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  • 1
    Publication Date: 2018-03-01
    Print ISSN: 1088-1913
    Electronic ISSN: 1520-6483
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Published by Wiley
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  • 2
    Publication Date: 2023-10-09
    Description: Abstract
    Description: The DFG Priority Program 1803 "EarthShape - Earth Surface Shaping by Biota” (www.earthshape.net, short description of the project below) installed a meteorological station network consisting of four stations between ~26 °S to ~38 °S in the Coastal Cordillera of Chile, South America. The stations are intended to provide baseline meteorological data along the climate and ecological gradient investigated in the EarthShape program. The stations are located in the EarthShape study areas, encompassing desert, semi-desert, mediterranean, and temperate climate zones. Each station is configured to include sensors that record precipitation at ground level, radiation at 2.8 m height, wind at 3 m height, 25 cm depth soil temperature, soil water content and bulk electrical conductivity, 2 m air temperature and relative humidity, and barometric pressure at 30-minute intervals. The data recording started in March/April 2016. The EarthShape project runs until December 2021. Data collection will continue until that date, and potentially longer depending on available funds. This publication provides two sets of data: raw data and processed data. The raw data contains 2 file types per meteorological station: (1) all measured parameters of the whole dataset measured in 30 minutes intervals as downloaded from the station. Furthermore, we provide (2) one table per station of high-resolution precipitation events, measured in 5 min. intervals that were triggered during rain events at each station. The processed data consists of a continuous timeseries of observations since the activation of each station. The processing consists of the exclusion of erroneous data, caused by maintenance of the weather-stations and sporadic malfunction of sensors detected during data screening. The excluded data is communicated in a logfile (excel table), comments from data screening, solar eclipse and others are summarized in history files (ASCII ). the full description of the data and methods is provided in the data description file (Data description file).
    Description: Other
    Description: "EarthShape - Earth Surface Shaping by Biota" bridges between scientific disciplines and includes geoscientists and biologists to study from different viewpoints the complex question how microorganisms, animals, and plants influence the shape and development of the Earth’s surface over time scales from the present-day to the distant geologic past. All study sites are located in the north-to-south trending Coastal Cordillera mountains of Chile, South America. These sites span from the Atacama Desert in the north to the Araucaria forests approximately 1300 km to the south. The site selection contains a large ecological and climate gradient ranging from very dry to humid climate conditions.
    Keywords: South America ; Chile ; Cordillera de la Costa ; National Park Pan de Azúcar ; National Park Nahuelbuta ; National Park La Campana ; Private Reserve Santa Gracia ; EarthShape ; Campbell scientific ; radiation ; wind ; soil ; temperature ; precipitation ; pressure ; humidity ; weather station ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ATMOSPHERIC RADIATION 〉 SOLAR RADIATION ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ATMOSPHERIC TEMPERATURE 〉 AIR TEMPERATURE ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ATMOSPHERIC WATER VAPOR 〉 HUMIDITY ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ATMOSPHERIC WINDS 〉 SURFACE WINDS 〉 WIND SPEED/WIND DIRECTION ; EARTH SCIENCE 〉 ATMOSPHERE 〉 PRECIPITATION
    Type: Dataset , Dataset
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  • 3
    Publication Date: 2024-04-20
