scholarly journals Iceberg properties and distributions in three Greenlandic fjords using satellite imagery

2017 ◽  
Vol 58 (74) ◽  
pp. 92-106 ◽  
Author(s):  
Daniel J. Sulak ◽  
David A. Sutherland ◽  
Ellyn M. Enderlin ◽  
Leigh A. Stearns ◽  
Gordon S. Hamilton
Keyword(s):  
Size Distribution ◽  
Satellite Imagery ◽  
Power Law ◽  
Greenland Ice Sheet ◽  
Freshwater Flux ◽  
Tidewater Glaciers ◽  
Grounding Line ◽  
Order Of Magnitude ◽  
Power Law Distributions ◽  
Line Depth

ABSTRACT Icebergs calved from tidewater glaciers represent about one third to one half of the freshwater flux from the Greenland ice sheet to the surrounding ocean. Using multiple satellite datasets, we quantify the first fjord-wide distributions of iceberg sizes and characteristics for three fjords with distinct hydrography and geometry: Sermilik Fjord, Rink Isbræ Fjord and Kangerlussuup Sermia Fjord. We estimate average total iceberg volumes in summer in the three fjords to be 6.4 ± 1.5, 1.7 ± 0.40 and 0.16 ± 0.09 km3, respectively. Iceberg properties are influenced by glacier calving style and grounding line depth, with variations in size distribution represented by exponents of power law distributions that are −1.95 ± 0.06, −1.87 ± 0.05 and −1.62 ± 0.04, respectively. The underwater surface area of icebergs exceeds the subsurface area of glacial termini by at least one order of magnitude in all three fjords, underscoring the need to include iceberg melt in fjord freshwater budgets. Indeed, in Sermilik Fjord, we calculate summertime freshwater flux from iceberg melt of 620 m3 s−1 (±140 m3 s−1), similar in magnitude to subglacial discharge. The method developed here can be extended across Greenland to assess relationships between glacier calving, iceberg discharge and freshwater production.

scholarly journals Discharge of debris from ice at the margin of the Greenland ice sheet

2002 ◽  
Vol 48 (161) ◽  
pp. 192-198 ◽  
Author(s):  
Peter G. Knight ◽  
Richard I. Waller ◽  
Carrie J. Patterson ◽  
Alison P. Jones ◽  
Zoe P. Robinson
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Rate ◽  
Outlet Glacier ◽  
Tidewater Glaciers ◽  
Sediment Production ◽  
Basal Ice ◽  
Order Of Magnitude ◽  
Sediment Transfer ◽  
A Minor

AbstractSediment production at a terrestrial section of the ice-sheet margin in West Greenland is dominated by debris released through the basal ice layer. The debris flux through the basal ice at the margin is estimated to be 12–45 m3 m−1 a−1. This is three orders of magnitude higher than that previously reported for East Antarctica, an order of magnitude higher than sites reported from in Norway, Iceland and Switzerland, but an order of magnitude lower than values previously reported from tidewater glaciers in Alaska and other high-rate environments such as surging glaciers. At our site, only negligible amounts of debris are released through englacial, supraglacial or subglacial sediment transfer. Glaciofluvial sediment production is highly localized, and long sections of the ice-sheet margin receive no sediment from glaciofluvial sources. These findings differ from those of studies at more temperate glacial settings where glaciofluvial routes are dominant and basal ice contributes only a minor percentage of the debris released at the margin. These data on debris flux through the terrestrial margin of an outlet glacier contribute to our limited knowledge of debris production from the Greenland ice sheet.

Power Law Distributions and the Size Distribution of Strikes

2017 ◽  
Vol 48 (3) ◽  
pp. 561-587 ◽  
Author(s):  
Michele Campolieti
Keyword(s):  
Size Distribution ◽  
Power Law ◽  
Model Fit ◽  
Power Law Distribution ◽  
Policy Perspective ◽  
Methodological Research ◽  
Canadian Data ◽  
Alternative Measures ◽  
Power Law Distributions ◽  
Research And Policy

Using Canadian data from 1976 to 2014, I study the size distribution of strikes with three alternative measures of strike size: the number of workers on strike, strike duration in calendar days, and the number of person calendar days lost to a strike. I use a maximum likelihood framework that provides a way to estimate distributions, evaluate model fit, and also test against alternative distributions. I consider a few theories that can create power law distributions in strike size, such as the joint costs model that posits strike size is inversely proportional to dispute costs. I find that the power law distribution fits the data for the number of lost person calendar days relatively well and is also more appropriate than the lognormal distribution. I also discuss the implications of my findings from a methodological, research, and policy perspective.

