G. Gastineau, C. Frankignoul, Yongqi Gao, Yu‐Chiao Liang, Young‐Oh Kwon, A. Cherchi, R. Ghosh, E. Manzini, D. Matei, J. Mecking, L. Suo, T. Tian, Shuting Yang, Ying Zhang
Abstract. The main drivers of the continental Northern Hemisphere snow cover are investigated in the 1979–2014 period. Four observational datasets are used as are two large multi-model ensembles of atmosphere-only simulations with prescribed sea surface temperature (SST) and sea ice concentration (SIC). A first ensemble uses observed interannually varying SST and SIC conditions for 1979–2014, while a second ensemble is identical except for SIC with a repeated climatological cycle used. SST and external forcing typically explain 10 % to 25 % of the snow cover variance in model simulations, with a dominant forcing from the tropical and North Pacific SST during this period. In terms of the climate influence of the snow cover anomalies, both observations and models show no robust links between the November and April snow cover variability and the atmospheric circulation 1 month later. On the other hand, the first mode of Eurasian snow cover variability in January, with more extended snow over western Eurasia, is found to precede an atmospheric circulation pattern by 1 month, similar to a negative Arctic oscillation (AO). A decomposition of the variability in the model simulations shows that this relationship is mainly due to internal climate variability. Detailed outputs from one of the models indicate that the western Eurasia snow cover anomalies are preceded by a negative AO phase accompanied by a Ural blocking pattern and a stratospheric polar vortex weakening. The link between the AO and the snow cover variability is strongly related to the concomitant role of the stratospheric polar vortex, with the Eurasian snow cover acting as a positive feedback for the AO variability in winter. No robust influence of the SIC variability is found, as the sea ice loss in these simulations only drives an insignificant fraction of the snow cover anomalies, with few agreements among models.
{"title":"Forcing and impact of the Northern Hemisphere continental snow cover in 1979–2014","authors":"G. Gastineau, C. Frankignoul, Yongqi Gao, Yu‐Chiao Liang, Young‐Oh Kwon, A. Cherchi, R. Ghosh, E. Manzini, D. Matei, J. Mecking, L. Suo, T. Tian, Shuting Yang, Ying Zhang","doi":"10.5194/tc-17-2157-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2157-2023","url":null,"abstract":"Abstract. The main drivers of the continental Northern Hemisphere snow cover are investigated in the 1979–2014 period. Four observational datasets are used\u0000as are two large multi-model ensembles of atmosphere-only simulations with prescribed sea surface temperature (SST) and sea ice concentration (SIC). A\u0000first ensemble uses observed interannually varying SST and SIC conditions for 1979–2014, while a second ensemble is identical except for SIC with\u0000a repeated climatological cycle used. SST and external forcing typically explain 10 % to 25 % of the snow cover variance in model\u0000simulations, with a dominant forcing from the tropical and North Pacific SST during this period. In terms of the climate influence of the snow cover\u0000anomalies, both observations and models show no robust links between the November and April snow cover variability and the atmospheric circulation\u00001 month later. On the other hand, the first mode of Eurasian snow cover variability in January, with more extended snow over western Eurasia, is\u0000found to precede an atmospheric circulation pattern by 1 month, similar to a negative Arctic oscillation (AO). A decomposition of the variability\u0000in the model simulations shows that this relationship is mainly due to internal climate variability. Detailed outputs from one of the models\u0000indicate that the western Eurasia snow cover anomalies are preceded by a negative AO phase accompanied by a Ural blocking pattern and a\u0000stratospheric polar vortex weakening. The link between the AO and the snow cover variability is strongly related to the concomitant role of the\u0000stratospheric polar vortex, with the Eurasian snow cover acting as a positive feedback for the AO variability in winter. No robust influence of the\u0000SIC variability is found, as the sea ice loss in these simulations only drives an insignificant fraction of the snow cover anomalies, with few\u0000agreements among models.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41682900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Thompson-Munson, N. Wever, C. Stevens, J. Lenaerts, B. Medley
Abstract. The Greenland Ice Sheet's (GrIS) firn layer buffers the ice sheet's contribution to sea level rise by storing meltwater in its pore space. However, available pore space and meltwater retention capability is lost due to ablation of the firn layer and refreezing of meltwater as near-surface ice slabs in the firn. Understanding how firn properties respond to climate is important for constraining the GrIS's future contribution to sea level rise in a warming climate. Observations of firn density provide detailed information about firn properties, but they are spatially and temporally limited. Here we use two firn models, the physics-based SNOWPACK model and the Community Firn Model configured with a semi-empirical densification equation (CFM-GSFC), to quantify firn properties across the GrIS from 1980 through 2020. We use an identical forcing (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) atmospheric reanalysis) for SNOWPACK and the CFM-GSFC in order to isolate firn model differences. To evaluate the models, we compare simulated firn properties, including firn air content (FAC), to measurements from the Surface Mass Balance and Snow on Sea Ice Working Group (SUMup) dataset of snow and firn density. Both models perform well (mean absolute percentage errors of 14 % in SNOWPACK and 16 % in the CFM-GSFC), though their performance is hindered by the spatial resolution of the atmospheric forcing. In the ice-sheet-wide simulations, the 1980–1995 average spatially integrated FAC (i.e., air volume in the firn) for the upper 100 m is 34 645 km3 from SNOWPACK and 28 581 km3 from the CFM-GSFC. The discrepancy in the magnitude of the modeled FAC stems from differences in densification with depth and variations in the sensitivity of the models to atmospheric forcing. In more recent years (2005–2020), both models simulate substantial depletion of pore space. During this period, the spatially integrated FAC across the entire GrIS decreases by 3.2 % (−66.6 km3 yr−1) in SNOWPACK and 1.5 % (−17.4 km3 yr−1) in the CFM-GSFC. These differing magnitudes demonstrate how model differences propagate throughout the FAC record. Over the full modeled record (1980–2020), SNOWPACK simulates a loss of pore space equivalent to 3 mm of sea level rise buffering, while the CFM-GSFC simulates a loss of 1 mm. The greatest depletion in FAC is along the margins and especially along the western margin where observations and models show the formation of near-surface, low-permeability ice slabs that may inhibit meltwater storage.
{"title":"An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020)","authors":"M. Thompson-Munson, N. Wever, C. Stevens, J. Lenaerts, B. Medley","doi":"10.5194/tc-17-2185-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2185-2023","url":null,"abstract":"Abstract. The Greenland Ice Sheet's (GrIS) firn layer buffers the ice sheet's contribution to sea level rise by storing meltwater in its pore space. However, available pore space and meltwater retention capability is lost due to ablation of the firn layer and refreezing of meltwater as near-surface ice slabs in the firn. Understanding how firn properties respond to climate is important for constraining the GrIS's future contribution to sea level rise in a warming climate. Observations of firn density provide detailed information about firn properties, but they are spatially and temporally limited. Here we use two firn models, the physics-based SNOWPACK model and the Community Firn Model configured with a semi-empirical densification equation (CFM-GSFC), to quantify firn properties across the GrIS from 1980 through 2020. We use an identical forcing (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) atmospheric reanalysis) for SNOWPACK and the CFM-GSFC in order to isolate firn model differences. To evaluate the models, we compare simulated firn properties, including firn air content (FAC), to measurements from the Surface Mass Balance and Snow on Sea Ice Working Group (SUMup) dataset of snow and firn density. Both models perform well (mean absolute percentage errors of 14 % in SNOWPACK and 16 % in the CFM-GSFC), though their performance is hindered by the spatial resolution of the atmospheric forcing. In the ice-sheet-wide simulations, the 1980–1995 average spatially integrated FAC (i.e., air volume in the firn) for the upper 100 m is 34 645 km3 from SNOWPACK and 28 581 km3 from the CFM-GSFC. The discrepancy in the magnitude of the modeled FAC stems from differences in densification with depth and variations in the sensitivity of the models to atmospheric forcing. In more recent years (2005–2020), both models simulate substantial depletion of pore space. During this period, the spatially integrated FAC across the entire GrIS decreases by 3.2 % (−66.6 km3 yr−1) in SNOWPACK and 1.5 % (−17.4 km3 yr−1) in the CFM-GSFC. These differing magnitudes demonstrate how model differences propagate throughout the FAC record. Over the full modeled record (1980–2020), SNOWPACK simulates a loss of pore space equivalent to 3 mm of sea level rise buffering, while the CFM-GSFC simulates a loss of 1 mm. The greatest depletion in FAC is along the margins and especially along the western margin where observations and models show the formation of near-surface, low-permeability ice slabs that may inhibit meltwater storage.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49641108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daniel Moreno-Parada, J. Alvarez-Solas, Javier Blasco, M. Montoya, A. Robinson
Abstract. In the last decades, great effort has been made to reconstruct the Laurentide Ice Sheet (LIS) during the Last Glacial Maximum (LGM; ca. 21 000 years before present, 21 kyr ago). Uncertainties underlying its modelling have led to notable differences in fundamental features such as its maximum elevation, extent and total volume. As a result, the uncertainty in ice dynamics and thus in ice extent, volume and ice stream stability remains large. We herein use a higher-order three-dimensional ice sheet model to simulate the LIS under LGM boundary conditions for a number of basal friction formulations of varying complexity. Their consequences for the Laurentide ice streams, configuration, extent and volume are explicitly quantified. Total volume and ice extent generally reach a constant equilibrium value that falls close to prior LIS reconstructions. Simulations exhibit high sensitivity to the dependency of the basal shear stress on the sliding velocity. In particular, a regularised Coulomb friction formulation appears to be the best choice in terms of ice volume and ice stream realism. Pronounced differences are found when the basal friction stress is thermomechanically coupled: the base remains colder, and the LIS volume is lower than in the purely mechanical friction scenario counterpart. Thermomechanical coupling is fundamental for producing rapid ice streaming, yet it leads to a similar ice distribution overall.
