Extending the record of glacier area changes into the past improves our understanding of climate change impacts. Although analogue maps showing historic glacier extents are abundant, digital outlines from before the satellite era are sparse as the digitisation of moraines and trimlines on freely available satellite images is challenging. With the now available very high-resolution images provided by Web Map Services (WMS), new doors are open for the precise digitisation. Here, we used the ESRI WMS to digitise Little Ice Age (LIA) glacier extents and present area changes since the LIA in four selected regions along with a detailed uncertainty analysis. We used modern glacier outlines as a starting point and additionally consulted Sentinel-2 images, the ArcticDEM and historic maps for interpretation. Dating records from the literature allowed calculating area change rates. In total, 493 LIA glaciers (4640 km2, now 891 ice bodies with 3590 km2) were digitised, yielding relative area changes of −20% (−0.14% a−1), −15% (−0.10% a−1), −26% (−0.16% a−1) and −61% (−0.19% a−1) for Alaska, Baffin Island, Novaya Zemlya and the tropics, respectively. The ESRI WMS images are a great asset to precisely map moraines and trimlines, but information about the timing of the related extents requires further sources.
将冰川面积变化的记录延伸到过去，可以提高我们对气候变化影响的理解。虽然显示历史冰川范围的模拟地图丰富，但卫星时代之前的数字轮廓很少，因为免费卫星图像上的冰碛和边线的数字化具有挑战性。随着网络地图服务(WMS)提供的高分辨率图像的出现，为精确的数字化打开了新的大门。在这里，我们使用ESRI WMS对四个选定地区的小冰期(LIA)冰川范围和小冰期以来的面积变化进行了数字化，并进行了详细的不确定性分析。我们使用现代冰川轮廓作为起点，并参考了Sentinel-2图像、ArcticDEM和历史地图进行解释。根据文献记录的年代可以计算出面积变化率。共有493个冰川(4640 km2)和891个冰体(3590 km2)被数字化，阿拉斯加、巴芬岛、新地岛和热带地区的相对面积变化分别为- 20% (- 0.14% a - 1)、- 15% (- 0.10% a - 1)、- 26% (- 0.16% a - 1)和- 61% (- 0.19% a - 1)。ESRI WMS图像是精确绘制冰碛和边线的重要资产，但有关相关范围的时间信息需要进一步的来源。
{"title":"Using a Web Map Service to map Little Ice Age glacier extents at regional scales","authors":"Johannes Reinthaler, F. Paul","doi":"10.1017/aog.2023.39","DOIUrl":"https://doi.org/10.1017/aog.2023.39","url":null,"abstract":"\u0000 Extending the record of glacier area changes into the past improves our understanding of climate change impacts. Although analogue maps showing historic glacier extents are abundant, digital outlines from before the satellite era are sparse as the digitisation of moraines and trimlines on freely available satellite images is challenging. With the now available very high-resolution images provided by Web Map Services (WMS), new doors are open for the precise digitisation. Here, we used the ESRI WMS to digitise Little Ice Age (LIA) glacier extents and present area changes since the LIA in four selected regions along with a detailed uncertainty analysis. We used modern glacier outlines as a starting point and additionally consulted Sentinel-2 images, the ArcticDEM and historic maps for interpretation. Dating records from the literature allowed calculating area change rates. In total, 493 LIA glaciers (4640 km2, now 891 ice bodies with 3590 km2) were digitised, yielding relative area changes of −20% (−0.14% a−1), −15% (−0.10% a−1), −26% (−0.16% a−1) and −61% (−0.19% a−1) for Alaska, Baffin Island, Novaya Zemlya and the tropics, respectively. The ESRI WMS images are a great asset to precisely map moraines and trimlines, but information about the timing of the related extents requires further sources.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43825480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nicole Abib, D. Sutherland, J. Amundson, D. Duncan, E. Eidam, R. H. Jackson, C. Kienholz, M. Morlighem, R. Motyka, J. Nash, Bridget Ovall, E. Pettit
Frontal ablation, the combination of submarine melting and iceberg calving, changes the geometry of a glacier's terminus, influencing glacier dynamics, the fate of upwelling plumes and the distribution of submarine meltwater input into the ocean. Directly observing frontal ablation and terminus morphology below the waterline is difficult, however, limiting our understanding of these coupled ice–ocean processes. To investigate the evolution of a tidewater glacier's submarine terminus, we combine 3-D multibeam point clouds of the subsurface ice face at LeConte Glacier, Alaska, with concurrent observations of environmental conditions during three field campaigns between 2016 and 2018. We observe terminus morphology that was predominately overcut (52% in August 2016, 63% in May 2017 and 74% in September 2018), accompanied by high multibeam sonar-derived melt rates (4.84 m d−1 in 2016, 1.13 m d−1 in 2017 and 1.85 m d−1 in 2018). We find that periods of high subglacial discharge lead to localized undercut discharge outlets, but adjacent to these outlets the terminus maintains significantly overcut geometry, with an ice ramp that protrudes 75 m into the fjord in 2017 and 125 m in 2018. Our data challenge the assumption that tidewater glacier termini are largely undercut during periods of high submarine melting.
