Valentina Premier, C. Marín, G. Bertoldi, R. Barella, C. Notarnicola, L. Bruzzone
Abstract. The hydrological cycle is strongly influenced by the accumulation and melting of seasonal snow. For this reason, mountains are often claimed to be the “water towers” of the world. In this context, a key variable is the snow water equivalent (SWE). However, the complex processes of snow accumulation, redistribution, and ablation make its quantification and prediction very challenging. In this work, we explore the use of multi-source data to reconstruct SWE at a high spatial resolution (HR) of 25 m. To this purpose, we propose a novel approach based on (i) in situ snow depth or SWE observations, temperature data and synthetic aperture radar (SAR) images to determine the pixel state, i.e., whether it is undergoing an SWE increase (accumulation) or decrease (ablation), (ii) a daily HR time series of snow cover area (SCA) maps derived by high- and low-resolution multispectral optical satellite images to define the days of snow presence, and (iii) a degree-day model driven by in situ temperature to determine the potential melting. Given the typical high spatial heterogeneity of snow in mountainous areas, the use of HR images represents an important novelty that allows us to sample its distribution more adequately, thus resulting in highly detailed spatialized information. The proposed SWE reconstruction approach also foresees a novel SCA time series regularization technique that models impossible transitions based on the pixel state, i.e., the erroneous change in the pixel class from snow to snow-free when it is expected to be in accumulation or equilibrium and, vice versa, from snow-free to snow when it is expected to be in ablation or equilibrium. Furthermore, it reconstructs the SWE for the entire hydrological season, including late snowfall. The approach does not require spatialized precipitation information as input, which is usually affected by uncertainty. The method provided good results in two different test catchments: the South Fork of the San Joaquin River, California, and the Schnals catchment, Italy. It obtained good agreement when evaluated against HR spatialized reference maps (showing an average bias of −22 mm, a root mean square error – RMSE – of 212 mm, and a correlation of 0.74), against a daily dataset at coarser resolution (showing an average bias of −44 mm, an RMSE of 127 mm, and a correlation of 0.66), and against manual measurements (showing an average bias of −5 mm, an RMSE of 191 mm, and a correlation of 0.35). The main sources of error are discussed to provide insights into the main advantages and disadvantages of the method that may be of interest for several hydrological and ecological applications.
摘要水文循环受季节积雪的积累和融化的强烈影响。因此，山脉常被称为世界的“水塔”。在这种情况下，一个关键变量是雪水当量(SWE)。然而，积雪积累、再分布和消融的复杂过程给其量化和预测带来了很大的挑战。在这项工作中，我们探索了使用多源数据在25 m的高空间分辨率(HR)下重建SWE。为此，我们提出了一种基于(i)原位雪深或SWE观测、温度数据和合成孔径雷达(SAR)图像的新方法，以确定像元状态，即是否正在经历SWE增加(积累)或减少(消融);(ii)由高分辨率和低分辨率多光谱光学卫星图像导出的积雪面积(SCA)图的每日HR时间序列，以确定积雪存在的天数。(iii)由原位温度驱动的度-日模型，以确定潜在的融化。考虑到山区典型的高空间异质性，使用HR图像代表了一种重要的创新，使我们能够更充分地采样其分布，从而获得高度详细的空间化信息。所提出的SWE重建方法还预测了一种新的SCA时间序列正则化技术，该技术基于像素状态对不可能的转换进行建模，即，当预期像素类处于积累或平衡状态时，从雪到无雪的错误变化，反之亦然，当预期像素类处于消融或平衡状态时，从无雪到雪的错误变化。此外，它还重建了整个水文季节的SWE，包括晚降雪。该方法不需要空间化降水信息作为输入，而空间化降水信息通常受不确定性的影响。该方法在两个不同的测试集水区提供了良好的结果:加利福尼亚州圣华金河的南叉和意大利的Schnals集水区。当对HR空间化参考地图(显示平均偏差为- 22 mm，均方根误差- RMSE - 212 mm，相关性为0.74)，对较粗分辨率的日常数据集(显示平均偏差为- 44 mm, RMSE为127 mm，相关性为0.66)和手动测量(显示平均偏差为- 5 mm, RMSE为191 mm，相关性为0.35)进行评估时，它获得了良好的一致性。讨论了误差的主要来源，以提供对几种水文和生态应用可能感兴趣的方法的主要优点和缺点的见解。
{"title":"Exploring the use of multi-source high-resolution satellite data for snow water equivalent reconstruction over mountainous catchments","authors":"Valentina Premier, C. Marín, G. Bertoldi, R. Barella, C. Notarnicola, L. Bruzzone","doi":"10.5194/tc-17-2387-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2387-2023","url":null,"abstract":"Abstract. The hydrological cycle is strongly influenced by the accumulation and melting of seasonal snow. For this reason, mountains are often claimed to be the “water towers” of the world. In this context, a key variable is the snow water equivalent (SWE). However, the complex processes of snow accumulation, redistribution, and ablation make its quantification and prediction very challenging. In this work, we explore the use of multi-source data to reconstruct SWE at a high spatial resolution (HR) of 25 m. To this purpose, we propose a novel approach based on (i) in situ snow depth or SWE observations, temperature data and synthetic aperture radar (SAR) images to determine the pixel state, i.e., whether it is undergoing an SWE increase (accumulation) or decrease (ablation), (ii) a daily HR time series of snow cover area (SCA) maps derived by high- and low-resolution multispectral optical satellite images to define the days of snow presence, and (iii) a degree-day model driven by in situ temperature to determine the potential melting. Given the typical high spatial heterogeneity of snow in mountainous areas, the use of HR images represents an important novelty that allows us to sample its distribution more adequately, thus resulting in highly detailed spatialized information.