976 research outputs found
Insights into the seasonal dynamics of the lake-terminating glacier Fjallsjökull, South-East Iceland, inferred using ultra-high resolution repeat UAV imagery
No full textProglacial lakes are becoming ubiquitous at the termini of many glaciers worldwide, leading to increased glacier mass loss and terminus retreat due to the influence of these proglacial lakes on ice dynamics. However, despite the highly dynamic nature and relative insensitivity to climate of many lake-terminating glaciers, an understanding of the key processes forcing their behaviour is lacking. As a result, it is difficult at present to accurately assess and predict how these glaciers may respond in the future. A novel method to address this difficulty, however, is through the use of repeat uncrewed aerial vehicle (UAV) imagery, which can provide high to ultra-high resolution (cm-dm scale) imagery of the ice surface at varying spatial and temporal scales, depending on the needs of the study, although its use as a tool for investigating the dynamics of lake-terminating glaciers is so far limited. This research utilised ultra-high resolution repeat UAV imagery to provide insights into the changing dynamics of Fjallsjökull, a large lake-terminating glacier in southeast Iceland, across the 2019 and 2021 summer melt seasons. The findings indicate that the overall dynamics of the glacier are controlled by the ~120 m deep bedrock channel under the study region, which is causing the glacier to flow faster as it enters deeper water, leading to increased ice acceleration, thinning and retreat, with the glacier being decoupled from the local climate as a result. Such a close correspondence between ice velocity and surface thinning suggests the implementation of the positive feedback mechanism dynamic thinning in this region of Fjallsjökull, with such heightened rates of surface thinning and frontal retreat likely to continue in the future until the glacier recedes out of the bedrock channel into shallower water. Within this overall pattern, however, more localised, short-term changes in glacier dynamics were also observed, with these likely being forced primarily by subaqueous melting at the waterline, rather than the specific bedrock topography. Finally, supraglacial lake drainage may also be important for forcing sub-daily (e.g. hourly) increases in velocity, although further work is required to quantify its influence more accurately. As a result, these findings clearly indicate the complex nature of the calving process, as well as the dynamics of calving glaciers in general, highlighting the need for continued monitoring of lake-terminating glaciers at varying spatial and temporal scales in order to better understand and predict how they may respond in future
Insights into the seasonal dynamics of the lake-terminating glacier Fjallsjökull, south-east Iceland, inferred using ultra-high resolution repeat UAV imagery
No full textProglacial lakes are becoming ubiquitous at the termini of many glaciers worldwide, leading to increased glacier mass loss and terminus retreat due to the influence such lakes are having upon ice dynamics. However, despite the highly dynamic nature and relative insensitivity to climate of many lake-terminating glaciers, an understanding of the key processes forcing their behaviour is lacking. As a result, it is difficult at present to accurately assess and predict the future response of these glaciers to continued warming. In addition, current methods of investigating lake-terminating glacier dynamics primarily involve the use of satellite remote sensing, which despite its clear importance in cryospheric studies does suffer from important limitations. A novel alternative is the use of repeat unmanned aerial vehicle (UAV) imagery, which can provide high resolution (cm-scale) imagery of the ice surface at varying spatial and temporal scales, depending on the needs of the researcher. As a result, this study utilised ultra-high resolution repeat UAV imagery to provide insights into the changing dynamics of Fjallsjökull, a lake-terminating glacier in southeast Iceland, over two periods during the 2019 summer melt season. The findings indicate that the overall dynamics of the glacier are controlled by the ~120 m deep subglacial channel under the study region, which is causing the glacier to flow faster as it enters deeper water, leading to increased ice acceleration, thinning and retreat. Such a correspondence between ice velocity and surface thinning suggests the implementation of the positive feedback mechanism “dynamic thinning” in this region of Fjallsjökull, with such heightened rates of surface thinning and frontal retreat continuing in future until the glacier recedes out of the subglacial channel into shallower water. Within this overall pattern, however, more localised, short-term changes in glacier dynamics are also observed which are likely to be forced primarily by subaqueous melting at the waterline, rather than being solely influenced by the basal topography. Although further work is required to add additional support to these findings, they clearly indicate the complex nature of the calving process and the dynamics of calving glaciers in general, highlighting the need for continued monitoring of lake-terminating glaciers at varying spatial and temporal scales
UAV Laser Scanning surveys of the lake terminating glacier Fjallsjokull in SE Iceland, captured in July, 2021.
