scholarly journals RADAR-DERIVED INTERNAL LAYERING AND BASAL ROUGHNESS CHARACTERIZATION ALONG A TRAVERSE FROM ZHONGSHAN STATION TO DOME A, EAST ANTARCTICA

2020 ◽  
Vol XLIII-B3-2020 ◽  
pp. 905-910
Author(s):  
X. Tang ◽  
K. Luo ◽  
J. Guo
Keyword(s):  
Ice Sheet ◽  
Radar Data ◽  
Internal Layers ◽  
Dome A ◽  
Ice Flow ◽  
Zhongshan Station ◽  
Bed Topography ◽  
New Information ◽  
Flow Activity ◽  
Lambert Glacier

Abstract. The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the englacial conditions and ice-flow field. This paper presents a new detailed analysis of the spatial distribution characteristics of internal layers and subglacial topography of East Antarctic ice sheet (EAIS) from Zhongshan station to Dome A. Taking the internal layering continuity index (ILCI) and basal roughness as indicators, it provides an opportunity to evaluate the past internal environment and dynamics of ice sheet. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS was collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). Except for the upstream of Lambert Glacier, the patterns of the folds in the internal layers are basically similar to the bed topography. The relatively flat basal topography and the decrease of ILCI with the deepening of the depth provide evidence for identifying previous rapid ice flow areas that the satellite cannot obtain, especially in the upstream of Lambert Glacier. Well continuous internal layers of Dome A almost extend to the bed, with high ILCI and high roughness characteristics. There are three kinds of basal roughness patterns in the whole traverse. The characteristics of the internal layer and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS.

scholarly journals Radar-Derived Internal Structure and Basal Roughness Characterization along a Traverse from Zhongshan Station to Dome A, East Antarctica

2020 ◽  
Vol 12 (7) ◽  
pp. 1079
Author(s):  
Kun Luo ◽  
Sixin Liu ◽  
Jingxue Guo ◽  
Tiantian Wang ◽  
Lin Li ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Radar Data ◽  
Frequency Variation ◽  
Internal Layers ◽  
Dome A ◽  
Ice Flow ◽  
Zhongshan Station ◽  
Bed Topography ◽  
Flow Activity ◽  
Lambert Glacier

The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the ice-flow field and englacial conditions. This paper presents a new detailed analysis of spatial distribution characteristics of internal layers and subglacial topography of the East Antarctic ice sheet (EAIS) from Zhongshan Station to Dome A. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS were collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). In this study, the Internal Layering Continuity Index (ILCI) and basal roughness were taken as indicators to provide an opportunity to evaluate the past internal environment and dynamics of the ice sheet. Except for the upstream of Lambert Glacier, the fold patterns of internal layers are basically similar to that of the bed topography. The relatively flat basal topography and the decrease of ILCI with increasing depth provide evidence for identifying previous rapid ice flow areas that are unavailable to satellites, especially in the upstream of Lambert Glacier. Continuous internal layers of Dome A, recording the spatial change of past ice accumulation and ice-flow history over 160 ka, almost extend to the bed, with high ILCI and high basal roughness of the corresponding bed topography. There are three kinds of basal roughness patterns along the traverse, that is, “low ξt low η”, “low ξt high η”, and “high ξt high η”, where ξt represents the amplitude of the undulations, and quantifies the vertical variation of the bedrock, and η measures the frequency variation of fluctuations and the horizontal irregularity of the profile. The characteristics of internal layers and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS.

scholarly journals Ice velocity from static GPS observations along the transect from Zhongshan station to Dome A, East Antarctica

2008 ◽  
Vol 48 ◽  
pp. 113-118 ◽  
Author(s):  
Zhang Shengkai ◽  
E Dongchen ◽  
Wang Zemin ◽  
Li Yuansheng ◽  
Jin Bo ◽  
...  
Keyword(s):  
Ice Sheet ◽  
East Antarctica ◽  
Dual Frequency ◽  
Dome A ◽  
Ice Dynamics ◽  
Zhongshan Station ◽  
Plateau Area ◽  
Ice Sheet Dynamics ◽  
Surface Ice ◽  
Lambert Glacier

AbstractDome A, the highest point on the Antarctic ice sheet at just over 4000 ma.s.l., is located near the centre of East Antarctica. Chinese National Antarctic Research Expeditions have studied ice-sheet dynamics and mass balance along a traverse route from Zhongshan station to Dome A during the austral summers from 1996/97 to 2004/05. Nineteen GPS sites were occupied on at least two occasions at approximately 50 km intervals. The purpose of the surveys was to provide accurate ice-dynamics data. A dual-frequency GPS receiver was used and each site was occupied for 1–12 hours. GPS data were processed using GAMIT/GLOBK software, and horizontal accuracies were within 0.1 m. Repeat GPS measurements provided ice velocities. The horizontal surface ice velocities increase from the summit of the ice sheet to the coast. In the Dome A area, the velocities are <10ma–1; in the plateau area, velocities range from 8 to 24 ma–1 and reach about 98.2 ma–1 at a site (LT980) near the coast. The flow directions are roughly perpendicular to the ice-sheet surface elevation contours, primarily toward the Lambert Glacier basin.

