 2009–2010, after which cracking resumed during colder years. Ice‐wedge tops melted from 1992 to 2010 as the active layer thickened, indicating that top‐down ice‐wedge degradation can occur simultaneously with cracking and growth in width. Our predictions show that ice wedges in the valley will completely stop cracking between 2024 and 2096, first in sandy soils and later in soils with thicker organic horizons. The timing will also depend on greenhouse gas concentration trajectories. All ice wedges in the study area will probably experience some degradation of their main body before the end of the century, causing their roots to become relict ice by the end of the 21st century.
{"title":"Modeled (1990–2100) variations in active‐layer thickness and ice‐wedge activity near Salluit, Nunavik (Canada)","authors":"Samuel Gagnon, M. Allard","doi":"10.1002/ppp.2109","DOIUrl":"https://doi.org/10.1002/ppp.2109","url":null,"abstract":"Simulations with a one‐dimensional heat transfer model (TONE) were performed to reproduce the near surface ground temperature regime in the four main types of soil profiles found in Narsajuaq River Valley (Nunavik, Canada) for the period 1990–2100. The permafrost thermal regime was simulated using climate data from a reanalysis (1948–2002), climate stations (1989–1991, 2002–2019) and simulations based on climate warming scenarios RCP4.5 and RCP8.5 (2019–2100). The model was calibrated based on extensive field measurements made between 1989 and 2019. The results were used to estimate when soil thermal contraction cracking will eventually stop and to forecast the melting of ice wedges due to active‐layer thickening. For the period 1990–2019, all soil profiles experienced cracking every year until 2006, when cracking became intermittent during a warm period before completely stopping in 2009–2010, after which cracking resumed during colder years. Ice‐wedge tops melted from 1992 to 2010 as the active layer thickened, indicating that top‐down ice‐wedge degradation can occur simultaneously with cracking and growth in width. Our predictions show that ice wedges in the valley will completely stop cracking between 2024 and 2096, first in sandy soils and later in soils with thicker organic horizons. The timing will also depend on greenhouse gas concentration trajectories. All ice wedges in the study area will probably experience some degradation of their main body before the end of the century, causing their roots to become relict ice by the end of the 21st century.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"447 - 467"},"PeriodicalIF":5.0,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2109","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42612249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Near‐surface wedges of massive ice commonly outline polygons in tundra lowlands, but such polygons have been difficult to identify on hillslopes because soil movement flattens the ridges and infills the troughs that form beside and above the ice wedges. Over the past three decades, the active layer has thickened near the western Arctic coast of Canada and consequent thawing of ice wedges has been detected by remote sensing for flat terrain but not, generally, on hillslopes. Annual field surveys (1996–2018) at the Illisarvik field site of thaw depth and ground surface elevation show the mean subsidence rate above hillslope ice wedges has been up to 32 mm a−1 since thaw depth reached the ice‐wedge tops in 2007. Annual mean ground temperatures at the site are about −3.0°C beneath late‐winter snow depths characteristic of the ice‐wedge troughs but about −5.3°C under conditions of the intervening polygons. The rate of thaw subsidence is high for natural, subaerial disturbances because meltwater from the ice wedges runs off downslope. The rate is constant, because the thickness of seasonally thawed ground above the ice wedges and the ice content of the ground remain the same while the troughs develop. Observations of changes in surface elevation in northern Banks Island between the late 1970s and 2019 show troughs on hillslopes where none was previously visible. Development of these troughs creates regional thermokarst landscapes, distinct from the widely recognized results of thawing relict glacier ice, that are now widespread over Canada's western Arctic coastlands. Recognition of ice‐wedge occurrence and accelerated thaw subsidence on hillslopes is important in the design of infrastructure proposed for construction in rolling permafrost terrain.