锋面消融是海底融化和冰山崩解的结合，改变了冰川终点的几何形状，影响了冰川动力学、上升流羽流的命运以及输入海洋的海底融水的分布。然而，直接观察水线以下的锋面消融和终点形态是困难的，这限制了我们对这些冰-海耦合过程的理解。为了研究潮水冰川海底终点的演变，我们将阿拉斯加勒孔特冰川地下冰面的三维多波束点云与2016年至2018年三次野外活动期间的环境条件同时观测相结合。我们观察到末端形态主要是过度切割（2016年8月52%，2017年5月63%，2018年9月74%），并伴有高的多波束声纳衍生熔体速率（2016年4.84 m d−1，2017年1.13 m d−2，2018年1.85 m d−3）。我们发现，冰下高流量的时期会导致局部的底切排放口，但在这些出口附近，终点站保持着明显的超切几何形状，2017年有一个冰坡道伸入峡湾75米，2018年有125米。我们的数据挑战了这样一种假设，即在海底高度融化期间，潮水冰川末端在很大程度上被削弱。
{"title":"Persistent overcut regions dominate the terminus morphology of a rapidly melting tidewater glacier","authors":"Nicole Abib, D. Sutherland, J. Amundson, D. Duncan, E. Eidam, R. H. Jackson, C. Kienholz, M. Morlighem, R. Motyka, J. Nash, Bridget Ovall, E. Pettit","doi":"10.1017/aog.2023.38","DOIUrl":"https://doi.org/10.1017/aog.2023.38","url":null,"abstract":"\u0000 Frontal ablation, the combination of submarine melting and iceberg calving, changes the geometry of a glacier's terminus, influencing glacier dynamics, the fate of upwelling plumes and the distribution of submarine meltwater input into the ocean. Directly observing frontal ablation and terminus morphology below the waterline is difficult, however, limiting our understanding of these coupled ice–ocean processes. To investigate the evolution of a tidewater glacier's submarine terminus, we combine 3-D multibeam point clouds of the subsurface ice face at LeConte Glacier, Alaska, with concurrent observations of environmental conditions during three field campaigns between 2016 and 2018. We observe terminus morphology that was predominately overcut (52% in August 2016, 63% in May 2017 and 74% in September 2018), accompanied by high multibeam sonar-derived melt rates (4.84 m d−1 in 2016, 1.13 m d−1 in 2017 and 1.85 m d−1 in 2018). We find that periods of high subglacial discharge lead to localized undercut discharge outlets, but adjacent to these outlets the terminus maintains significantly overcut geometry, with an ice ramp that protrudes 75 m into the fjord in 2017 and 125 m in 2018. Our data challenge the assumption that tidewater glacier termini are largely undercut during periods of high submarine melting.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44365231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ron Simenhois, K. Birkeland, J. Gaume, A. van Herwijnen, Bastian Bergfeld, B. Trottet, E. Greene
Dry-snow slab avalanches release due to crack propagation in a weak snow layer under a cohesive snow slab. Crack propagation speeds can provide insights into the potential size of avalanches and inform fracture and avalanche release models. Despite their importance, slope-scale crack speed measurements from real avalanches are limited. Further, most existing slope-scale measurements utilize the appearance of slab fractures on the snow surface. However, we have no evidence that the appearance of surface cracking is a good indicator of the weak layer crack propagation tip. Here we present a novel method to estimate crack propagation speed from snow surface movements in avalanche videos. Our technique uses changes in frame pixel intensity, allowing us to detect the location of weak layer cracks well before slab fractures appear on the snow surface. We use field experiments and numerical simulations to validate our method before applying it to five avalanches. Our estimates show that cracks propagate faster up and down the slope than in the cross-slope direction; this suggests that different propagation regimes likely govern crack propagation up/down the slope, cross-slope and in flat terrain.