\u0000The proposed SWE reconstruction approach also foresees a novel SCA time series regularization technique that models impossible transitions based on the pixel state, i.e., the erroneous change in the pixel class from snow to snow-free when it is expected to be in accumulation or equilibrium and, vice versa, from snow-free to snow when it is expected to be in ablation or equilibrium. Furthermore, it reconstructs the SWE for the entire hydrological season, including late snowfall. The approach does not require spatialized precipitation information as input, which is usually affected by uncertainty. The method provided good results in two different test catchments: the South Fork of the San Joaquin River, California, and the Schnals catchment, Italy. It obtained good agreement when evaluated against HR spatialized reference maps (showing an average bias of −22 mm, a root mean square error – RMSE – of 212 mm, and a correlation of 0.74), against a daily dataset at coarser resolution (showing an average bias of −44 mm, an RMSE of 127 mm, and a correlation of 0.66), and against manual measurements (showing an average bias of −5 mm, an RMSE of 191 mm, and a correlation of 0.35).\u0000The main sources of error are discussed to provide insights into the main advantages and disadvantages of the method that may be of interest for several hydrological and ecological applications.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41742590","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}
Purevmaa Khandsuren, Y. Seong, H. Rhee, Cho-Hee Lee, M. Sarıkaya, Jeong-Sik Oh, Khadbaatar Sandag, Byung Yong Yu
Abstract. Mountain glacier mass balance is affected by factors other than climate, such as topography, slope, and aspect. In midlatitude high-mountain regions, the north–south aspect contrast can cause significant changes in insolation and melt, resulting in local asynchrony in glacial dynamics. This study documents the asynchronous response of two paleoglaciers in southwestern Mongolia to the local topoclimatic factors using 10Be exposure age dating and 2D ice surface modeling. 10Be surface exposure age dating revealed that the Ikh Artsan south-facing valley glacier culminated (MIA1) at 20.1 ± 0.7 ka, coinciding with the global Last Glacial Maximum (gLGM). In contrast, the north-facing Jargalant paleoglacier (MJ1) culminated at 17.2 ± 1.5 ka, around Heinrich Stadial 1 and during the post-gLGM Northern Hemisphere warming. Our temperature-index melt model predicts that ablation will be substantially lower on the north-facing slope, as it is exposed to less solar radiation and cooler temperatures than the south-facing slope. The 2D ice surface modeling also revealed that the south-facing Ikh Artsan Glacier abruptly retreated from its maximum extent at 20 ka, but the Jargalant Glacier on the shaded slope consistently advanced and thickened due to reduced melt until 17 ka. The timing of the modeled glacier culmination is consistent within ± 1σ of the 10Be exposure age results. Extremely old ages ranging from 636.2 to 35.9 ka were measured for the inner moraines in the Jargalant cirque (MJ2–MJ4), suggesting a problem with inheritance from boulders eroded from the summit plateau.
{"title":"Asynchronous glacial dynamics of Last Glacial Maximum mountain glaciers in the Ikh Bogd Massif, Gobi Altai mountain range, southwestern Mongolia: aspect control on glacier mass balance","authors":"Purevmaa Khandsuren, Y. Seong, H. Rhee, Cho-Hee Lee, M. Sarıkaya, Jeong-Sik Oh, Khadbaatar Sandag, Byung Yong Yu","doi":"10.5194/tc-17-2409-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2409-2023","url":null,"abstract":"Abstract. Mountain glacier mass balance is affected by factors other than\u0000climate, such as topography, slope, and aspect. In midlatitude high-mountain regions, the north–south aspect contrast can cause significant\u0000changes in insolation and melt, resulting in local asynchrony in glacial\u0000dynamics. This study documents the asynchronous response of two\u0000paleoglaciers in southwestern Mongolia to the local topoclimatic factors\u0000using 10Be exposure age dating and 2D ice surface modeling. 10Be\u0000surface exposure age dating revealed that the Ikh Artsan south-facing valley\u0000glacier culminated (MIA1) at 20.1 ± 0.7 ka, coinciding with the global Last Glacial Maximum\u0000(gLGM). In contrast, the north-facing Jargalant paleoglacier (MJ1)\u0000culminated at 17.2 ± 1.5 ka, around Heinrich Stadial 1 and during the\u0000post-gLGM Northern Hemisphere warming. Our temperature-index melt model\u0000predicts that ablation will be substantially lower on the north-facing slope,\u0000as it is exposed to less solar radiation and cooler temperatures than the\u0000south-facing slope. The 2D ice surface modeling also revealed that\u0000the south-facing Ikh Artsan Glacier abruptly retreated from its maximum\u0000extent at 20 ka, but the Jargalant Glacier on the shaded slope\u0000consistently advanced and thickened due to reduced melt until 17 ka. The\u0000timing of the modeled glacier culmination is consistent within ± 1σ of the 10Be exposure age results. Extremely old ages ranging\u0000from 636.2 to 35.9 ka were measured for the inner moraines in the\u0000Jargalant cirque (MJ2–MJ4), suggesting a problem with inheritance\u0000from boulders eroded from the summit plateau.