scholarly journals Flux of debris transported by ice at three Alaskan tidewater glaciers

1996 ◽  
Vol 42 (140) ◽  
pp. 123-135 ◽  
Author(s):  
Lewis E. Hunter ◽  
Ross D. Powell ◽  
Daniel E. Lawson
Keyword(s):  
Sediment Flux ◽  
Southeast Alaska ◽  
Tidewater Glaciers ◽  
Sediment Budgets ◽  
Grounding Line ◽  
Glacier Ice ◽  
Order Of Magnitude ◽  
Glacial Dynamics ◽  
Glacier Flow ◽  
The Stability

AbstractThe stability of a tidewater terminus is controlled by glacial dynamics, calving processes and sedimentary processes at the grounding line. An investigation of grounding-line sediment dynamics and morainal-bank sediment budgets in Glacier Bay, Alaska, U.S.A., has yielded data that enable us to determine the debris fluxes of Grand pacific, Margerie and Muir Glaciers. Debris flux ranges from 105 to 106 m3 a−1, one to two orders of magnitude lower than the glacifluvial sediment fluxes (106−107 m3 a−1). Combined, these fluxes represent the highest yields known for glacierized basins. Large debris fluxes reflect the combined effects of rapid glacier flow, driven by the maritime climate of southeast Alaska, and highly erodible bedrock. Englacial-debris distribution is affected by valley width and relief, both of which control the availability of sediment. The number of tributaries controls the distribution and volume of debris in englacial and supraglacial moraines. At the terminus, iceberg-rafting removes up to two orders of magnitude more sediment from the ice-proximal environment than is deposited by melt-out or is dumped during calving events. Rough estimates of the sediment flux by deforming beds suggests that soft-bed deformation may deliver up to an order of magnitude more sediment to the terminus than is released from within the glacier ice.

scholarly journals Scalings for Submarine Melting at Tidewater Glaciers from Buoyant Plume Theory

2016 ◽  
Vol 46 (6) ◽  
pp. 1839-1855 ◽  
Author(s):  
Donald A. Slater ◽  
Dan N. Goldberg ◽  
Peter W. Nienow ◽  
Tom R. Cowton
Keyword(s):  
Numerical Models ◽  
Greenland Ice Sheet ◽  
Buoyant Plume ◽  
Dynamic Changes ◽  
High Discharge ◽  
Tidewater Glaciers ◽  
Grounding Line ◽  
Plume Geometry ◽  
Rate Discharge ◽  
Point Line

AbstractRapid dynamic changes at the margins of the Greenland Ice Sheet, synchronous with ocean warming, have raised concern that tidewater glaciers can respond sensitively to ocean forcing. Understanding of the processes encompassing ocean forcing nevertheless remains embryonic. The authors use buoyant plume theory to study the dynamics of proglacial discharge plumes arising from the emergence of subglacial discharge into a fjord at the grounding line of a tidewater glacier, deriving scalings for the induced submarine melting. Focusing on the parameter space relevant for high discharge tidewater glaciers, the authors suggest that in an unstratified fjord the often-quoted relationship between total submarine melt volume and subglacial discharge raised to the ⅓ power is appropriate regardless of plume geometry, provided discharge lies below a critical value. In these cases it is then possible to formulate a simple equation estimating total submarine melt volume as a function of discharge, fjord temperature, and calving front height. However, once linear stratification is introduced—as may be more relevant for fjords in Greenland—the total melt rate discharge exponent may be as large as ¾ (⅔) for a point (line) source plume and display more complexity. The scalings provide a guide for more advanced numerical models, inform understanding of the processes encompassing ocean forcing, and facilitate assessment of the variability in submarine melting both in recent decades and under projected atmospheric and oceanic warming.