{"title":"Simulating the Laurentide Ice Sheet of the Last Glacial Maximum","authors":"Daniel Moreno-Parada, J. Alvarez-Solas, Javier Blasco, M. Montoya, A. Robinson","doi":"10.5194/tc-17-2139-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2139-2023","url":null,"abstract":"Abstract. In the last decades, great effort has been made to reconstruct the Laurentide Ice Sheet (LIS) during the Last Glacial Maximum (LGM; ca. 21 000 years before present, 21 kyr ago). Uncertainties underlying its modelling have led to notable differences in fundamental features such as its maximum elevation, extent and total volume. As a result, the uncertainty in ice dynamics and thus in ice extent, volume and ice stream stability remains large. We herein use a higher-order three-dimensional ice sheet model to simulate the LIS under LGM boundary conditions for a number of basal friction formulations of varying complexity. Their consequences for the Laurentide ice streams, configuration, extent and volume are explicitly quantified. Total volume and ice extent generally reach a constant equilibrium value that falls close to prior LIS reconstructions. Simulations exhibit high sensitivity to the dependency of the basal shear stress on the sliding velocity. In particular, a regularised Coulomb friction formulation appears to be the best choice in terms of ice volume and ice stream realism. Pronounced differences are found when the basal friction stress is thermomechanically coupled: the base remains colder, and the LIS volume is lower than in the purely mechanical friction scenario counterpart. Thermomechanical coupling is fundamental for producing rapid ice streaming, yet it leads to a similar ice distribution overall.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49358185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Eichler, M. Legrand, T. Jenk, S. Preunkert, C. Andersson, S. Eckhardt, M. Engardt, A. Plach, M. Schwikowski
Abstract. Individual high-Alpine ice cores have been proven to contain a well-preserved history of past anthropogenic air pollution in western Europe. The question of how representative one ice core is with respect to the reconstruction of atmospheric composition in the source region has not been addressed so far. Here, we present the first study systematically comparing longer-term ice-core records (1750–2015 CE) of various anthropogenic compounds, such as major inorganic aerosol constituents (NH4+, NO3-, SO42-), black carbon (BC), and trace species (Cd, F−, Pb). Depending on the data availability for the different air pollutants, up to five ice cores from four high-Alpine sites located in the European Alps analysed by different laboratories were considered. Whereas absolute concentration levels can partly differ depending on the prevailing seasonal distribution of accumulated precipitation, all seven investigated anthropogenic compounds are in excellent agreement between the various sites for their respective, species-dependent longer-term concentration trends. This is related to common source regions of air pollution impacting the four sites less than 100 km away including western European countries surrounding the Alps. For individual compounds, the Alpine ice-core composites developed in this study allowed us to precisely time the onset of pollution caused by industrialization in western Europe. Extensive emissions from coal combustion and agriculture lead to an exceeding of pre-industrial (1750–1850) concentration levels already at the end of the 19th century for BC, Pb, exSO42- (non-dust, non-sea salt SO42-), and NH4+, respectively. However, Cd, F−, and NO3- concentrations started surpassing pre-industrial values only in the 20th century, predominantly due to pollution from zinc and aluminium smelters and traffic. The observed maxima of BC, Cd, F−, Pb, and exSO42- concentrations in the 20th century and a significant decline afterwards clearly reveal the efficiency of air pollution control measures such as the desulfurization of coal, the introduction of filters and scrubbers in power plants and metal smelters, and the ban of leaded gasoline improving the air quality in western Europe. In contrast, NO3- and NH4+ concentration records show levels in the beginning of the 21th century which are unprecedented in the context of the past 250 years, indicating that the introduced abatement measures to reduce these pollutants were insufficient to have a major effect at high altitudes in western Europe. Only four ice-core composite records (BC, F−, Pb, exSO42-) of the seven investigated pollutants correspond well with modelled trends, suggesting inaccuracies of the emission estimates or an incomplete representation of chemical reaction mechanisms in the models for the other pollutants. Our results demonstrate that individual ice-core records from different sites in the European Alps generally provide a spatially representative signal of anthropogeni
