Holocene Ice Margin Fluctuations of the Greenland Ice Sheet in the Disko Bugt Region, West Greenland

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ISBN 13 :
Total Pages : 173 pages
Book Rating : 4.:/5 (91 download)

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Book Synopsis Holocene Ice Margin Fluctuations of the Greenland Ice Sheet in the Disko Bugt Region, West Greenland by :

Download or read book Holocene Ice Margin Fluctuations of the Greenland Ice Sheet in the Disko Bugt Region, West Greenland written by and published by . This book was released on 2014 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current response of the Greenland Ice Sheet (GrIS) margin to climate change is spatially and temporally variable. Understanding the mechanisms that control this variability is crucial for accurate predictions of how the GrIS will change in the future. One factor that appears to play a role in driving the varying response exhibited along the margin of the GrIS is the ice margin setting (marine-terminating or land-terminating). Recent research has demonstrated that basal melting of marine-terminating glaciers may increase their vulnerability to climatic perturbations, while their land-terminating counterparts may lag in their reaction similar climatic changes. While these trends are illustrated in historic and modern records, longer temporal records are needed to place these observations in context. Here, I present a chronology of GrIS fluctuations within the Disko Bugt region of West Greenland. This record spans the Holocene, and is constrained by 10Be and radiocarbon ages. Through building this chronology, I reconstruct the pattern and timing of Holocene ice margin fluctuations and evaluate the response of differing ice margin types (marine-based or land-based) to regional climate forcing. From my chronology it is apparent that, on millennial timescales early Holocene ice margin retreat rates were synchronous within Disko Bugt. This pattern extends along the western margin of the GrIS, with all the sections of the ice margin examined displaying similar retreat rates despite dissimilar marginal settings. This is strikingly different than modern trends, where marine-based outlet glaciers exhibit significantly higher retreat rates than their land-based counterparts. The record of ice margin reaction to recent warming demonstrates a distinct pattern of asynchrony. In my late Holocene records, marine-based glaciers initiate retreat much sooner than land-based sectors of the ice margin. I believe this feature demonstrates a relationship between ice margin type and response time. I propose that in West Greenland faster glaciers maintain a closer equilibrium with changing climate than slower flowing glaciers. In total, the historic pattern of relative stability of land-based sectors of the GrIS is in contrast with the longer records of Holocene ice margin fluctuation. Additionally, a relationship between ice margin type and response time suggests that land-based sectors of the ice margin lag in their reaction to climate forcing on decadal scales. This indicates that historically stable sectors of the ice margin may be expected to undergo significant future retreat, as a larger percentage of the GrIS margin begins to react to 20th century warming.

Holocene Ice Sheet Dynamics and Detrital Provenance Shifts Along the West Greenland Margin

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (128 download)

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Book Synopsis Holocene Ice Sheet Dynamics and Detrital Provenance Shifts Along the West Greenland Margin by : Lina Madaj