{"title":"Long‐term field measurements of climate‐induced thaw subsidence above ice wedges on hillslopes, western Arctic Canada","authors":"C. Burn, A. Lewkowicz, M. Wilson","doi":"10.1002/ppp.2113","DOIUrl":"https://doi.org/10.1002/ppp.2113","url":null,"abstract":"Near‐surface wedges of massive ice commonly outline polygons in tundra lowlands, but such polygons have been difficult to identify on hillslopes because soil movement flattens the ridges and infills the troughs that form beside and above the ice wedges. Over the past three decades, the active layer has thickened near the western Arctic coast of Canada and consequent thawing of ice wedges has been detected by remote sensing for flat terrain but not, generally, on hillslopes. Annual field surveys (1996–2018) at the Illisarvik field site of thaw depth and ground surface elevation show the mean subsidence rate above hillslope ice wedges has been up to 32 mm a−1 since thaw depth reached the ice‐wedge tops in 2007. Annual mean ground temperatures at the site are about −3.0°C beneath late‐winter snow depths characteristic of the ice‐wedge troughs but about −5.3°C under conditions of the intervening polygons. The rate of thaw subsidence is high for natural, subaerial disturbances because meltwater from the ice wedges runs off downslope. The rate is constant, because the thickness of seasonally thawed ground above the ice wedges and the ice content of the ground remain the same while the troughs develop. Observations of changes in surface elevation in northern Banks Island between the late 1970s and 2019 show troughs on hillslopes where none was previously visible. Development of these troughs creates regional thermokarst landscapes, distinct from the widely recognized results of thawing relict glacier ice, that are now widespread over Canada's western Arctic coastlands. Recognition of ice‐wedge occurrence and accelerated thaw subsidence on hillslopes is important in the design of infrastructure proposed for construction in rolling permafrost terrain.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"261 - 276"},"PeriodicalIF":5.0,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2113","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45702783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two years after the sad and sudden loss of Professor Hugh M. French (May 11, 2019), we commemorate his scientific life, leadership, and friendship with this special issue of Permafrost and Periglacial Processes (PPP), the journal that he founded in 1990 and edited for almost 16 years until 2006. This is the second such issue in his honour, because volume 16 number 1 appeared in 2005 on the occasion of his retirement from the University of Ottawa, where he taught and carried out research from 1967 until 2003. This special issue examines some of the topics particularly dear to Hugh within areas of the world that he loved, such as the Canadian Arctic (Figure 1), the UK, and China. During his long career, Hugh wrote more than 160 papers covering many periglacial and permafrost topics. He adeptly incorporated his knowledge and field experience in The Periglacial Environment, his well-known and much-used textbook, which ran to four editions published in 1976, 1996, 2007, and 2017. While he particularly focused on ground ice and cryostratigraphy, he made substantial contributions to topics such as thermokarst processes and landforms (Figure 2), frost mounds, slope processes and pediments, periglacial involutions, and weathering processes and related landforms including in hot deserts such as in Australia (Figure 3). His interest in Quaternary environments started during his early research in the UK and continued throughout his life, with analyses of deposits and relict landforms in many parts of the world, including the eastern USA, Europe, China and Antarctica. Hugh also worked on engineering problems in permafrost areas, especially in the Canadian Arctic, including those related to oil exploratory drilling and disposal of drilling fluids. He wrote conceptual papers, especially about periglacial environments and geomorphology and geocryology, and also assessed the scientific lives of the pioneering permafrost scientists such as J. R. Mackay and S. Taber. Given the great variety of topics to which Hugh contributed, we start this special issue with the broad field of conceptual and historical papers.
{"title":"Hugh French memorial for Permafrost and Periglacial Processes","authors":"M. Guglielmin, J. Murton, A. Lewkowicz","doi":"10.1002/ppp.2112","DOIUrl":"https://doi.org/10.1002/ppp.2112","url":null,"abstract":"Two years after the sad and sudden loss of Professor Hugh M. French (May 11, 2019), we commemorate his scientific life, leadership, and friendship with this special issue of Permafrost and Periglacial Processes (PPP), the journal that he founded in 1990 and edited for almost 16 years until 2006. This is the second such issue in his honour, because volume 16 number 1 appeared in 2005 on the occasion of his retirement from the University of Ottawa, where he taught and carried out research from 1967 until 2003. This special issue examines some of the topics particularly dear to Hugh within areas of the world that he loved, such as the Canadian Arctic (Figure 1), the UK, and China. During his long career, Hugh wrote more than 160 papers covering many periglacial and permafrost topics. He adeptly incorporated his knowledge and field experience in The Periglacial Environment, his well-known and much-used textbook, which ran to four editions published in 1976, 1996, 2007, and 2017. While he particularly focused on ground ice and cryostratigraphy, he made substantial contributions to topics such as thermokarst processes and landforms (Figure 2), frost mounds, slope processes and pediments, periglacial involutions, and