Unearthing the forgotten record of glacier change in southeast Greenland

2020 ◽  
Author(s):  
Michael Cooper ◽  
Paulina Lewinska ◽  
Julian Dowdeswell ◽  
Edwin Hancock ◽  
William Smith ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Quantitative Information ◽  
Glacier Change ◽  
Regular Time ◽  
History Of ◽  
Long Term Trends ◽  
Surface Profiles ◽  
Volume Estimates

<p>Prior to the satellite era (pre-1970s) knowledge of long-term glacier change is sparse. Although some glacier-wide mass balance datasets are available, few records extend beyond twenty years in length, or indeed, start prior to the 1980s; as such, identifying long-term trends between glacier change and global temperatures is difficult. As a result, extending the record of glacier change will not only help to identify such trends, but may also facilitate more robust understanding of future glacier response under a perturbed and varying climate.</p><p>Since the ‘heroic age of Arctic (and Antarctic) exploration’, many photographs of polar environments have been captured and stored for historic interest. These photographs, depicting images of past glaciers and ice sheet margins, have, as of yet, untapped potential to provide important insights into past glacier extent, and long-term behaviour.</p><p>Using computer-vision methodologies, we present a unique record of georeferenced 3-D elevation models using declassified aerial imagery dating from the 1930s—1980s at quasi-regular time steps. This study focusses upon two sections (ca. 190 km total length) of the southeast margin of the Greenland Ice Sheet (in the vicinity of Kangerlussuaq Glacier), capturing the history of both land- and marine-terminating outlet glaciers, and local glaciers. We examine quantitative information extracted from these reconstructions, allowing us to ‘back extend’ the record of glacial change in this region, by measuring changes in glacial extent, surface profiles and height (elevation), and calculating volume estimates.</p>

Greenland Ice Sheet History Since the Last Glaciation

1974 ◽  
Vol 4 (4) ◽  
pp. 429-440 ◽  
Author(s):  
Norman W. Ten Brink ◽  
Anker Weidick
Keyword(s):  
Average Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Large Area ◽  
West Greenland ◽  
Last Glaciation ◽  
History Of ◽  
Inland Ice

The position of the Inland Ice margin during the late Wisconsin-Würm glaciation (ca. 15,000 yr BP) is probably marked by offshore banks (submarine moraines?) in the Davis Strait. The history of the Inland Ice since the late Wisconsin-Würm can be divided into four principal phases: (1) Relatively slow retreat from the offshore banks occurred at an average rate of approximately 1 km/100 yr until ca. 10,000 yr BP (Younger Dryas?) when the Taserqat moraine system was formed by a readvance. (2) At ca. 9500 yr BP, the rate of retreat increased markedly to about 3 km/100 yr, and although nearly 100 km of retreat occurred by ca. 6500 yr BP, it was punctuated by frequent regional reexpansions of the Inland Ice that formed extensive moraine systems at ca. 8800-8700 yr BP (Avatdleq-Sarfartôq moraines), 8400-8100 yr BP (Angujârtorfik-Fjord moraines), 7300 yr BP (Umîvît moraines), and 7200-6500 yr BP (Keglen-Mt, Keglen moraines). (3) Between 6500 and 700 yr BP, discontinous ice-margin deposits and ice-disintegration features were formed during retreat, which may have continued until the ice margin was near or behind its present position by ca. 6000 yr BP. Most of the discontinuous ice-margin deposits occur within 5–10 km of the present ice margin, and may have been formed by two main phases of readvance at ca. 4800-4000 yr BP and 2500-2000 yr BP. (4) Since a readvance at ca. 700 yr BP, the Inland Ice margin has undergone several minor retreats and readvances resulting in deposition of numerous closely spaced moraines within about 3 km of the present ice margin. The young moraines are difficult to correlate regionally, but several individual moraines have the following approximate ages: A.D. 1650, 1750, and 1880–1920.Inland Ice fluctuations in West Greenland were very closely paralleled by Holocene glacial events in East Greenland and the eastern Canadian Arctic. Such similarity of glacier behavior over a large area strongly suggests that widespread climatic change was the direct cause of Holocene glacial fluctuations. Moreover, historical advances of the Inland Ice margin followed slight temperature decreases by no more than a few decades, and 18O data from Greenland ice cores show that slight temperature decreases occurred frequently throughout the Holocene. Therefore, we conclude that construction of the major Holocene moraine systems in West Greenland was caused by slight temperature decreases, which decreased rates of ablation and thereby produced practically immediate advances of the ice sheet margin, but did not necessarily affect the long-term equilibrium of the ice sheet.