Download or read book Holocene Ice Sheet Dynamics and Detrital Provenance Shifts Along the West Greenland Margin written by Lina Madaj and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the effect of Arctic Amplification the Arctic is currently warming at least twice as fast as the rest of the planet. Seasonal sea-ice extent has been alarmingly declining in the past decade. Glaciers and ice caps along the Greenland coast and in the Canadian Arctic have been losing mass on an accelerated rate during the past century. As the global climate system is a complex system connecting different regions via atmospheric transport, changes in Arctic climate patterns are affecting the climate and weather conditions in the lower latitudes. The Greenland Ice Sheet as well as glaciers and ice caps in the Canadian Arctic are the largest freshwater storages on the northern hemisphere and expected to be among the highest contributors to global sea level rise. Freshwater input through meltwater discharge is not only affecting sea level rise but further influencing deep water formation in the Labrador Sea and the subpolar North Atlantic and hence global ocean circulation and climate patterns. To be able to sufficiently predict future developments of the Greenland Ice Sheet with respect to mass loss and resulting impacts on the global climate, data from past climate and Greenland Ice Sheet extents are crucially important. The Holocene spanning the last period of the deglaciation after the Last Glacial Maximum culminating in the Holocene Thermal Maximum when atmospheric temperatures were warmer and glacier and ice-sheet extent smaller than today represents the closest analogue to current atmospheric warming and Greenland Ice Sheet mass loss. The wide west Greenland shelf of Baffin Bay and Labrador Sea hosts thick marine sediments archiving around ten thousand years of this past climate and ice-sheet history. Siliciclastic detrital material discharged into Baffin Bay and the Labrador Sea via meltwater and erosion can be separated from those sedimentary archives and traced back to its source region. Radiogenic isotopes (Sr, Nd, Pb) label the source regions of those sediments by fingerprinting the isotopic composition of the prevailing bedrock. Hence, they can be used as reliable provenance tracers. Retreating land-ice masses expose bedrock that before was not subject to erosion, influencing the isotopic signatures delivered into the surrounding ocean. Based on this theory, radiogenic isotopes can record changes in siliciclastic detrital sediment provenance and hence, indirectly trace ice-sheet dynamics. The overall aim of this thesis work is to reconstruct changes in detrital sediment provenance along the west Greenland shelf to gain new insights into Holocene Greenland Ice Sheet dynamics and ocean current-induced sediment transport. Sedimentary archives from three main research areas (eastern Labrador Sea, northeastern Baffin Bay, and Kane Basin, central Nares Strait) record obvious shifts in sediment provenance throughout the Holocene. Those shifts coincide with major regional climatic changes in the research area. Generally, all records reveal the local bedrock as the main source region of detrital material and distal-sourced material transported along the coast via the West Greenland Current as a secondary source. Although the proportion of distal sourced material appears to be small, changes in West Greenland Current strength have been recorded in the isotopic composition. In southwestern Greenland and the Labrador Sea radiogenic isotope records reveal a shift towards a higher proportion of the local Archean Block in the late Holocene caused by Neoglacial ice advance and a reduction in West Greenland Current speed delivering less material from southern most Greenland. Farther north in the Upernavik region, midwest Greenland coast, the isotopic composition marks a change with the transition from early to mid Holocene caused by increased West Greenland Current strength and the opening of Vaigat Strait which enabled erosion and transport of freshly exposed basalts from the Disko Bay area due to ice-sheet retreat. This basalt input is, however, not transported all the way to northernmost Melville Bay (northern Baffin Bay) where the detrital sediment composition is clearly dominated by contribution of the local Committee-Melville Belt without any significant provenance changes throughout the Holocene. Farthest north, the sedimentary record from Kane Basin records provenance shifts that confirm the opening of Nares Strait around 8.3 ka BP. This event is followed by an increased delivery of carbonate-rich detrital sediments from northern Ellesmere Island due to the newly established gateway of Arctic Ocean water transporting sediments from further north to the core location. Additionally determined mineralogical composition of the sedimentary records along the west Greenland coast supports the interpretation drawn from the radiogenic isotopic composition. Furthermore, it points out the additional value of radiogenic isotopes through variations only visible in isotopic composition but not in the mineralogical composition. Further comparison to other studies from the region based on different tracers confirms the reliability and sufficient application of radiogenic isotopes in provenance studies as well as the advantage of multi-proxy approaches in paleoclimatological studies. Overall, this study highlights the advantages and reliability of radiogenic isotopes in provenance studies with regards to reconstructions of ice-sheet dynamics. The combination of the three isotopic systems (Sr, Nd, Pb) enables source region determination with a higher probability compensating for overlapping signatures within individual isotopic systems. The transect of sedimentary records along the west Greenland coast identifies clearly distinguishable isotopic ranges for the different Greenland bedrock terrains, qualifying this approach for further high-resolution investigation in past Greenland Ice Sheet development.

Late Glacial and Holocene Fluctuations of Local Glaciers and the Greenland Ice Sheet, Eastern and Western Greenland

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ISBN 13 :
Total Pages : 408 pages
Book Rating : 4.:/5 (884 download)

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Book Synopsis Late Glacial and Holocene Fluctuations of Local Glaciers and the Greenland Ice Sheet, Eastern and Western Greenland by : Laura B. Levy

