scholarly journals Sedimentary architecture and landforms of the Late Saalian (MIS 6) ice sheet margin, offshore the Netherlands

2021 ◽  
Author(s):  
Víctor Cartelle ◽  
Natasha L. M. Barlow ◽  
David M. Hodgson ◽  
Freek S. Busschers ◽  
Kim M. Cohen ◽  
...  
Keyword(s):  
The Netherlands ◽  
Global Climate ◽  
Ice Sheet ◽  
Ice Dynamics ◽  
Shallow Subsurface ◽  
Local Evidence ◽  
Sedimentary Architecture ◽  
Ice Retreat ◽  
Glaciogenic Sediments ◽  
Subglacial Meltwater

Abstract. Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding the relationships between global climate and sea-level change, and to testing numerical ice sheet models. In this study, we integrate recently acquired high-resolution 2D-seismic reflection and borehole datasets from two windfarm sites offshore the Netherlands to investigate the sedimentary, geomorphological and glaciotectonic records left by the Saalian Drenthe substage glaciation, when Scandinavian land ice reached its southernmost extent in the southern North Sea (ca. 160 ka, Marine Isotope Stage 6). A complex assemblage of glaciogenic sediments and glaciotectonic structures are buried in the shallow subsurface. The northern windfarm site revealed a set of NE-SW oriented subglacial meltwater channels filled with till and glaciofluvial sediments and an E-W trending composite ridge with local evidence of intense glaciotectonic deformation that denotes the maximum limit reached by the ice. Based on the identified glacial geomorphology, we refine the mapping of the maximum ice-sheet extent offshore the Netherlands, revealing that the ice margin morphology is more complex than previously envisaged, displaying a lobate shape. Ice retreat left an unusual paraglacial landscape characterised by the progressive infilling of topographic depressions carved during the ice advance and a diffuse drainage network of outwash channels. The net direction of outwash was to the west and southwest into a nearby glacial basin. Antecedent topography influenced subglacial bed conditions, and their impact on ice dynamics during the glaciation and deglaciation stages. We demonstrate the utility of offshore windfarm data in refining palaeo ice margin limits, and the record of processes interactions preserved in buried landscapes to help inform longer-term drivers of change at low relief ice margins.

scholarly journals Sedimentary architecture and landforms of the late Saalian (MIS 6) ice sheet margin offshore of the Netherlands

2021 ◽  
Vol 9 (6) ◽  
pp. 1399-1421
Author(s):  
Víctor Cartelle ◽  
Natasha L. M. Barlow ◽  
David M. Hodgson ◽  
Freek S. Busschers ◽  
Kim M. Cohen ◽  
...  
Keyword(s):  
The Netherlands ◽  
Wind Farm ◽  
Global Climate ◽  
Ice Sheet ◽  
Offshore Wind ◽  
Shallow Subsurface ◽  
Local Evidence ◽  
Sedimentary Architecture ◽  
Ice Retreat ◽  
Subglacial Meltwater

Abstract. Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding the relationships between global climate and sea-level change and to testing numerical ice sheet models. In this study, we integrate recently acquired high-resolution 2D seismic reflection and borehole datasets from two wind-farm sites offshore of the Netherlands to investigate the sedimentary, geomorphological, and glaciotectonic records left by the Saalian Drenthe substage glaciation, when Scandinavian land ice reached its southernmost extent in the southern North Sea (ca. 160 ka, Marine Isotope Stage 6). A complex assemblage of glaciogenic sediments and glaciotectonic structures is buried in the shallow subsurface. The northern wind-farm site revealed a set of NE–SW-oriented subglacial meltwater channels filled with till and glaciofluvial sediments and an E–W-trending composite ridge with local evidence of intense glaciotectonic deformation that denotes the maximum limit reached by the ice. Based on the identified glacial geomorphology, we refine the mapping of the maximum ice sheet extent offshore, revealing that the ice margin morphology is more complex than previously envisaged and displaying a lobate shape. Ice retreat left an unusual paraglacial landscape characterised by the progressive infilling of topographic depressions carved by ice-driven erosion and a diffuse drainage network of outwash channels. The net direction of outwash was to the west and southwest into a nearby glacial basin. We demonstrate the utility of offshore wind-farm data as records of process–form relationships preserved in buried landscapes, which can be utilised in refining palaeo-ice sheet margins and informing longer-term drivers of change in low-relief settings.