    Description: This dataset is supplementary material for the manuscript "Autonomous Rover Enables Radar Profiling of Ice-Fabric Properties in Antarctica" submitted to TGRS-IEEE journal (under review). The dataset comprises phase-sensitive radio echo sounder (pRES) radar data collected in quad-polarimetric Multiple Input Multiple Output (MIMO) mode during the Antarctic field season 2021-22 at the grounding zone of Ekström Ice Shelf in East Antarctica and was gathered with the logistical support of the Neumayer III station (Wesche et al., 2016). The dataset consists of several profiles: 1. Profile 1: 18 km, along-flow across grounding zone; 5 km were collected with 20 m shot spacing (QP_AlongFlow_20mSpacing) and 13 km with 100 m shot spacing (QP_AlongFlow_100mSpacing). 2. Profile 2: 5 km across-flow measurement at the grounding zone with 100 m spacings (QP_AcrossFlow_100mSpacing). 3. Profile 3: 0.7 km west of Neumayer III station with 1.5 m shot spacings (Neumayer_SAR_1.5mSpacing). 4. Two datasets of continuous measurements were obtained in a single burst while the rover was in motion (ContinuousQP). The data were collected to detect the change of ice fabric anisotropy in the grounding zone, where the ice transitions from grounded to floating. Additionally, the collection of quad-polarimetric MIMO pRES data was a proof of concept for autonomous data acquisition. The radar system was towed by an autonomous ice rover to predefined coordinates, triggering the radar. The antenna setup used a non-standard [Transmitter (VH) - (HV) Receiver] combination for quad-polarimetric (QP) data acquisition, requiring special consideration during processing, as detailed in the main paper (under review - TGRS IEEE) and RezaErshadi/pRES_InTheField_101 GitHub repository (doi:10.5281/zenodo.10064672). For the SAR profile the [Transmitter (HH) - (HH) Receiver] antenna setup was used. The pRES data were collected in standard mode using a 1-s chirp (Nicholls et al., 2015) in start-stop mode unless otherwise specified.
    Keywords: Binary Object; Binary Object (File Size); Binary Object (MD5 Hash); DATE/TIME; Ekstrom_Ice_Shelf_2022_pRES; LATITUDE; Local Time; LONGITUDE; Phase-sensitive radio echo sounder; pRES; Profile
    Type: Dataset
    Format: text/tab-separated-values, 2814 data points
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  • 4
    Publication Date: 2024-05-16
    Description: We estimated monthly mean basal melt rates in the Lagrangian frame from autonomous phase-sensitive radar (ApRES) measurements at the center of Ekström Ice Shelf, Antarctica (70.82°S, 8.73°W) between April 2020 and December 2022. The data we recorded with a measurement interval of one hour. Basal melt rates are based on the analysis of firn densification, strain thinning, and the change in ice thickness from the determination of vertical displacements. We calculated the mean basal melt rate as well as the standard deviation, and maximum for each month.
    Keywords: Antarctica; ANT-Land_2021_MIMO-EIS; ANT-Land_2022_MIMO-EIS; ANT-Land_2023_MIMO-EIS; ApRES; Autonomous phase-sensitive radio-echo sounder; Basal melt rates; DATE/TIME; EIS-8_ApRES_2020; EIS-8_ApRES_2021; EIS-8_ApRES_2022; Ekström; Ekström Ice Shelf; ice shelf basal melting; Melt rate; Melt rate, maximum; Melt rate, standard deviation; Monitoring Melt where Ice Meets Ocean; NEUMAYER III
    Type: Dataset
    Format: text/tab-separated-values, 99 data points
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  • 5
    Publication Date: 2022-05-18
    Description: Ice crystals are mechanically and dielectrically anisotropic. They progressively align under cumulative deformation, forming an ice-crystal-orientation fabric that, in turn, impacts ice deformation. However, almost all the observations of ice fabric are from ice core analysis, and its influence on the ice flow is unclear. Here, we present a non-linear inverse approach to process co- and cross-polarized phase-sensitive radar data. We estimate the continuous depth profile of georeferenced ice fabric orientation along with the reflection ratio and horizontal anisotropy of the ice column. Our method approximates the complete second-order orientation tensor and all the ice fabric eigenvalues. As a result, we infer the vertical ice fabric anisotropy, which is an essential factor to better understand ice deformation using anisotropic ice flow models. The approach is validated at two Antarctic ice core sites (EPICA (European Project for Ice Coring in Antarctica) Dome C and EPICA Dronning Maud Land) in contrasting flow regimes. Spatial variability in ice fabric characteristics in the dome-to-flank transition near Dome C is quantified with 20 more sites located along with a 36 km long cross-section. Local horizontal anisotropy increases under the dome summit and decreases away from the dome summit. We suggest that this is a consequence of the non-linear rheology of ice, also known as the Raymond effect. On larger spatial scales, horizontal anisotropy increases with increasing distance from the dome. At most of the sites, the main driver of ice fabric evolution is vertical compression, yet our data show that the horizontal distribution of the ice fabric is consistent with the present horizontal flow. This method uses polarimetric-radar data, which are suitable for profiling radar applications and are able to constrain ice fabric distribution on a spatial scale comparable to ice flow observations and models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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  • 6