Download or read book Late Glacial and Holocene Fluctuations of Local Glaciers and the Greenland Ice Sheet, Eastern and Western Greenland written by Laura B. Levy and published by . This book was released on 2014 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The Greenland Ice Sheet (GrIS) is responding sensitively to climate change and its meltwater has the potential to influence global sea level. Recently, large changes in the GrIS have occurred including increased velocities of outlet glaciers and melt over ~97% of the ice sheet. One means to understand modern and help predict future changes in the GrIS is to examine how it responded to past climate conditions. In this dissertation I provide a longer-term perspective of changes in the GrIS as well as in smaller, independent glaciers near the ice sheet margins (i.e., "local" glaciers). My research documents the past extents of the GrIS in central East and southern West Greenland during the Holocene Epoch (11,600 yrs ago-present) and provides evidence for climate conditions along the ice sheet margin during late glacial time (~17,500-11,600 yrs ago) and the Holocene Epoch. I use geomorphic mapping, surface exposure dating and lake sediment analyses to demonstrate that the GrIS and local glaciers in central East Greenland were receding during the Younger Dryas cold event (~12,900-11,600 yrs ago) and deposited the Milne Land stade moraines at the end of the Younger Dryas. I hypothesize that these ice marginal fluctuations were primarily influenced by air or ocean surface temperatures. I document the Holocene fluctuations of a local glacier that completely disappeared indicating peak warm conditions between ~9.3 and 6.0 cal kyr BP. The formation of this glacier at 2.6 cal kyr BP and its persistence from ~1.9 cal kyr BP-present suggests cold conditions during late Holocene time. I also use geomorphic mapping and surface exposure dating to document the extents of the GrIS in southern West Greenland, near Kangerlussuaq. I show that the Keglen, Ørkendalen and Historical moraines were deposited at 7.3 ka, 6.3 ka, and by ~AD 1950, respectively. These data indicate that the GrIS was as small as or smaller than at present during much of middle to late Holocene time. Finally, I synthesize my results and discuss possible causes of GrIS marginal changes in central East and southern West Greenland including changes in air and ocean temperatures and changes in sea level."

Quaternary Glaciation History and Glaciology of Jakobshavn Isbrae and the Disko Bugt Region, West Greenland

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ISBN 13 :
Total Pages : 88 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Quaternary Glaciation History and Glaciology of Jakobshavn Isbrae and the Disko Bugt Region, West Greenland by : Anker Weidick

Download or read book Quaternary Glaciation History and Glaciology of Jakobshavn Isbrae and the Disko Bugt Region, West Greenland written by Anker Weidick and published by . This book was released on 2007 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Reconstructing Ice Sheet and Alpine Glacier Margins During the Early Holocene on Nuussuaq in Central West Greenland

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ISBN 13 :
Total Pages : 99 pages
Book Rating : 4.:/5 (96 download)

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Book Synopsis Reconstructing Ice Sheet and Alpine Glacier Margins During the Early Holocene on Nuussuaq in Central West Greenland by : Sandra L. Cronauer

Download or read book Reconstructing Ice Sheet and Alpine Glacier Margins During the Early Holocene on Nuussuaq in Central West Greenland written by Sandra L. Cronauer and published by . This book was released on 2014 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparison of past ice sheet margin and alpine glacier reconstructions to paleoclimate records can offer insight into the dominant forcing mechanisms that determine glacial response to changes in climate. Previous research on a major ice stream in central West Greenland reveals that the Greenland Ice Sheet (GrIS) responded to abrupt centennial-scale cold periods at ~9. 3 and ~8. 2 ka. The aim of this thesis is to determine whether or not alpine glaciers and a land-terminating ice sheet margin on the peninsula of Nuussuaq in central West Greenland also responded to abrupt climate changes in the early Holocene. To this end, I reconstructed ice sheet and alpine glacier histories on Nuussuaq using cosmogenic 10Be surface exposure dating (herein 10Be dating) and lake sediment analysis. Neither the ice margin nor alpine glacier chronologies indicate a response to abrupt climate change at 9. 3 ka or 8. 2 ka. I found that the Drygalski Moraines are early Holocene in age, with mean moraine ages of 8. 6 ℗ł 0. 4 ka (n=2), 8. 5 ℗ł 0. 2 ka (n=3), and 7. 6 ℗ł 0. 1 ka (n=2) from outer to inner. The moraine chronology, combined with radiocarbon dated lake sediment stratigraphy from an adjacent proglacial lake, reveal that the ice margin remained within about one kilometer of its present position from ~9. 9 to 5. 4 ka. This evidence for ice sheet stability during the first half of the Holocene, followed by minimum ice extent between ~5. 4 and 0. 6 ka, contrasts with many records of early Holocene warmth during the Holocene maximum of Northern Hemisphere summer insolation. This period of ice margin stability may relate to adjacent ocean temperatures, which did not increase until the middle Holocene. A 10Be chronology of moraines deposited by a nearby alpine glacier reveals glacier stability at 10. 5 ℗ł 0. 3 ka, during the Preboreal period. Moraine deposition at this time is potentially due to increased moisture availability as the GrIS retreated and sea ice declined. The alpine glacier chronology also fits well within an emerging pattern of alpine glacier advance during the Preboreal period on East and West Greenland. The results presented in this thesis suggest that GrIS and alpine glacier margin response to changes in climate is complex, and that detailed chronologies from moraines on Greenland can shed light on the intricate processes that link glaciers and climate.