scholarly journals ICESHEET 1.0: a program to produce paleo-ice sheet reconstructions with minimal assumptions

2016 ◽  
Vol 9 (5) ◽  
pp. 1673-1682 ◽  
Author(s):  
Evan J. Gowan ◽  
Paul Tregoning ◽  
Anthony Purcell ◽  
James Lea ◽  
Oscar J. Fransner ◽  
...  
Keyword(s):  
Steady State ◽  
Barents Sea ◽  
Global Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Computational Time ◽  
Climate Modelling ◽  
Ice Dynamics ◽  
Perfectly Plastic ◽  
Input Parameters

Abstract. We describe a program that produces paleo-ice sheet reconstructions using an assumption of steady-state, perfectly plastic ice flow behaviour. It incorporates three input parameters: ice margin, basal shear stress and basal topography. Though it is unlikely that paleo-ice sheets were ever in complete steady-state conditions, this method can produce an ice sheet without relying on complicated and unconstrained parameters such as climate and ice dynamics. This makes it advantageous to use in glacial-isostatic adjustment ice sheet modelling, which are often used as input parameters in global climate modelling simulations. We test this program by applying it to the modern Greenland Ice Sheet and Last Glacial Maximum Barents Sea Ice Sheet and demonstrate the optimal parameters that balance computational time and accuracy.

A LiDAR-based glacial landform map of the Kebnekaise massif, northern Sweden

2020 ◽  
Author(s):  
Calum Edward ◽  
Robin Blomdin ◽  
Gunhild Rosqvist
Keyword(s):  
Global Climate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Aerial Photographs ◽  
Terrain Model ◽  
Scandinavian Ice Sheet ◽  
The Face ◽  
Ice Retreat ◽  
Ground Truthing ◽  
Glacial Landforms

<p>In the face of global climate change, and the associated melting of the modern-day ice sheets, the understanding and reconstruction of the dynamics and retreats of former ice sheets has become an increasingly valuable tool and indicator of the future behaviour of present-day ice masses. The deglacial period that followed the Last Glacial Maximum (~22-9 thousand years ago) represents the most recent major warming event, and final ice sheet decay, in Earth history, and is an important analogue for the threat of present-day ice sheet collapse. The recent availability of the 2m-resolution Swedish LiDAR based terrain model provides the opportunity to map glacial landforms and landscapes over large areas with greater accuracy than was previously possible through satellite images or aerial photographs. In combination with field observation-based ground-truthing, this LiDAR resource is employed to map the geomorphology of the Kebnekaise region of the northern Swedish mountains with the principal aim of producing a landform-driven reconstruction of the deglaciation of the remnant Scandinavian Ice Sheet during its final stage of retreat. The complex ‘palimpsest’ landscape is delineated and interpreted through the classification of landforms according to their relative age and respective origin. In particular, attention will be given to the segregation of glacial (e.g., terminal moraines, lineations), deglacial (e.g., eskers, lateral meltwater channels, glacial lake shorelines) and ‘relict’ (i.e., pre-glacial palaeosurfaces) landform assemblages, in order to demarcate those formed during the final deglaciation.   The resulting landform selections are used to delineate high-resolution ice retreat patterns, giving indication to the nature of the basal thermal regime, topographic response and final remnant location of the ice sheet. Additionally, this assay serves as an evaluation of the use of the Swedish LiDAR database as a means of efficiently and accurately mapping previously-glaciated landscapes. Our deglaciation reconstruction will finally be tested against formerly produced regional reconstructions.</p>

scholarly journals ICESHEET 1.0: A program to produce paleo-ice sheet models with minimal assumptions

2016 ◽  
Author(s):  
E. J. Gowan ◽  
P. Tregoning ◽  
A. Purcell ◽  
J. Lea ◽  
O. J. Fransner ◽  
...  
Keyword(s):  
Steady State ◽  
Barents Sea ◽  
Global Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Computational Time ◽  
Climate Modelling ◽  
Ice Dynamics ◽  
Perfectly Plastic ◽  
Input Parameters

