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

Author: Nicole Syring
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author:
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Category :
Languages : en
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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.

Author: Johannes Oerlemans
Publisher: Springer Science & Business Media
ISBN: 9400963254
Category : Science
Languages : en
Pages : 220

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Climate modelling is a field in rapid development, and the fltudy of cryospheric processes has become an important part of it. On smaller time scales, the effect of snow cover and sea ice on the atmospheric circulation is of concern for long-range weather forecasting. Thinking in decades or centuries, the effect of a C02 climatic warming on the present-day ice sheets, and the resulting changes in global sea level, has drawn a lot of attention. In particular, the dynamics of marine ice sheets (ice sheets on a bed that would be below sea level after removal of ice and full isostatic rebound) is a subject of continuous research. This interest stems from the fact that the West Antarctic Ice Sheet is a marine ice sheet which, according to some workers, may be close to a complete collapse. The Pleistocene ice ages, or glacial cycles, are best characterized by total ice volume on earth, indicating that on 4 5 large time scales (10 to 10 yr) ice sheets are a dominant component of the climate system. The enormous amount of paleoclimatic information obtained from deep-sea sediments in the last few decades has led to a complete revival of iriterest in the physical aspects of the Pleistocene climatic evolution.

Author: Robert A. Bindschadler
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 68

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Proceedings of a workshop on the possibility of a rapid rise in sea level following the response of the West Antarctic ice sheet to global warming, and outline of a project to study the phenomenon, called SEARISE : Sea Level Response to Ice Sheet Evolution.

Author: Thomas R. Gregory
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Marine sedimentation from the Adélie Land continental margin of East Antarctica provides unique high resolution records of Holocene environmental change. The subannually resolved sediment cores MD03-2601 (66°03.07'S, 138°33.43'E) and IODP-318-U1357B (66°24.7990'S, 140°25.5705'E) from the Dumont d'Urville Trough,Adélie Land, document atmospheric and oceanic processes impacting on biogenic sedimentation on the Adélie Land continental shelf during the Holocene. Resin embedded, continuous polished thin sections from each core were analysed for diatom content and sediment microfabric using scanning electron microscope backscattered electron imagery. The sediments contained repeating sequences of seasonal diatom-rich laminae which enabled multi-taper method time series analysis. Time series analysis shows that in the Hypsithermal there appears to have been an external (solar) control on interannual sedimentation as well as internal controls (e.g. the southern annular mode, SAM, and El Nino-southern Oscillation, ENSO); whilst in the Neoglacial internal climatic modes exerted a much stronger control. Quasi-biennial (2 - 3 year) peaks commonly occurred in analysis of both Hypsitherml and Neoglacial sequences. The distribution of resting spore-rich laminae in these sections suggests that a multidecadal (>50-years) variation between phasing of the SAM and ENSO systems may exert an important control on interannual environmental variability in the sections analysed. The distribution of diatom-derived biomarker proxies, namely C25 highly branched isoprenoid (HBI) alkenes, was compared to the diatom lamina-based record in core MD03-2601. At the Holocene scale, HBI diene and triene molecules have a positive association to sea ice associated diatom-rich laminae, with greater abundances of both HBI molecules and sea ice associated diatom laminae in the Neoglacial interval. However, at a sub-annual resolution there is no strong association between lamina type and HBI concentrations. This is attributed to a combination of: (i) the HBI alkenes recording a different signal to that of the diatom-rich laminae; (ii) interannual variation in HBI export that is greater than inter-seasonal variation, for which there is little modern data for comparison; (iii) possible diagenetic alteration of the HBI signal.