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45522115","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. Ice thickness across lake ice is mainly influenced by the presence of snow and its distribution, which affects the rate of lake ice growth. The distribution of snow depth over lake ice varies due to wind redistribution and snowpack metamorphism, affecting the variability of lake ice thickness. Accurate and consistent snow depth data on lake ice are sparse and challenging to obtain. However, high spatial resolution lake snow depth observations are necessary for the next generation of thermodynamic lake ice models to improve the understanding of how the varying distribution of snow depth influences lake ice formation and growth. This study was conducted using ground-penetrating radar (GPR) acquisitions with ∼9 cm sampling resolution along transects totalling ∼44 km to map snow depth over four Canadian sub-arctic freshwater lakes. The lake snow depth derived from GPR two-way travel time (TWT) resulted in an average relative error of under 10 % when compared to 2430 in situ snow depth observations for the early and late winter season. The snow depth derived from GPR TWTs for the early winter season was estimated with a root mean square error (RMSE) of 1.6 cm and a mean bias error of 0.01 cm, while the accuracy for the late winter season on a deeper snowpack was estimated with a RMSE of 2.9 cm and a mean bias error of 0.4 cm. The GPR-derived snow depths were interpolated to create 1 m spatial resolution snow depth maps. The findings showed improved lake snow depth retrieval accuracy and introduced a fast and efficient method to obtain high spatial resolution snow depth information. The results suggest that GPR acquisitions can be used to derive lake snow depth, providing a viable alternative to manual snow depth monitoring methods. The findings can lead to an improved understanding of snow and lake ice interactions, which is essential for northern communities' safety and wellbeing and the scientific modelling community.
{"title":"Mapping snow depth on Canadian sub-arctic lakes using ground-penetrating radar","authors":"Alicia F. Pouw, H. Kheyrollah Pour, Alex Maclean","doi":"10.5194/tc-17-2367-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2367-2023","url":null,"abstract":"Abstract. Ice thickness across lake ice is mainly influenced by the presence of snow\u0000and its distribution, which affects the rate of lake ice growth. The\u0000distribution of snow depth over lake ice varies due to wind redistribution\u0000and snowpack metamorphism, affecting the variability of lake ice thickness.\u0000Accurate and consistent snow depth data on lake ice are sparse and\u0000challenging to obtain. However, high spatial resolution lake snow depth\u0000observations are necessary for the next generation of thermodynamic lake ice models to improve the understanding of how the varying distribution of snow depth influences lake ice formation and growth. This study was conducted using ground-penetrating radar (GPR) acquisitions with ∼9 cm sampling resolution along transects totalling ∼44 km to map\u0000snow depth over four Canadian sub-arctic freshwater lakes. The lake snow\u0000depth derived from GPR two-way travel time (TWT) resulted in an average relative error of under\u000010 % when compared to 2430 in situ snow depth observations for the early and late winter season. The snow depth derived from GPR TWTs for the early winter season was estimated with a root mean square error (RMSE) of 1.6 cm and a mean bias error of 0.01 cm, while the accuracy for the late winter season on a deeper snowpack was estimated with a RMSE of 2.9 cm and a mean bias error of 0.4 cm. The GPR-derived snow depths were interpolated to create 1 m spatial resolution snow depth maps. The findings showed improved lake snow depth retrieval accuracy and introduced a fast and efficient method to obtain high spatial resolution snow depth information. The results suggest that GPR acquisitions can be used to derive lake snow depth, providing a viable alternative to manual snow depth monitoring methods. The findings can lead to an improved understanding of snow and lake ice interactions, which is essential for northern communities' safety and wellbeing and the scientific modelling community.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45188875","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}
Franziska Temme, David Farías-Barahona, T. Seehaus, R. Jaña, J. Arigony-Neto, I. González, A. Arndt, T. Sauter, C. Schneider, J. Fürst
Abstract. This study investigates strategies for calibration of surface mass balance (SMB) models in the Monte Sarmiento Massif (MSM), Tierra del Fuego, with the goal of achieving realistic simulations of the regional SMB. Applied calibration strategies range from a local single-glacier calibration to a regional calibration with the inclusion of a snowdrift parameterization. We apply four SMB models of different complexity. In this way, we examine the model transferability in space, the benefit of regional mass change observations and the advantage of increasing the complexity level regarding included processes. Measurements include ablation and ice thickness observations at Schiaparelli Glacier as well as elevation changes and flow velocity from satellite data for the entire study site. Performance of simulated SMB is validated against geodetic mass changes and stake observations of surface melting. Results show that transferring SMB models in space is a challenge, and common practices can produce distinctly biased estimates. Model performance can be significantly improved by the use of remotely sensed regional observations. Furthermore, we have shown that snowdrift does play an important role in the SMB in the Cordillera Darwin, where strong and consistent winds prevail. The massif-wide average annual SMB between 2000 and 2022 falls between −0.28 and −0.07 m w.e. yr−1, depending on the applied model. The SMB is mainly controlled by surface melting and snowfall. The model intercomparison does not indicate one obviously best-suited model for SMB simulations in the MSM.