weathering processes and related landforms including in hot deserts such as in Australia (Figure 3). His interest in Quaternary environments started during his early research in the UK and continued throughout his life, with analyses of deposits and relict landforms in many parts of the world, including the eastern USA, Europe, China and Antarctica. Hugh also worked on engineering problems in permafrost areas, especially in the Canadian Arctic, including those related to oil exploratory drilling and disposal of drilling fluids. He wrote conceptual papers, especially about periglacial environments and geomorphology and geocryology, and also assessed the scientific lives of the pioneering permafrost scientists such as J. R. Mackay and S. Taber. Given the great variety of topics to which Hugh contributed, we start this special issue with the broad field of conceptual and historical papers.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2112","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45147774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Shur, B. Jones, M. Kanevskiy, T. Jorgenson, M. Jones, David H. Fortier, E. Stephani, A. Vasiliev
Riverbank erosion in yedoma regions strongly affects landscape evolution, biogeochemical cycling, sediment transport, and organic and nutrient fluxes to the Arctic Ocean. Since 2006, we have studied the 35‐m‐high Itkillik River yedoma bluff in northern Alaska, whose retreat rate during 1995–2010 was up to 19 m/yr, which is among the highest rates worldwide. This study extends our previous observations of bluff evolution and shows that average bluff‐top retreat rates decreased from 8.7–10.0 m/yr during 2011–2014 to 4.5–5.8 m/yr during 2015–2019, and bluff‐base retreat rates for the same time period decreased from 4.7–7.5 m/yr to 1.3–1.7 m/yr, correspondingly. Bluff evolution initially involves rapid fluvio‐thermal erosion at the base and block collapse, following by slowdown in river erosion and continuing thermal denudation of the retreating headwall with formation of baydzherakhs. Eventually, input of sediment and water from the headwall diminishes, vegetation develops, and slope gradually stabilizes. The step change in the fluvial–geomorphic system has resulted in a 60% decline in the volumetric mobilization of sediment and organic carbon between 2011 and 2019. Our findings stress the importance of sustained observations at key permafrost region study sites to elucidate critical information related to past and potential landscape evolution in the Arctic.
{"title":"Fluvio‐thermal erosion and thermal denudation in the yedoma region of northern Alaska: Revisiting the Itkillik River exposure","authors":"Y. Shur, B. Jones, M. Kanevskiy, T. Jorgenson, M. Jones, David H. Fortier, E. Stephani, A. Vasiliev","doi":"10.1002/ppp.2105","DOIUrl":"https://doi.org/10.1002/ppp.2105","url":null,"abstract":"Riverbank erosion in yedoma regions strongly affects landscape evolution, biogeochemical cycling, sediment transport, and organic and nutrient fluxes to the Arctic Ocean. Since 2006, we have studied the 35‐m‐high Itkillik River yedoma bluff in northern Alaska, whose retreat rate during 1995–2010 was up to 19 m/yr, which is among the highest rates worldwide. This study extends our previous observations of bluff evolution and shows that average bluff‐top retreat rates decreased from 8.7–10.0 m/yr during 2011–2014 to 4.5–5.8 m/yr during 2015–2019, and bluff‐base retreat rates for the same time period decreased from 4.7–7.5 m/yr to 1.3–1.7 m/yr, correspondingly. Bluff evolution initially involves rapid fluvio‐thermal erosion at the base and block collapse, following by slowdown in river erosion and continuing thermal denudation of the retreating headwall with formation of baydzherakhs. Eventually, input of sediment and water from the headwall diminishes, vegetation develops, and slope gradually stabilizes. The step change in the fluvial–geomorphic system has resulted in a 60% decline in the volumetric mobilization of sediment and organic carbon between 2011 and 2019. Our findings stress the importance of sustained observations at key permafrost region study sites to elucidate critical information related to past and potential landscape evolution in the Arctic.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"277 - 298"},"PeriodicalIF":5.0,"publicationDate":"2021-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44929585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stephen Taber's early work on ice segregation and frost heaving was far ahead of its time. His laboratory experiments regarding ice segregation led to our current understanding of frost heave by civil and geotechnical engineers building roads and other structures in cold regions. It also laid the foundation for later process‐oriented field studies of cold‐climate geomorphic processes. Taber's 1943 regional monograph on the origin and history of perennially frozen ground in Alaska, published by the Geological Society of America, was the earliest example of regional cryostratigraphy, and pioneered the regional permafrost and Quaternary studies undertaken later by Katasonov, Popov, Mackay, Péwé, Hopkins, and others. An important dimension of Taber's Alaska work was his application of knowledge gained through laboratory experimentation to the interpretation of ground‐ice exposures in the field. While S. W. Muller is widely regarded as the “father” of permafrost studies in North America, Taber is properly viewed as the “progenitor” of cryostratigraphic studies, although he is not yet widely regarded as such. This study uses archival resources to provide historical context regarding the development of Taber's monograph, to investigate details about the review and publication process it underwent, and to explore the question of why it remains undervalued.