BUSINESS CYCLE FLUCTUATIONS AND FIRMS' SIZE DISTRIBUTION DYNAMICS

2004 ◽  
Vol 07 (02) ◽  
pp. 223-240 ◽  
Author(s):  
DOMENICO DELLI GATTI ◽  
CORRADO DI GUILMI ◽  
EDOARDO GAFFEO ◽  
GIANFRANCO GIULIONI ◽  
MAURO GALLEGATI ◽  
...  
Keyword(s):  
Size Distribution ◽  
Power Law ◽  
Power Law Distribution ◽  
Distribution Dynamics ◽  
Size Change ◽  
Empirical Distributions ◽  
Straight Line ◽  
Distribution Shifts ◽  
Time Invariant ◽  
Power Law Distributions

Power law behavior is an emerging property of many economic models. In this paper we emphasize the fact that power law distributions are persistent but not time invariant. In fact, the scale and shape of the firms' size distribution fluctuate over time. In particular, on a log–log space, both the intercept and the slope of the power law distribution of firms' size change over the cycle: during expansions (recessions) the straight line representing the distribution shifts up and becomes less steep (steeper). We show that the empirical distributions generated by simulations of the model presented in Ref. 11 mimic real empirical distributions remarkably well.

scholarly journals Flux of debris transported by ice at three Alaskan tidewater glaciers

1996 ◽  
Vol 42 (140) ◽  
pp. 123-135 ◽  
Author(s):  
Lewis E. Hunter ◽  
Ross D. Powell ◽  
Daniel E. Lawson
Keyword(s):  
Sediment Flux ◽  
Southeast Alaska ◽  
Tidewater Glaciers ◽  
Sediment Budgets ◽  
Grounding Line ◽  
Glacier Ice ◽  
Order Of Magnitude ◽  
Glacial Dynamics ◽  
Glacier Flow ◽  
The Stability

AbstractThe stability of a tidewater terminus is controlled by glacial dynamics, calving processes and sedimentary processes at the grounding line. An investigation of grounding-line sediment dynamics and morainal-bank sediment budgets in Glacier Bay, Alaska, U.S.A., has yielded data that enable us to determine the debris fluxes of Grand pacific, Margerie and Muir Glaciers. Debris flux ranges from 105to 106m3a−1, one to two orders of magnitude lower than the glacifluvial sediment fluxes (106−107m3a−1). Combined, these fluxes represent the highest yields known for glacierized basins. Large debris fluxes reflect the combined effects of rapid glacier flow, driven by the maritime climate of southeast Alaska, and highly erodible bedrock. Englacial-debris distribution is affected by valley width and relief, both of which control the availability of sediment. The number of tributaries controls the distribution and volume of debris in englacial and supraglacial moraines. At the terminus, iceberg-rafting removes up to two orders of magnitude more sediment from the ice-proximal environment than is deposited by melt-out or is dumped during calving events. Rough estimates of the sediment flux by deforming beds suggests that soft-bed deformation may deliver up to an order of magnitude more sediment to the terminus than is released from within the glacier ice.

The effects of particle size distribution on the settleability of CSOs pollutants

2001 ◽  
Vol 43 (5) ◽  
pp. 103-110 ◽  
Author(s):  
E. B. Shin ◽  
H. S. Yoon ◽  
Y. D. Lee ◽  
Y. S. Pae ◽  
S. W. Hong ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Power Law ◽  
Particle Diameter ◽  
Size Spectrum ◽  
Average Particle ◽  
Factors Affecting ◽  
Major Factors ◽  
Power Law Distributions

Over the past decades, flocculation and/or sedimentation processes have been adopted to remove pollutants from CSOs. It has been learned that major factors affecting settlement of pollutants are the particle size distribution, their settling velocities and their specific gravity. It is, therefore, a good idea to analyze the particle size distribution and settleability of CSOs pollutants in order to develop details in designing a process. Discussed in this study are pollutant characteristics of CSOs such as particle size distribution and settleability of pollutants. The power law function is applied and is found to be an effective and reliable index for expressing the particle size distribution of pollutants in CSOs. Based on the particle size spectrum analysis, the tendency toward settling and simultaneous flocculation-settling phenomenon of CSOs pollutants is described. Based on the regression analysis it is observed that the derived constants of curves representing settling velocity profile are proportional to the initial concentration of particles and to the β-values of power law distributions. It is also revealed that the simultaneous flocculation-settling processes are effectively described by the changes of the average particle diameter and of the β-values of power law distributions.

scholarly journals Set-Min sketch: a probabilistic map for power-law distributions with application to k-mer annotation

2020 ◽  
Author(s):  
Yoshihiro Shibuya ◽  
Gregory Kucherov
Keyword(s):  
Power Law ◽  
Error Rate ◽  
Explicit Representation ◽  
The Other ◽  
Memory Usage ◽  
Power Law Distribution ◽  
Space Efficiency ◽  
Order Of Magnitude ◽  
Power Law Distributions ◽  
Probabilistic Map