{"title":"Strategies for regional modeling of surface mass balance at the Monte Sarmiento Massif, Tierra del Fuego","authors":"Franziska Temme, David Farías-Barahona, T. Seehaus, R. Jaña, J. Arigony-Neto, I. González, A. Arndt, T. Sauter, C. Schneider, J. Fürst","doi":"10.5194/tc-17-2343-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2343-2023","url":null,"abstract":"Abstract. This study investigates strategies for calibration of surface mass balance (SMB) models in the Monte Sarmiento Massif (MSM), Tierra del Fuego, with the goal of achieving realistic simulations of the\u0000regional SMB. Applied calibration strategies range from a local\u0000single-glacier calibration to a regional calibration with the inclusion of a\u0000snowdrift parameterization. We apply four SMB models of different complexity. In this way, we examine the model transferability in space, the benefit of regional mass change observations and the advantage of increasing the\u0000complexity level regarding included processes. Measurements include ablation\u0000and ice thickness observations at Schiaparelli Glacier as well as elevation\u0000changes and flow velocity from satellite data for the entire study site.\u0000Performance of simulated SMB is validated against geodetic mass changes and\u0000stake observations of surface melting. Results show that transferring SMB\u0000models in space is a challenge, and common practices can produce distinctly\u0000biased estimates. Model performance can be significantly improved by the use\u0000of remotely sensed regional observations. Furthermore, we have shown that\u0000snowdrift does play an important role in the SMB in the Cordillera Darwin, where strong and consistent winds prevail. The massif-wide average annual\u0000SMB between 2000 and 2022 falls between −0.28 and −0.07 m w.e. yr−1,\u0000depending on the applied model. The SMB is mainly controlled by surface\u0000melting and snowfall. The model intercomparison does not indicate one\u0000obviously best-suited model for SMB simulations in the MSM.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44478861","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. The grain size of the superficial snow layer is a key determinant of the surface albedo in Antarctica. Its evolution is the result of multiple interacting processes, such as dry and wet metamorphism, melt, snow drift, and precipitation. Among them, snow drift has the least known and least predictable impact. The goal of this study is to relate the variations in surface snow grain size to these processes in a windy location of the Antarctic coast. For this, we retrieved the daily grain size from 5-year-long in situ observations of the spectral albedo recorded by a new multi-band albedometer, unique in terms of autonomy and described here for the first time. An uncertainty assessment and a comparison with satellite-retrieved grain size were carried out to verify the reliability of the instrument, and an RMSE up to 0.16 mm in the observed grain size was found. By relating these in situ measurements to time series of snow drift, surface temperature, snow surface height and snowfall, we established that the evolution of the grain size in the presence of snow drift is complex and follows two possible pathways: (1) a decrease in the grain size (about half of our measurements) resulting from the deposition of small grains advected by the wind (surprisingly, this decrease is often – 2/3 of the cases– associated with a decrease in the surface height, i.e., a net erosion over the drift episode), (2) an increase in the grain size (the other half) due to either the removal of the surface layer or metamorphism. However, we note that this increase is often limited with respect to the increase predicted by a theoretical metamorphism model, suggesting that a concomitant deposition of small grains is likely. At last, we found that wind also completely impedes the deposition of snowfall during half of the observed precipitation events. When this happens, the grain size evolves as if precipitation were not occurring. As a result of all these processes, we conclude that the grain size in a windy area remains more stable than it would be in the absence of snow drift, hence limiting the variations in the albedo and in the radiative energy budget.