{"title":"Using video detection of snow surface movements to estimate weak layer crack propagation speeds","authors":"Ron Simenhois, K. Birkeland, J. Gaume, A. van Herwijnen, Bastian Bergfeld, B. Trottet, E. Greene","doi":"10.1017/aog.2023.36","DOIUrl":"https://doi.org/10.1017/aog.2023.36","url":null,"abstract":"\u0000 Dry-snow slab avalanches release due to crack propagation in a weak snow layer under a cohesive snow slab. Crack propagation speeds can provide insights into the potential size of avalanches and inform fracture and avalanche release models. Despite their importance, slope-scale crack speed measurements from real avalanches are limited. Further, most existing slope-scale measurements utilize the appearance of slab fractures on the snow surface. However, we have no evidence that the appearance of surface cracking is a good indicator of the weak layer crack propagation tip. Here we present a novel method to estimate crack propagation speed from snow surface movements in avalanche videos. Our technique uses changes in frame pixel intensity, allowing us to detect the location of weak layer cracks well before slab fractures appear on the snow surface. We use field experiments and numerical simulations to validate our method before applying it to five avalanches. Our estimates show that cracks propagate faster up and down the slope than in the cross-slope direction; this suggests that different propagation regimes likely govern crack propagation up/down the slope, cross-slope and in flat terrain.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44531008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Arctic rain-on-snow (ROS) events can have significant impacts on Arctic wildlife and socio-economic systems. This study addresses the meteorology of two different Arctic ROS events. The first, occurring near Nuuk, Greenland, generated significant impacts, including slush avalanches. The second, less severe, event occurred within the community of Iqaluit, Nunavut, Canada. This research utilizes atmospheric reanalysis, automated surface observation station data and atmospheric soundings to determine the meteorological conditions driving these events and the differences between each case. In both cases, atmospheric blocking played a leading role in ROS initiation, with atmospheric rivers – narrow bands of high water vapor transport, typically originating from the tropics and subtropics – having both direct and indirect effects. Cyclone-induced low-level jets and resultant ‘warm noses’ of higher air temperatures and moisture transport were other key features in ROS generation. To our knowledge, our study is the first to visualize how the varying strength and manifestation of these coupled features contribute to differences in the severity of Arctic ROS events. The meteorological drivers identified here find support from other studies on Arctic ROS events and are similar to weather features associated with Arctic precipitation events of extreme magnitude.
{"title":"A tale of two events: Arctic rain-on-snow meteorological drivers","authors":"Jessica Voveris, M. Serreze","doi":"10.1017/aog.2023.25","DOIUrl":"https://doi.org/10.1017/aog.2023.25","url":null,"abstract":"\u0000 Arctic rain-on-snow (ROS) events can have significant impacts on Arctic wildlife and socio-economic systems. This study addresses the meteorology of two different Arctic ROS events. The first, occurring near Nuuk, Greenland, generated significant impacts, including slush avalanches. The second, less severe, event occurred within the community of Iqaluit, Nunavut, Canada. This research utilizes atmospheric reanalysis, automated surface observation station data and atmospheric soundings to determine the meteorological conditions driving these events and the differences between each case. In both cases, atmospheric blocking played a leading role in ROS initiation, with atmospheric rivers – narrow bands of high water vapor transport, typically originating from the tropics and subtropics – having both direct and indirect effects. Cyclone-induced low-level jets and resultant ‘warm noses’ of higher air temperatures and moisture transport were other key features in ROS generation. To our knowledge, our study is the first to visualize how the varying strength and manifestation of these coupled features contribute to differences in the severity of Arctic ROS events. The meteorological drivers identified here find support from other studies on Arctic ROS events and are similar to weather features associated with Arctic precipitation events of extreme magnitude.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42465113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Selyuzhenok, T. Krumpen, D. Demchev, R. Gerdes, C. Haas
Using operational sea-ice maps, we provide first insight into the seasonal evolution of fast ice in the East Siberian Sea for the period between 1999 and 2021. The fast ice season tends to start later by 4.7 d per decade and to end earlier by 9.7 d per decade. As a result, there is a trend towards a shorter length of fast ice season by 2 weeks per decade. The analysis of air temperatures indicates that onset and end of the fast ice season are largely driven by thermodynamic processes. Two spatial modes (large, L-mode and small, S-mode) of East Siberian fast ice cover which have significant areal differences were distinguished. The occurrence of L- and S-modes was linked to the polarity of the Arctic Oscillation (AO) index. Negative AO phase leads to increased sea-ice convergence in the region, which in turn favours sea-ice grounding and promotes the development of large fast ice extent (L-mode). Lower deformation rates in the region during positive AO phase does not allow the formation of grounded features which results in small fast ice extent (S-mode). An analysis of sea-ice divergence confirms that L-mode seasons are characterised by higher on-shore convergence compared with S-mode seasons.
