Pub Date : 2022-11-01DOI: 10.1080/15230430.2022.2123859
F. Torricella, Viviana Maria Gamboa Sojo, K. Gariboldi, N. Douss, M. Musco, C. Caricchi, R. Lucchi, Katia Carbonara, C. Morigi
ABSTRACT A reconstruction of the last 2,000 years BP of environmental and oceanographic changes on the western margin of Spitsbergen was performed using a multidisciplinary approach including the fossil assemblages of diatoms, planktic and benthic foraminifera and calcareous nannofossils and the use of geochemistry (X-ray fluorescence spectroscopy, X-ray diffraction). We identified two warm periods (2,000–1,600 years BP and 1,300–700 years BP) that were associated with the Roman Warm Period and the Medieval Warm Period that alternate with colder oceanic conditions and sea ice coverage occurred during the Dark Ages (1,600–1,300 years BP) and the beginning of the Little Ice Age. During the Medieval Warm Period the occurrence of ice-rafted debris and Aulocoseira spp., a specific diatom genus commonly associated with continental freshwater, suggests significant runoff of meltwaters from local glaciers.
{"title":"Multiproxy investigation of the last 2,000 years BP marine paleoenvironmental record along the western Spitsbergen margin","authors":"F. Torricella, Viviana Maria Gamboa Sojo, K. Gariboldi, N. Douss, M. Musco, C. Caricchi, R. Lucchi, Katia Carbonara, C. Morigi","doi":"10.1080/15230430.2022.2123859","DOIUrl":"https://doi.org/10.1080/15230430.2022.2123859","url":null,"abstract":"ABSTRACT A reconstruction of the last 2,000 years BP of environmental and oceanographic changes on the western margin of Spitsbergen was performed using a multidisciplinary approach including the fossil assemblages of diatoms, planktic and benthic foraminifera and calcareous nannofossils and the use of geochemistry (X-ray fluorescence spectroscopy, X-ray diffraction). We identified two warm periods (2,000–1,600 years BP and 1,300–700 years BP) that were associated with the Roman Warm Period and the Medieval Warm Period that alternate with colder oceanic conditions and sea ice coverage occurred during the Dark Ages (1,600–1,300 years BP) and the beginning of the Little Ice Age. During the Medieval Warm Period the occurrence of ice-rafted debris and Aulocoseira spp., a specific diatom genus commonly associated with continental freshwater, suggests significant runoff of meltwaters from local glaciers.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"562 - 583"},"PeriodicalIF":2.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46109486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-31DOI: 10.1080/15230430.2022.2123858
L. Kuentz, J. Levy, M. Salvatore
ABSTRACT Antarctic water tracks and ephemeral wetlands are a primary location for biogeochemical soil processes driving cold desert soil formation. Though the spatial extent of water tracks and wetted soils has been mapped in the McMurdo Dry Valleys (MDV) on the basis of mapping darkened pixels in high-resolution commercial satellite imagery, the timescale over which water tracks and wetlands form and the duration of these biogeochemically active environments remain unknown. Here, we determine the start date and end dates and the duration of wetted soils at ten sites located across the MDV using a combination of in situ soil sensors and two complementary remote imaging platforms (Planet and WorldView) to understand the hydroclimatic processes that drive water track and wetland formation. Our remote sensing employs a terrain correction workflow that removes the contribution of differential direct illumination and small-scale shadowing on pixel brightness, reducing false positives (soils identified as wetted when in fact they are shadowed or darkened as a consequence of high phase angle). Our findings extend the water track and wetland hydroperiod by over a month, showing darkening occurring from November to March, suggesting hydrological contributions from ground ice thaw, snowmelt, and salt deliquescence and soil brine growth.
