scholarly journals From surge-type to non-surge-type glacier behaviour: midre Lovénbreen, Svalbard

2003 ◽  
Vol 36 ◽  
pp. 97-102 ◽  
Author(s):  
Siri Hansen
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
20Th Century ◽  
Longitudinal Profile ◽  
Limited Evidence ◽  
Negative Mass ◽  
Glacier Forefield ◽  
Area 5 ◽  
Valley Glacier ◽  
History Of

AbstractSince the beginning of the 1900s, the polythermal valley glacier midre Lovénbreen (area 5 km2) in northwestern Svalbard has retreated approximately 1km. The glacier has not surged for at least 110 years, and the present smooth longitudinal profile and negative mass balance suggest that it is not currently building up to a surge. Based on limited evidence, it has often been assumed that midre Lovénbreen surged around 1880. The ongoing retreat is probably due to quiescent-phase stagnation amplified by 20th-century climate change, as is the case for several other glaciers in Svalbard. Recently, small eskers have been found in the glacier forefield. Based on their geomorphological appearance, these are interpreted as concertina eskers, and they add to the dynamic history of the glacier. Midre Lovénbreen is interpreted as an example of a change from surge-type to non-surge-type glacier behaviour.

scholarly journals Characteristic mass-balance scaling with valley glacier size

1999 ◽  
Vol 45 (149) ◽  
pp. 17-21 ◽  
Author(s):  
David B. Bahr ◽  
Mark Dyurgerov
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
Scaling Exponent ◽  
Scaling Relation ◽  
Glacier Recession ◽  
Glacier Terminus ◽  
Valley Glacier ◽  
Glacier Length ◽  
The Impact ◽  
Characteristic Mass

AbstractPrevious work on the relation between glacier volume and area and on accumulation area ratios suggests that balance rates measured at the glacier terminus are not constant or random from glacier to glacier but instead scale with glacier length. Using mass-balance data from a collection of 68 valley and cirque glaciers, we show that the terminus mass-balance rate scales roughly linearly with surface area and scales with length raised to an exponent constrained to fall roughly between 0.5 and 2 with 1.7 preferred if a glacier’s length is dependent on the mass-balance conditions (rather than balance being dependent on length). When these exponents are used to predict valley-glacier volume–area scaling, the results are very close to empirical volume–area observations. Although the data are noisy and the proposed fits could be modified by improved observations, the scaling trend for terminus balance vs length remains clear. Although the exact value of the scaling exponent is not well determined, establishing the existence of this scaling relation will be important for studies of climate change and the impact of glacier recession on sea level.

scholarly journals Relation between glacier-termini variations and summer temperature in Iceland since 1930

2007 ◽  
Vol 46 ◽  
pp. 170-176 ◽  
Author(s):  
Oddur Sigurđsson ◽  
Trausti Jónsson ◽  
Tómas Jóhannesson
Keyword(s):  
Mass Balance ◽  
20Th Century ◽  
Careful Analysis ◽  
Summer Temperature ◽  
Climate Forcing ◽  
Correct Interpretation ◽  
Negative Mass ◽  
Climate History ◽  
Climate Fluctuations ◽  
Slowing Down

AbstractMeasurements of the retreat and advance of glacier termini are simple and straightforward and in many cases give clear indications about climate history. A careful analysis of glacier type and the processes that override the climate forcing of the mass balance are important for the correct interpretation of terminus variations in terms of climate fluctuations. Regular measurements of glacier variations in Iceland were started in 1930. The Iceland Glaciological Society is now responsible for the monitoring programme. The observed front variations of non-surge-type outlet glaciers of various sizes have closely mimicked major variations of the climate in Iceland during the 20th century. Most of the glaciers retreated rapidly during the warm decades from 1930 to 1960, slowing down as the climate cooled during the following decade, and started to advance after 1970. The rate of advance peaked in the 1980s, after which it slowed down as a consequence of rapid warming of the climate that has taken place since the mid-1980s. Mass-balance measurements show alternating positive and negative mass balance of glaciers during the period 1987–95, but the mass balance has been predominantly negative since 1996. Most glaciers in Iceland began to retreat after 1990, and by 2000 all monitored non-surge-type glaciers in Iceland were retreating. A comparison of the front variations of non-surge-type glaciers and mean summer temperature shows that the major shifts in the climate were followed by a change in the rate of advance or retreat at the termini with a delay of only a few years. This delay does not seem to correlate with the size, the mass turnover or other characteristics of the glacier.

