scholarly journals Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

2021 ◽  
Vol 15 (3) ◽  
pp. 1435-1451
Author(s):  
Nathan Maier ◽  
Florent Gimbert ◽  
Fabien Gillet-Chaulet ◽  
Adrien Gilbert
Keyword(s):  
Spatial Relationship ◽  
Surface Geometry ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Warming Climate ◽  
Interpretation Biases ◽  
Type Rate ◽  
The Relationship ◽  
Insight Into ◽  
Large Grid

Abstract. On glaciers and ice sheets, identifying the relationship between velocity and traction is critical to constrain the bed physics that controls ice flow. Yet in Greenland, these relationships remain unquantified. We determine the spatial relationship between velocity and traction in all eight major drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize interpretation biases associated with unconstrained rheologic parameters used in numerical inversions. We find the relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr–Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the traction relationships suggest that the flow field and surface geometry of the grounded regions in Greenland is mainly dictated by Weertman-type hard-bed physics up to velocities of approximately 450 m yr−1, except within the Northeast Greenland Ice Stream and areas near floatation. Depending on the catchment, behavior of the fastest-flowing ice (∼ 1000 m yr−1) directly inland from marine-terminating outlets exhibits Weertman-type rate strengthening, Mohr–Coulomb-like behavior, or is not confidently resolved given our methodology. Given the complex basal boundary across Greenland, the relationships are captured reasonably well by simple traction laws which provide a parameterization that can be used to model ice dynamics at large scales. The results and analysis serve as a first constraint on the physics of basal motion over the grounded regions of Greenland and provide unique insight into future dynamics and vulnerabilities in a warming climate.

scholarly journals Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

2020 ◽  
Author(s):  
Nathan Maier ◽  
Florent Gimbert ◽  
Fabien Gillet-Chaulet ◽  
Adrien Gilbert
Keyword(s):  
Spatial Relationship ◽  
Greenland Ice Sheet ◽  
Surface Geometry ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Warming Climate ◽  
Interpretation Biases ◽  
The Relationship ◽  
Insight Into ◽  
Large Grid

Abstract. On glaciers and ice sheets, identifying the relationship between velocity and traction is critical to constrain the bed physics that control ice flow. Yet in Greenland, these relationships remain unquantified. We determine the spatial relationship between velocity and traction in all eight drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize interpretation biases associated with unconstrained rheologic parameters used in numerical inversions. We find the relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr-Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the traction relationships suggest that the flow field and surface geometry over the grounded regions of the Greenland ice sheet is mainly dictated by Weertman-type hard-bed physics. Given the complex basal boundary across Greenland, the relationships are captured surprisingly well by simple traction laws over the entire velocity range, including regions with velocities over 1000 m/yr, which provide a parameterization that can be used to model ice dynamics at large scales. The results and analysis serve as a fundamental constraint on the physics of basal motion in Greenland and provide unique insight into future dynamics and vulnerabilities in a warming climate.

Constraints on the relationship between velocity and basal traction over the grounded regions of Greenland

2021 ◽  
Author(s):  
Nathan Maier ◽  
Florent Gimbert ◽  
Fabien Gillet-Chaulet ◽  
Adrien Gilbert
Keyword(s):  
Flow Field ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Spatial Relationship ◽  
Greenland Ice Sheet ◽  
Ice Flow ◽  
Warming Climate ◽  
The Relationship ◽  
Insight Into ◽  
Large Grid

<p>On glaciers and ice sheets, constraints on the bed physics which control the relationship between velocity and traction are critical for simulating ice flow. However, in Greenland the relationship between velocity and traction remains unquantified over much of the ice sheet. In this work, we determine the spatial relationship between velocity and traction in all eight drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize biases associated with unconstrained rheologic parameters used in numerical inversions. We find that the velocity-traction relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr-Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the velocity-traction relationships suggest that the flow field and surface geometries over the grounded regions of the Greenland ice sheet are mainly dictated by Weertman-type physics. This data- and modeling based analysis provides a first constraint on the physics of basal motion over the grounded regions of Greenland and gives unique insight into future dynamics and vulnerabilities in a warming climate.</p>

Debris cover and the thinning of Kennicott Glacier, Alaska

2021 ◽  
Author(s):  
Leif S. Anderson ◽  
William H. Armstrong ◽  
Robert S. Anderson ◽  
Dirk Scherler
Keyword(s):  
Satellite Imagery ◽  
Hot Spots ◽  
High Mountain ◽  
Threshold Method ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Debris Cover ◽  
A Chain ◽  
The Relationship