Holocene Reconstruction of the West Greenland Current and the Greenland Ice Sheet Margin Near Disko Bay Using Foraminiferal Assemblages

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ISBN 13 :
Total Pages : 114 pages
Book Rating : 4.:/5 (764 download)

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Book Synopsis Holocene Reconstruction of the West Greenland Current and the Greenland Ice Sheet Margin Near Disko Bay Using Foraminiferal Assemblages by : Mariah E. Walton

Download or read book Holocene Reconstruction of the West Greenland Current and the Greenland Ice Sheet Margin Near Disko Bay Using Foraminiferal Assemblages written by Mariah E. Walton and published by . This book was released on 2010 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent Greenland Ice Sheet retreat has been shown to be caused at least in part by ocean subsurface warming. Foraminiferal assemblages and IRD counts from four marine sediment cores in the region of Disko Bay (West Greenland) are presented here to help explore the relationship between oceans and ice sheets. Faunal shifts indicate that Atlantic Waters via the West Greenland Current (WGC) were first felt in the bay sometime between 9 and 8.5 cal. kyr BP. A dramatic rise in calcareous fauna from 6.2 - 3.5 cal. kyr BP in all cores indicates a significant shift in the strength of the WGC, with Atlantic associated fauna peaking at 4.5 cal. kyr BP. This coincides with the believed retreat of Jakobshavn Isbrae behind its present margin, suggesting that subsurface warming may have played a part in the ice stream's retreat in the past.

Quaternary Glaciations - Extent and Chronology

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Publisher : Elsevier
ISBN 13 : 0444535373
Total Pages : 1127 pages
Book Rating : 4.4/5 (445 download)

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Book Synopsis Quaternary Glaciations - Extent and Chronology by : J. Ehlers

Download or read book Quaternary Glaciations - Extent and Chronology written by J. Ehlers and published by Elsevier. This book was released on 2011-06-29 with total page 1127 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents an up-to-date, detailed overview of the Quaternary glaciations all over the world, not only with regard to stratigraphy but also with regard to major glacial landforms and the extent of the respective ice sheets. The locations of key sites are included. The information is presented in digital, uniformly prepared maps which can be used in a Geographical Information System (GIS) such as ArcView or ArcGIS. The accompanying text supplies the information on how the data were obtained (geomorphology, geological mapping, air photograph evaluation, satellite imagery), how the features were dated (14C, TL, relative stratigraphy) and how reliable they are supposed to be. All references to the underlying basic publications are included. Where controversial interpretations are possible e.g. in Siberia or Tibet, this is pointed out. As a result, the information on Quaternary glaciations worldwide will be much improved and supplied in a uniform digital format. The information on the glacial limits is compiled in digital form by the coordinators of the project, and is available for download at: http://booksite.elsevier.com/9780444534477/ - Completely updated detailed coverage of worldwide Quaternary glaciations - Information in digital, uniformly prepared maps which can be used in a GIS such as ArcView or ArcGis - Step-by-step guideline how to open and use ArcGis files - Possibility to convert the shapefiles into GoogleEarth kmz-files - Availability of chronological controls

Late Glacial and Holocene History of the Greenland Ice Sheet Margin in Nunatarssuaq, Northwestern Greenland

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ISBN 13 :
Total Pages : 136 pages
Book Rating : 4.:/5 (961 download)

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Book Synopsis Late Glacial and Holocene History of the Greenland Ice Sheet Margin in Nunatarssuaq, Northwestern Greenland by : Lauren Brett Farnsworth