scholarly journals Characteristic mass-balance scaling with valley glacier size

1999 ◽  
Vol 45 (149) ◽  
pp. 17-21
Author(s):  
David B. Bahr ◽  
Mark Dyurgerov
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
Scaling Exponent ◽  
Scaling Relation ◽  
Glacier Recession ◽  
Glacier Terminus ◽  
Valley Glacier ◽  
Glacier Length ◽  
The Impact ◽  
Characteristic Mass

Abstract Previous work on the relation between glacier volume and area and on accumulation area ratios suggests that balance rates measured at the glacier terminus are not constant or random from glacier to glacier but instead scale with glacier length. Using mass-balance data from a collection of 68 valley and cirque glaciers, we show that the terminus mass-balance rate scales roughly linearly with surface area and scales with length raised to an exponent constrained to fall roughly between 0.5 and 2 with 1.7 preferred if a glacier’s length is dependent on the mass-balance conditions (rather than balance being dependent on length). When these exponents are used to predict valley-glacier volume–area scaling, the results are very close to empirical volume–area observations. Although the data are noisy and the proposed fits could be modified by improved observations, the scaling trend for terminus balance vs length remains clear. Although the exact value of the scaling exponent is not well determined, establishing the existence of this scaling relation will be important for studies of climate change and the impact of glacier recession on sea level.

Millennial Hope

2009 ◽  
Author(s):  
David W. Orr
Keyword(s):  
Climate Change ◽  
Water Stress ◽  
20Th Century ◽  
Human Activity ◽  
Natural World ◽  
Great Difficulty ◽  
Extinct Species ◽  
Healthy Environment ◽  
The World ◽  
History Of

For two centuries and longer, humankind has been on a collision course with the limits of the Earth. The inertial momentum—the scale and velocity of the human enterprise—has grown so rapidly since the mid-20th century that virtually every indicator of planetary health is in decline (McNeill, 2000). Even an otherwise self-characterized “optimistic” analysis concludes that: . . . The momentum toward an unsustainable future can be reversed, but only with great difficulty. [The reversal] assumes fundamental shifts in desired lifestyles, values and technology. Yet, even under these assumptions, it takes many decades to realign human activity with a healthy environment, make poverty obsolete, and ameliorate the deep fissures that divide people. Some climate change is irrevocable, water stress will persist in many places, extinct species will not return, and lives will be lost to deprivation. (Raskin et al., 2002, pp. 94–95) . . . Considerably less optimistic, Thomas Berry concludes that “It is already determined that our children and grandchildren will live amid the ruined infrastructures of the industrial world and amid the ruins of the natural world itself ” (2006, p. 95). James Lovelock’s view is even darker: “the acceleration of the climate change now under way will sweep away the comfortable environment to which we are adapted . . . . [There is evidence of ] an imminent shift in our climate towards one that could easily be described as Hell” (2006, pp. 7, 147; The Vanishing Face of Gaia, 2009). Given such dire predictions, theologian Jack Miles, author of A History of God (2000), suggests that we begin to ponder the possibility that “the effort to produce a sustainable society has definitively failed . . . that we are irreversibly en route to extinction.” Alan Weisman, in a striking exercise of journalistic imagination, describes in The World Without Us how our infrastructure would then crumble, collapse, and finally disappear (2007). These are only a few of the recent musings about the human prospect.

scholarly journals After six decades of monitoring glacier mass balance we still need data but it should be richer data

2009 ◽  
Vol 50 (50) ◽  
pp. 191-197 ◽  
Author(s):  
Roger J. Braithwaite
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
Glacier Mass Balance ◽  
Climate Data ◽  
Spatial And Temporal Patterns ◽  
Negative Mass ◽  
Intergovernmental Panel ◽  
Global Average ◽  
Continuous Mass ◽  
Current Mass