{"title":"Timing and duration of ephemeral Antarctic water tracks and wetlands using high temporal–resolution satellite imagery, high spatial–resolution satellite imagery, and ground-based sensors in the McMurdo Dry Valleys","authors":"L. Kuentz, J. Levy, M. Salvatore","doi":"10.1080/15230430.2022.2123858","DOIUrl":"https://doi.org/10.1080/15230430.2022.2123858","url":null,"abstract":"ABSTRACT Antarctic water tracks and ephemeral wetlands are a primary location for biogeochemical soil processes driving cold desert soil formation. Though the spatial extent of water tracks and wetted soils has been mapped in the McMurdo Dry Valleys (MDV) on the basis of mapping darkened pixels in high-resolution commercial satellite imagery, the timescale over which water tracks and wetlands form and the duration of these biogeochemically active environments remain unknown. Here, we determine the start date and end dates and the duration of wetted soils at ten sites located across the MDV using a combination of in situ soil sensors and two complementary remote imaging platforms (Planet and WorldView) to understand the hydroclimatic processes that drive water track and wetland formation. Our remote sensing employs a terrain correction workflow that removes the contribution of differential direct illumination and small-scale shadowing on pixel brightness, reducing false positives (soils identified as wetted when in fact they are shadowed or darkened as a consequence of high phase angle). Our findings extend the water track and wetland hydroperiod by over a month, showing darkening occurring from November to March, suggesting hydrological contributions from ground ice thaw, snowmelt, and salt deliquescence and soil brine growth.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"538 - 561"},"PeriodicalIF":2.0,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48722963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-20DOI: 10.1080/15230430.2022.2121246
Natalie Baillargeon, G. Pold, S. Natali, S. Sistla
ABSTRACT The Arctic is experiencing the greatest increase in average surface temperature globally, which is projected to amplify wildfire frequency and severity. Wildfire alters the biogeochemical characteristics of arctic ecosystems. However, the extent of these changes over time—particularly with regard to plant stoichiometries relative to community structure—is not well documented. Four years after the Yukon-Kuskokwim Delta, Alaska, experienced its largest fire season, aboveground plant and lichen biomass was harvested across a gradient of burn history: unburned (“reference”), 2015 burn (“recent burn”), and 1972 burn (“historic burn”) to assess the resilience of tundra plant communities to fire disturbance. Fire reduced aboveground biomass in the recent burn; early recovery was characterized by evergreen shrub and graminoid dominance. In the historic burn, aboveground biomass approached reference conditions despite a sustained reduction of lichen biomass. Although total plant and lichen carbon (C) and nitrogen (N) were reduced immediately following fire, N stocks recovered to a greater degree—reducing community-level C:N. Notably, at the species level, N enrichment was observed only in the recent burn. Yet, community restructuring persisted for decades following fire, reflecting a sustained reduction in N-poor lichens relative to more N-rich vascular plant species.
{"title":"Lowland tundra plant stoichiometry is somewhat resilient decades following fire despite substantial and sustained shifts in community structure","authors":"Natalie Baillargeon, G. Pold, S. Natali, S. Sistla","doi":"10.1080/15230430.2022.2121246","DOIUrl":"https://doi.org/10.1080/15230430.2022.2121246","url":null,"abstract":"ABSTRACT The Arctic is experiencing the greatest increase in average surface temperature globally, which is projected to amplify wildfire frequency and severity. Wildfire alters the biogeochemical characteristics of arctic ecosystems. However, the extent of these changes over time—particularly with regard to plant stoichiometries relative to community structure—is not well documented. Four years after the Yukon-Kuskokwim Delta, Alaska, experienced its largest fire season, aboveground plant and lichen biomass was harvested across a gradient of burn history: unburned (“reference”), 2015 burn (“recent burn”), and 1972 burn (“historic burn”) to assess the resilience of tundra plant communities to fire disturbance. Fire reduced aboveground biomass in the recent burn; early recovery was characterized by evergreen shrub and graminoid dominance. In the historic burn, aboveground biomass approached reference conditions despite a sustained reduction of lichen biomass. Although total plant and lichen carbon (C) and nitrogen (N) were reduced immediately following fire, N stocks recovered to a greater degree—reducing community-level C:N. Notably, at the species level, N enrichment was observed only in the recent burn. Yet, community restructuring persisted for decades following fire, reflecting a sustained reduction in N-poor lichens relative to more N-rich vascular plant species.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"525 - 536"},"PeriodicalIF":2.0,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41634461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-18DOI: 10.1080/15230430.2022.2123254
Agraj Upadhyay, Rajneesh Sharma, P. Mahajan
ABSTRACT Fracture initiation and propagation in a weak snow layer are two primary processes of the slab avalanche formation process. This study proposes a model for the weak snow layer and investigates the fracture propagation process. The weak snow layer is conceptualized as columns of ice sandwiched between two strong layers of snow. The strong layers are modeled as linear elastic, whereas the ice is characterized as a damaging elastoplastic material. The effective mechanical properties of the model weak layer are examined using finite element analysis and are close to the snow properties reported in the literature. This model is used in numerical propagation saw tests (PSTs) to investigate the fracture propagation process in the weak snow layer. Critical crack length (CCL) and fracture propagation speed (FPS) in PST simulations are obtained by tracking the crack tip and are in good agreement with the previously reported results. An insight into the fracture propagation process in the weak snow layer is presented through energy variation analysis in PST simulations and shown that the FPS during dynamic fracture propagation varies with the top slab’s elastic modulus, the weak layer’s fracture energy, and inertia of the overlying slab.