No full textThis dataset consists of 5 separate laser scanning surveys performed between the 8th and 15th July, 2021. Two surveys were conducted in the morning and afternoon of the 8th and the 9th, and then only the morning of the 15th. The point clouds have been cleaned to remove erroneous points. The point clouds were processed using the methods and code available at Direct_Georeferencing. All point clouds are georeferenced in the projected WGS 1984 UTM 28N system, and provided in the widely used compressed 'laz' format. An accuracy assessment of the data showed that all surveys were consistent to within 0.1 m of each other, apart from the second flight (afternoon) on the 8th July. Any users of this data should be aware of its limitations in a challenging cryospheric environment.</span
Processed UAV orthomosaics and DEMs of Fjallsjökull, southeast Iceland (2 of 2)
No full textOrthomosaics of the lower ice surface of Fjallsjökull, southeast Iceland, produced from high resolution UAV surveys undertaken in July 2021. This data was produced as part of my PhD research, and therefore, forms a significant component of my final PhD thesis. All files are in UTM Zone 28N. The resolution of the all the uploaded orthomosaics in this dataset is 0.02 m. Please note this is dataset 2 out of 2 (due to the 50 GB limit of file uploads). The DEMs and orthomosaics from 2019, DEMs from 2021, as well as three of the orthomosaics from 2021, have been uploaded to dataset 1 of 2 (DOI: 10.5281/zenodo.7105133). For reference, this dataset includes the orthomosaics produced from the following days in July 2021 (in separate files): 1) 8th 2) 9th 3) 10th 4) 11th 5) 12th 6) 15th</span
Processed UAV orthomosaics and DEMs of Fjallsjökull, southeast Iceland (1 of 2)
No full textOrthomosaics and DEMs of the lower ice surface of Fjallsjökull, southeast Iceland, produced from high resolution UAV surveys undertaken in July and September 2019, and July 2021. This data was produced as part of my PhD research, and therefore, forms a significant component of my final PhD thesis. All files are in UTM Zone 28N. The resolution of the uploaded orthomosaics and DEMs are given below. 2019 Orthomosaics and DEMs exported at 0.03 m and 0.07 m resolution, respectively. 2021 Orthomosaics and DEMs exported at 0.02 m and 0.05 m resolution, respectively. Please note this is dataset 1 out of 2 (due to the 50 GB limit of file uploads). The remaining orthomosaics from 2021 have been uploaded to dataset 2 of 2 (DOI: 10.5281/zenodo.7111111). Consequently this dataset only includes the following: 1) All orthomosaics and DEMs from 2019, produced from the following dates: 5th, 6th, 7th and 9th of July; 19th, 20th and 21st of September. 2) All DEMs from 2021, produced from the following dates: 4th, 6th, 7th, 8th, 9th, 10th, 11th, 12th and 15th of July. 3) Three orthomosaics from July 2021, produced from the following dates: 4th, 6th and 7th of July.</span
Evolution of the seasonal dynamics of the lake-terminating glacier Fjallsjökull, southeast Iceland, inferred using high-resolution repeat UAV imagery
No full textProglacial lakes are becoming ubiquitous at the termini of many glaciers worldwide, leading to increased glacier mass loss and terminus retreat, yet an understanding of the key processes forcing their behaviour is lacking. This study utilised high-resolution repeat uncrewed aerial vehicle (UAV)-Structure from Motion (SfM) imagery to provide insights into the changing dynamics of Fjallsjökull, a large lake-terminating glacier in southeast Iceland, across the 2019 and 2021 summer melt seasons. We show that the overall dynamics of the glacier are controlled by the ~120 m deep bedrock channel under the study region, which has caused the glacier to flow faster as it enters deeper water, leading to increased ice acceleration, thinning and retreat, with the glacier decoupled from local climate as a result. The close correspondence between ice velocity and surface thinning suggests the implementation of the dynamic thinning feedback mechanism, with such a response likely to continue in future until the glacier recedes out of the bedrock channel into shallower water. As a result, these findings clearly indicate the complex nature of the calving process, highlighting the need for continued monitoring of lake-terminating glaciers in order to better understand and predict how they may respond in future
Assessing UAV-based laser scanning for monitoring glacial processes and interactions at high spatial and temporal resolutions