Three-dimensional ice sheet structure at Dome C, central East Antarctica: implications for the interpretation of the EPICA ice core

2001 ◽  
Vol 13 (2) ◽  
pp. 182-187 ◽  
Author(s):  
Martin J. Siegert ◽  
Richard D. Eyers ◽  
Ignazio E. Tabacco
Keyword(s):  
Ice Core ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Local Variation ◽  
Radar Data ◽  
East Antarctica ◽  
Airborne Radar ◽  
Internal Layers ◽  
Ice Flow ◽  
Core Site

Airborne radar data acquired in 1995 by the Italian Antarctic Programme over Dome C in central East Antarctica were processed to develop maps of internal isochronous ice sheet layering around the EPICA ice core site. Three internal layers were traced continuously across the radar-survey area at ice depths of 1–2 km. The maps reveal that the ice core site is located where internal layers are near horizontal to depths of at least 2 km. The Italian radar data do not resolve internal layers below 2 km. However, radar data collected over this part of East Antarctica in the 1970s show the internal layers to depths of up to 4 km. These internal layers reveal the regional structure of ice to the west of Dome C. Layers from both surveys are dated through an existing chronostratigraphic link between the Vostok ice core site and Dome C. The pattern of internal layering at Dome C reflects relatively steady conditions of ice flow and accumulation for the last 100 000 years. However, for ice older than this we show that there is significant local variation in the thickness between internal layers and the ice-sheet base. Our maps provide an indication of the structure of the ice sheet from which the EPICA deep ice core will be taken.

scholarly journals A new bedrock and surface elevation dataset for modelling the Greenland ice sheet

2003 ◽  
Vol 37 ◽  
pp. 351-356 ◽  
Author(s):  
Jonathan L. Bamber ◽  
Duncan J. Baldwin ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Detailed Comparison ◽  
Radar Data ◽  
The Arctic ◽  
Small Scale ◽  
Surface Model ◽  
Rock Outcrops ◽  
Bed Topography ◽  
Elevation Model

AbstractA new digital elevation model of the surface of the Greenland ice sheet and surrounding rock outcrops has been produced from a comprehensive suite of satellite and airborne remote-sensing and cartographic datasets. The surface model has been regridded to a resolution of 5 km, and combined with a new ice-thickness grid derived from ice-penetrating radar data collected in the 1970s and 1990s. A further dataset, the International Bathymetric Chart of the Arctic Ocean, was used to extend the bed elevations to include the continental shelf. The new bed topography was compared with a previous version used for ice-sheet modelling. Near the margins of the ice sheet and, in particular, in the vicinity of small-scale features associated with outlet glaciers and rapid ice motion, significant differences were noted. This was highlighted by a detailed comparison of the bed topography around the northeast Greenland ice stream.

scholarly journals Of isbræ and ice streams

2003 ◽  
Vol 36 ◽  
pp. 66-72 ◽  
Author(s):  
Martin Truffer ◽  
Keith A. Echelmeyer
Keyword(s):  
Ice Sheet ◽  
Shear Zones ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Bed Topography ◽  
Ice Stream ◽  
Fast Ice ◽  
Fast Flow ◽  
End Members