{"title":"Modeling weak snow layer fracture in propagation saw test using an ice column model","authors":"Agraj Upadhyay, Rajneesh Sharma, P. Mahajan","doi":"10.1080/15230430.2022.2123254","DOIUrl":"https://doi.org/10.1080/15230430.2022.2123254","url":null,"abstract":"ABSTRACT Fracture initiation and propagation in a weak snow layer are two primary processes of the slab avalanche formation process. This study proposes a model for the weak snow layer and investigates the fracture propagation process. The weak snow layer is conceptualized as columns of ice sandwiched between two strong layers of snow. The strong layers are modeled as linear elastic, whereas the ice is characterized as a damaging elastoplastic material. The effective mechanical properties of the model weak layer are examined using finite element analysis and are close to the snow properties reported in the literature. This model is used in numerical propagation saw tests (PSTs) to investigate the fracture propagation process in the weak snow layer. Critical crack length (CCL) and fracture propagation speed (FPS) in PST simulations are obtained by tracking the crack tip and are in good agreement with the previously reported results. An insight into the fracture propagation process in the weak snow layer is presented through energy variation analysis in PST simulations and shown that the FPS during dynamic fracture propagation varies with the top slab’s elastic modulus, the weak layer’s fracture energy, and inertia of the overlying slab.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"507 - 524"},"PeriodicalIF":2.0,"publicationDate":"2022-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47682674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-12DOI: 10.1080/15230430.2022.2121243
Jordan H. Seider, T. Lantz, C. Bone
ABSTRACT Warming across the low Arctic is increasing tundra vegetation productivity and facilitating the expansion of upright shrubs. We modeled the effects of warming on habitat suitability in green alder, dwarf birch, Labrador tea, bog bilberry, and lingonberry and assessed the influence of data type (true absence or pseudo-absence) on species distribution models (SDMs). We generated SDMs using the two absence data types under current (1970–2000) and future (2061–2080) climate projections. Our results show that warming leads to range expansion of all shrubs, though responses vary in magnitude and extent, with mean increases in suitability ranging from 0.080 (Labrador tea) to 0.369 (lingonberry) with true absences. Differences in driving variables and suitability projections suggest that physiological and ecological variability between species mediate responses to warming. Between data types, we observed inconsistencies in model performance, suitability projections, and variable importance. Bog bilberry and lingonberry exhibited larger differences in suitability (0.201 and 0.288, respectively), whereas alder showed similar responses (difference of 0.01). These results are important to consider when assessing changes in habitat suitability or identifying environmental or climatic determinants of species’ distributions. We suggest further development of open data repositories, facilitating access to true absence data to support conservation and land use planning.