Motivation: In many bioinformatics pipelines, k-mer counting is often a required step, with existing methods focusing on optimizing time or memory usage. These methods usually produce very large count tables explicitly representing k-mers themselves. Solutions avoiding explicit representation of k-mers include Minimal Perfect Hash Functions (MPHFs) or Count-Min sketches. The former is only applicable to static maps not subject to updates, while the latter suffers from potentially very large point-query errors, making it unsuitable when counters are required to be highly accurate. Results: We introduce Set-Min sketch, a sketching technique inspired by Count-Min sketch, for representing associative maps, more specifically, k-mer count tables. We show that Set-Min sketch provides a very low error rate, both in terms of the probability and the size of errors, much lower than a Count-Min sketch of similar dimensions. On the other hand, Set-Min sketches are shown to take up to an order of magnitude less space than MPHF-based solutions, especially for large values of k. Space-efficiency of Set-min takes advantage of the power-law distribution of k-mer counts in genomic datasets.

scholarly journals Classification of cryptocurrency coins and tokens by the dynamics of their market capitalizations

2018 ◽  
Vol 5 (9) ◽  
pp. 180381 ◽  
Author(s):  
Ke Wu ◽  
Spencer Wheatley ◽  
Didier Sornette
Keyword(s):  
Size Distribution ◽  
Power Law ◽  
Technological Innovations ◽  
Size Distribution Of Firms ◽  
The Future ◽  
Theoretical Predictions ◽  
New Entrants ◽  
Power Law Distributions ◽  
Remarkable Agreement

We empirically verify that the market capitalizations of coins and tokens in the cryptocurrency universe follow power-law distributions with significantly different values for the tail exponent falling between 0.5 and 0.7 for coins, and between 1.0 and 1.3 for tokens. We provide a rationale for this, based on a simple proportional growth with birth and death model previously employed to describe the size distribution of firms, cities, webpages, etc. We empirically validate the model and its main predictions, in terms of proportional growth (Gibrat's Law) of the coins and tokens. Estimating the main parameters of the model, the theoretical predictions for the power-law exponents of coin and token distributions are in remarkable agreement with the empirical estimations, given the simplicity of the model. Our results clearly characterize coins as being ‘entrenched incumbents’ and tokens as an ‘explosive immature ecosystem’, largely due to massive and exuberant Initial Coin Offering activity in the token space. The theory predicts that the exponent for tokens should converge to 1 in the future, reflecting a more reasonable rate of new entrants associated with genuine technological innovations.

scholarly journals Sensitivity of submarine melting on North East Greenland towards ocean forcing

2019 ◽  
Author(s):  
Philipp Anhaus ◽  
Lars H. Smedsrud ◽  
Marius Årthun ◽  
Fiammetta Straneo
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Rate Sensitivity ◽  
Atlantic Water ◽  
Maximum Temperature ◽  
Freshwater Flux ◽  
Ice Shelf ◽  
North East ◽  
Grounding Line ◽  
Ice Shelf Water

Abstract. The Nioghalvfjerdsbræ (79NG) is a floating ice tongue on Northeast Greenland draining a large part of the Greenland Ice Sheet. A CTD profile from a rift on the ice tongue close to the northern front shows that Atlantic Water (AW) is present in the cavity below, with maximum temperature of approximately 1 °C at 610 m depth. The AW present in the cavity thus has the potential to drive submarine melting along the ice base. Here, we simulate melt rates from the 79NG with a 1D numerical Ice Shelf Water (ISW) plume model. A meltwater plume is initiated at the grounding line depth (600 m) and rises along the ice base as a result of buoyancy contrast to the underlying AW. Ice melts as the plume entrains the warm AW. Maximum simulated melt rates are 50–76 m yr−1 within 10 km of the grounding line. Within a zone of rapid decay between 10 km and 20 km melt rates drop to roughly 6 m yr−1. Further downstream, melt rates are between 15 m yr−1 and 6 m yr−1. The melt-rate sensitivity to variations in AW temperatures is assessed by forcing the model with AW temperatures between 0.1–1.4 °C, as identified from the ECCOv4 ocean state estimate. The melt rates increase linearly with rising AW temperature, ranging from 10 m yr−1 to 21 m yr−1 along the centerline. The corresponding freshwater flux ranges between 11 km3 yr−1 (0.4 mSv) and 30 km3 yr−1 (1.0 mSv), which is 5 % and 12 % of the total freshwater flux from the Greenland Ice Sheet since 1995, respectively. Our results improve the understanding of processes driving submarine melting of marine-terminating glaciers around Greenland, and its sensitivity to changing ocean conditions.

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