“Theoretically all Children are Equal. Practically this can Never be So”: The History of the District Property Tax in California and the Choice of Inequality

2020 ◽  
Vol 122 (2) ◽  
pp. 1-32
Author(s):  
Matthew Gardner Kelly
Keyword(s):  
School Finance ◽  
Research Question ◽  
Property Tax ◽  
School Funding ◽  
State Governments ◽  
Property Taxation ◽  
History Of ◽  
Long Term Trends ◽  
Funding Disparities

Background/Context Dealing mostly in aggregate statistics that mask important regional variations, scholars often assume that district property taxation and the resource disparities this approach to school funding creates are deeply rooted in the history of American education. Purpose/Objective/Research Question/Focus of Study This article explores the history of district property taxation and school funding disparities in California during the 19th and 20th centuries. First, the article documents the limited use of district property taxation for school funding in California and several other Western states during the 19th century, showing that the development of school finance was more complicated than standard accounts suggest. Then, the article examines how a coalition of experts, activists, and politicians worked together during the early 20th century to promote district property taxation and institutionalize the idea that the wealth of local communities, rather than the wealth of the entire state, should determine the resources available for public schooling. Research Design This article draws on primary source documents from state and regional archives, including district-level funding data from nine Northern California counties, to complete a historical analysis. Conclusions/Recommendations The history of California's district property tax suggests the need for continued research on long-term trends in school finance and educational inequality. Popular accounts minimizing the historical role of state governments in school funding obscure how public policies, not just market forces shaping property values, create funding inequalities. In turn, these accounts communicate powerful messages about the supposed inevitability of funding disparities and the responsibility of state governments to correct them. Through increased attention to long-term trends in school funding, scholars can help popular commentators and policymakers avoid assumptions that naturalize inequality and narrow the possibilities for future funding reforms.

11. The United Kingdom: Towards a Parting of the Ways

2020 ◽  
pp. 257-279
Author(s):  
Anand Menon ◽  
Luigi Scazzieri
Keyword(s):  
European Union ◽  
Public Opinion ◽  
Institutional Development ◽  
The European Union ◽  
Integration Process ◽  
The United Kingdom ◽  
History Of ◽  
Long Term Trends ◽  
The Uk

This chapter examines the history of the United Kingdom’s relationship with the European integration process. The chapter dissects the long-term trends in public opinion and the more contingent, short-term factors that led to the referendum vote to leave the European Union. The UK was a late joiner and therefore unable to shape the early institutional development of the EEC. British political parties and public opinion were always ambiguous about membership and increasingly Eurosceptic from the early 1990s. Yet the UK had a significant impact on the EU’s development, in the development of the single market programme and eastward enlargement. If Brexit goes through, Britain will nevertheless maintain relations with the EU in all policy areas from agriculture to energy and foreign policy. Europeanization will remain a useful theoretical tool to analyse EU–UK relations even if the UK leaves the Union.

scholarly journals Economics and evolution

1992 ◽  
Vol 6 ◽  
pp. 298-298
Author(s):  
Geerat J. Vermeij
Keyword(s):  
Energy Use ◽  
Construction Materials ◽  
Ripple Effect ◽  
Use Of Resources ◽  
Economic Interpretation ◽  
History Of ◽  
Long Term Trends ◽  
Random Nature ◽  
Antagonistic Interactions

Individual organisms compete for resources. Among competitive dominants, per-capita energy use has generally increased through time. This increase has had a ripple effect on all other species by increasing the number of competitive and predatory encounters among individuals. Species unable to cope with such biological rigors have become restricted to environments where resource supply is low and where encounters with enemies are few. Among species that hold their own in biologically rigorous habitats, construction materials that are cheap to produce and that enable individuals to grow and respond quickly have generally been favored over those that exact a high cost in energy and time. Extinction interrupts but does not reverse or fundamentally alter these long-term between-clade evolutionary trends. The availability of resources to organisms, as well as the opportunity for evolutionary change, depends on extrinsic events and factors as well as on the competitive abilities of organisms.Those who have raised methodological and theoretical objections against this economic interpretation of the history of life deny the overriding importance of organisms as agents of natural selection, emphasize the random nature of extinction, deny the existence of long-term trends, favor a larger role for mutualistic as opposed to antagonistic interactions, or accord a larger role to species-level attributes in evolution that are not reducible to the properties of individual organisms. These arguments are either unpersuasive or incorrect. The long-term economics of life may have important lessons for our own use of resources.