{"title":"Tundra shrub expansion in a warming climate and the influence of data type on models of habitat suitability","authors":"Jordan H. Seider, T. Lantz, C. Bone","doi":"10.1080/15230430.2022.2121243","DOIUrl":"https://doi.org/10.1080/15230430.2022.2121243","url":null,"abstract":"ABSTRACT Warming across the low Arctic is increasing tundra vegetation productivity and facilitating the expansion of upright shrubs. We modeled the effects of warming on habitat suitability in green alder, dwarf birch, Labrador tea, bog bilberry, and lingonberry and assessed the influence of data type (true absence or pseudo-absence) on species distribution models (SDMs). We generated SDMs using the two absence data types under current (1970–2000) and future (2061–2080) climate projections. Our results show that warming leads to range expansion of all shrubs, though responses vary in magnitude and extent, with mean increases in suitability ranging from 0.080 (Labrador tea) to 0.369 (lingonberry) with true absences. Differences in driving variables and suitability projections suggest that physiological and ecological variability between species mediate responses to warming. Between data types, we observed inconsistencies in model performance, suitability projections, and variable importance. Bog bilberry and lingonberry exhibited larger differences in suitability (0.201 and 0.288, respectively), whereas alder showed similar responses (difference of 0.01). These results are important to consider when assessing changes in habitat suitability or identifying environmental or climatic determinants of species’ distributions. We suggest further development of open data repositories, facilitating access to true absence data to support conservation and land use planning.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"488 - 506"},"PeriodicalIF":2.0,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44273200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-11DOI: 10.1080/15230430.2022.2121245
A. Townsend, Kevin Berthiaume, M. Klett, J. Munroe, M. Rowlandson
ABSTRACT Most ecological studies are by necessity cast on rather short timescales, such that documenting change in phenomena that occur slowly (e.g., over decades to centuries) is quite difficult. Here, we explore variation in and covariation of two sources of information to address rates of treeline change on one mountain face in the central Rocky Mountains: repeat photography and remote sensing. The repeat photography work involved assembling and quantitatively comparing four photographs that span 148 years. The remote sensing analyses covered a shorter period (35 years) but provided quantitative measurements and fuller landscape coverage. The repeat photography results demonstrated pronounced elevational advance of erect forest, at a rate <0.3 m/year during 1873–1979 but accelerating to >1.8 m/year during 2004–2020. The remote sensing analyses reflected similar processes but also reflected considerable infilling of tree cover near treeline; consequent increases in Normalized Difference Vegetation Index (NDVI) values in the upper forested areas may thus indicate treeline advance or changes in forest characteristics below treeline. Overall, these results document (1) acceleration in rise of treeline at this site in recent decades and (2) elevational compression of vegetation zones above treeline, with important implications for conservation of nonforested alpine ecosystems. Integrating multiple streams of evidence offers complementary views and insights in analyzing this phenomenon.
{"title":"Linking repeat photography and remote sensing to assess treeline rise with climate warming: Mount of the Holy Cross, Colorado","authors":"A. Townsend, Kevin Berthiaume, M. Klett, J. Munroe, M. Rowlandson","doi":"10.1080/15230430.2022.2121245","DOIUrl":"https://doi.org/10.1080/15230430.2022.2121245","url":null,"abstract":"ABSTRACT Most ecological studies are by necessity cast on rather short timescales, such that documenting change in phenomena that occur slowly (e.g., over decades to centuries) is quite difficult. Here, we explore variation in and covariation of two sources of information to address rates of treeline change on one mountain face in the central Rocky Mountains: repeat photography and remote sensing. The repeat photography work involved assembling and quantitatively comparing four photographs that span 148 years. The remote sensing analyses covered a shorter period (35 years) but provided quantitative measurements and fuller landscape coverage. The repeat photography results demonstrated pronounced elevational advance of erect forest, at a rate <0.3 m/year during 1873–1979 but accelerating to >1.8 m/year during 2004–2020. The remote sensing analyses reflected similar processes but also reflected considerable infilling of tree cover near treeline; consequent increases in Normalized Difference Vegetation Index (NDVI) values in the upper forested areas may thus indicate treeline advance or changes in forest characteristics below treeline. Overall, these results document (1) acceleration in rise of treeline at this site in recent decades and (2) elevational compression of vegetation zones above treeline, with important implications for conservation of nonforested alpine ecosystems. Integrating multiple streams of evidence offers complementary views and insights in analyzing this phenomenon.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"478 - 487"},"PeriodicalIF":2.0,"publicationDate":"2022-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41765180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-03DOI: 10.1080/15230430.2022.2120246