Abstract. We describe a program that produces paleo-ice sheet models using an assumption of steady state, perfectly plastic ice flow behaviour. It incorporates three input parameters: ice margin, basal shear stress and basal topography. Though it is unlikely that paleo-ice sheets were ever in complete steady-state conditions, this method can produce an ice sheet without relying on complicated and unconstrained parameters such as climate and ice dynamics. This makes it advantageous to use in glacial-isostatic adjustment ice sheet models, which are often used as input parameters in global climate modelling simulations. We test this program by applying it to the modern Greenland Ice Sheet and Last Glacial Maximum Barents Sea ice sheet and demonstrate the optimal parameters that balance computational time and accuracy.

THE ASSOCIATION OF SUBGLACIAL MELTWATER ACTIVITY WITH ICE-SHEET RETREAT IN MARGUERITE BAY, ANTARCTICA

2020 ◽  
Author(s):  
Lindsay Prothro ◽  
◽  
John B. Anderson ◽  
Wojciech Majewski ◽  
Yusuke Yokoyama
Keyword(s):  
Ice Sheet ◽  
Marguerite Bay ◽  
Subglacial Meltwater

scholarly journals Attention Multi-Scale Network for Automatic Layer Extraction of Ice Radar Topological Sequences

2021 ◽  
Vol 13 (12) ◽  
pp. 2425
Author(s):  
Yiheng Cai ◽  
Dan Liu ◽  
Jin Xie ◽  
Jingxian Yang ◽  
Xiangbin Cui ◽  
...  
Keyword(s):  
Deep Learning ◽  
Global Climate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Learning Methods ◽  
Convolutional Network ◽  
Multi Scale ◽  
Ice Surface ◽  
Layer Extraction

Analyzing the surface and bedrock locations in radar imagery enables the computation of ice sheet thickness, which is important for the study of ice sheets, their volume and how they may contribute to global climate change. However, the traditional handcrafted methods cannot quickly provide quantitative, objective and reliable extraction of information from radargrams. Most traditional handcrafted methods, designed to detect ice-surface and ice-bed layers from ice sheet radargrams, require complex human involvement and are difficult to apply to large datasets, while deep learning methods can obtain better results in a generalized way. In this study, an end-to-end multi-scale attention network (MsANet) is proposed to realize the estimation and reconstruction of layers in sequences of ice sheet radar tomographic images. First, we use an improved 3D convolutional network, C3D-M, whose first full connection layer is replaced by a convolution unit to better maintain the spatial relativity of ice layer features, as the backbone. Then, an adjustable multi-scale module uses different scale filters to learn scale information to enhance the feature extraction capabilities of the network. Finally, an attention module extended to 3D space removes a redundant bottleneck unit to better fuse and refine ice layer features. Radar sequential images collected by the Center of Remote Sensing of Ice Sheets in 2014 are used as training and testing data. Compared with state-of-the-art deep learning methods, the MsANet shows a 10% reduction (2.14 pixels) on the measurement of average mean absolute column-wise error for detecting the ice-surface and ice-bottom layers, runs faster and uses approximately 12 million fewer parameters.

scholarly journals Subglacial hydrology and the formation of ice streams

2014 ◽  
Vol 470 (2161) ◽  
pp. 20130494 ◽  
Author(s):  
T. M Kyrke-Smith ◽  
R. F Katz ◽  
A. C Fowler
Keyword(s):  
Ice Sheet ◽  
Water System ◽  
Coupled Model ◽  
Water Film ◽  
Mass Conservation ◽  
Ice Streams ◽  
Base Level ◽  
Ice Sheet Dynamics ◽  
Ice Water ◽  
Subglacial Meltwater

