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Author: Odile Crabeck
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Abstract Past and recent literature have highlighted that sea ice might play a crucial role in controlling and contributing to the exchange of significant climatically active biogases between the ocean and the atmosphere in polar areas. However, the formation of air inclusions and the transport of gases within sea ice cover are still poorly understood. Thanks to development of a new fast and non-destructive X-ray computed tomography (CT) technique to quantify the air volume fraction and the characterization of gas concentration profiles (Ar, O2, N2, CH4 and pCO2) in natural (Kapisillit fjord, Greenland) and artificial (Sea Ice Research Facility, Winnipeg, Canada) cold sea ice, we revealed some key properteies of gas content and transport in sea ice. We concluded that gases are incorporated in dissolved phase in the brine during ice growth. Nucleation further happened in the brine inclusions at rate depending of the gas saturation factor and the brine volume. Nucleation exerts a strong control on gas content and transport because at any given time when bubbles form in the brine, they are segregated from the transport pathway of dissolved salts and dissolved gas. Due to their low density, bubbles will not drain out of the ice by convection. Instead, nucleation leads to the forced buoyant upward transport and an accumulation of gas in sea ice. In addition, we show that the gas content of air bubbles can be exchanged with the brine medium and diffuse within the brine network at a comparable rate (10-5 cm2 s-1) than aqueous diffusivities. In addition, CT-X-ray results showed that air volume fraction was 2% in most of the internal layers and systematically 5% at the ice-atmosphere interface (top 2 cm). The evidence of air volume fraction over 5% in granular top layers with the presence of macro bubbles introduces new challenges for the interpretation of sea ice atmosphere gas exchange. Substantiation of air porosity in columnar internal layers and granular top layers questions the current sea ice mathematical description in which the air volume fraction is currently neglected.
Author: Odile Crabeck
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Abstract Past and recent literature have highlighted that sea ice might play a crucial role in controlling and contributing to the exchange of significant climatically active biogases between the ocean and the atmosphere in polar areas. However, the formation of air inclusions and the transport of gases within sea ice cover are still poorly understood. Thanks to development of a new fast and non-destructive X-ray computed tomography (CT) technique to quantify the air volume fraction and the characterization of gas concentration profiles (Ar, O2, N2, CH4 and pCO2) in natural (Kapisillit fjord, Greenland) and artificial (Sea Ice Research Facility, Winnipeg, Canada) cold sea ice, we revealed some key properteies of gas content and transport in sea ice. We concluded that gases are incorporated in dissolved phase in the brine during ice growth. Nucleation further happened in the brine inclusions at rate depending of the gas saturation factor and the brine volume. Nucleation exerts a strong control on gas content and transport because at any given time when bubbles form in the brine, they are segregated from the transport pathway of dissolved salts and dissolved gas. Due to their low density, bubbles will not drain out of the ice by convection. Instead, nucleation leads to the forced buoyant upward transport and an accumulation of gas in sea ice. In addition, we show that the gas content of air bubbles can be exchanged with the brine medium and diffuse within the brine network at a comparable rate (10-5 cm2 s-1) than aqueous diffusivities. In addition, CT-X-ray results showed that air volume fraction was 2% in most of the internal layers and systematically 5% at the ice-atmosphere interface (top 2 cm). The evidence of air volume fraction over 5% in granular top layers with the presence of macro bubbles introduces new challenges for the interpretation of sea ice atmosphere gas exchange. Substantiation of air porosity in columnar internal layers and granular top layers questions the current sea ice mathematical description in which the air volume fraction is currently neglected.
Author: Thomas Anthony Gosink
Publisher:
ISBN:
Category :
Languages : en
Pages : 57
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Book Description
This research is a continuation of the previous year's work on the migration of gases through sea ice and the transport of gases across the ice-snow-air boundary. Carbon dioxide, and possibly carbon monoxide, were observed to be replenished faster than other non-water interacting gases such as nitrogen, oxygen, neon, and methane in flushed probe holes and at the surface. Large pulses of carbon dioxide were observed and suspected as the result of internal stresses in sea ice. The flux of gases in probe holes was near 2-4 microliter/sq cm/hr, and 1-2 microliter/sq cm/hr at the surface, relatively insignificant for oxygen, but very significant for trace gases such as carbon dioxide. The ocean was observed to be a source of carbon dioxide, carbon monoxide and methane to the atmosphere by way of the sea ice. Brine content in the ice varies strongly with temperature, and may be the cause of the large variations in the transport of carbon dioxide. A late spring observation of bubbles from rotting sea ice disclosed very high levels of carbon monoxide. Observations of the atmosphere over sea ice (to 78 degrees N) through the summer tends to confirm a continued high atmospheric level of CO2 beyond the time period when it diminishes at Point Barrow, Alaska (71.4 degrees N).
