Last Glacial Maximum to Holocene Arctic Sea-ice Variability PDF Download

Author: Xiaotong Xiao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Juliane Müller
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Peter Lemke
Publisher: Springer Science & Business Media
ISBN: 9400720270
Category : Science
Languages : en
Pages : 473

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The Arctic is now experiencing some of the most rapid and severe climate change on earth. Over the next 100 years, climate change is expected to accelerate, contributing to major physical, ecological, social, and economic changes, many of which have already begun. Changes in arctic climate will also affect the rest of the world through increased global warming and rising sea levels. The volume addresses the following major topics: - Research results in observing aspects of the Arctic climate system and its processes across a range of time and space scales - Representation of cryospheric, atmospheric, and oceanic processes in models, including simulation of their interaction with coupled models - Our understanding of the role of the Arctic in the global climate system, its response to large-scale climate variations, and the processes involved.

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

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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 ...

Author: Eric T. DeWeaver
Publisher: John Wiley & Sons
ISBN: 1118671589
Category : Science
Languages : en
Pages : 431

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Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 180. This volume addresses the rapid decline of Arctic sea ice, placing recent sea ice decline in the context of past observations, climate model simulations and projections, and simple models of the climate sensitivity of sea ice. Highlights of the work presented here include An appraisal of the role played by wind forcing in driving the decline; A reconstruction of Arctic sea ice conditions prior to human observations, based on proxy data from sediments; A modeling approach for assessing the impact of sea ice decline on polar bears, used as input to the U.S. Fish and Wildlife Service's decision to list the polar bear as a threatened species under the Endangered Species Act; Contrasting studies on the existence of a "tipping point," beyond which Arctic sea ice decline will become (or has already become) irreversible, including an examination of the role of the small ice cap instability in global warming simulations; A significant summertime atmospheric response to sea ice reduction in an atmospheric general circulation model, suggesting a positive feedback and the potential for short-term climate prediction. The book will be of interest to researchers attempting to understand the recent behavior of Arctic sea ice, model projections of future sea ice loss, and the consequences of sea ice loss for the natural and human systems of the Arctic.

Author: Andreas Schmittner
Publisher: John Wiley & Sons
ISBN: 1118671880
Category : Science
Languages : en
Pages : 752

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Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 173. The ocean's meridional overturning circulation (MOC) is a key factor in climate change. The Atlantic MOC, in particular, is believed to play an active role in the regional and global climate variability. It is associated with the recent debate on rapid climate change, the Atlantic Multi-Decadal Oscillation (AMO), global warming, and Atlantic hurricanes. This is the first book to deal with all aspects of the ocean's large-scale meridional overturning circulation, and is a coherent presentation, from a mechanistic point of view, of our current understanding of paleo, present-day, and future variability and change. It presents the current state of the science by bringing together the world's leading experts in physical, chemical, and biological oceanography, marine geology, geochemistry, paleoceanography, and climate modeling. A mix of overview and research papers makes this volume suitable not only for experts in the field, but also for students and anyone interested in climate change and the oceans.

Author: Sydney Levitus
Publisher:
ISBN:
Category : Climatology
Languages : en
Pages : 196

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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.

Author: Defang You
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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In the context of global warming, the accelerated melting of the Greenland Ice Sheet (GrIS) and Arctic sea ice in recent years has led to increased meltwater discharge and subsequent sea-level rise. The meltwater discharge may affect sea surface characteristics in the polar and subpolar regions and potentially yield significant influence on ocean circulation patterns. Additionally, the far-reaching implications of ocean forcings on ice sheet instability and sea ice retreat have also raised considerable attention. To enhance our understanding of the influences of meltwater discharge on abrupt climatic changes and interactions among ice sheet instability, sea ice variability, and sea surface characteristics, it is essential to investigate sedimentary records on different timescales beyond modern observation. To achieve these objectives, we conducted detailed paleoenvironmental reconstructions from three sediment cores: one obtained from the eastern Labrador Sea (Core MSM12/2-05-01) and two others from southern Baffin Bay (Core SL170 and SL174). This study provides new insights into variations in sea surface characteristics and their interactions with ice sheet activities in the Labrador Sea and Baffin Bay during the last glacial-deglacial-Holocene period. Meanwhile, our findings provide more information about the impact of freshwater forcing/ice sheet activities on abrupt climate changes. Furthermore, these findings highlight the significance of oceanic processes within the polar and subpolar regions and their contributions to paleoclimate changes.

Author: J.A. Chapman
Publisher: Routledge
ISBN: 1134640331
Category : Science
Languages : en
Pages : 381

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Documents and explains the natural climatic and ecological changes that have occurred during the past 2.6 million years. It also outlines the emergence and global impact of humans during this period.