V. M. Gamboa-Sojo, K. Husum, C. Morigi, D. Divine, A. Miettinen
ABSTRACT Environmental changes for the past ca. 50 years were studied in a short sediment core from inner Krossfjorden, Svalbard, investigating benthic foraminifera and stable isotopes (δ18O, δ13C). A depth–age model based on anthropogenic 137Cs time markers indicates that record covers the period from 1955 to 2007 and has sediment accumulation rates of ca. 0.3 to 1 cm/year. The benthic foraminifera are arctic and/or common in glaciomarine environments. Six fauna assemblages were identified using stratigraphically constrained cluster analysis. Benthic foraminiferal fauna assemblages are mainly dominated by Cassidulina reniforme. Elphidium clavatum is dominant from 1973 to 1986 and 2002 to 2007, likely due to greater turbidity in the water column. We interpret the increased percentages of Spiroplectammina biformis over the same intervals to reflect a slightly lower salinity probably caused by meltwater. During a short time period, 1970 to 1973, Stainforthia concava dominates the benthic foraminiferal fauna interpreted to reflect increased productivity within a marginal ice zone. Other species as Islandiella norcrossi, Nonionellina labradorica, Islandiella helenae, and Melonis barleanus also indicate more nutrient-rich waters are present but not very abundant throughout the record probably due to the glacier proximal position of the study site. The stable isotope record (δ18O) shows lighter values from 2001 to 2007, which seem to correlate well with oceanographic monitoring data showing increasing core temperatures of West Spitsbergen Current.
{"title":"Environmental changes in Krossfjorden, Svalbard, since 1950: Benthic foraminiferal and stable isotope evidence","authors":"V. M. Gamboa-Sojo, K. Husum, C. Morigi, D. Divine, A. Miettinen","doi":"10.1080/15230430.2022.2120246","DOIUrl":"https://doi.org/10.1080/15230430.2022.2120246","url":null,"abstract":"ABSTRACT Environmental changes for the past ca. 50 years were studied in a short sediment core from inner Krossfjorden, Svalbard, investigating benthic foraminifera and stable isotopes (δ18O, δ13C). A depth–age model based on anthropogenic 137Cs time markers indicates that record covers the period from 1955 to 2007 and has sediment accumulation rates of ca. 0.3 to 1 cm/year. The benthic foraminifera are arctic and/or common in glaciomarine environments. Six fauna assemblages were identified using stratigraphically constrained cluster analysis. Benthic foraminiferal fauna assemblages are mainly dominated by Cassidulina reniforme. Elphidium clavatum is dominant from 1973 to 1986 and 2002 to 2007, likely due to greater turbidity in the water column. We interpret the increased percentages of Spiroplectammina biformis over the same intervals to reflect a slightly lower salinity probably caused by meltwater. During a short time period, 1970 to 1973, Stainforthia concava dominates the benthic foraminiferal fauna interpreted to reflect increased productivity within a marginal ice zone. Other species as Islandiella norcrossi, Nonionellina labradorica, Islandiella helenae, and Melonis barleanus also indicate more nutrient-rich waters are present but not very abundant throughout the record probably due to the glacier proximal position of the study site. The stable isotope record (δ18O) shows lighter values from 2001 to 2007, which seem to correlate well with oceanographic monitoring data showing increasing core temperatures of West Spitsbergen Current.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"465 - 477"},"PeriodicalIF":2.0,"publicationDate":"2022-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46918573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-29DOI: 10.1080/15230430.2022.2118639
H. Rodenhizer, F. Belshe, G. Celis, J. Ledman, M. Mauritz, S. Goetz, T. Sankey, E. Schuur
ABSTRACT Abrupt thaw could cause permafrost ecosystems to release more carbon than is predicted from gradual thaw alone. However, thermokarst feature mapping is limited in scope, and observed responses of carbon fluxes to abrupt thaw are variable. We developed a thermokarst detection algorithm that identifies thermokarst features from a single elevation dataset with 71.5 percent accuracy and applied it in Healy, Alaska. Additionally, we investigated the landscape-level variation in carbon dioxide and methane fluxes by extent of abrupt thaw using eddy covariance. Seven percent of the site was classified as thermokarst. Water tracks were the most extensive form of thermokarst, although small pits were much more numerous. Abrupt thaw was positively correlated with carbon uptake during the growing season, when increases in gross primary productivity outpaced increases in ecosystem respiration in vegetation-dense water tracks. However, this was outweighed by higher carbon release in thermokarst features during the nongrowing season. Additionally, abrupt thaw was positively correlated with methane production nearly year-round. Our findings support the hypothesis that abrupt thaw of permafrost carbon will contribute to the permafrost climate feedback above and beyond that associated with gradual thaw and highlights the need to map thermokarst and incorporate abrupt thaw into Earth System Models.