{"title":"The bimodality of the East Siberian fast ice extent: mechanisms and changes","authors":"V. Selyuzhenok, T. Krumpen, D. Demchev, R. Gerdes, C. Haas","doi":"10.1017/aog.2023.22","DOIUrl":"https://doi.org/10.1017/aog.2023.22","url":null,"abstract":"\u0000 Using operational sea-ice maps, we provide first insight into the seasonal evolution of fast ice in the East Siberian Sea for the period between 1999 and 2021. The fast ice season tends to start later by 4.7 d per decade and to end earlier by 9.7 d per decade. As a result, there is a trend towards a shorter length of fast ice season by 2 weeks per decade. The analysis of air temperatures indicates that onset and end of the fast ice season are largely driven by thermodynamic processes. Two spatial modes (large, L-mode and small, S-mode) of East Siberian fast ice cover which have significant areal differences were distinguished. The occurrence of L- and S-modes was linked to the polarity of the Arctic Oscillation (AO) index. Negative AO phase leads to increased sea-ice convergence in the region, which in turn favours sea-ice grounding and promotes the development of large fast ice extent (L-mode). Lower deformation rates in the region during positive AO phase does not allow the formation of grounded features which results in small fast ice extent (S-mode). An analysis of sea-ice divergence confirms that L-mode seasons are characterised by higher on-shore convergence compared with S-mode seasons.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44677574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.1130/abs/2020am-359713
Melisa A. Diaz, C. Gardner, D. Elliot, B. Adams, W. Lyons
Over the last two decades, anomalous warming events have been observed in coastal Antarctic regions. While these events have been documented in the Ross Sea sector, the Antarctic interior is believed to have been buffered from warming. In this work, we present data from lakes located near Mt. Heekin and Thanksgiving Valley (~85° S) along the Shackleton Glacier, which are believed to be the southern-most Antarctic dry valley lakes. In 2018, the lakes were characterized, repeat satellite images were examined, and lake water chemistry was measured. Our analysis shows that lake areas recently increased, and the water-soluble ion chemistry indicates a flushing of salts from periglacial soils, likely from increased glacial melt as illustrated by water isotope data. Our results show that high southern latitude ice-free areas have likely been affected by warm pulses over the past 60 years and these pulses may be quasi-synchronous throughout the Transantarctic Mountains.