Download or read book Late Glacial and Holocene History of the Greenland Ice Sheet Margin in Nunatarssuaq, Northwestern Greenland written by Lauren Brett Farnsworth and published by . This book was released on 2016 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is uncertain as to how the Greenland Ice Sheet (GrIS) will respond to future climate changes. One means of assessing the sensitivity of the GrIS to projected climate conditions is to determine its response to past conditions. I reconstructed late glacial and Holocene (~15 ka-present) GrIS extents in the Nunatarssuaq, northwestern Greenland. I applied geomorphic mapping, 10Be surface exposure dating and 14C dating of subfossil plants to determine a chronology of past GrIS extents. I also analyzed sediment cores from a glacially fed lake. 10Be ages of boulders and bedrock exposed during deglaciation from the Last Glacial Maximum (LGM; ~26-19.5 ka) are apparently old due to 10Be inherited from prior periods of exposure. The youngest 10Be age (~15 ka) may also contain inherited 10Be but approximates the time of deglaciation. Subfossil plants transported to the GrIS margin on shear planes date to ~4.6 cal ka BP and indicate a less extensive GrIS during middle Holocene time. Geomorphic mapping documents higher levels of Nordsø, a glacial lake dammed by a more extensive GrIS margin. I constrain the age of this GrIS extent to ~3-2 ka using 14C ages of in situ subfossil plants on nunataks and 10Be ages of boulders on the drift deposited during the advance. A fresh drift occurs ~30-50 m beyond the present GrIS margin. 10Be ages of this fresh drift range from 2.2 to 0.5 ka. I interpret the youngest 10Be age (~0.5 ka) as the time the drift was exposed. 14C ages of in situ subfossil plants indicate that the GrIS was at or behind its present margin at AD ~1662-1897. I compare my record of GrIS extents to other glacial fluctuations and climate records. I find that the GrIS margin in Nunatarssuaq fluctuated at similar times as local ice masses and other GrIS margins. The middle Holocene GrIS recession occurred during relatively warm conditions registered by regional climate records and the late Holocene GrIS advances occurred during cooler conditions. I also document asynchronous GrIS margin fluctuations in Nunatarssuaq. These require further investigation to determine whether they were influenced by climate conditions or ice dynamics.

Encyclopedia of Quaternary Science

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Publisher : Newnes
ISBN 13 : 0444536426
Total Pages : 3883 pages
Book Rating : 4.4/5 (445 download)

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Book Synopsis Encyclopedia of Quaternary Science by : Cary Mock

Download or read book Encyclopedia of Quaternary Science written by Cary Mock and published by Newnes. This book was released on 2013-03-25 with total page 3883 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second revised edition of the Encyclopedia of Quaternary Science, Four Volume Set, provides both students and professionals with an up-to-date reference work on this important and highly varied area of research. There are lots of new articles, and many of the articles that appeared in the first edition have been updated to reflect advances in knowledge since 2006, when the original articles were written. The second edition will contain about 375 articles, written by leading experts around the world. This major reference work is richly illustrated with more than 3,000 illustrations, most of them in colour. Research in the Quaternary sciences has advanced greatly in the last 10 years, especially since topics like global climate change, geologic hazards and soil erosion were put high on the political agenda. This second edition builds upon its award-winning predecessor to provide the reader assured quality along with essential updated coverage Contains 357 broad-ranging articles (4310 pages) written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource for information in the field. Facilitates teaching and learning The first edition was regarded by many as the most significant single overview of Quaternary science ever, yet Editor-in-Chief, Scott Elias, has managed to surpass that in this second edition by securing even more expert reviews whilst retaining his renowned editorial consistency that enables readers to navigates seamlessly from one unfamiliar topic to the next

Reconstructing Holocene Glacier Changes in West Greenland from Multispectral Imagery

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ISBN 13 :
Total Pages : 290 pages
Book Rating : 4.:/5 (148 download)

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Book Synopsis Reconstructing Holocene Glacier Changes in West Greenland from Multispectral Imagery by : Kyung In Huh

Download or read book Reconstructing Holocene Glacier Changes in West Greenland from Multispectral Imagery written by Kyung In Huh and published by . This book was released on 2007 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The Greenland Ice Sheet (GIS), the second largest ice mass on Earth, is generally believed to be vulnerable to changes in climate due to its location at more temperate latitudes. Its mass balance and equilibrium state are complex functions of external climate forcing and internal dynamical processes. To understand the mass balance of the Greenland Ice Sheet it is crucial to construct longer temporal records, reaching back to the Little Ice Age (LIA) or beyond. Jakobshavn Isbr in central west Greenland is one of the most dynamically thinning outlet glaciers draining the interior of the Greenland Ice Sheet, contributing 0.06 mm/yr to global sea level rise (Joughin and others, 2004). In this study, multispectral ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) imagery was used to develop procedures for mapping glacial trimlines and terminal moraines around Jakobshavn Isbne. The motivation for using satellite imagery for mapping glacial-geological features is the greater spatial coverage that can be achieved, as opposed to the traditional method of field mapping in restricted areas. ASTER imagery provides spectral bands spanning from the visible to the thermal infrared bands, including two stereo bands, enabling us to map the spectral properties of the Earth's surface as well as to obtain surface topography. With these great opportunities from ASTER, glacial trimlines and major moraine systems around the study area were efficiently mapped and results were verified by other data such as stereo pairs of aerial photographs and GPS data. Extracted trimzone from ASTER classification image and ASTER DEM were applied to calculate ice volume shrinkage since LIA and this is related to Greenland Ice Sheet volume changes and the potential for future changes.