{"title":"Stephen Taber and the development of North American cryostratigraphy and periglacial geomorphology","authors":"F. Nelson, H. French","doi":"10.1002/ppp.2096","DOIUrl":"https://doi.org/10.1002/ppp.2096","url":null,"abstract":"Stephen Taber's early work on ice segregation and frost heaving was far ahead of its time. His laboratory experiments regarding ice segregation led to our current understanding of frost heave by civil and geotechnical engineers building roads and other structures in cold regions. It also laid the foundation for later process‐oriented field studies of cold‐climate geomorphic processes. Taber's 1943 regional monograph on the origin and history of perennially frozen ground in Alaska, published by the Geological Society of America, was the earliest example of regional cryostratigraphy, and pioneered the regional permafrost and Quaternary studies undertaken later by Katasonov, Popov, Mackay, Péwé, Hopkins, and others. An important dimension of Taber's Alaska work was his application of knowledge gained through laboratory experimentation to the interpretation of ground‐ice exposures in the field. While S. W. Muller is widely regarded as the “father” of permafrost studies in North America, Taber is properly viewed as the “progenitor” of cryostratigraphic studies, although he is not yet widely regarded as such. This study uses archival resources to provide historical context regarding the development of Taber's monograph, to investigate details about the review and publication process it underwent, and to explore the question of why it remains undervalued.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"266 ","pages":"213 - 230"},"PeriodicalIF":5.0,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2096","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50932285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Iwahana, Zachary S Cooper, S. Carpenter, J. Deming, H. Eicken
Cryopeg is a layer within permafrost containing a significant amount of cryotic unfrozen water due to dissolved salts. To explore the origin and development of cryopeg and associated brines found near Utqiaġvik, we sampled extensively within the Barrow Permafrost Tunnel. We found two types of cryopeg brines based on their distinctive locations: (a) intra‐ice brine (IiB), entirely bounded by massive ground ice, and not previously observed in the Northern Hemisphere; and (b) intra‐sediment brine (IsB), found as expected in unfrozen sediments within permafrost. The encountered IiBs were situated in small ellipsoidal or more complex shaped pockets within the massive ice at roughly atmospheric pressure. Radiocarbon dating suggests that the IiB segregated from IsB‐bearing cryopeg beneath the massive ice at about 11 ka BP, at the earliest. From geochemical analyses, IsB lenses were interpreted as having developed through repeated evaporation and cryoconcentration of seawater in a lagoonal environment, then isolated when the surrounding sediment froze and became covered by an upper sediment unit around 40 ka BP or earlier. The discovery of IiB and development of origin scenarios for both brine types validate the importance of high‐resolution sampling as enabled by the unique facility of a permafrost tunnel.
Cryopeg是永久冻土中的一层，由于溶解的盐，含有大量的冷冻未冻水。为了探索Utqiaġvik附近发现的冷冻冰和相关盐水的起源和发展，我们在巴罗永久冻土隧道内进行了广泛采样。根据其独特的位置，我们发现了两种类型的冷冻卤水：（a）冰内卤水（IiB），完全由大块地面冰包围，以前在北半球没有观测到；和（b）沉积物内盐水（IsB），如预期的那样，在永久冻土内的未冻结沉积物中发现。遇到的IIB位于大致大气压下的大块冰内的小椭球或形状更复杂的口袋中。放射性碳年代测定表明，IiB最早在约11 ka BP的温度下从大块冰下的含IsB的冷冻样品中分离出来。根据地球化学分析，IsB透镜体被解释为是通过泻湖环境中海水的反复蒸发和低温浓缩而形成的，然后在周围沉积物冻结并被40 ka BP或更早的上层沉积物单元覆盖时被分离。IiB的发现和两种盐水类型的起源场景的开发验证了高分辨率采样的重要性，因为永久冻土隧道的独特设施。
{"title":"Intra‐ice and intra‐sediment cryopeg brine occurrence in permafrost near Utqiaġvik (Barrow)","authors":"G. Iwahana, Zachary S Cooper, S. Carpenter, J. Deming, H. Eicken","doi":"10.1002/ppp.2101","DOIUrl":"https://doi.org/10.1002/ppp.2101","url":null,"abstract":"Cryopeg is a layer within permafrost containing a significant amount of cryotic unfrozen water due to dissolved salts. To explore the origin and development of cryopeg and associated brines found near Utqiaġvik, we sampled extensively within the Barrow Permafrost Tunnel. We found two types of cryopeg brines based on their distinctive locations: (a) intra‐ice brine (IiB), entirely bounded by massive ground ice, and not previously observed in the Northern Hemisphere; and (b) intra‐sediment brine (IsB), found as expected in unfrozen sediments within permafrost. The encountered IiBs were situated in small ellipsoidal or more complex shaped pockets within the massive ice at roughly atmospheric pressure. Radiocarbon dating suggests that the IiB segregated from IsB‐bearing cryopeg beneath the massive ice at about 11 ka BP, at the earliest. From geochemical analyses, IsB lenses were interpreted as having developed through repeated evaporation and cryoconcentration of seawater in a lagoonal environment, then isolated when the surrounding sediment froze and became covered by an upper sediment unit around 40 ka BP or earlier. The discovery of IiB and development of origin scenarios for both brine types validate the importance of high‐resolution sampling as enabled by the unique facility of a permafrost tunnel.