{"title":"CHANGE AT 85 DEGREES SOUTH: SHACKLETON GLACIER REGION PROGLACIAL LAKES FROM 1960 TO 2020","authors":"Melisa A. Diaz, C. Gardner, D. Elliot, B. Adams, W. Lyons","doi":"10.1130/abs/2020am-359713","DOIUrl":"https://doi.org/10.1130/abs/2020am-359713","url":null,"abstract":"\u0000 Over the last two decades, anomalous warming events have been observed in coastal Antarctic regions. While these events have been documented in the Ross Sea sector, the Antarctic interior is believed to have been buffered from warming. In this work, we present data from lakes located near Mt. Heekin and Thanksgiving Valley (~85° S) along the Shackleton Glacier, which are believed to be the southern-most Antarctic dry valley lakes. In 2018, the lakes were characterized, repeat satellite images were examined, and lake water chemistry was measured. Our analysis shows that lake areas recently increased, and the water-soluble ion chemistry indicates a flushing of salts from periglacial soils, likely from increased glacial melt as illustrated by water isotope data. Our results show that high southern latitude ice-free areas have likely been affected by warm pulses over the past 60 years and these pulses may be quasi-synchronous throughout the Transantarctic Mountains.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45184409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Melisa A. Diaz, Christopher B. Gardner, David H. Elliot, Byron J. Adams, W. Berry Lyons
Abstract Over the last two decades, anomalous warming events have been observed in coastal Antarctic regions. While these events have been documented in the Ross Sea sector, the Antarctic interior is believed to have been buffered from warming. In this work, we present data from lakes located near Mt. Heekin and Thanksgiving Valley (~85° S) along the Shackleton Glacier, which are believed to be the southern-most Antarctic dry valley lakes. In 2018, the lakes were characterized, repeat satellite images were examined, and lake water chemistry was measured. Our analysis shows that lake areas recently increased, and the water-soluble ion chemistry indicates a flushing of salts from periglacial soils, likely from increased glacial melt as illustrated by water isotope data. Our results show that high southern latitude ice-free areas have likely been affected by warm pulses over the past 60 years and these pulses may be quasi-synchronous throughout the Transantarctic Mountains.
{"title":"Change at 85 degrees south: Shackleton Glacier region proglacial lakes from 1960 to 2020","authors":"Melisa A. Diaz, Christopher B. Gardner, David H. Elliot, Byron J. Adams, W. Berry Lyons","doi":"10.1017/aog.2023.27","DOIUrl":"https://doi.org/10.1017/aog.2023.27","url":null,"abstract":"Abstract Over the last two decades, anomalous warming events have been observed in coastal Antarctic regions. While these events have been documented in the Ross Sea sector, the Antarctic interior is believed to have been buffered from warming. In this work, we present data from lakes located near Mt. Heekin and Thanksgiving Valley (~85° S) along the Shackleton Glacier, which are believed to be the southern-most Antarctic dry valley lakes. In 2018, the lakes were characterized, repeat satellite images were examined, and lake water chemistry was measured. Our analysis shows that lake areas recently increased, and the water-soluble ion chemistry indicates a flushing of salts from periglacial soils, likely from increased glacial melt as illustrated by water isotope data. Our results show that high southern latitude ice-free areas have likely been affected by warm pulses over the past 60 years and these pulses may be quasi-synchronous throughout the Transantarctic Mountains.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136231635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
At any one time 130 000 icebergs are afloat in the Southern Ocean; 97% of these are too small to be registered in current satellite-based databases, yet the melting of these small icebergs provides a major input to the Southern Ocean. We use a unique set of visual size observations of 53 000 icebergs in the South Atlantic Ocean, the SCAR International Iceberg Database, to derive average iceberg dissolution rates. Fracture into two parts is the dominant dissolution process for tabular icebergs, with an average half-life of 30 days for icebergs <4 km length and 60 days for larger icebergs. Complete shatter producing many icebergs <1 km length is rare. A side attrition rate of 0.23 m d−1 combined with drift speed of 6 km d−1, or any proportional change in both numbers fits the observed changes in iceberg distribution. The largest injection into the Southern Ocean of fresh water and any iceberg-transported material takes place in a ~2.3 × 10⁶ km2 zone extending east-northeast from the Antarctic Peninsula to the Greenwich meridian. The iceberg contribution to salinities and temperatures, with maximum contribution north of the Weddell Sea, differs in some regions, from those indicated by tracking large icebergs.