{"title":"Consistent histories of anthropogenic western European air pollution preserved in different Alpine ice cores","authors":"A. Eichler, M. Legrand, T. Jenk, S. Preunkert, C. Andersson, S. Eckhardt, M. Engardt, A. Plach, M. Schwikowski","doi":"10.5194/tc-17-2119-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2119-2023","url":null,"abstract":"Abstract. Individual high-Alpine ice cores have been proven to contain a well-preserved history of past anthropogenic air pollution in western Europe. The\u0000question of how representative one ice core is with respect to the reconstruction of atmospheric composition in the source region has not been\u0000addressed so far. Here, we present the first study systematically comparing longer-term ice-core records (1750–2015 CE) of various anthropogenic\u0000compounds, such as major inorganic aerosol constituents (NH4+, NO3-, SO42-), black carbon (BC), and trace\u0000species (Cd, F−, Pb). Depending on the data availability for the different air pollutants, up to five ice cores from four\u0000high-Alpine sites located in the European Alps analysed by different laboratories were considered. Whereas absolute concentration levels can partly\u0000differ depending on the prevailing seasonal distribution of accumulated precipitation, all seven investigated anthropogenic compounds are in\u0000excellent agreement between the various sites for their respective, species-dependent longer-term concentration trends. This is related to common\u0000source regions of air pollution impacting the four sites less than 100 km away including western European countries surrounding the\u0000Alps. For individual compounds, the Alpine ice-core composites developed in this study allowed us to precisely time the onset of pollution caused by\u0000industrialization in western Europe. Extensive emissions from coal combustion and agriculture lead to an exceeding of pre-industrial\u0000(1750–1850) concentration levels already at the end of the 19th century for BC, Pb, exSO42- (non-dust, non-sea salt\u0000SO42-), and NH4+, respectively. However, Cd, F−, and NO3- concentrations started surpassing\u0000pre-industrial values only in the 20th century, predominantly due to pollution from zinc and aluminium smelters and traffic. The observed maxima of\u0000BC, Cd, F−, Pb, and exSO42- concentrations in the 20th century and a significant decline afterwards clearly\u0000reveal the efficiency of air pollution control measures such as the desulfurization of coal, the introduction of filters and scrubbers in power plants\u0000and metal smelters, and the ban of leaded gasoline improving the air quality in western Europe. In contrast, NO3- and NH4+\u0000concentration records show levels in the beginning of the 21th century which are unprecedented in the context of the past 250 years, indicating\u0000that the introduced abatement measures to reduce these pollutants were insufficient to have a major effect at high altitudes in western Europe. Only\u0000four ice-core composite records (BC, F−, Pb, exSO42-) of the seven investigated pollutants correspond well with\u0000modelled trends, suggesting inaccuracies of the emission estimates or an incomplete representation of chemical reaction mechanisms in the models for\u0000the other pollutants. Our results demonstrate that individual ice-core records from different sites in the European Alps generally provide a spatially\u0000representative signal of anthropogeni","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48813576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Coastal polynyas around the Antarctic continent are regions of very strong ocean–atmosphere heat and moisture exchange that are important for local and regional weather, sea ice production, and water mass formation. Due to extreme atmospheric conditions (very strong offshore winds, low air temperature, as well as humidity) the surface ocean layer in polynyas is highly turbulent, with mixing due to combined Langmuir, wind-induced, and buoyancy-driven turbulence. One of the visible signs of complex interactions between the mixed-layer dynamics and the forming sea ice are frazil streaks, elongated patches of high ice concentration separated by areas of open water. In spite of their ubiquity, observational and modelling analyses of frazil streaks have been very limited largely due to the fact that their significance for heat flux and ice production is only just becoming apparent. In this study, the first comprehensive analysis of the spatial variability of surface frazil concentration is performed for the Terra Nova Bay Polynya (TNBP). Frazil streaks are identified in high-resolution (pixel size 10–15 m) visible satellite imagery, and their properties (surface area, width, spacing, and orientation) are linked to the meteorological forcing (wind speed and air temperature). This provides a simple statistical tool for estimating the extent and ice coverage of the region of high ice production under given meteorological conditions. It is also shown that the orientation of narrow streaks tends to agree with the wind direction, suggesting the dominating role of the local wind forcing in their formation. Very wide streaks, in turn, deviate from that pattern, as they are presumably influenced by several additional factors, including local water circulation and the associated convergence zones. An analysis of peak wavelengths and directions determined from the images, compared to analogous open-water wavelengths computed with a spectral wave model, demonstrates a significant slow-down in the observed wave growth in TNBP. This suggests an important role of frazil streaks in modifying wind-wave growth and/or dissipation in polynyas.