{"title":"Dynamics of the snow grain size in a windy coastal area of Antarctica from continuous in situ spectral-albedo measurements","authors":"Sara Arioli, G. Picard, L. Arnaud, V. Favier","doi":"10.5194/tc-17-2323-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2323-2023","url":null,"abstract":"Abstract. The grain size of the superficial snow layer is a key determinant of the surface albedo in Antarctica. Its evolution is the result of multiple interacting processes, such as dry and wet metamorphism, melt, snow drift, and precipitation. Among them, snow drift has the least known and least predictable impact. The goal of this study is to relate the variations in surface snow grain size to these processes in a windy location of the Antarctic coast. For this, we retrieved the daily grain size from 5-year-long in situ observations of the spectral albedo recorded by a new multi-band albedometer, unique in terms of autonomy and described here for the first time. An uncertainty assessment and a comparison with satellite-retrieved grain size were carried out to verify the reliability of the instrument, and an RMSE up to 0.16 mm in the observed grain size was found. By relating these in situ measurements to time series of snow drift, surface temperature, snow surface height and snowfall, we established that the evolution of the grain size in the presence of snow drift is complex and follows two possible pathways: (1) a decrease in the grain size (about half of our measurements) resulting from the deposition of small grains advected by the wind (surprisingly, this decrease is often – 2/3 of the cases– associated with a decrease in the surface height, i.e., a net erosion over the drift episode), (2) an increase in the grain size (the other half) due to either the removal of the surface layer or metamorphism. However, we note that this increase is often limited with respect to the increase predicted by a theoretical metamorphism model, suggesting that a concomitant deposition of small grains is likely. At last, we found that wind also completely impedes the deposition of snowfall during half of the observed precipitation events. When this happens, the grain size evolves as if precipitation were not occurring. As a result of all these processes, we conclude that the grain size in a windy area remains more stable than it would be in the absence of snow drift, hence limiting the variations in the albedo and in the radiative energy budget.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43011288","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. In order to assess future glacier evolution and meltwater runoff, accurate knowledge on the volume and the ice thickness distribution of glaciers is crucial. However, in situ observations of glacier thickness are sparse in many regions worldwide due to the difficulty of undertaking field surveys. This lack of in situ measurements can be partially overcome by remote-sensing information. Multi-temporal and contemporaneous data on glacier extent and surface elevation provide past information on ice thickness for retreating glaciers in the newly deglacierized regions. However, these observations are concentrated near the glacier snouts, which is disadvantageous because it is known to introduce biases in ice thickness reconstruction approaches. Here, we show a strategy to overcome this generic limitation of so-called retreat thickness observations by applying an empirical relationship between the ice viscosity at locations with in situ observations and observations from digital elevation model (DEM) differencing at the glacier margins. Various datasets from the European Alps are combined to model the ice thickness distribution of Alpine glaciers for two time steps (1970 and 2003) based on the observed thickness in regions uncovered from ice during the study period. Our results show that the average ice thickness would be substantially underestimated (∼ 40 %) when relying solely on thickness observations from previously glacierized areas. Thus, a transferable topography-based viscosity scaling is developed to correct the modelled ice thickness distribution. It is shown that the presented approach is able to reproduce region-wide glacier volumes, although larger uncertainties remain at a local scale, and thus might represent a powerful tool for application in regions with sparse observations.
{"title":"Constraining regional glacier reconstructions using past ice thickness of deglaciating areas – a case study in the European Alps","authors":"C. Sommer, J. Fürst, M. Huss, M. Braun","doi":"10.5194/tc-17-2285-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2285-2023","url":null,"abstract":"Abstract. In order to assess future glacier evolution and\u0000meltwater runoff, accurate knowledge on the volume and the ice thickness\u0000distribution of glaciers is crucial. However, in situ observations of\u0000glacier thickness are sparse in many regions worldwide due to the difficulty\u0000of undertaking field surveys. This lack of in situ measurements can be\u0000partially overcome by remote-sensing information. Multi-temporal and\u0000contemporaneous data on glacier extent and surface elevation provide past\u0000information on ice thickness for retreating glaciers in the newly\u0000deglacierized regions. However, these observations are concentrated near the\u0000glacier snouts, which is disadvantageous because it is known to introduce\u0000biases in ice thickness reconstruction approaches. Here, we show a strategy\u0000to overcome this generic limitation of so-called retreat thickness\u0000observations by applying an empirical relationship between the ice viscosity\u0000at locations with in situ observations and observations from digital elevation model (DEM) differencing at the glacier margins. Various datasets from the European\u0000Alps are combined to model the ice thickness distribution of Alpine glaciers\u0000for two time steps (1970 and 2003) based on the observed thickness in regions\u0000uncovered from ice during the study period. Our results show that the\u0000average ice thickness would be substantially underestimated (∼ 40 %) when relying solely on thickness observations from previously\u0000glacierized areas. Thus, a transferable topography-based viscosity scaling\u0000is developed to correct the modelled ice thickness distribution. It is shown\u0000that the presented approach is able to reproduce region-wide glacier\u0000volumes, although larger uncertainties remain at a local scale, and thus might\u0000represent a powerful tool for application in regions with sparse\u0000observations.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44179098","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. Active rock glaciers are viscous flow features embodying ice-rich permafrost and other ice masses. They contain significant amounts of ground ice and serve as potential freshwater reservoirs as mountain glaciers melt in response to climate warming. However, current knowledge about ice content in rock glaciers has been acquired mainly from in situ investigations in limited study areas, which hinders a comprehensive understanding of ice storage in rock glaciers situated in remote mountains over local to regional scales. This study proposes a novel approach for assessing the hydrological value of rock glaciers in a more quantitative way and presents exploratory results focusing on a small region. We develop an empirical rheological model to infer ice content of rock glaciers using readily available input data, including rock glacier planar shape, surface slope angle, active layer thickness, and surface velocity. The model is calibrated and validated using observational data from the Chilean Andes and the Swiss Alps. We apply the model to five rock glaciers in the Khumbu and Lhotse valleys, northeastern Nepal. The velocity constraints applied to the model are derived from interferometric synthetic aperture radar (InSAR) measurements. The volume of rock glacier is estimated based on an existing scaling approach. The inferred volumetric ice fraction in the Khumbu and Lhotse valleys ranges from 70 ± 8 % to 74 ± 8 %, and the water volume equivalents lie between 1.4 ± 0.2 and 5.9±0.6×106 m3 for the coherently moving parts of individual rock glaciers. Due to the accessibility of the model inputs, our approach is applicable to permafrost regions where observational data are lacking, which is valuable for estimating the water storage potential of rock glaciers in remote areas.