No full textUncrewed Aerial Vehicles (UAVs), in combination with Structure from Motion (SfM) photogrammetry, have become an established tool for reconstructing glacial and ice-marginal topography, yet the method is highly dependent on several factors, all of which can be highly variable in glacial environments. However, recent technological advancements, related primarily to the miniaturisation of new payloads such as compact Laser Scanners (LS), has provided potential new opportunities for cryospheric investigation. Indeed, UAV-LS systems have shown promise in forestry, river, and snow depth research, but to date the method has yet to be deployed in glacial settings. As such, in this study we assessed the suitability of UAV-LS for glacial research by investigating short-term changes in ice surface elevation, calving front geometry and crevasse morphology over the near-terminus region of an actively calving glacier in southeast Iceland. We undertook repeat surveys over a 0.1 km2 region of the glacier at sub-daily, daily, and weekly temporal intervals, producing directly georeferenced point clouds at very high spatial resolutions (average of >300 points per m−2 at 40 m flying height). Our data has enabled us to: 1) Accurately map surface elevation changes (Median errors under 0.1 m), 2) Reconstruct the geometry and evolution of an active calving front, 3) Produce more accurate estimates of the volume of ice lost through calving, and 4) Better detect surface crevasse morphology, providing future scope to extract size, depth and improve the monitoring of their evolution through time. We also compared our results to data obtained in parallel using UAV-SfM, which further emphasised the relative advantages of our method and suitability in glaciology. Consequently, our study highlights the potential of UAV-LS in glacial research, particularly for investigating glacier mass balance, changing ice dynamics, and calving glacier behaviour, and thus we suggest it has a significant role in advancing our knowledge of, and ability to monitor, rapidly changing glacial environments in future
Quantifying subglacial soft bed sedimentary processes
No full textAn understanding of subglacial processes are a vital component of ice-sheet models for sea level rise prediction as the use of different sliding laws can result in very different outcomes. In particular, the West Antarctic ice streams, are potentially unstable, and are underlain by soft (unconsolidated) beds, which have rarely been studied. Innovative in situ wireless subglacial experiments and web connected RTK GPS data from Iceland have shown that stick-slick motion can occur at different time scales throughout the whole year, and this allowed the quantification of different sedimentary processes. We investigate the results from four soft bedded glaciers. We compare the similarities and differences; and in particular describe the relationship with subglacial hydrological processes and temperature rise. We discuss the implications for ice sheet models and reconstructions of Quaternary sedimentary processes
Increased winter warm events in Iceland drive enhanced glacier velocity and melting
No full textA key element in the comprehension of the response of glaciers to climate change is an understanding of the bed conditions, and these are a vital component of ice sheet models. The West Antarctic ice streams are potentially highly unstable, with implications for rapid sea level rise. These are underlain by unconsolidated sediments (soft-bed), which have a distinct but rarely studied subglacial hydrology. We present a detailed data set from Skálafellsjökull, a soft-bedded glacier in Iceland, as an analogue for other soft-bedded glaciers. These data include wireless in situ till water pressure, meteorological, surface melt, discharge and glacier surface velocity from GPS as well as remote sensing imagery. We show how short-term warm events during winter can effect annual velocity, and how the number of warm events has increased over the last 10 years. We argue this was because water was stored in a soft-bed subglacial reservoir where it could be rapidly released during winter, with the resultant storage levels effecting the following summer dynamics. To test whether warm winter events are unique to Iceland, we analyzed the daily air temperatures record of 18 World Glacier Monitoring Service ‘reference’ glaciers (1979-2018). We were able to show that periods of warm temperatures during winter were present in maritime locations, and the number of these events had increased in locations where winter temperatures had also increased. We propose that winter events are an important component of glacier retreat and sea level rise that have hitherto not been examined in detail
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