AbstractFast-flowing ice streams and outlet glaciers provide the major avenues for ice flow from past and present ice sheets. These ice streams move faster than the surrounding ice sheet by a factor of 100 or more. Several mechanisms for fast ice-stream flow have been identified, leading to a spectrum of different ice-stream types. In this paper we discuss the two end members of this spectrum, which we term the “ice-stream” type (represented by the Siple Coast ice streams in West Antarctica) and the “isbræ” type (represented by Jakobshavn Isbræ in Greenland). The typical ice stream is wide, relatively shallow (∼1000 m), has a low surface slope and driving stress (∼10 kPa), and ice-stream location is not strongly controlled by bed topography. Fast flow is possible because the ice stream has a slippery bed, possibly underlain by weak, actively deforming sediments. The marginal shear zones are narrow and support most of the driving stress, and the ice deforms almost exclusively by transverse shear. The margins seem to be inherently unstable; they migrate, and there are plausible mechanisms for such ice streams to shut down. The isbræ type of ice stream is characterized by very high driving stresses, often exceeding 200 kPa. They flow through deep bedrock channels that are significantly deeper than the surrounding ice, and have steep surface slopes. Ice deformation includes vertical as well as lateral shear, and basal motion need not contribute significantly to the overall motion. The marginal shear zone stend to be wide relative to the isbræ width, and the location of isbræ and its margins is strongly controlled by bedrock topography. They are stable features, and can only shut down if the high ice flux cannot be supplied from the adjacent ice sheet. Isbræs occur in Greenland and East Antarctica, and possibly parts of Pine Island and Thwaites Glaciers, West Antarctica. In this paper, we compare and contrast the two types of ice streams, addressing questions such as ice deformation, basal motion, subglacial hydrology, seasonality of ice flow, and stability of the ice streams.

scholarly journals Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream

2020 ◽  
Vol 61 (81) ◽  
pp. 143-153 ◽  
Author(s):  
Steven Franke ◽  
Daniela Jansen ◽  
Tobias Binder ◽  
Nils Dörr ◽  
Veit Helm ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ultra Wideband ◽  
Ice Flow ◽  
Detailed Model ◽  
Dynamic Component ◽  
Bed Topography ◽  
Ice Stream ◽  
Topography Model

AbstractThe Northeast Greenland Ice Stream (NEGIS) is an important dynamic component for the total mass balance of the Greenland ice sheet, as it reaches up to the central divide and drains 12% of the ice sheet. The geometric boundary conditions and in particular the nature of the subglacial bed of the NEGIS are essential to understand its ice flow dynamics. We present a record of more than 8000 km of radar survey lines of multi-channel, ultra-wideband radio echo sounding data covering an area of 24 000 km2, centered on the drill site for the East Greenland Ice-core Project (EGRIP), in the upper part of the NEGIS catchment. Our data yield a new detailed model of ice-thickness distribution and basal topography in the region. The enhanced resolution of our bed topography model shows features which we interpret to be caused by erosional activity, potentially over several glacial–interglacial cycles. Off-nadir reflections from the ice–bed interface in the center of the ice stream indicate a streamlined bed with elongated subglacial landforms. Our new bed topography model will help to improve the basal boundary conditions of NEGIS prescribed for ice flow models and thus foster an improved understanding of the ice-dynamic setting.

scholarly journals Primary results of glaciological studies along an 1100 km transect from Zhongshan station to Dome A, East Antarctic ice sheet

2000 ◽  
Vol 31 ◽  
pp. 198-204 ◽  
Author(s):  
Qin Dahe ◽  
Ren Jiawen ◽  
Kang Jiancheng ◽  
Xiao Cunde ◽  
Li Zhongqin ◽  
...  
Keyword(s):  
Mass Balance ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Ice Cores ◽  
Spatial And Temporal Variability ◽  
Dome A ◽  
Antarctic Ice Sheet ◽  
Zhongshan Station ◽  
Inaccessible Area ◽  
East Antarctic Ice Sheet

AbstractThe Chinese National Antarctic Research Expedition (GHINARE) carried out three traverses from Zhongshan station to Dome A, Princess Elizabeth Land and Inaccessible Area, East Antarctic ice sheet, during the 1996/97 to 1998/99 Antarctic field seasons. The expeditions are part of the Chinese International Trans-Antarctic Scientific Expedition program. In this project, glaciological investigations of mass balance, ice temperature, ice flow, stratigraphy in snow pits and snow/firn ice cores, as well as the glaciochemical study of surface snow and shallow ice cores, have been carried out. In the 1998/99 field season, CHINARE extended the traverse route to 1128 km inland from Zhongshan station. The density profiles show that firnification over Princess Elizabeth Land and Inaccessible Area (290–1100 km along the route) is fairly slow, and the accumulation rate recovered from snow pits along the initial 460 km of the route is 4.6–21 cm (46–210 kg m–2a–1 ) water equivalent. The initial 460 km of the route can be divided into four sections based on the differences of accumulation rate. This pattern approximately coincides with the study on the Lambert Glacier basin (LGB) by Australian scientists. During the past 50 years, the trends of both air temperature and accumulation rate show a slight increase in this area, in contrast to the west side of the LGB. Data on surface accumulation rates and their spatial and temporal variability over ice-drainage areas such as the LGB are essential for precise mass-balance calculation of the whole ice sheet, and are important for driving ice-sheet models and testing atmospheric models.