{"title":"Modelling rock glacier ice content based on InSAR-derived velocity, Khumbu and Lhotse valleys, Nepal","authors":"Yan Hu, S. Harrison, Lin Liu, J. Wood","doi":"10.5194/tc-17-2305-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2305-2023","url":null,"abstract":"Abstract. Active rock glaciers are viscous flow features embodying\u0000ice-rich permafrost and other ice masses. They contain significant amounts\u0000of ground ice and serve as potential freshwater reservoirs as mountain\u0000glaciers melt in response to climate warming. However, current knowledge\u0000about ice content in rock glaciers has been acquired mainly from in situ\u0000investigations in limited study areas, which hinders a comprehensive\u0000understanding of ice storage in rock glaciers situated in remote mountains\u0000over local to regional scales. This study proposes a novel approach for\u0000assessing the hydrological value of rock glaciers in a more quantitative way\u0000and presents exploratory results focusing on a small region. We develop an\u0000empirical rheological model to infer ice content of rock glaciers using\u0000readily available input data, including rock glacier planar shape, surface\u0000slope angle, active layer thickness, and surface velocity. The model is\u0000calibrated and validated using observational data from the Chilean Andes and\u0000the Swiss Alps. We apply the model to five rock glaciers in the Khumbu and\u0000Lhotse valleys, northeastern Nepal. The velocity constraints\u0000applied to the model are derived from interferometric synthetic aperture\u0000radar (InSAR) measurements. The volume of rock glacier is estimated based on\u0000an existing scaling approach. The inferred volumetric ice fraction in the Khumbu\u0000and Lhotse valleys ranges from 70 ± 8 % to 74 ± 8 %, and the\u0000water volume equivalents lie between 1.4 ± 0.2 and 5.9±0.6×106 m3 for the coherently moving parts of individual rock glaciers.\u0000Due to the accessibility of the model inputs, our approach is applicable to\u0000permafrost regions where observational data are lacking, which is valuable for\u0000estimating the water storage potential of rock glaciers in remote areas.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43488526","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. Poinelli, M. Schodlok, E. Larour, M. Vizcaíno, R. Riva
Abstract. Land ice discharge from the Antarctic continent into the ocean is restrained by ice shelves, floating extensions of grounded ice that buttress the glacier outflow. The ongoing thinning of these ice shelves – largely due to enhanced melting at their base in response to global warming – is known to accelerate the release of glacier meltwater into the world oceans, augmenting global sea level. Mechanisms of ocean heat intrusion under the ice base are therefore crucial to project the future of Antarctic ice shelves. Furthermore, ice shelves are weakened by the presence of kilometer-wide full-thickness ice rifts, which are observed all around Antarctica. However, their impact on ocean circulation around and below ice shelves has been largely unexplored as ocean models are commonly characterized by resolutions that are too coarse to resolve their presence. Here, we apply the Massachusetts Institute of Technology general circulation model at high resolution to investigate the sensitivity of sub-shelf ocean dynamics and ice-shelf melting to the presence of a kilometer-wide rift in proximity of the ice front. We find that (a) the rift curtails water and heat intrusion beneath the ice-shelf base and (b) the basal melting of a rifted ice shelf is on average 20 % lower than for an intact ice shelf under identical forcing. Notably, we calculate a significant reduction in melting rates of up to 30 % near the grounding line of a rifted ice shelf. We therefore posit that rifts and their impact on the sub-shelf dynamics are important to consider in order to accurately reproduce and project pathways of heat intrusion into the ice-shelf cavity.