    Publication Date: 2022-10-24
    Description: Anisotropic crystal fabrics in ice sheets develop as a consequence of deformation and hence record information of past ice flow. Simultaneously, the fabric affects the present-day bulk mechanical properties of glacier ice because the susceptibility of ice crystals to deformation is highly anisotropic. This is particularly relevant in dynamic areas such as fast-flowing glaciers and ice streams, where the formation of strong fabrics might play a critical role in facilitating ice flow. Anisotropy is ignored in most state-of-the-art ice sheet models, and while its importance has long been recognized, accounting for fabric evolution and its impact on the ice viscosity has only recently become feasible. Both the application of such models to ice streams and their verification through in-situ observations are still rare. Ice cores provide direct and detailed information on the crystal fabric, but the logistical cost, technical challenges, particularly in fast-flowing ice and shear margins, difficulty in reconstructing the absolute orientation of the core, and their limitation of being a point measurement, make ice cores impractical for a spatially extensive evaluation of the fabric type. Indirect geophysical methods applied from or above the ice surface create the link between the small scale of laboratory experiments and ice–core observations to the large-scale coverage required for ice flow models and the complete understanding of ice stream dynamics. Here, we present a comprehensive analysis of the distribution of the ice fabric in the upstream part of the North-East Greenland Ice Stream (NEGIS). Our results are based on a combination of methods applied to extensive airborne and ground-based radar surveys, ice- and firn-core observations, and numerical ice-flow modelling. They show that in the onset region of NEGIS and around the EGRIP ice core drilling site, the fabric is horizontally strongly anisotropic, forming a horizontal girdle perpendicular to the ice flow, while the horizontal anisotropy reduces quickly over distances of less than five ice thicknesses outside of the ice stream’s shear margins. Downstream of the drill site, the fabric develops into a more vertically symmetric configuration on a time scale of around 2 ka, the first observation of this kind. Our study shows how ice-core based fabric observations, geophysical surveys and ice-flow modelling complement each other to obtain a more comprehensive picture of the spatially strongly varying fabric.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
    Format: application/pdf
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  • 7
    Publication Date: 2022-10-04
    Description: Anisotropic crystal fabrics in ice sheets develop as a consequence of deformation and hence record information of past ice flow. Simultaneously, the fabric affects the present-day bulk mechanical properties of glacier ice because the susceptibility of ice crystals to deformation is highly anisotropic. This is particularly relevant in dynamic areas such as fast-flowing glaciers and ice streams, where the formation of strong fabrics might play a critical role in facilitating ice flow. This fact is ignored in most state-of-the-art ice sheet models, and while their importance has been recognized years ago, accounting for fabrics evolution and their impact on the ice viscosity has only recently become feasible. Both, the application of such models in ice streams as well as their verification through in-situ observations are, however, still rare. We present an extensive dataset of fabric anisotropy derived from radar data recorded in the onset region of the Northeast Greenland Ice Stream by air-borne and ground-based systems. Our methods yield the horizontal anisotropy and are based on travel time anisotropy and splitting as well as birefringence-induced power modulation of radar signals. They complement each other and show good agreement. We compare these in-situ observations with the results obtained from a fabric-evolution model employed along flow tubes in the ice stream onset to discuss the fabric in light of past flow history and its significance for the current flow mechanics of the ice stream.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
    Publication Date: 2023-10-19