scholarly journals EXTRACTION OF ICE SHEET LAYERS FROM TWO INTERSECTED RADAR ECHOGRAMS NEAR NEEM ICE CORE IN GREENLAND

2016 ◽  
Vol XLI-B7 ◽  
pp. 585-591 ◽  
Author(s):  
S. Xiong ◽  
J.-P. Muller
Keyword(s):  
Ice Core ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Electromagnetic Properties ◽  
Flow Mode ◽  
Internal Layers ◽  
Ice Flow ◽  
The North ◽  
Radar Echo ◽  
Echo Sounder

Accumulation of snow and ice over time result in ice sheet layers. These can be remotely sensed where there is a contrast in electromagnetic properties, which reflect variations of the ice density, acidity and fabric orientation. Internal ice layers are assumed to be isochronous, deep beneath the ice surface, and parallel to the direction of ice flow. The distribution of internal layers is related to ice sheet dynamics, such as the basal melt rate, basal elevation variation and changes in ice flow mode, which are important parameters to model the ice sheet. Radar echo sounder is an effective instrument used to study the sedimentology of the Earth and planets. Ice Penetrating Radar (IPR) is specific kind of radar echo sounder, which extends studies of ice sheets from surface to subsurface to deep internal ice sheets depending on the frequency utilised. In this study, we examine a study site where folded ice occurs in the internal ice sheet south of the North Greenland Eemian ice drilling (NEEM) station, where two intersected radar echograms acquired by the Multi-channel Coherent Radar Depth Sounder (MCoRDS) employed in the NASA’s Operation IceBridge (OIB) mission imaged this folded ice. We propose a slice processing flow based on a Radon Transform to trace and extract these two sets of curved ice sheet layers, which can then be viewed in 3-D, demonstrating the 3-D structure of the ice folds.

scholarly journals Stochastic modeling of subglacial topography exposes uncertainty in water routing at Jakobshavn Glacier

2020 ◽  
pp. 1-9
Author(s):  
Emma J. MacKie ◽  
Dustin M. Schroeder ◽  
Chen Zuo ◽  
Zhen Yin ◽  
Jef Caers
Keyword(s):  
Mass Conservation ◽  
Simulation Method ◽  
Radar Data ◽  
Geostatistical Simulation ◽  
Ice Flow ◽  
Bed Topography ◽  
Drainage Patterns ◽  
Secondary Constraint ◽  
Subglacial Topography ◽  
Data Coverage

Abstract Subglacial topography is an important feature in numerous ice-sheet analyses and can drive the routing of water at the bed. Bed topography is primarily measured with ice-penetrating radar. Significant gaps, however, remain in data coverage that require interpolation. Topographic interpolations are typically made with kriging, as well as with mass conservation, where ice flow dynamics are used to constrain bed geometry. However, these techniques generate bed topography that is unrealistically smooth at small scales, which biases subglacial water flowpath models and makes it difficult to rigorously quantify uncertainty in subglacial drainage patterns. To address this challenge, we adapt a geostatistical simulation method with probabilistic modeling to stochastically simulate bed topography such that the interpolated topography retains the spatial statistics of the ice-penetrating radar data. We use this method to simulate subglacial topography using mass conservation topography as a secondary constraint. We apply a water routing model to each of these realizations. Our results show that many of the flowpaths significantly change with each topographic realization, demonstrating that geostatistical simulation can be useful for assessing confidence in subglacial flowpaths.

Relict flow stripes on the Ross Ice Shelf

1991 ◽  
Vol 15 ◽  
pp. 132-138 ◽  
Author(s):  
G. Casassa ◽  
K.C. Jezek ◽  
J. Turner ◽  
I.M. Whillans
Keyword(s):  
Ice Sheet ◽  
Radar Data ◽  
Present Position ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Flow ◽  
Ross Ice Shelf ◽  
Avhrr Data ◽  
Complex Patterns

Analysis of AVHRR data collected during the summer and winter over the Ross Ice Shelf reveals complex patterns of curvilinear stripes. In particular, a large, looping pattern of stripes is observed west of Crary Ice Rise in an area where conventional glaciological data collected with surface and airborne methods have been interpreted to suggest uncomplicated flow. On the basis of previous work using radar data to study ice flow downstream of Crary Ice Rise, we conclude that the stripes represent relict flowlines. The mechanism that produces these stripes is unclear, but we hypothesize that they are associated with subtle topography. Based solely on the patterns of stripes and their location in the outflow of major ice streams, we propose that they are related to an ice raft torn from the grounded ice sheet about 400 km upstream from its present position.

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