{"title":"Can rifts alter ocean dynamics beneath ice shelves?","authors":"M. Poinelli, M. Schodlok, E. Larour, M. Vizcaíno, R. Riva","doi":"10.5194/tc-17-2261-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2261-2023","url":null,"abstract":"Abstract. Land ice discharge from the Antarctic continent into the ocean is restrained by ice shelves, floating extensions of grounded ice that buttress the glacier outflow. The ongoing thinning of these ice shelves – largely due to enhanced melting at their base in response to global warming – is known to accelerate the release of glacier meltwater into the world oceans, augmenting global sea level. Mechanisms of ocean heat intrusion under the ice base are therefore crucial to project the future of Antarctic ice shelves. Furthermore, ice shelves are weakened by the presence of kilometer-wide full-thickness ice rifts, which are observed all around Antarctica. However, their impact on ocean circulation around and below ice shelves has been largely unexplored as ocean models are commonly characterized by resolutions that are too coarse to resolve their presence. Here, we apply the Massachusetts Institute of Technology general circulation model at high resolution to investigate the sensitivity of sub-shelf ocean dynamics and ice-shelf melting to the presence of a kilometer-wide rift in proximity of the ice front. We find that (a) the rift curtails water and heat intrusion beneath the ice-shelf base and (b) the basal melting of a rifted ice shelf is on average 20 % lower than for an intact ice shelf under identical forcing. Notably, we calculate a significant reduction in melting rates of up to 30 % near the grounding line of a rifted ice shelf. We therefore posit that rifts and their impact on the sub-shelf dynamics are important to consider in order to accurately reproduce and project pathways of heat intrusion into the ice-shelf cavity.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48135501","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}
H. Hu, Jiechen Zhao, P. Heil, Zhiliang Qin, Jingkai Ma, F. Hui, Xiao Cheng
Abstract. High-frequency observations of the ice–ocean interaction and high-precision estimation of the ice–ocean heat exchange are critical to understanding the thermodynamics of the landfast ice mass balance in Antarctica. To investigate the oceanic contribution to the evolution of the landfast ice, an integrated ocean observation system, including an acoustic Doppler velocimeter (ADV), conductivity–temperature–depth (CTD) sensors, and a sea ice mass balance array (SIMBA), was deployed on the landfast ice near the Chinese Zhongshan Station in Prydz Bay, East Antarctica, from April to November 2021. The CTD sensors recorded the ocean temperature and salinity. The ocean temperature experienced a rapid increase in late April, from −1.62 to the maximum of −1.30 ∘C, and then it gradually decreased to −1.75 ∘C in May and remained at this temperature until November. The seawater salinity and density exhibited similar increasing trends during April and May, with mean rates of 0.04 psu d−1 and 0.03 kg m−3 d−1, respectively, which was related to the strong salt rejection caused by freezing of the landfast ice. The ocean current observed by the ADV had mean horizontal and vertical velocities of 9.5 ± 3.9 and 0.2 ± 0.8 cm s−1, respectively. The domain current direction was ESE (120∘)–WSW (240∘), and the domain velocity (79 %) was 5–15 cm s−1. The oceanic heat flux (Fw) estimated using the residual method reached a peak of 41.3 ± 9.8 W m−2 in April, and then it gradually decreased to a stable level of 7.8 ± 2.9 W m−2 from June to October. The Fw values calculated using three different bulk parameterizations exhibited similar trends with different magnitudes due to the uncertainties of the empirical friction velocity. The spectral analysis results suggest that all of the observed ocean variables exhibited a typical half-day period, indicating the strong diurnal influence of the local tidal oscillations. The large-scale sea ice distribution and ocean circulation contributed to the seasonal variations in the ocean variables, revealing the important relationship between the large-scale and local phenomena. The high-frequency and cross-seasonal observations of oceanic variables obtained in this study allow us to deeply investigate their diurnal and seasonal variations and to evaluate their influences on the landfast ice evolution.
{"title":"Annual evolution of the ice–ocean interaction beneath landfast ice in Prydz Bay, East Antarctica","authors":"H. Hu, Jiechen Zhao, P. Heil, Zhiliang Qin, Jingkai Ma, F. Hui, Xiao Cheng","doi":"10.5194/tc-17-2231-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2231-2023","url":null,"abstract":"Abstract. High-frequency observations of the ice–ocean interaction and high-precision estimation of the ice–ocean heat exchange are critical\u0000to understanding the thermodynamics of the landfast ice mass balance in\u0000Antarctica. To investigate the oceanic contribution to the evolution of the\u0000landfast ice, an integrated ocean observation system, including an acoustic\u0000Doppler velocimeter (ADV), conductivity–temperature–depth (CTD) sensors,\u0000and a sea ice mass balance array (SIMBA), was deployed on the landfast ice\u0000near the Chinese Zhongshan Station in Prydz Bay, East Antarctica, from April to November 2021. The CTD sensors recorded the ocean temperature and salinity.\u0000The ocean temperature experienced a rapid increase in late April, from\u0000−1.62 to the maximum of −1.30 ∘C, and then it gradually decreased to −1.75 ∘C in May and remained at this\u0000temperature until November. The seawater salinity and density exhibited\u0000similar increasing trends during April and May, with mean rates of 0.04 psu d−1 and 0.03 kg m−3 d−1, respectively, which was related\u0000to the strong salt rejection caused by freezing of the landfast ice. The\u0000ocean current observed by the ADV had mean horizontal and vertical\u0000velocities of 9.5 ± 3.9 and 0.2 ± 0.8 cm s−1,\u0000respectively. The domain current direction was ESE (120∘)–WSW\u0000(240∘), and the domain velocity (79 %) was 5–15 cm s−1.