    Description: The dynamic mass loss of ice sheets constitutes one of the biggest uncertainties in projections of ice-sheet evolution. One central, understudied aspect of ice flow is how the bulk orientation of the crystal orientation fabric translates to the mechanical anisotropy of ice. Here we show the spatial distribution of the depth-averaged horizontal anisotropy and corresponding directional flow-enhancement factors covering a large area of the Northeast Greenland Ice Stream onset. Our results are based on airborne and ground-based radar surveys, ice-core observations, and numerical ice-flow modelling. They show a strong spatial variability of the horizontal anisotropy and a rapid crystal reorganisation on the order of hundreds of years coinciding with the ice-stream geometry. Compared to isotropic ice, parts of the ice stream are found to be more than one order of magnitude harder for along-flow extension/compression while the shear margins are potentially softened by a factor of two for horizontal-shear deformation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Copernicus Publications
    In:  EPIC3The Cryosphere, Copernicus Publications, 17(3), pp. 1097-1105, ISSN: 1994-0416
    Publication Date: 2024-03-14
    Description: The bulk crystal orientation in ice influences the flow of glaciers and ice streams. The ice c-Axes fabric is most reliably derived from ice cores. Because these are sparse, the spatial and vertical distribution of the fabric in the Greenland and Antarctic ice sheets is largely unknown. In recent years, methods have been developed to determine fabric characteristics from polarimetric radar measurements. The aim of this paper is to present an improved method to infer the horizontal fabric asymmetry by precisely determining the travel-Time difference using co-polarised phase-sensitive radar data. We applied this method to six radar measurements from the East Greenland Ice-core Project (EastGRIP) drill site on Greenland's largest ice stream to give a proof of concept by comparing the results with the horizontal asymmetry of the bulk crystal anisotropy derived from the ice core. This comparison shows an excellent agreement, which is a large improvement compared to previously used methods. Our approach is particularly useful for determining the vertical profile of the fabric asymmetry in higher resolution and over larger depths than was achievable with previous methods, especially in regions with strong asymmetry.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
    Publication Date: 2021-01-09
    Description: The DFG Priority Program 1803 "EarthShape - Earth Surface Shaping by Biota” (www.earthshape.net, short description of the project below) installed a meteorological station network consisting of four stations between ~}26 °S to {~38 °S in the Coastal Cordillera of Chile, South America. The stations are intended to provide baseline meteorological data along the climate and ecological gradient investigated in the EarthShape program. The stations are located in the EarthShape study areas, encompassing desert, semi-desert, mediterranean, and temperate climate zones. Each station is configured to include sensors that record precipitation at ground level, radiation at 2.8 m height, wind at 3 m height, 25 cm depth soil temperature, soil water content and bulk electrical conductivity, 2 m air temperature and relative humidity, and barometric pressure at 30-minute intervals. The data recording started in March/April 2016. The EarthShape project runs until December 2021. Data collection will continue until that date, and potentially longer depending on available funds. This publication provides two sets of data: raw data and processed data. The raw data contains 2 file types per meteorological station: (1) all measured parameters of the whole dataset measured in 30 minutes intervals as downloaded from the station. Furthermore, we provide (2) one table per station of high-resolution precipitation events, measured in 5 min. intervals that were triggered during rain events at each station. The processed data consists of a continuous timeseries of observations since the activation of each station. The processing consists of the exclusion of erroneous data, caused by maintenance of the weather-stations and sporadic malfunction of sensors detected during data screening. The excluded data is communicated in a logfile (excel table), comments from data screening, solar eclipse and others are summarized in history files (ASCII ). the full description of the data and methods is provided in the data description file (Data description file).
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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