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"427 - 446"},"PeriodicalIF":5.0,"publicationDate":"2021-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2101","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43179905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Uncertainties about landscape evolution under cold, nonglacial conditions raise a question fundamental to periglacial geomorphology: what and where are periglacial landscapes? To answer this, with an emphasis on lowland periglacial areas, the present study distinguishes between characteristic and polygenetic periglacial landscapes, and considers how complete is the footprint of periglaciation? Using a conceptual framework of landscape sensitivity and change, the study applies four geological criteria (periglacial persistence, extraglacial regions, ice‐rich substrates, and aggradation of sediment and permafrost) through the last 3.5 million years of the late Cenozoic to identify permafrost regions in the Northern Hemisphere. In limited areas of unglaciated permafrost regions are characteristic periglacial landscapes whose morphology has been adjusted essentially to present (i.e., Holocene interglacial) process conditions, namely thermokarst landscapes, and mixed periglacial–alluvial and periglacial–deltaic landscapes. More widespread in past and present permafrost regions are polygenetic periglacial landscapes, which inherit ancient landsurfaces on which periglacial landforms are superimposed to varying degrees, presently or previously. Such landscapes comprise relict accumulation plains and aprons, frost‐susceptible and nonfrost‐susceptible terrains, cryopediments, and glacial–periglacial landscapes. Periglaciation can produce topographic fingerprints at mesospatial scales (103–105 m): (1) relict accumulation plains and aprons form where long‐term sedimentation buried landsurfaces; and (2) plateaux with convexo–concave hillslopes and inset with valleys, formed by bedrock brecciation, mass wasting, and stream incision in frost‐susceptible terrain.
{"title":"What and where are periglacial landscapes?","authors":"J. Murton","doi":"10.1002/ppp.2102","DOIUrl":"https://doi.org/10.1002/ppp.2102","url":null,"abstract":"Uncertainties about landscape evolution under cold, nonglacial conditions raise a question fundamental to periglacial geomorphology: what and where are periglacial landscapes? To answer this, with an emphasis on lowland periglacial areas, the present study distinguishes between characteristic and polygenetic periglacial landscapes, and considers how complete is the footprint of periglaciation? Using a conceptual framework of landscape sensitivity and change, the study applies four geological criteria (periglacial persistence, extraglacial regions, ice‐rich substrates, and aggradation of sediment and permafrost) through the last 3.5 million years of the late Cenozoic to identify permafrost regions in the Northern Hemisphere. In limited areas of unglaciated permafrost regions are characteristic periglacial landscapes whose morphology has been adjusted essentially to present (i.e., Holocene interglacial) process conditions, namely thermokarst landscapes, and mixed periglacial–alluvial and periglacial–deltaic landscapes. More widespread in past and present permafrost regions are polygenetic periglacial landscapes, which inherit ancient landsurfaces on which periglacial landforms are superimposed to varying degrees, presently or previously. Such landscapes comprise relict accumulation plains and aprons, frost‐susceptible and nonfrost‐susceptible terrains, cryopediments, and glacial–periglacial landscapes. Periglaciation can produce topographic fingerprints at mesospatial scales (103–105 m): (1) relict accumulation plains and aprons form where long‐term sedimentation buried landsurfaces; and (2) plateaux with convexo–concave hillslopes and inset with valleys, formed by bedrock brecciation, mass wasting, and stream incision in frost‐susceptible terrain.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"186 - 212"},"PeriodicalIF":5.0,"publicationDate":"2021-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2102","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45917518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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