\u0000The oceanic heat flux (Fw) estimated using the residual method reached a\u0000peak of 41.3 ± 9.8 W m−2 in April, and then it gradually decreased to a stable level of 7.8 ± 2.9 W m−2 from June to\u0000October. The Fw values calculated using three different bulk\u0000parameterizations exhibited similar trends with different magnitudes due to\u0000the uncertainties of the empirical friction velocity. The spectral analysis\u0000results suggest that all of the observed ocean variables exhibited a typical\u0000half-day period, indicating the strong diurnal influence of the local tidal\u0000oscillations. The large-scale sea ice distribution and ocean circulation\u0000contributed to the seasonal variations in the ocean variables, revealing the\u0000important relationship between the large-scale and local phenomena. The high-frequency and cross-seasonal observations of oceanic variables obtained in\u0000this study allow us to deeply investigate their diurnal and seasonal\u0000variations and to evaluate their influences on the landfast ice evolution.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46754133","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}
V. Nandan, R. Willatt, R. Mallett, J. Stroeve, T. Geldsetzer, R. Scharien, R. Tonboe, J. Yackel, J. Landy, D. Clemens-Sewall, Arttu Jutila, D. Wagner, D. Krampe, M. Huntemann, Mallik S. Mahmud, David Jensen, T. Newman, S. Hendricks, G. Spreen, Amy R. Macfarlane, M. Schneebeli, J. Mead, R. Ricker, Michael R. Gallagher, C. Duguay, Ian A. Raphael, C. Polashenski, M. Tsamados, I. Matero, M. Hoppmann
Abstract. Wind-driven redistribution of snow on sea ice alters its topography and microstructure, yet the impact of these processes on radar signatures is poorly understood. Here, we examine the effects of snow redistribution over Arctic sea ice on radar waveforms and backscatter signatures obtained from a surface-based, fully polarimetric Ka- and Ku-band radar at incidence angles between 0∘ (nadir) and 50∘. Two wind events in November 2019 during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition are evaluated. During both events, changes in Ka- and Ku-band radar waveforms and backscatter coefficients at nadir are observed, coincident with surface topography changes measured by a terrestrial laser scanner. At both frequencies, redistribution caused snow densification at the surface and the uppermost layers, increasing the scattering at the air–snow interface at nadir and its prevalence as the dominant radar scattering surface. The waveform data also detected the presence of previous air–snow interfaces, buried beneath newly deposited snow. The additional scattering from previous air–snow interfaces could therefore affect the range retrieved from Ka- and Ku-band satellite altimeters. With increasing incidence angles, the relative scattering contribution of the air–snow interface decreases, and the snow–sea ice interface scattering increases. Relative to pre-wind event conditions, azimuthally averaged backscatter at nadir during the wind events increases by up to 8 dB (Ka-band) and 5 dB (Ku-band). Results show substantial backscatter variability within the scan area at all incidence angles and polarizations, in response to increasing wind speed and changes in wind direction. Our results show that snow redistribution and wind compaction need to be accounted for to interpret airborne and satellite radar measurements of snow-covered sea ice.
{"title":"Wind redistribution of snow impacts the Ka- and Ku-band radar signatures of Arctic sea ice","authors":"V. Nandan, R. Willatt, R. Mallett, J. Stroeve, T. Geldsetzer, R. Scharien, R. Tonboe, J. Yackel, J. Landy, D. Clemens-Sewall, Arttu Jutila, D. Wagner, D. Krampe, M. Huntemann, Mallik S. Mahmud, David Jensen, T. Newman, S. Hendricks, G. Spreen, Amy R. Macfarlane, M. Schneebeli, J. Mead, R. Ricker, Michael R. Gallagher, C. Duguay, Ian A. Raphael, C. Polashenski, M. Tsamados, I. Matero, M. Hoppmann","doi":"10.5194/tc-17-2211-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2211-2023","url":null,"abstract":"Abstract. Wind-driven redistribution of snow on sea ice alters its\u0000topography and microstructure, yet the impact of these processes on radar\u0000signatures is poorly understood. Here, we examine the effects of snow\u0000redistribution over Arctic sea ice on radar waveforms and backscatter\u0000signatures obtained from a surface-based, fully polarimetric Ka- and Ku-band\u0000radar at incidence angles between 0∘ (nadir) and 50∘.\u0000Two wind events in November 2019 during the Multidisciplinary drifting Observatory for\u0000the Study of Arctic Climate (MOSAiC) expedition are evaluated. During both events, changes in Ka- and\u0000Ku-band radar waveforms and backscatter coefficients at nadir are observed,\u0000coincident with surface topography changes measured by a terrestrial laser\u0000scanner. At both frequencies, redistribution caused snow densification at\u0000the surface and the uppermost layers, increasing the scattering at the\u0000air–snow interface at nadir and its prevalence as the dominant radar scattering surface. The waveform data also detected the presence of previous\u0000air–snow interfaces, buried beneath newly deposited snow. The additional\u0000scattering from previous air–snow interfaces could therefore affect the\u0000range retrieved from Ka- and Ku-band satellite altimeters. With increasing\u0000incidence angles, the relative scattering contribution of the air–snow\u0000interface decreases, and the snow–sea ice interface scattering increases.\u0000Relative to pre-wind event conditions, azimuthally averaged backscatter at\u0000nadir during the wind events increases by up to 8 dB (Ka-band) and 5 dB (Ku-band). Results show substantial backscatter variability within the scan\u0000area at all incidence angles and polarizations, in response to increasing\u0000wind speed and changes in wind direction. Our results show that snow\u0000redistribution and wind compaction need to be accounted for to interpret\u0000airborne and satellite radar measurements of snow-covered sea ice.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44958360","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}
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