摘要南极大陆周围的沿海波利尼西亚是海洋-大气热量和水分交换非常强烈的区域，这对当地和区域天气、海冰产生和水团形成非常重要。由于极端的大气条件（非常强的离岸流、低空气温度和湿度），波利尼西亚的表层海洋高度湍流，由于Langmuir、风致和浮力驱动的组合湍流而混合。混合层动力学和形成的海冰之间复杂相互作用的一个明显迹象是frazil条纹，这是由开阔水域隔开的高冰浓度的细长斑块。尽管frazil条纹无处不在，但其观测和建模分析一直非常有限，这在很大程度上是因为它们对热通量和冰产生的意义才刚刚变得明显。在本研究中，首次对Terra Nova Bay Polynya（TNBP）的地表frazil浓度的空间变异性进行了综合分析。Frazil条纹以高分辨率（像素大小为10-15 m） 可见卫星图像及其特性（表面积、宽度、间距和方向）与气象强迫（风速和气温）有关。这为估计给定气象条件下高冰产量地区的范围和冰覆盖率提供了一个简单的统计工具。研究还表明，窄条纹的方向往往与风向一致，这表明局部风力在其形成中起主导作用。非常宽的条纹反过来偏离了这种模式，因为它们可能受到几个其他因素的影响，包括地表水循环和相关的辐合带。与用光谱波模型计算的模拟开放水域波长相比，对图像中确定的峰值波长和方向的分析表明，TNBP中观测到的波增长显著放缓。这表明frazil条纹在改变波阵中的风浪增长和/或消散方面发挥了重要作用。
{"title":"Spatial characteristics of frazil streaks in the Terra Nova Bay Polynya from high-resolution visible satellite imagery","authors":"K. Bradtke, A. Herman","doi":"10.5194/tc-17-2073-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2073-2023","url":null,"abstract":"Abstract. Coastal polynyas around the Antarctic continent are\u0000regions of very strong ocean–atmosphere heat and moisture exchange that are\u0000important for local and regional weather, sea ice production, and water mass\u0000formation. Due to extreme atmospheric conditions (very strong offshore\u0000winds, low air temperature, as well as humidity) the surface ocean layer in\u0000polynyas is highly turbulent, with mixing due to combined Langmuir,\u0000wind-induced, and buoyancy-driven turbulence. One of the visible signs of\u0000complex interactions between the mixed-layer dynamics and the forming sea\u0000ice are frazil streaks, elongated patches of high ice concentration\u0000separated by areas of open water. In spite of their ubiquity, observational\u0000and modelling analyses of frazil streaks have been very limited largely due\u0000to the fact that their significance for heat flux and ice production is only\u0000just becoming apparent. In this study, the first comprehensive analysis of\u0000the spatial variability of surface frazil concentration is performed for the\u0000Terra Nova Bay Polynya (TNBP). Frazil streaks are identified in\u0000high-resolution (pixel size 10–15 m) visible satellite imagery, and their\u0000properties (surface area, width, spacing, and orientation) are linked to the\u0000meteorological forcing (wind speed and air temperature). This provides a\u0000simple statistical tool for estimating the extent and ice coverage of the\u0000region of high ice production under given meteorological conditions. It is\u0000also shown that the orientation of narrow streaks tends to agree with the\u0000wind direction, suggesting the dominating role of the local wind forcing in\u0000their formation. Very wide streaks, in turn, deviate from that pattern, as\u0000they are presumably influenced by several additional factors, including\u0000local water circulation and the associated convergence zones. An analysis of\u0000peak wavelengths and directions determined from the images, compared to\u0000analogous open-water wavelengths computed with a spectral wave model,\u0000demonstrates a significant slow-down in the observed wave growth in TNBP.\u0000This suggests an important role of frazil streaks in modifying wind-wave\u0000growth and/or dissipation in polynyas.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47232551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Antarctic ice shelves provide buttressing support to the ice sheet, stabilising the flow of grounded ice and its contribution to global sea levels. Over the past 50 years, satellite observations have shown ice shelves collapse, thin, and retreat; however, there are few measurements of the Antarctic-wide change in ice shelf area. Here, we use MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data to measure the change in ice shelf calving front position and area on 34 ice shelves in Antarctica from 2009 to 2019. Over the last decade, a reduction in the area on the Antarctic Peninsula (6693 km2) and West Antarctica (5563 km2) has been outweighed by area growth in East Antarctica (3532 km2) and the large Ross and Ronne–Filchner ice shelves (14 028 km2). The largest retreat was observed on the Larsen C Ice Shelf, where 5917 km2 of ice was lost during an individual calving event in 2017, and the largest area increase was observed on Ronne Ice Shelf in East Antarctica, where a gradual advance over the past decade (535 km2 yr−1) led to a 5889 km2 area gain from 2009 to 2019. Overall, the Antarctic ice shelf area has grown by 5305 km2 since 2009, with 18 ice shelves retreating and 16 larger shelves growing in area. Our observations show that Antarctic ice shelves gained 661 Gt of ice mass over the past decade, whereas the steady-state approach would estimate substantial ice loss over the same period, demonstrating the importance of using time-variable calving flux observations to measure change.