Author: Jens Bischof
Publisher: Springer Science & Business Media
ISBN: 9781852336486
Category : Nature
Languages : en
Pages : 254

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The issue of global warming and climate change is of continuous concern. Since the 1970s, it bas been shown that the pack-ice around the Arctic Ocean is thinning, the margin of permafrost is moving north and the vegetation in the high northern parts of the world is changing (the 'greening' of the Arctic). But are these changes the result of human activity or simply regular variations of the Earth's climate system? Over thousands of years, a continuous archive of iceberg and sea ice drift bas formed in the deep-sea sediments, revealing the place of the ice's origin and allowing a reconstruction of the surface currents and the climate of the past. However, the drift of floating ice from one place to another is not just a passive record of past ocean circulation. It actively influences and changes the surface ocean circulation, thus having a profound effect on climate change. Ice Drift, Ocean Circulation and Climate Change is the first book to focus on the interactions between ice, the ocean and the atmosphere and to describe how these three components of the climate system influence each other. It makes clear the positive contribution of paleoclimatology and paleoceanography and should be read by anyone concerned with global warming and climate change.

Author: Lina Madaj
Publisher:
ISBN:
Category :
Languages : en
Pages :

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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.

Author: Sebastian Jan Koenig
Publisher:
ISBN:
Category : Greenland
Languages : en
Pages : 196

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The cryosphere and its interactions with other components of the climate system are considered to be major influences on global climate change through the Cenozoic and into the future. However, fundamental dynamics and secondary feedbacks that drive long-term ice sheet variability on Greenland remain poorly understood. Here, a numerical climate-ice sheet modeling study is conducted with the aim of reconstructing most likely locations, timing and variability of continental ice in the mid to late Pliocene and the transition into the Pleistocene. Simulations using the GENESIS v3 General Circulation Model coupled to the Penn State Ice Sheet-Shelf Model are compared with a range of independent numerical ice sheet model simulations under Pliocene boundary conditions and validated against available proxy reconstructions. This study aims at investigating the sensitivity of an ice-free and glaciated Greenland to changes in climate forcings, and the modulation of those forcings through internal feedbacks with focus on the dynamical thresholds involved in the growth and retreat of continental ice on Greenland. ^ Orbital changes of latitudinal and seasonal solar radiation, in combination with prevalent atmospheric pCO2 levels, are found to pace the timing of the cryospheric response. Internal feedbacks invoked though local surface characteristics on Greenland in concert with far field changes in Arctic sea surface temperature and sea ice conditions control the energy and moisture budget on Greenland with consequences for its mass balance. In the Pliocene, inception of Greenland ice is inhibited during interglacials and ice volume is limited even when orbits are favorable for ice sheet growth. During Pliocene warmth, a present-day Greenland Ice Sheet cannot be maintained and ice was most likely restricted to the highest elevations in the East and South, contributing around 6m of equivalent sea level rise. This assessment of the sensitivity and survivability of Greenland Ice Sheet in a warmer-than-modern world implies the potential for a long-term commitment to future sea level rise from a smaller Greenland Ice Sheet.

Author: David N. Thomas
Publisher: John Wiley & Sons
ISBN: 9781444317152
Category : Technology & Engineering
Languages : en
Pages : 641

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Book Description
As the Arctic perennial sea ice continues to disappear at an alarming rate, a full understanding of sea ice as a crucial global ecosystem, and the effects of its loss is vital for all those working with and studying global climate change. Building on the success of the previous edition, the second edition of Sea Ice, now much expanded and in full colour throughout, includes six completely new chapters with complete revisions of all the chapters included from the first edition. The Editors, Professor David Thomas and Dr Gerhard Dieckmann have once again drawn together an extremely impressive group of internationally respected contributing authors, ensuring a comprehensive worldwide coverage of this incredibly important topic. Sea Ice, second edition, is an essential purchase for oceanographers and marine scientists, environmental scientists, biologists, geochemists and geologists. All those involved in the study of global climate change will find this book to contain a wealth of important information. All libraries in universities and research establishments where these subjects are studied and taught will need multiple copies of this book on their shelves. truly multidisciplinary approach world leading authors and editors international in scope, covering both Arctic and Antarctic work of vital interest to all those involved in global warming and climate change research highly illustrated full colour book with colour images throughout

Author: Roger G. Barry
Publisher: Cambridge University Press
ISBN: 1108423167
Category : History
Languages : en
Pages : 445

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Surveys atmospheric, oceanic and cryospheric processes, present and past conditions, and changes in polar environments.