Late Quaternary Ice-ocean Interactions in Central West Greenland

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (757 download)

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Book Synopsis Late Quaternary Ice-ocean Interactions in Central West Greenland by : David John McCarthy

Download or read book Late Quaternary Ice-ocean Interactions in Central West Greenland written by David John McCarthy and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A greater knowledge of the interactions between the Greenland Ice Sheet and climate is critical to understanding the possible impacts of future global warming, including ice sheet contribution to global sea-level rise and perturbations to ocean circulation. Recent acceleration, thinning and retreat of major tidewater glaciers in Greenland and Antarctica during the past two decades demonstrate the potential for ice sheets to respond to climate change much faster than previously assumed. One approach to understanding the role of atmospheric and oceanic warming to ice sheet dynamics is to investigate how ice sheets responded to past periods of climate change. This thesis uses benthic foraminifera as a proxy to reconstruct past changes in the temperature of the relatively warm West Greenland Current, to investigate the possible influence of ocean warming on ice sheet dynamics during the initial marine-based deglaciation phase, and throughout the Holocene, when the ice was positioned close to the present margin. This thesis finds that the marine-based ice sheet in central West Greenland collapsed rapidly due to a combination of high relative sea-level and ice sheet thinning due to climatic warming. Foraminiferal evidence does not support a major influence of ocean forcing on initial deglaciation. However, Holocene changes in the relative temperature of the West Greenland Current may have had a more significant influence on ice stream dynamics following the marine-based ice retreat, when outlet glaciers were positioned within coastal fjords. Changes in the relative temperature of the West Greenland Current are determined?upstream? by wider scale changes in the North Atlantic region.

Fluctuations of the West Greenland Ice Sheet, Independent Ice Caps and Mountain Glaciers During the Twentieth Century

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ISBN 13 :
Total Pages : 205 pages
Book Rating : 4.:/5 (911 download)

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Book Synopsis Fluctuations of the West Greenland Ice Sheet, Independent Ice Caps and Mountain Glaciers During the Twentieth Century by :

Download or read book Fluctuations of the West Greenland Ice Sheet, Independent Ice Caps and Mountain Glaciers During the Twentieth Century written by and published by . This book was released on 2010 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Greenland Ice Sheet contains enough water to raise global sea levels by ~7 metres, but predictions of the actual potential future contribution in a warming climate vary widely. These can be improved through a better understanding of how the whole ice sheet and its outlet glaciers have responded to past and present climate fluctuations. Recent studies have observed that Greenland Ice Sheet outlet glaciers have been retreating and thinning at increasingly faster rates since the 1990s. However, few studies have investigated the behaviour of the numerous independent ice caps that surround the ice sheet, or the land-terminating outlet glaciers. In addition, recent retreat is rarely put into context with long-term twentieth century fluctuations. This study has mapped ice sheet outlet glaciers and margins, independent ice cap outlets and mountain/valley glaciers at 11 time steps between the Little Ice Age and 2009 in northwest and southwest Greenland. Length changes of different glacier classes and terminus environments are examined, and overall glacier fluctuations compared to regional air temperatures and precipitation. Glaciers in the northwest have retreated further than those in the southwest at most time periods, with the exception of 1943/53-1964 when southwest glaciers underwent their most rapid rate of retreat. Length changes in both regions are driven by air temperature and precipitation changes. Tidewater outlet glaciers have generally retreated shorter distances than land-terminating glaciers in both absolute and relative terms over long time periods. These results imply that recent rapid retreat of many tidewater outlet glaciers in Greenland is not unprecedented, and may represent natural cyclical fluctuations rather than a long-term shift in behaviour. Ice sheet outlet glaciers have retreated shorter relative distances than independent ice caps and mountain/valley glaciers. Ice sheet margins advanced in the southwest between 1964 and 2001, and a slight and a slight advance of independent glaciers was observed from ~1964-1987. It is unclear why this advance occurred. This study highlights the need for more research into the fluctuations of the independent ice caps and land-terminating glaciers in all regions of Greenland. In addition, more detailed research into the response of glaciers of all classes and terminus environments to climate change during the whole of the twentieth century is required to put recent changes into context.