{"title":"Abrupt permafrost thaw accelerates carbon dioxide and methane release at a tussock tundra site","authors":"H. Rodenhizer, F. Belshe, G. Celis, J. Ledman, M. Mauritz, S. Goetz, T. Sankey, E. Schuur","doi":"10.1080/15230430.2022.2118639","DOIUrl":"https://doi.org/10.1080/15230430.2022.2118639","url":null,"abstract":"ABSTRACT Abrupt thaw could cause permafrost ecosystems to release more carbon than is predicted from gradual thaw alone. However, thermokarst feature mapping is limited in scope, and observed responses of carbon fluxes to abrupt thaw are variable. We developed a thermokarst detection algorithm that identifies thermokarst features from a single elevation dataset with 71.5 percent accuracy and applied it in Healy, Alaska. Additionally, we investigated the landscape-level variation in carbon dioxide and methane fluxes by extent of abrupt thaw using eddy covariance. Seven percent of the site was classified as thermokarst. Water tracks were the most extensive form of thermokarst, although small pits were much more numerous. Abrupt thaw was positively correlated with carbon uptake during the growing season, when increases in gross primary productivity outpaced increases in ecosystem respiration in vegetation-dense water tracks. However, this was outweighed by higher carbon release in thermokarst features during the nongrowing season. Additionally, abrupt thaw was positively correlated with methane production nearly year-round. Our findings support the hypothesis that abrupt thaw of permafrost carbon will contribute to the permafrost climate feedback above and beyond that associated with gradual thaw and highlights the need to map thermokarst and incorporate abrupt thaw into Earth System Models.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"54 1","pages":"443 - 464"},"PeriodicalIF":2.0,"publicationDate":"2022-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48450356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-27DOI: 10.30758/0555-2648-2022-68-3-216-233
E. S. Egorova, Y. Mironov
The paper presents the key results of investigating Barents Sea ice age composition during the winter season, from the beginning of ice formation in October to its termination in May. To analyze the seasonal and interannual changes in the amount of ice of different age categories, we used ice charts for the Barents Sea for the period 1997–2021, produced by the Arctic and Antarctic Research Institute. The age composition of the ice cover in the Barents Sea is represented by seven standard ice categories (thickness ranges). The areas of ice of different age categories were calculated for a ten-day time interval (in percentage of the total ice area). The results are provided for three parts of the Barents Sea: western, northeastern and southeastern.The interannual changes in the amount of ice in relative fractions of ice of different age categories in the ice cover of the Barents Sea do not show significant trends for the period 1997–2021. Thus, with the observed reduction in the Barents Sea total ice area, the amount of ice of different age categories ranges within the limits of its own natural variability. Therefore, it is impossible to draw a definite conclusion about a decrease in ice cover thickness in the Barents Sea based only on data on the ice age composition over a 24-year period of observations analyzed in this study. On comparing the estimates obtained in this study of the age structure of the ice cover in the Barents Sea with those of the previous studies on this subject, we can argue that its average thickness at the beginning of the 21st century decreased, compared to the period 1971–1976. Taking into account the statistical insignificance of the trends in interannual variations in the amount of ice of different age gradations, one can maintain that quantitative changes in the age structure of the Barents Sea ice cover began earlier than 1997.