<p>Many glaciers in High Mountain Asia are experiencing the debris-cover anomaly. The Kennicott Glacier, a large Alaskan Glacier, is also thinning most rapidly under debris cover. This contradiction has been explained by melt hotspots, such as ice cliffs, streams, or ponds scattered within the debris cover or by declining ice flow in time. We collected abundant in situ measurements of debris thickness, sub-debris melt, and ice cliff backwasting, allowing for extrapolation across the debris-covered tongue. A newly developed automatic ice cliff delineation method is the first to use only optical satellite imagery. The adaptive binary threshold method accurately estimates ice cliff coverage even where ice cliffs are small and debris color varies. We also develop additional remotely-sensed datasets of ice dynamical variables, other melt hot spots, and glacier thinning.</p><p>Kennicott Glacier exhibits the highest fractional area of ice cliffs (11.7 %) documented to date. Ice cliffs contribute 26 % of total melt across the glacier tongue. Although the <em>relative</em> importance of ice cliffs to area-average melt is significant, the<em> absolute</em> area-averaged melt is dominated by debris. At Kennicott Glacier, glacier-wide melt rates are not maximized in the zone of maximum thinning. Declining ice discharge through time therefore explains the rapid thinning. Through this study, Kennicott Glacier is the first glacier in Alaska, and the largest glacier globally, where melt across its debris-covered tongue has been rigorously quantified.</p><p>We also carefully explore the relationship between debris, melt hotspots, ice dynamics, and thinning across the debris-covered tongue. In doing so we reveal a chain of linked processes that can explain the striking patterns expressed on the debris-covered tongue of Kennicott Glacier.</p>

Greenland ice sheet supraglacial lake drainages between 2000 and 2019

2020 ◽  
Author(s):  
Stephen Brough ◽  
James Lea
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Google Earth ◽  
Ice Dynamics ◽  
Supraglacial Lakes ◽  
Warming Climate ◽  
Google Earth Engine ◽  
Insight Into ◽  
Rapid Transfer ◽  
Fundamental Mechanism

<p>The drainage of supraglacial lakes provides a fundamental mechanism for the rapid transfer of surface meltwater to the bed of an ice sheet, impacting both subglacial hydrology and ice dynamics. As a consequence, it is crucial to understand where and when these lakes drain, and how or if this has changed through time. Given that lakes are now occurring in greater numbers and at higher elevations, identifying changing modes in behaviour will have significant implications for the future dynamics of the Greenland ice sheet. Nevertheless, previous studies of supraglacial lakes and associated drainage events have been limited in spatial and/or temporal scale relative to the entire ice sheet.</p><p>Here we use daily maps of Greenland wide supraglacial lake coverage – derived from MODIS Terra within Google Earth Engine – to investigate the style, pattern and timing of lake drainages between 2000 and 2019. Results from this study: i) add to the understanding of how supraglacial hydrology and its coupling to the bed has changed in response to more extensive supraglacial lake cover over the last 20 years; and ii) provide insight into how these lakes and associated drainage events can be expected to respond to increased surface meltwater production under a warming climate.</p>

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

On Metaphysics and the Political: A Polemics of Reading Baudelaire in the 1930s

2019 ◽  
Vol 58 (2) ◽  
pp. 249-259
Author(s):  
Joseph Acquisto
Keyword(s):  
Twentieth Century ◽  
Political Crisis ◽  
The Political ◽  
Modern Poetry ◽  
Progressive Politics ◽  
The World ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

This essay examines a polemic between two Baudelaire critics of the 1930s, Jean Cassou and Benjamin Fondane, which centered on the relationship of poetry to progressive politics and metaphysics. I argue that a return to Baudelaire's poetry can yield insight into what seems like an impasse in Cassou and Fondane. Baudelaire provides the possibility of realigning metaphysics and politics so that poetry has the potential to become the space in which we can begin to think the two of them together, as opposed to seeing them in unresolvable tension. Or rather, the tension that Baudelaire animates between the two allows us a new way of thinking about the role of esthetics in moments of political crisis. We can in some ways see Baudelaire as responding, avant la lettre, to two of his early twentieth-century readers who correctly perceived his work as the space that breathes a new urgency into the questions of how modern poetry relates to the world from which it springs and in which it intervenes.

