Miocene atmospheric carbon dioxide concentrations and paleoceanography PDF Download
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Author: Mark Pagani
Publisher:
ISBN:
Category : Paleoceanography
Languages : en
Pages : 211
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Book Description
Author: Mark Pagani
Publisher:
ISBN:
Category : Paleoceanography
Languages : en
Pages : 211
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Book Description
Author: Eric T. Sundquist
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 648
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Book Description
Author: Akil Hossain
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The Miocene (23.03-5.33 Ma) was a time period with a warmer climate than today. During this period, changes in ocean gateways and atmospheric CO2 levels largely control ocean circulation and climate changes. However, the underlying ocean processes and dynamics are poorly understood and it remains a challenge to simulate Miocene climate key characteristics such as pronounced polar warming and a reduced meridional temperature gradient. By applying state-of-the-art fully coupled atmosphere-ocean-sea-ice model approaches Miocene climate conditions at different atmospheric CO2 concentrations are simulated and thermohaline changes in response to the subsidence of Atlantic-Arctic gateways for various Greenland-Scotland Ridge (GSR) and Fram Strait (FS) configurations are investigated. For a singular subsidence of the GSR, warming and a salinity increase in the Nordic Seas and the Arctic Ocean is detected. As convection sites shift to the north of Iceland, North Atlantic Deep Water (NADW) is formed at cooler temperatures. The associated deep ocean cooling and upwelling of deep waters to the Southern Ocean surface can cause a cooling in the southern high latitudes. These characteristic responses to the GSR deepening are independent of the FS being shallow or deep. An isolated subsidence or widening of the FS gateway for a deep GSR shows less pronounced warming and salinity increase in the Nordic Seas. Arctic temperatures remain unaltered, but a stronger salinity increase is detected, which further increases the density of NADW. The increase in salinity enhances the contribution of NADW to the abyssal ocean at the expense of the colder southern source water component. These relative changes cause a negligible warming in the upwelling regions of the Southern Ocean. For a sill depth of ~1500 m, ventilation of the Arctic Ocean is achieved due to enhanced import of saline Atlantic water through a FS width of ~105 km. Moreover, at this width and depth, a modern-like three-layer stratification in the Arctic Ocean is detected. The exchange flow through FS is characterized by vertical separation of a low salinity cold outflow from the Arctic Ocean confined to a thin upper layer, an intermediate saline inflow from the Atlantic Ocean below and a cold bottom Arctic outflow. These characteristics are comparable to the present-day hydrography, in spite of significantly shallower and narrower FS configurations during the early Miocene, suggesting that the ventilation mechanisms and stratification in the Arctic Ocean have been similar. In simulations with different CO2 levels (280, 450 and 720 ppm) surface temperatures show the best fit to proxy reconstructions for atmospheric CO2 concentrations of 720 ppm, since in particular the high latitude cooling bias becomes least pronounced. For a CO2 increase from 280 to 450 ppm polar amplification is simulated in the northern high latitudes, which is stronger than for the same radiative CO2 forcing from 450 to 720 ppm. At higher CO2 levels the Miocene climate also shows a reduced climate sensitivity, since the warmest Miocene climate scenario with a CO2 level of 720 ppm is characterized by a seasonality breakdown in the Arctic Ocean. A pronounced warming in boreal winter is detected for a CO2 increase from 450 to 720 ppm, in contrast to a moderate boreal summer temperature increase. This change in the seasonal temperature signature is accompanied by a strong sea-ice concentration decline and enhanced moisture availability promotes cloud formation in the summer months. As a consequence the planetary albedo increases and dampens the temperature response to the CO2 forcing at a warmer Miocene background climate.
Author: Rachel Brown
Publisher:
ISBN:
Category :
Languages : en
Pages : 43
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Book Description
Author: Vivien Gornitz
Publisher: Springer Science & Business Media
ISBN: 1402045514
Category : Science
Languages : en
Pages : 1062
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Book Description
One of Springer’s Major Reference Works, this book gives the reader a truly global perspective. It is the first major reference work in its field. Paleoclimate topics covered in the encyclopedia give the reader the capability to place the observations of recent global warming in the context of longer-term natural climate fluctuations. Significant elements of the encyclopedia include recent developments in paleoclimate modeling, paleo-ocean circulation, as well as the influence of geological processes and biological feedbacks on global climate change. The encyclopedia gives the reader an entry point into the literature on these and many other groundbreaking topics.
Author: R.E. Zeebe
Publisher: Elsevier
ISBN: 0080529224
Category : Science
Languages : en
Pages : 361
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Book Description
Carbon dioxide is the most important greenhouse gas after water vapor in the atmosphere of the earth. More than 98% of the carbon of the atmosphere-ocean system is stored in the oceans as dissolved inorganic carbon. The key for understanding critical processes of the marine carbon cycle is a sound knowledge of the seawater carbonate chemistry, including equilibrium and nonequilibrium properties as well as stable isotope fractionation. Presenting the first coherent text describing equilibrium and nonequilibrium properties and stable isotope fractionation among the elements of the carbonate system. This volume presents an overview and a synthesis of these subjects which should be useful for graduate students and researchers in various fields such as biogeochemistry, chemical oceanography, paleoceanography, marine biology, marine chemistry, marine geology, and others. The volume includes an introduction to the equilibrium properties of the carbonate system in which basic concepts such as equilibrium constants, alkalinity, pH scales, and buffering are discussed. It also deals with the nonequilibrium properties of the seawater carbonate chemistry. Whereas principle of chemical kinetics are recapitulated, reaction rates and relaxation times of the carbonate system are considered in details. The book also provides a general introduction to stable isotope fractionation and describes the partitioning of carbon, oxygen, and boron isotopes between the species of the carbonate system. The appendix contains formulas for the equilibrium constants of the carbonate system, mathematical expressions to calculate carbonate system parameters, answers to exercises and more.
Author: James R. Ehleringer
Publisher: Springer Science & Business Media
ISBN: 0387270485
Category : Science
Languages : en
Pages : 545
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Book Description
Based in extensive research in geology, atmospheric science, and paleontology, this book offers a detailed history of CO2 in the atmosphere, and an understanding of factors that have influenced changes in the past. The text illuminates the role of atmospheric CO2 in the modern carbon cycle and in the evolution of plants and animals, and addresses the future role of atmospheric CO2 and its likely effects on ecosystems.
Author: Roger G. Barry
Publisher: Cambridge University Press
ISBN: 1108423167
Category : History
Languages : en
Pages : 445
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Book Description
Surveys atmospheric, oceanic and cryospheric processes, present and past conditions, and changes in polar environments.
Author: Melanie J. Leng
Publisher: Springer Science & Business Media
ISBN: 9781402025037
Category : Science
Languages : en
Pages : 334
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Book Description
This thorough reference shows how stable isotopes can be applied to understanding the palaeoenvironment, with chapters on the interpretation of isotopes in water, tree rings, bones and teeth, lake sediments, speleothems and marine sediments. The book offers detailed advice on calibration, including a multi-proxy approach, using isotope signals from different materials or combined with other palaeoenvironmental techniques, to enhance the reliability of readings.
Author: Brian Walker
Publisher: Cambridge University Press
ISBN: 9780521624800
Category : Nature
Languages : en
Pages : 462
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Book Description
Summarises understanding of global change interactions with terrestrial ecosystems.