{"title":"Ice age composition in the Barents sea","authors":"E. S. Egorova, Y. Mironov","doi":"10.30758/0555-2648-2022-68-3-216-233","DOIUrl":"https://doi.org/10.30758/0555-2648-2022-68-3-216-233","url":null,"abstract":"The paper presents the key results of investigating Barents Sea ice age composition during the winter season, from the beginning of ice formation in October to its termination in May. To analyze the seasonal and interannual changes in the amount of ice of different age categories, we used ice charts for the Barents Sea for the period 1997–2021, produced by the Arctic and Antarctic Research Institute. The age composition of the ice cover in the Barents Sea is represented by seven standard ice categories (thickness ranges). The areas of ice of different age categories were calculated for a ten-day time interval (in percentage of the total ice area). The results are provided for three parts of the Barents Sea: western, northeastern and southeastern.The interannual changes in the amount of ice in relative fractions of ice of different age categories in the ice cover of the Barents Sea do not show significant trends for the period 1997–2021. Thus, with the observed reduction in the Barents Sea total ice area, the amount of ice of different age categories ranges within the limits of its own natural variability. Therefore, it is impossible to draw a definite conclusion about a decrease in ice cover thickness in the Barents Sea based only on data on the ice age composition over a 24-year period of observations analyzed in this study. On comparing the estimates obtained in this study of the age structure of the ice cover in the Barents Sea with those of the previous studies on this subject, we can argue that its average thickness at the beginning of the 21st century decreased, compared to the period 1971–1976. Taking into account the statistical insignificance of the trends in interannual variations in the amount of ice of different age gradations, one can maintain that quantitative changes in the age structure of the Barents Sea ice cover began earlier than 1997.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"24 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87635399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-27DOI: 10.30758/0555-2648-2022-68-3-248-257
N. Blagoveshchenskaya, T. Borisova, A. Kalishin, I. M. Egorov, G. A. Zagorskiy
The paper presents experimental results concerning disturbances of electron density in the high latitude ionosphere F-region, induced by powerfulHF radio waves (pump waves) with extraordinary (X-mode) polarization. The experiments were carried out at the EISCAT/Heating facility at Tromsø, Norway. The EISCAT UHF incoherent scatter radar (ISR), running at 930 MHz, co-located with a heating facility, was used to detect the disturbances of electron density. In the course of the experiments, the X-mode HF pump waves radiated into the F-region towards the magnetic zenith at different pump frequencies and ratios of the pump frequency to the critical frequency of the F2 layer.The effective radiated power was ERP = 360–820 MW. An increase in electron densities was found in a wide altitude range, giving rise to field-aligned ducts with enhanced electron density. The features and behavior of the ducts were investigated. It was revealed that the ducts are formed under quiet background geophysical conditions in a wide altitude range up to the upper altitude limit of EISCAT ISR measurements, when the pump frequencies were both below and above the critical frequency of the F2 layer (fH ≤ foF2 or fH > foF2). A plausible formation mechanism of the ducts is discussed.
{"title":"Disturbances of electron density in the high latitude upper (F-region) ionosphere induced by X-mode HF pump waves from EISCAT UHF radar observations","authors":"N. Blagoveshchenskaya, T. Borisova, A. Kalishin, I. M. Egorov, G. A. Zagorskiy","doi":"10.30758/0555-2648-2022-68-3-248-257","DOIUrl":"https://doi.org/10.30758/0555-2648-2022-68-3-248-257","url":null,"abstract":"The paper presents experimental results concerning disturbances of electron density in the high latitude ionosphere F-region, induced by powerfulHF radio waves (pump waves) with extraordinary (X-mode) polarization. The experiments were carried out at the EISCAT/Heating facility at Tromsø, Norway. The EISCAT UHF incoherent scatter radar (ISR), running at 930 MHz, co-located with a heating facility, was used to detect the disturbances of electron density. In the course of the experiments, the X-mode HF pump waves radiated into the F-region towards the magnetic zenith at different pump frequencies and ratios of the pump frequency to the critical frequency of the F2 layer.The effective radiated power was ERP = 360–820 MW. An increase in electron densities was found in a wide altitude range, giving rise to field-aligned ducts with enhanced electron density. The features and behavior of the ducts were investigated. It was revealed that the ducts are formed under quiet background geophysical conditions in a wide altitude range up to the upper altitude limit of EISCAT ISR measurements, when the pump frequencies were both below and above the critical frequency of the F2 layer (fH ≤ foF2 or fH > foF2). A plausible formation mechanism of the ducts is discussed.","PeriodicalId":8391,"journal":{"name":"Arctic, Antarctic, and Alpine Research","volume":"95 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87679176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：