{"title":"Change in Antarctic ice shelf area from 2009 to 2019","authors":"Julia R. Andreasen, A. Hogg, H. Selley","doi":"10.5194/tc-17-2059-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2059-2023","url":null,"abstract":"Abstract. Antarctic ice shelves provide buttressing support to the ice sheet, stabilising the flow of grounded ice and its contribution to global sea levels. Over the past 50 years, satellite observations have shown ice shelves collapse, thin, and retreat; however, there are few measurements of the Antarctic-wide change in ice shelf area. Here, we use MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data to measure the change in ice shelf calving front position and area on 34 ice shelves in Antarctica from 2009 to 2019. Over the last decade, a reduction in the area on the Antarctic Peninsula (6693 km2) and West Antarctica (5563 km2) has been outweighed by area growth in East Antarctica (3532 km2) and the large Ross and Ronne–Filchner ice shelves (14 028 km2). The largest retreat was observed on the Larsen C Ice Shelf, where 5917 km2 of ice was lost during an individual calving event in 2017, and the largest area increase was observed on Ronne Ice Shelf in East Antarctica, where a gradual advance over the past decade (535 km2 yr−1) led to a 5889 km2 area gain from 2009 to 2019. Overall, the Antarctic ice shelf area has grown by 5305 km2 since 2009, with 18 ice shelves retreating and 16 larger shelves growing in area. Our observations show that Antarctic ice shelves gained 661 Gt of ice mass over the past decade, whereas the steady-state approach would estimate substantial ice loss over the same period, demonstrating the importance of using time-variable calving flux observations to measure change.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46722134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yaodan Zhang, M. Fregona, John Loehr, Joonatan Ala-Könni, Shuang Song, M. Leppäranta, Zhijun Li
Abstract. Lake ice melting and breakup form a fast, nonlinear process with important mechanical, chemical, and biological consequences. The process is difficult to study in the field due to safety issues, and therefore only little is known about its details. In the present work, the field data were collected on foot, by hydrocopter, and by boat for a full time series of the evolution of ice thickness, structure, and geochemistry through the melting period. The observations were made in lake Pääjärvi in 2018 (pilot study) and 2022. In 2022, the maximum thickness of ice was 55 cm with 60 % snow ice, and in 40 d the ice melted by 33 cm from the surface and 22 cm from the bottom while the porosity increased from less than 5 % to 40 %–50 % at breakup. In 2018, the snow-ice layer was thin, and bottom and internal melting dominated the ice decay. The mean melting rates were 1.31 cm d−1 in 2022 and 1.55 cm d−1 in 2018. In 2022 the electrical conductivity (EC) of ice was 11.4 ± 5.79 µS cm−1, which is 1 order of magnitude lower than in the lake water, and ice pH was 6.44 ± 0.28, which is lower by 0.4 than in water. The pH and EC of ice and water decreased during the ice decay except for slight increases in ice due to flushing by lake water. Chlorophyll a was less than 0.5 µg L−1 in porous ice, approximately one-third of that in the lake water. The results are important for understanding the process of ice decay with consequences for lake ecology, further development of numerical lake ice models, and modeling the safety of ice cover and ice loads.