Author: David N. Thomas
Publisher: John Wiley & Sons
ISBN: 1118778383
Category : Science
Languages : en
Pages : 666
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Book Description
Over the past 20 years the study of the frozen Arctic and Southern Oceans and sub-arctic seas has progressed at a remarkable pace. This third edition of Sea Ice gives insight into the very latest understanding of the how sea ice is formed, how we measure (and model) its extent, the biology that lives within and associated with sea ice and the effect of climate change on its distribution. How sea ice influences the oceanography of underlying waters and the influences that sea ice has on humans living in Arctic regions are also discussed. Featuring twelve new chapters, this edition follows two previous editions (2001 and 2010), and the need for this latest update exhibits just how rapidly the science of sea ice is developing. The 27 chapters are written by a team of more than 50 of the worlds’ leading experts in their fields. These combine to make the book the most comprehensive introduction to the physics, chemistry, biology and geology of sea ice that there is. This third edition of Sea Ice will be a key resource for all policy makers, researchers and students who work with the frozen oceans and seas.
Author: Donald K. Perovich
Publisher:
ISBN:
Category : Arctic regions
Languages : en
Pages : 18
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Book Description
Sea ice is a defining feature of the polar marine environment. It is a critical domain for marine biota and it regulates ocean-atmosphere exchange, including the exchange of greenhouse gases such as CO2 and CH4. In this study, we determined the rates and pathways that govern gas transport through a mixed sea ice cover. N2O, SF6, 3He, 4He, and Ne were used as gas tracers of the exchange processes that take place at the ice-water and air-water interfaces in a laboratory sea ice experiment. Observation of the changes in gas concentrations during freezing revealed that He is indeed more soluble in ice than in water; Ne is less soluble in ice, and the larger gases (N2O and SF6) are mostly excluded during the freezing process. Model estimates of gas diffusion through ice were calibrated using measurements of bulk gas content in ice cores, yielding gas transfer velocity through ice (kice) of ∼5 × 10−4 m d−1. In comparison, the effective air-sea gas transfer velocities (keff) ranged up to 0.33 m d−1 providing further evidence that very little mixed-layer ventilation takes place via gas diffusion through columnar sea ice. However, this ventilation is distinct from air-ice gas fluxes driven by sea ice biogeochemistry. The magnitude of keff showed a clear increasing trend with wind speed and current velocity beneath the ice, as well as the combination of the two. This result indicates that gas transfer cannot be uniquely predicted by wind speed alone in the presence of sea ice.
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309456002
Category : Science
Languages : en
Pages : 83
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Book Description
The sea ice surrounding Antarctica has increased in extent and concentration from the late 1970s, when satellite-based measurements began, until 2015. Although this increasing trend is modest, it is surprising given the overall warming of the global climate and the region. Indeed, climate models, which incorporate our best understanding of the processes affecting the region, generally simulate a decrease in sea ice. Moreover, sea ice in the Arctic has exhibited pronounced declines over the same period, consistent with global climate model simulations. For these reasons, the behavior of Antarctic sea ice has presented a conundrum for global climate change science. The National Academies of Sciences, Engineering, and Medicine held a workshop in January 2016, to bring together scientists with different sets of expertise and perspectives to further explore potential mechanisms driving the evolution of recent Antarctic sea ice variability and to discuss ways to advance understanding of Antarctic sea ice and its relationship to the broader ocean-climate system. This publication summarizes the presentations and discussions from the workshop.
Author: Gordon F. N. Cox
Publisher:
ISBN:
Category : Gases
Languages : en
Pages : 24
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Book Description
Author: Robert R. Dickson
Publisher: Springer Science & Business Media
ISBN: 1402067747
Category : Science
Languages : en
Pages : 728
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Book Description
We are only now beginning to understand the climatic impact of the remarkable events that are now occurring in subarctic waters. Researchers, however, have yet to agree upon a predictive model that links change in our northern seas to climate. This volume brings together the body of evidence needed to develop climate models that quantify the ocean exchanges through subarctic seas, measure their variability, and gauge their impact on climate.
Author: A. Assur
Publisher:
ISBN:
Category : Salt
Languages : en
Pages : 68
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Book Description
Part of the salts contained in sea water are trapped in sea ice upon freezing. They form liquid and solid inclusions in a systematic pattern. The amount depends upon temperature and salinity. A detailed table of phase relations is given and a general theory is derived to show how the internal cavities may affect the strength of sea ice. The general theory leads to specific models. The principle of ring tensile strength tests is explained and a series for evaluation is given. Test data lead to a substantiation of theoretical principles and to an illustration of several hypotheses concerning the effect of solid salt inclusions upon strength. Observed sea ice phenomena are explained on the basis of internal structure. (Author).
Author:
Publisher:
ISBN:
Category : Sea ice
Languages : en
Pages : 13
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Book Description
Author: Norbert Untersteiner
Publisher: Springer
ISBN: 1489953523
Category : Science
Languages : en
Pages : 1197
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Book Description
Based on the proceedings of the NATO Advanced Study Institute on Air-Sea-Ice Interaction held September 28-October 10, 1981 in Acquafredda di maratea, Italy. Intent is to present the topic of sea ice in the broad and interdisciplinary context of atmospheric and oceanographic science.