Antarctic ice streams are associated with pressurized subglacial meltwater but the role this water plays in the dynamics of the streams is not known. To address this, we present a model of subglacial water flow below ice sheets, and particularly below ice streams. The base-level flow is fed by subglacial melting and is presumed to take the form of a rough-bedded film, in which the ice is supported by larger clasts, but there is a millimetric water film which submerges the smaller particles. A model for the film is given by two coupled partial differential equations, representing mass conservation of water and ice closure. We assume that there is no sediment transport and solve for water film depth and effective pressure. This is coupled to a vertically integrated, higher order model for ice-sheet dynamics. If there is a sufficiently small amount of meltwater produced (e.g. if ice flux is low), the distributed film and ice sheet are stable, whereas for larger amounts of melt the ice–water system can become unstable, and ice streams form spontaneously as a consequence. We show that this can be explained in terms of a multi-valued sliding law, which arises from a simplified, one-dimensional analysis of the coupled model.

scholarly journals Refined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme

2011 ◽  
Vol 5 (3) ◽  
pp. 551-560 ◽  
Author(s):  
J. L. Roberts ◽  
R. C. Warner ◽  
D. Young ◽  
A. Wright ◽  
T. D. van Ommen ◽  
...  
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
East Antarctica ◽  
Geometric Constraints ◽  
Ice Thickness ◽  
Interpolation Scheme ◽  
Ice Dynamics ◽  
High Resolution Data ◽  
Physically Based ◽  
Glacial Morphology

Abstract. Ice thickness data over much of East Antarctica are sparse and irregularly distributed. This poses difficulties for reconstructing the homogeneous coverage needed to properly assess underlying sub-glacial morphology and fundamental geometric constraints on sea level rise. Here we introduce a new physically-based ice thickness interpolation scheme and apply this to existing ice thickness data in the Aurora Subglacial Basin region. The skill and robustness of the new reconstruction is demonstrated by comparison with new data from the ICECAP project. The interpolated morphology shows an extensive marine-based ice sheet, with considerably more area below sea-level than shown by prior studies. It also shows deep features connecting the coastal grounding zone with the deepest regions in the interior. This has implications for ice sheet response to a warming ocean and underscores the importance of obtaining additional high resolution data in these marginal zones for modelling ice sheet evolution.

Greenland land-terminating glaciers velocity trends during the last two decades

2021 ◽  
Author(s):  
Paul Halas ◽  
Jeremie Mouginot ◽  
Basile de Fleurian ◽  
Petra Langebroek
Keyword(s):  
Water Pressure ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Melting ◽  
Limited Area ◽  
Ice Dynamics ◽  
Basal Sliding ◽  
Surface Melt ◽  
Ice Sheet Dynamics ◽  
The Impact

<div> <p>Ice losses from the Greenland Ice Sheet have been increasing in the last two decades, leading to a larger contribution to the global sea level rise. Roughly 40% of the contribution comes from ice-sheet dynamics, mainly regulated by basal sliding. The sliding component of glaciers has been observed to be strongly related to surface melting, as water can eventually reach the bed and impact the subglacial water pressure, affecting the basal sliding.  </p> </div><div> <p>The link between ice velocities and surface melt on multi-annual time scale is still not totally understood even though it is of major importance with expected increasing surface melting. Several studies showed some correlation between an increase in surface melt and a slowdown in velocities, but there is no consensus on those trends. Moreover those investigations only presented results in a limited area over Southwest Greenland.  </p> </div><div> <p>Here we present the ice motion over many land-terminating glaciers on the Greenland Ice Sheet for the period 2000 - 2020. This type of glacier is ideal for studying processes at the interface between the bed and the ice since they are exempted from interactions with the sea while still being relevant for all glaciers since they share the same basal friction laws. The velocity data was obtained using optical Landsat 7 & 8 imagery and feature-tracking algorithm. We attached importance keeping the starting date of our image pairs similar, and avoided stacking pairs starting before and after melt seasons, resulting in multiple velocity products for each year.  </p> </div><div> <p>Our results show similar velocity trends for previously studied areas with a slowdown until 2012 followed by an acceleration. This trend however does not seem to be observed on the whole ice sheet and is probably specific to this region’s climate forcing. </p> </div><div> <p>Moreover comparison between ice velocities from different parts of Greenland allows us to observe the impact of different climatic trends on ice dynamics.</p> </div>

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