{"title":"A field study on ice melting and breakup in a boreal lake, Pääjärvi, in Finland","authors":"Yaodan Zhang, M. Fregona, John Loehr, Joonatan Ala-Könni, Shuang Song, M. Leppäranta, Zhijun Li","doi":"10.5194/tc-17-2045-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2045-2023","url":null,"abstract":"Abstract. Lake ice melting and breakup form a fast, nonlinear process with\u0000important mechanical, chemical, and biological consequences. The process is\u0000difficult to study in the field due to safety issues, and therefore only\u0000little is known about its details. In the present work, the field data were\u0000collected on foot, by hydrocopter, and by boat for a full time series of the\u0000evolution of ice thickness, structure, and geochemistry through the melting\u0000period. The observations were made in lake Pääjärvi in 2018\u0000(pilot study) and 2022. In 2022, the maximum thickness of ice was 55 cm with\u000060 % snow ice, and in 40 d the ice melted by 33 cm from the surface\u0000and 22 cm from the bottom while the porosity increased from less than 5 %\u0000to 40 %–50 % at breakup. In 2018, the snow-ice layer was thin, and bottom\u0000and internal melting dominated the ice decay. The mean melting rates were\u00001.31 cm d−1 in 2022 and 1.55 cm d−1 in 2018. In 2022 the\u0000electrical conductivity (EC) of ice was 11.4 ± 5.79 µS cm−1, which is\u00001 order of magnitude lower than in the lake water, and ice pH was 6.44 ± 0.28, which is lower by 0.4 than in water. The pH and EC of ice and water\u0000decreased during the ice decay except for slight increases in ice due to\u0000flushing by lake water. Chlorophyll a was less than 0.5 µg L−1 in\u0000porous ice, approximately one-third of that in the lake water. The results\u0000are important for understanding the process of ice decay with consequences\u0000for lake ecology, further development of numerical lake ice models, and\u0000modeling the safety of ice cover and ice loads.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46935337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Temperature-index models have been widely used for glacier-mass projections spanning the 21st century. The ability of temperature-index models to capture non-linear responses of glacier surface mass balance (SMB) to high deviations in air temperature and solid precipitation was recently discussed in the context of mass-balance simulations employing advanced machine-learning techniques. Here, we performed numerical experiments with a classic temperature-index model and confirmed that such models are capable of detecting non-linear responses of glacier SMB to temperature and precipitation changes. Non-linearities derive from the change in the degree-day factor over the ablation season and from the lengthening of the ablation season.
{"title":"Brief communication: Non-linear sensitivity of glacier mass balance to climate attested by temperature-index models","authors":"C. Vincent, E. Thibert","doi":"10.5194/tc-17-1989-2023","DOIUrl":"https://doi.org/10.5194/tc-17-1989-2023","url":null,"abstract":"Abstract. Temperature-index models have been widely used for glacier-mass projections\u0000spanning the 21st century. The ability of temperature-index models to\u0000capture non-linear responses of glacier surface mass balance (SMB) to high deviations in air temperature and solid precipitation was recently discussed in the context of mass-balance simulations employing advanced\u0000machine-learning techniques. Here, we performed numerical experiments with a\u0000classic temperature-index model and confirmed that such models are capable\u0000of detecting non-linear responses of glacier SMB to temperature and precipitation changes. Non-linearities derive from the change in the degree-day factor over the ablation season and from the lengthening of the\u0000ablation season.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47348375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nicolas Stoll, Julien Westhoff, P. Bohleber, A. Svensson, D. Dahl-Jensen, C. Barbante, I. Weikusat
Abstract. Impurities in polar ice play a critical role in ice flow, deformation, and the integrity of the ice core record. Especially cloudy bands, visible layers with high impurity concentrations, are prominent features in ice from glacial periods. Their physical and chemical properties are poorly understood, highlighting the need to analyse them in more detail. We bridge the gap between decimetre and micrometre scales by combining the visual stratigraphy line scanner, fabric analyser, microstructure mapping, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry 2D impurity imaging. We classified approximately 1300 cloudy bands from glacial ice from the East Greenland Ice-core Project (EGRIP) ice core into seven different types. We determine the localisation and mineralogy of more than 1000 micro-inclusions at 13 depths. The majority of the minerals found are related to terrestrial dust, such as quartz, feldspar, mica, and hematite. We further found carbonaceous particles, dolomite, and gypsum in high abundance. Rutile, anatase, epidote, titanite, and grossular are infrequently observed. The 2D impurity imaging at 20 µm resolution revealed that cloudy bands are clearly distinguishable in the chemical data. Na, Mg, and Sr are mainly present at grain boundaries, whereas dust-related analytes, such as Al, Fe, and Ti, are located in the grain interior, forming clusters of insoluble impurities. We present novel vast micrometre-resolution insights into cloudy bands and describe the differences within and outside these bands. Combining the visual and chemical data results in new insights into the formation of different cloudy band types and could be the starting point for future in-depth studies on impurity signal integrity and internal deformation in deep polar ice cores.