On fragile democracy: Contemporary and historical perspectives—Introduction

2019 ◽  
Vol 17 (4) ◽  
pp. 422-431
Author(s):  
Martin Conway
Keyword(s):  
Twentieth Century ◽  
Special Issue ◽  
Historical Perspectives ◽  
Alternative Means ◽  
History Of ◽  
Long Term Trends

The concept of fragility provides an alternative means of approaching the history of democracy, which has often been seen as the ineluctable consequence of Europe’s social and political modernisation. This is especially so in Scandinavia, as well as in Finland, where the emergence of a particular Nordic model of democracy from the early decades of the twentieth century onwards has often been explained with reference to embedded traditions of local self-government and long-term trends towards social egalitarianism. In contrast, this article emphasises the tensions present within the practices and understandings of democracy in the principal states of Scandinavia during the twentieth century. In doing so, it provides an introduction to the articles that compose this Special Issue, as well as contributing to the wider literature on the fragility of present-day structures of democracy.

scholarly journals Mass Balance of the Greenland Ice Sheet from GRACE and Surface Mass Balance Modelling

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1847 ◽  
Author(s):  
Fang Zou ◽  
Robert Tenzer ◽  
Hok Fok ◽  
Janet Nichol
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Rapid Decline ◽  
Surface Mass Balance ◽  
Discharge Data ◽  
Surface Mass ◽  
Term Trend ◽  
Long Term Trend

The Greenland Ice Sheet (GrIS) is losing mass at a rate that represents a major contribution to global sea-level rise in recent decades. In this study, we use the Gravity Recovery and Climate Experiment (GRACE) data to retrieve the time series variations of the GrIS from April 2002 to June 2017. We also estimate the mass balance from the RACMO2.3 and ice discharge data in order to obtain a comparative analysis and cross-validation. A detailed analysis of long-term trend and seasonal and inter-annual changes in the GrIS is implemented by GRACE and surface mass balance (SMB) modeling. The results indicate a decrease of −267.77 ± 8.68 Gt/yr of the GrIS over the 16-year period. There is a rapid decline from 2002 to 2008, which accelerated from 2009 to 2012 before declining relatively slowly from 2013 to 2017. The mass change inland is significantly smaller than that detected along coastal regions, especially in the southeastern, southwestern, and northwestern regions. The mass balance estimates from GRACE and SMB minus ice discharge (SMB-D) are very consistent. The ice discharge manifests itself mostly as a long-term trend, whereas seasonal mass variations are largely attributed to surface mass processes. The GrIS mass changes are mostly attributed to mass loss during summer. Summer mass changes are highly correlated with climate changes.

Seasonal to multi-annual speedup and slowdown of Greenland outlet glaciers inferred from time-dependent remote sensing observations

2020 ◽  
Author(s):  
Lizz Ultee ◽  
Bryan Riel ◽  
Brent Minchew
Keyword(s):  
Time Series ◽  
Flow Velocity ◽  
Ice Sheet ◽  
Surface Air Temperature ◽  
Greenland Ice Sheet ◽  
Time Dependent ◽  
Surface Velocity ◽  
Short Term ◽  
Ice Flow

<p>The rate of ice flux from the Greenland Ice Sheet to the ocean depends on the ice flow velocity through outlet glaciers. Ice flow velocity, in turn, evolves in response to multiple geographic and environmental forcings at different timescales. For example, velocity may vary daily in response to ocean tides, seasonally in response to surface air temperature, and multi-annually in response to long-term trends in climate. The satellite observations processed as part of the NASA MEaSUREs Greenland Ice Sheet Velocity Map allow us to analyse variations in ice surface velocity at multiple timescales. Here, we decompose short-term and long-term signals in time-dependent velocity fields for Greenland outlet glaciers based on the methods of Riel et al. (2018). Patterns found in short-term signals can constrain basal sliding relations and ice rheology, while the longer-term signals hint at decadal in/stability of outlet glaciers. We present example velocity time series for outlets including Sermeq Kujalleq (Jakobshavn Isbrae) and Helheim Glacier, and we highlight features indicative of dynamic drawdown or advective restabilization. Finally, we comment on the capabilities of a time series analysis software under development for glaciological applications.</p>

What Moves Macropartisanship? A Response to Green, Palmquist, and Schickler

1998 ◽  
Vol 92 (4) ◽  
pp. 901-912 ◽  
Author(s):  
Robert S. Erikson ◽  
Michael B. Mackuen ◽  
James A. Stimson
Keyword(s):  
Consumer Sentiment ◽  
Presidential Approval ◽  
Weak Force ◽  
Economic News ◽  
Presidential Popularity ◽  
History Of ◽  
Long Term Trends ◽  
Near Future

Contrary to the claim by Green, Palmquist, and Schickler (1998), macropartisanship is largely shaped by presidential approval and consumer sentiment. It is not the case, however, that macropartisanship mirrors the ever-changing levels of current presidential popularity and prosperity. Rather, macropartisanship reflects the cumulation of political and economic news that shapes approval and consumer sentiment. Using ECM technology, we show that, far from being the weak force that Green et al. suggest, the cumulation of innovations in presidential approval and consumer sentiment largely account for the long-term trends in macropartisanship. For forecasting macropartisanship in the near future, it is better to predict from the fundamentals represented by the history of approval and consumer sentiment up to a given moment than from current values of macropartisanship itself.

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