AbstractThis paper reviews data on glacier mass balance together with extra metadata on topography and climate to put the data into context. The 2007 Intergovernmental Panel on Climate Change (IPCC) estimates of global average glacier mass balance may not be much different from simple averages. A more mathematically correct approach is to analyse long and continuous mass-balance series measured in different regions, but there are few long series and they do not cover the globe in any representative way. However, 30 year series from 30 glaciers confirm a recent (1996–2005) trend to very negative mass balance after two decades of nearly zero mass balance. Climate data from a global gridded climatology are applied to datasets for global glacier cover, for 318 glaciers with mass-balance data for at least 1 year and for 30 glaciers with 30 year series of measurements. Results show that mean precipitation is relatively low in the global glacier-cover dataset and much higher for the observed glaciers. This shows that current mass-balance measurements are biased towards wetter conditions than are typical for global glacier cover. We urgently need to find better ways of analysing sparse datasets with ‘complex spatial and temporal patterns’ like the present mass-balance dataset.

scholarly journals Modelling the 20th and 21st century evolution of Hoffellsjökull glacier, SE-Vatnajökull, Iceland

2011 ◽  
Vol 5 (2) ◽  
pp. 1055-1088
Author(s):  
G. Aðalgeirsdóttir ◽  
S. Guðmundsson ◽  
H. Björnsson ◽  
F. Pálsson ◽  
T. Jóhannesson ◽  
...  
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
20Th Century ◽  
21St Century ◽  
Ice Age ◽  
Surface Velocity ◽  
Balance Model ◽  
Climate Change Scenarios ◽  
Outlet Glacier ◽  
The Future

Abstract. The Little Ice Age maximum extent of glaciers in Iceland was reached about 1890 AD and most glaciers in the country have retreated during the 20th century. A model for the surface mass balance and the flow of glaciers is used to reconstruct the 20th century retreat history of Hoffellsjökull, a south-flowing outlet glacier of Vatnajökull, which is located close to the southeast coast of Iceland. The bedrock topography was surveyed with radio-echo soundings in 2001. A wealth of data are available to force and constrain the model, e.g. surface elevation maps from ~1890, 1936, 1946, 1986, 2001, 2008 and 2010, mass balance observations conducted in 1936–1938 and after 2001, energy balance measurements after 2001, and glacier surface velocity derived by DGPS and correlation of SPOT5 images. The 21% volume loss of this glacier in the period 1895–2010 is realistically simulated with the model. After calibration of the model with past observations, it is used to simulate the future response of the glacier during the 21st century. The mass balance model was forced with an ensemble of temperature and precipitation scenarios from a study of the effect of climate change on energy production in the Nordic countries (the CES project). If the average climate of 2000–2009 is maintained into the future, the volume of the glacier is projected to be reduced by 30% with respect to the present at the end of this century, and the glacier will almost disappear if the climate warms as suggested by most of the climate change scenarios. Runoff from the glacier is predicted to increase for the next 30–40 years and decrease after that as a consequence of the diminishing ice-covered area.

Economic Views of L. Trotsky

2004 ◽  
pp. 142-157
Author(s):  
M. Voeikov ◽  
S. Dzarasov
Keyword(s):  
Civil War ◽  
20Th Century ◽  
Significant Role ◽  
Historical Perspective ◽  
Russian Revolution ◽  
Russian History ◽  
History Of

The paper written in the light of 125th birth anniversary of L. Trotsky analyzes the life and ideas of one of the most prominent figures in the Russian history of the 20th century. He was one of the leaders of the Russian revolution in its Bolshevik period, worked with V. Lenin and played a significant role in the Civil War. Rejected by the party bureaucracy L. Trotsky led uncompromising struggle against Stalinism, defending his own understanding of the revolutionary ideals. The authors try to explain these events in historical perspective, avoiding biases of both Stalinism and anticommunism.

History of thyroid surgery

2020 ◽  
Vol 99 (11) ◽  
Keyword(s):  
Surgical Technique ◽  
20Th Century ◽  
Thyroid Surgery ◽  
History Of ◽  
Ancient Times

The authors present an outline of the development of thyroid surgery from the ancient times to the beginning of the 20th century, when the definitive surgical technique have been developed and the physiologic and pathopfysiologic consequences of thyroid resections have been described. The key representatives, as well as the contribution of the most influential czech surgeons are mentioned.

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