The Annual Reports of the Prison Commissioners for Scotland and Religion, 1903–1931

2019 ◽  
Vol 48 (1) ◽  
pp. 83-101
Author(s):  
Cameron McKay
Keyword(s):  
Annual Report ◽  
Annual Reports ◽  
Individual Choice ◽  
Drinking Habits ◽  
Parental Neglect ◽  
Late Nineteenth ◽  
Causes Of Crime ◽  
Criminological Theories ◽  
The Relationship ◽  
Insight Into

During the late nineteenth and early twentieth century penologists began to explore the possibility that environment and upbringing, as opposed to individual choice, were the causes criminality. The Prison Commissioners for Scotland, the devolved body who administered prisons north of the border, were not immune to this wider trend. Smith has argued that from the 1890s onwards the Commissioners began to accept that criminality was caused by social problems, namely alcoholism, but also parental neglect, poor education and poverty. In their efforts to test these new criminological theories, the Commissioners began to make more careful enquiries into the backgrounds of their charges. From 1896 to 1931 the Commissioners interviewed a sample of prisoners each year and included the findings in their annual report. Although the main focus of these interviews was on the upbringing and drinking habits of prisoners; by the 1900s the Commissioners seem to have added irreligion to the growing list of etiological causes of crime, and from 1903 onwards prisoners were asked to give details on their religious habits. Although it is debateable how much the Prison Commissioners revealed about the relationship between religion and crime, they did however provide a useful insight into the religiosity of the average prisoner.

The Relationship between Seeker and Spiritual Guide as portrayed in contemporary Western Sufi Autobiographies

2011 ◽  
Vol 5 (2) ◽  
pp. 297-332
Author(s):  
Kate Zebiri
Keyword(s):  
Life Writing ◽  
New Age ◽  
The Self ◽  
Individual Autonomy ◽  
Religious Authority ◽  
The Face ◽  
The Relationship ◽  
Insight Into ◽  
Continuity And Discontinuity

This article aims to explore the Shaykh-mur?d (disciple) or teacher-pupil relationship as portrayed in Western Sufi life writing in recent decades, observing elements of continuity and discontinuity with classical Sufism. Additionally, it traces the influence on the texts of certain developments in religiosity in contemporary Western societies, especially New Age understandings of religious authority. Studying these works will provide an insight into the diversity of expressions of contemporary Sufism, while shedding light on a phenomenon which seems to fly in the face of contemporary social and religious trends which deemphasize external authority and promote the authority of the self or individual autonomy.

Empathy as moderator of gender differences in Chinese insurance agents' business ethical sensitivity

2017 ◽  
Vol 45 (6) ◽  
pp. 1029-1042 ◽  
Author(s):  
Na Zhang ◽  
Jian Zhang ◽  
Jing Wang
Keyword(s):  
Gender Differences ◽  
Business Ethics ◽  
Research Field ◽  
Ethical Sensitivity ◽  
Men And Women ◽  
Insurance Agents ◽  
Factors Associated ◽  
Ethics Research ◽  
The Relationship ◽  
Insight Into

To expand the business ethics research field, and to increase society's understanding of Chinese insurance agents' business ethics, we investigated how gender differences are related to agents' business ethical sensitivity and whether or not these relationships are moderated by empathy. Through a regression analysis of the factors associated with the business ethical sensitivity of 417 Chinese insurance agents, we found that gender played an important role in affecting business ethical sensitivity, and empathy significantly affected business ethical sensitivity. Furthermore, empathy had a moderating effect on the relationship between gender and business ethical sensitivity. Both men and women with strong empathy scored high on business ethical sensitivity; however, men with strong empathy had higher levels of business ethical sensitivity than did women with little empathy. The findings add to the literature by providing insight into the mechanisms responsible for the benefits of empathy in increasing business ethical sensitivity.

AI Narratives

2020 ◽  
Keyword(s):  
Artificial Intelligence ◽  
New Technologies ◽  
Ancient Greece ◽  
Historical Overview ◽  
Intelligent Machines ◽  
Narrative History ◽  
History Of ◽  
Imaginative Thinking ◽  
The Relationship ◽  
Insight Into

This book is the first to examine the history of imaginative thinking about intelligent machines. As real artificial intelligence (AI) begins to touch on all aspects of our lives, this long narrative history shapes how the technology is developed, deployed, and regulated. It is therefore a crucial social and ethical issue. Part I of this book provides a historical overview from ancient Greece to the start of modernity. These chapters explore the revealing prehistory of key concerns of contemporary AI discourse, from the nature of mind and creativity to issues of power and rights, from the tension between fascination and ambivalence to investigations into artificial voices and technophobia. Part II focuses on the twentieth and twenty-first centuries in which a greater density of narratives emerged alongside rapid developments in AI technology. These chapters reveal not only how AI narratives have consistently been entangled with the emergence of real robotics and AI, but also how they offer a rich source of insight into how we might live with these revolutionary machines. Through their close textual engagements, these chapters explore the relationship between imaginative narratives and contemporary debates about AI’s social, ethical, and philosophical consequences, including questions of dehumanization, automation, anthropomorphization, cybernetics, cyberpunk, immortality, slavery, and governance. The contributions, from leading humanities and social science scholars, show that narratives about AI offer a crucial epistemic site for exploring contemporary debates about these powerful new technologies.

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