The Evolution of the Greenland Ice Sheet from the Last Glacial Maximum to Present-day: An Assessment Using Glaciological and Glacial Isostatic Adjustment Modelling

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (669 download)

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Book Synopsis The Evolution of the Greenland Ice Sheet from the Last Glacial Maximum to Present-day: An Assessment Using Glaciological and Glacial Isostatic Adjustment Modelling by :

Download or read book The Evolution of the Greenland Ice Sheet from the Last Glacial Maximum to Present-day: An Assessment Using Glaciological and Glacial Isostatic Adjustment Modelling written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we constrain a three-dimensional thermomechanical model of Greenland ice sheet (GrIS) evolution from the Last Glacial Maximum (LGM, 21 ka BP) to the present-day using, primarily, observations of relative sea level (RSL) as well as field data on past ice extent. The new model (Huy2) fits a majority of the observations and is characterised by a number of key features: (i) the ice sheet had an excess volume (relative to present) of 4.1 m ice-equivalent sea level at the LGM, which increased to reach a maximum value of 4.6 m at 16.5 ka BP; (ii) retreat from the continental shelf was not continuous around the entire margin, as there was a Younger Dryas readvance in some areas. The final episode of marine retreat was rapid and relatively late (c. 12 ka BP), leaving the ice sheet land based by 10 ka BP; (iii) in response to the Holocene Thermal Maximum (HTM) the ice margin retreated behind its present-day position by up to 80 km in the southwest, 20 km in the south and 80 km in a small area of the northeast. As a result of this retreat the modelled ice sheet reaches a minimum extent between 5 and 4 ka BP, which corresponds to a deficit volume (relative to present) of 0.17 m ice-equivalent sea level. The results suggest that remaining discrepancies between the model and the observations are likely associated with non-Greenland ice load, differences between modelled and observed present-day ice elevation around the margin, lateral variations in Earth structure and/or the pattern of ice margin retreat. Predictions of present-day vertical land motion generated using the new Huy2 model are highly sensitive to variations of upper mantle viscosity. Depending on the Earth model adopted, different periods of post-LGM ice loading change dominate the present-day response in particular regions of Greenland. These results will be a useful resource when interpreting existing and future observations of vertical land motion in Greenland. In comparison to the sparse number of.

Holocene Sedimentation History of the Shallow Kangerlussuaq Lakes, West Greenland

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Publisher : Museum Tusculanum Press
ISBN 13 : 9788763512596
Total Pages : 52 pages
Book Rating : 4.5/5 (125 download)

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Book Synopsis Holocene Sedimentation History of the Shallow Kangerlussuaq Lakes, West Greenland by : Nico W. Willemse

Download or read book Holocene Sedimentation History of the Shallow Kangerlussuaq Lakes, West Greenland written by Nico W. Willemse and published by Museum Tusculanum Press. This book was released on with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Holocene Sea-ice and Ice-sheet Variability on the Northeast Greenland Continental Shelf

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Book Rating : 4.:/5 (122 download)

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Book Synopsis Holocene Sea-ice and Ice-sheet Variability on the Northeast Greenland Continental Shelf by : Nicole Syring