{"title":"Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within","authors":"Nicolas Stoll, Julien Westhoff, P. Bohleber, A. Svensson, D. Dahl-Jensen, C. Barbante, I. Weikusat","doi":"10.5194/tc-17-2021-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2021-2023","url":null,"abstract":"Abstract. Impurities in polar ice play a critical role in ice flow, deformation, and the integrity of the ice core record. Especially cloudy bands, visible layers with high impurity concentrations, are prominent features in ice from glacial periods. Their physical and chemical properties are poorly understood, highlighting the need to analyse them in more detail. We bridge the gap between decimetre and micrometre scales by combining the visual stratigraphy line scanner, fabric analyser, microstructure mapping, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry 2D impurity imaging. We classified approximately 1300 cloudy bands from glacial ice from the East Greenland Ice-core Project (EGRIP) ice core into seven different types. We determine the localisation and mineralogy of more than 1000 micro-inclusions at 13 depths. The majority of the minerals found are related to terrestrial dust, such as quartz, feldspar, mica, and hematite. We further found carbonaceous particles, dolomite, and gypsum in high abundance. Rutile, anatase, epidote, titanite, and grossular are infrequently observed. The 2D impurity imaging at 20 µm resolution revealed that cloudy bands are clearly distinguishable in the chemical data. Na, Mg, and Sr are mainly present at grain boundaries, whereas dust-related analytes, such as Al, Fe, and Ti, are located in the grain interior, forming clusters of insoluble impurities. We present novel vast micrometre-resolution insights into cloudy bands and describe the differences within and outside these bands. Combining the visual and chemical data results in new insights into the formation of different cloudy band types and could be the starting point for future in-depth studies on impurity signal integrity and internal deformation in deep polar ice cores.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":" ","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45619444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
John M Tarricone, R. Webb, H. Marshall, A. Nolin, F. Meyer
Abstract. Snow is a critical water resource for the western United States and many regions across the globe. However, our ability to accurately measure and monitor changes in snow mass from satellite remote sensing, specifically its water equivalent, remains a challenge. To confront these challenges, NASA initiated the SnowEx program, a multiyear effort to address knowledge gaps in snow remote sensing. During SnowEx 2020, the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) team acquired an L-band interferometric synthetic aperture radar (InSAR) data time series to evaluate the capabilities and limitations of repeat-pass L-band InSAR for tracking changes in snow water equivalent (SWE). The goal was to develop a more comprehensive understanding of where and when L-band InSAR can provide SWE change estimates, allowing the snow community to leverage the upcoming NASA–ISRO (NASA–Indian Space Research Organization) SAR (NISAR) mission. Our study analyzed three InSAR image pairs from the Jemez Mountains, NM, between 12 and 26 February 2020. We developed a snow-focused multi-sensor method that uses UAVSAR InSAR data synergistically with optical fractional snow-covered area (fSCA) information. Combining these two remote sensing datasets allows for atmospheric correction and delineation of snow-covered pixels within the radar swath. For all InSAR pairs, we converted phase change values to SWE change estimates between the three acquisition dates. We then evaluated InSAR-derived retrievals using a combination of fSCA, snow pits, meteorological station data, in situ snow depth sensors, and ground-penetrating radar (GPR). The results of this study show that repeat-pass L-band InSAR is effective for estimating both snow accumulation and ablation with the proper measurement timing, reference phase, and snowpack conditions.
{"title":"Estimating snow accumulation and ablation with L-band interferometric synthetic aperture radar (InSAR)","authors":"John M Tarricone, R. Webb, H. Marshall, A. Nolin, F. Meyer","doi":"10.5194/tc-17-1997-2023","DOIUrl":"https://doi.org/10.5194/tc-17-1997-2023","url":null,"abstract":"Abstract. Snow is a critical water resource for the western United States and many regions across the globe. However, our ability to accurately measure and monitor changes in snow mass from satellite remote sensing, specifically its water equivalent, remains a challenge. To confront these challenges, NASA initiated the SnowEx program, a multiyear effort to address knowledge gaps in snow remote sensing. During SnowEx 2020, the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) team acquired an L-band interferometric synthetic aperture radar (InSAR) data time series to evaluate the capabilities and limitations of repeat-pass L-band InSAR for tracking changes in snow water equivalent (SWE). The goal was to develop a more comprehensive understanding of where and when L-band InSAR can provide SWE change estimates, allowing the snow community to leverage the upcoming NASA–ISRO (NASA–Indian Space Research Organization) SAR (NISAR) mission. Our study analyzed three InSAR image pairs from the Jemez Mountains, NM, between 12 and 26 February 2020. We developed a snow-focused multi-sensor method that uses UAVSAR InSAR data synergistically with optical fractional snow-covered area (fSCA) information. Combining these two remote sensing datasets allows for atmospheric correction and delineation of snow-covered pixels within the radar swath. For all InSAR pairs, we converted phase change values to SWE change estimates between the three acquisition dates. We then evaluated InSAR-derived retrievals using a combination of fSCA, snow pits, meteorological station data, in situ snow depth sensors, and ground-penetrating radar (GPR). The results of this study show that repeat-pass L-band InSAR is effective for estimating both snow accumulation and ablation with the proper measurement timing, reference phase, and snowpack conditions.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":"1 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70704371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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：