在任何时候，南大洋上都漂浮着13万座冰山;其中97%的冰山太小，无法在目前的卫星数据库中登记，然而这些小冰山的融化为南大洋提供了一个主要的输入。我们利用SCAR国际冰山数据库对南大西洋53000座冰山进行的一组独特的视觉尺寸观测，得出冰山的平均溶解速率。崩裂成两段是板状冰山的主要溶解过程，长度<4 km的冰山平均半衰期为30天，长度较大的冰山平均半衰期为60天。完全破碎产生许多长度小于1公里的冰山是罕见的。0.23 m d - 1的侧磨率加上6 km d - 1的漂移速度，或者两者的任何比例变化都符合观测到的冰山分布变化。从南极半岛到格林威治子午线，向南大洋注入的最大淡水和冰山运输的物质约2.3 × 10 26平方公里。冰山对盐度和温度的贡献，在威德尔海以北的贡献最大，在一些地区与追踪大型冰山所显示的不同。
{"title":"Quantifying dissolution rates of Antarctic icebergs in open water","authors":"O. Orheim, A. B. Giles, T. H. Jacka, G. Moholdt","doi":"10.1017/aog.2023.26","DOIUrl":"https://doi.org/10.1017/aog.2023.26","url":null,"abstract":"\u0000 At any one time 130 000 icebergs are afloat in the Southern Ocean; 97% of these are too small to be registered in current satellite-based databases, yet the melting of these small icebergs provides a major input to the Southern Ocean. We use a unique set of visual size observations of 53 000 icebergs in the South Atlantic Ocean, the SCAR International Iceberg Database, to derive average iceberg dissolution rates. Fracture into two parts is the dominant dissolution process for tabular icebergs, with an average half-life of 30 days for icebergs <4 km length and 60 days for larger icebergs. Complete shatter producing many icebergs <1 km length is rare. A side attrition rate of 0.23 m d−1 combined with drift speed of 6 km d−1, or any proportional change in both numbers fits the observed changes in iceberg distribution. The largest injection into the Southern Ocean of fresh water and any iceberg-transported material takes place in a ~2.3 × 10⁶ km2 zone extending east-northeast from the Antarctic Peninsula to the Greenwich meridian. The iceberg contribution to salinities and temperatures, with maximum contribution north of the Weddell Sea, differs in some regions, from those indicated by tracking large icebergs.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46889963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Huidobro, J. Aramendia, G. Arana, E. Hausrath, J. Madariaga
Raman spectra (532 nm diode laser) of gypsum, syngenite and görgeyite powders were studied from 273 to 83 K every −10 K. Although it was found that not all the Raman peaks are temperature-sensitive, the effect of temperature on the Raman signal of some bands was modelled. It was observed that the main bands of the three sulfates shift toward higher wavenumbers as temperature decreases. The strengthening of the bonds causes an increase in energy and, consequently, higher wavenumbers. However, –OH bands shift depending on the crystal structure they acquire as the temperature decreases, so not all –OH bands behave in the same way. Finally, the gypsum –OH bands change to more ordered crystalline structures with decreasing temperature, so their bandwidths become narrower and sharper.
{"title":"The effect of low temperature on the Raman spectra of calcium-rich sulfates on Mars","authors":"J. Huidobro, J. Aramendia, G. Arana, E. Hausrath, J. Madariaga","doi":"10.1017/aog.2023.29","DOIUrl":"https://doi.org/10.1017/aog.2023.29","url":null,"abstract":"\u0000 Raman spectra (532 nm diode laser) of gypsum, syngenite and görgeyite powders were studied from 273 to 83 K every −10 K. Although it was found that not all the Raman peaks are temperature-sensitive, the effect of temperature on the Raman signal of some bands was modelled. It was observed that the main bands of the three sulfates shift toward higher wavenumbers as temperature decreases. The strengthening of the bonds causes an increase in energy and, consequently, higher wavenumbers. However, –OH bands shift depending on the crystal structure they acquire as the temperature decreases, so not all –OH bands behave in the same way. Finally, the gypsum –OH bands change to more ordered crystalline structures with decreasing temperature, so their bandwidths become narrower and sharper.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44605648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Steven Franke, Daniela Jansen, Tobias Binder, Nils Dörr, Veit Helm, John Paden, Daniel Steinhage, Olaf Eisen
An abstract is not available for this content. As you have access to this content, full HTML content is provided on this page. A PDF of this content is also available in through the ‘Save PDF’ action button.
{"title":"Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream – CORRIGENDUM","authors":"Steven Franke, Daniela Jansen, Tobias Binder, Nils Dörr, Veit Helm, John Paden, Daniel Steinhage, Olaf Eisen","doi":"10.1017/aog.2023.33","DOIUrl":"https://doi.org/10.1017/aog.2023.33","url":null,"abstract":"An abstract is not available for this content. As you have access to this content, full HTML content is provided on this page. A PDF of this content is also available in through the ‘Save PDF’ action button.","PeriodicalId":8211,"journal":{"name":"Annals of Glaciology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136319634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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