Download or read book Holocene Sea-ice and Ice-sheet Variability on the Northeast Greenland Continental Shelf written by Nicole Syring and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Sea ice; Biomarker; Holocene; Northeast Greenland. - When will all the Arctic sea ice in summer be gone? The rapid decline in average sea-ice extent by more than one-third during the last 3 to 4 decades leaves a sad note in terms of climate model projections. Dramatic Arctic sea-ice loss generally appears faster than climate models have forecasted. Nowadays, rapidly changing environmental conditions in the Fram Strait, the passage between Greenland and Spitsbergen, are of particular concern. Sea-ice loss here is rising and the Northeast Greenland Ice Sheet is thinning. During past decades, the amount of drift ice export has increased through Fram Strait, contributing with a significant number to the freshwater budget of the Nordic seas and global ocean circulation. Here our analysis of the Northeast Greenland continental shelf located in the western Fram Strait, uniquely records past climate changes in a highly versatile environmental system of the Arctic Ocean. Multivariate analysis of molecular highly branched isoprenoids (HBIs), specific sterols, foraminifers and organic/inorganic bulk parameters were carried out on selected downcore records and surface samples from the Northeast Greenland continental shelf. These proxies allow reconstructions of past changes in sea-ice cover, primary production, terrigenous input as well as ice-sheet extent. The first manuscript provides insights into past sea-ice variability on the outer Northeast Greenland continental shelf and the seasonal formation of the Northeast Water Polynya since the onset of the Holocene to present-day. This outer shelf regime is highly influenced by drift ice and cold water from the central Arctic Ocean and annually occurring local sea-ice formation. Interactive sea-ice and ocean dynamics regulate the regional climate and biology on the marginal shelf. Continuous seasonal sea-ice presence throughout the Holocene within three prominent stages mark relatively abrupt shifts at ~9 ka and ~1 ka. A reduced to variable sea-ice cover with an overall high primary productivity most likely driven by maximum solar insolation was observed during the early Holocene. Sea-ice melt and the intensified inflow of warmer recirculating Atlantic Water favored intensive planktic blooms and fluxes of both marine and terrigenous organic matter. Environmental conditions changed towards seasonal sea-ice conditions and a stronger drift ice signal rather than local one, evidenced by terrigenous biomarkers and IRD content during the mid Holocene. Finally, a stable seasonal sea-ice margin within a fully developed polynya environment occurred during the late Holocene and highlights the last 1 ka. To understand ocean - sea ice - ice sheet interactions, a second study focuses on the inner Northeast Greenland continental shelf where marine terminating outlet glaciers of the Northeast Greenland Ice Stream are bounded by a near permanent lastfast ice barrier named Norske Øer. A downcore record that fronts the 79°Glacier embayment and includes sedimentological, micropaleontological and organic-geochemical data sets, provides fundamental insights into the detailed initial late Weichselian deglacial to Holocene sea-ice and ice sheet history. In contrast to the outer shelf, drift ice is rather trivial while the local ice barrier plays a fundamental role by preventing glaciers from calving due to the buttressing effect. A reconstruction of the waxing/waning 79°Glacier and changes in the Norske Øer ice barrier during this specific interval was generated, showing the timing of 79°Glacier retreat and disintegration, accompanied by the intensification in sea-ice conditions. Distinct lithofacies types represent the transition from deglacial conditions with a grounded 79°Glacier through a proximal to a distal glaciomarine environment displaying the onset of the 79°Glacier retreat and total disintegration of the ice shelf at 7.9 ka. Our biomarker and foraminiferal proxy records reflect local sea-ice conditions that changed from a stable sea-ice margin and high productivity system during the early Holocene Thermal Maximum (~10.6 to 9.6 ka) to prolonged seasonal sea-ice conditions in the late early Holocene (9.6 to 7.9 ka) and near perennial sea-ice conditions in the mid to late Holocene (7.9 ka to present). These changes are strongly triggered by Atlantic Water inflow decreasing from early to late Holocene times. The intrusion of warmer Atlantic Water towards the Northeast Greenland continental shelf and changes in the solar insolation supposed to be the main climate drivers. A third study addresses ways of possible diagenetic alteration on organic bulk parameters and biomarkers in recent and sub-recent samples from the Northeast Greenland continental shelf in comparison with other Arctic records. Multicorer records may be altered by near-surface degradation processes, suggested from the extremely high concentration values in the surface sediments sharply decreasing to minimum values within the uppermost about ~5 cm. Downcore records, however, predominately still reflect a primary signal. In summary ...

Holocene Relative Sea Level Changes in Disko Bugt, West Greenland

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Book Synopsis Holocene Relative Sea Level Changes in Disko Bugt, West Greenland by : Morten Rasch

Download or read book Holocene Relative Sea Level Changes in Disko Bugt, West Greenland written by Morten Rasch and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Holocene Interaction Between Ocean Circulation and the West Greenland Ice Sheet

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Book Synopsis Holocene Interaction Between Ocean Circulation and the West Greenland Ice Sheet by : Kerstin Perner

Download or read book Holocene Interaction Between Ocean Circulation and the West Greenland Ice Sheet written by Kerstin Perner and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: