Impact of Clouds and Large-Scale Climate Forcing on the Surface Energy Balance and Melting of West Antarctica PDF Download
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Author: Ryan Scott
Publisher:
ISBN:
Category :
Languages : en
Pages : 172
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Book Description
West Antarctica is experiencing rapid ice loss and complex regional climate change. This dissertation investigates how cloud properties and the large-scale atmospheric circulation influence surface heat exchange and melting on West Antarctic ice shelves and ice sheet margins using field measurements, satellite observations, and atmospheric reanalysis data. Surface-based shortwave spectral irradiance measurements and satellite data reveal strong orographic controls on West Antarctic cloud formation and ice-phase microphysics. Orographically-forced updrafts and waves favor rapid conversion of supercooled liquid water into ice, which efficiently attenuates incoming solar near-infrared energy. Frequent intrusions of marine air from the Amundsen Sea anchor a semipermanent cloud band over the West Antarctic Ice Sheet (WAIS) that continues downstream along the Transantarctic Mountain range. Cloud systems sampled downstream at Ross Island tend to be optically thin and radiatively dominated by ice water. In contrast, direct onshore flows of marine air from the Southern Ocean bring low clouds with enhanced liquid-phase spectral signatures. Radiative transfer calculations using vertically-resolved cloud data indicate that, owing to a dominance of longwave effects, clouds radiatively warm the surface of the WAIS in every month of the year. On annual average, cloud cover is estimated to warm the grounded ice-sheet by 34 Watts per square-meter. Thin low-level liquid-bearing clouds, which favor strong radiative heat input to the snow surface, are common during the summer melt season. Summer atmospheric warming in West Antarctica is favored by blocking activity over the Amundsen Sea and a negative phase of the Southern Annular Mode, which both correlate with El Niño conditions in the tropical Pacific Ocean. Extensive melt events on the Ross and Pacific-sector coastal ice shelves are linked to persistent, intense Amundsen Sea anticyclones, which force intrusions of marine air over the ice-sheet. Surface melting is driven by enhanced downwelling longwave radiation from clouds and a warm, moist atmosphere and by downward turbulent mixing of sensible heat by föhn winds. Since the late 1990s, concurrent with accelerating ocean-driven WAIS mass loss, summer surface melt occurrence has increased from the Pine Island and Thwaites Glacier systems to the eastern Ross Ice Shelf, linked to increasing anticyclonic marine influence and regional sea-ice loss.
Author: Ryan Scott
Publisher:
ISBN:
Category :
Languages : en
Pages : 172
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Book Description
West Antarctica is experiencing rapid ice loss and complex regional climate change. This dissertation investigates how cloud properties and the large-scale atmospheric circulation influence surface heat exchange and melting on West Antarctic ice shelves and ice sheet margins using field measurements, satellite observations, and atmospheric reanalysis data. Surface-based shortwave spectral irradiance measurements and satellite data reveal strong orographic controls on West Antarctic cloud formation and ice-phase microphysics. Orographically-forced updrafts and waves favor rapid conversion of supercooled liquid water into ice, which efficiently attenuates incoming solar near-infrared energy. Frequent intrusions of marine air from the Amundsen Sea anchor a semipermanent cloud band over the West Antarctic Ice Sheet (WAIS) that continues downstream along the Transantarctic Mountain range. Cloud systems sampled downstream at Ross Island tend to be optically thin and radiatively dominated by ice water. In contrast, direct onshore flows of marine air from the Southern Ocean bring low clouds with enhanced liquid-phase spectral signatures. Radiative transfer calculations using vertically-resolved cloud data indicate that, owing to a dominance of longwave effects, clouds radiatively warm the surface of the WAIS in every month of the year. On annual average, cloud cover is estimated to warm the grounded ice-sheet by 34 Watts per square-meter. Thin low-level liquid-bearing clouds, which favor strong radiative heat input to the snow surface, are common during the summer melt season. Summer atmospheric warming in West Antarctica is favored by blocking activity over the Amundsen Sea and a negative phase of the Southern Annular Mode, which both correlate with El Niño conditions in the tropical Pacific Ocean. Extensive melt events on the Ross and Pacific-sector coastal ice shelves are linked to persistent, intense Amundsen Sea anticyclones, which force intrusions of marine air over the ice-sheet. Surface melting is driven by enhanced downwelling longwave radiation from clouds and a warm, moist atmosphere and by downward turbulent mixing of sensible heat by föhn winds. Since the late 1990s, concurrent with accelerating ocean-driven WAIS mass loss, summer surface melt occurrence has increased from the Pine Island and Thwaites Glacier systems to the eastern Ross Ice Shelf, linked to increasing anticyclonic marine influence and regional sea-ice loss.
Author: Eugene Domack
Publisher: American Geophysical Union
ISBN:
Category : Nature
Languages : en
Pages : 280
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Book Description
Published by the American Geophysical Union as part of the Antarctic Research Series, Volume 79. The Antarctic Peninsula region represents our best natural laboratory to investigate how earth's major climate systems interact and how such systems respond to rapid regional warming. The scale of environmental changes now taking place across the region is large and their pace rapid but the subsystems involved are still small enough to observe and accurately document cause and affect mechanisms. For example, clarification of ice shelf stability via the Larsen Ice Shelf is vital to understanding the entire Antarctic Ice Sheet, its climate evolution, and its response to and control of sea level. By encompassing the broadest range of interdisciplinary studies, this volume provides the global change research and educational communities a framework in which to advance our knowledge of the causes behind regional warming, the dramatic glacial and ecological responses, and the potential uniqueness of the event within the region's paleoclimate record. The volume also serves as a vital resource for public policy and governmental funding agencies as well as a means to educate the large number of ecotourists that visit the region each austral summer.
Author:
Publisher:
ISBN:
Category : Artificial satellites in earth sciences
Languages : en
Pages : 200
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Book Description
Author: Madison Ghiz
Publisher:
ISBN:
Category :
Languages : en
Pages : 100
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Book Description
Surface melting is an important mass loss process from ice sheets. In West Antarctica, the lack of direct surface observations poses difficulties in studying surface melt and loss of ice mass. This thesis presents seven contrasting cases in which surface melt was detected by satellite passive microwave sensors and analyzed using both reanalysis data and satellite data. During these melt events meteorological conditions caused the total melt energy to elevate for anywhere between 3-8 days, compared with the rest of the month. This elevated melt energy can be induced by four main mechanisms typical of the austral summer climate described in this study. These mechanisms are thermal blanketing from optically thick clouds; thin clouds enhancing all-wave radiation at the surface; sensible heat flux preconditioning the surface to melt; and föhn wind presence on the lee side of mountains. The study locations are Siple Dome, Pine Island and Thwaites Glaciers, the southern portion of the Ross Ice Shelf, and the Larsen C Ice Shelf. Through assessing the surface energy budget, total melt energy, temperature and wind components, and cloud microphysics with regards to both 25-km resolution and small-scale spatial variability, the importance of using the highest resolution data available is demonstrated. This study not only defines drivers of West Antarctic melt, but identifies improvements that could be made to the methods and data sets used to quantify the climatology of surface melt.
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: Kris Scarci
Publisher:
ISBN:
Category :
Languages : en
Pages : 78
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Book Description
Understanding the effect of clouds on atmospheric radiative processes affecting downwelling radiation is critical in discerning the causal nature of large-scale melt events in Antarctica. The influence of varying cloud types on solar and terrestrial radiation presents itself as a multifarious problem interwoven within many hierarchical orders of physical interactions across a range of spatial scales. In this work we show how large-scale meteorology leads to advection of moisture over varying terrain, influencing the microphysical properties of clouds and their effect on shortwave and longwave radiation at the Antarctic surface. Synoptic circulation patterns over West Antarctica (WA) were grouped and categorized by Scott et al. 2018 into four recurring meteorological regimes using k-means cluster analysis of daily 700 hPa geopotential height fields. Regime 1 is representative of warm surface air temperature, and moist marine air advection over WA with liquid-bearing and classical liquiddominated mixed-phase clouds. Regime 2 is characterized by large-scale subsidence, outflow of continental polar air, and anomalously clear skies. Regime 3 is of smaller sample size, and produces similar surface radiative flux levels to those of Regime 1. Regime 4 is distinguished by an orographic influence upstream of Ross Island, resulting in the formation of geometrically thick, mixed-phase clouds. This study focuses on the radiative differences in downwelling shortwave and longwave irradiance by comparing prevailing meteorological regimes and cloud properties therein. The influence of supplemental ice absorption on downwelling shortwave flux is highlighted when comparing cloud optical depth properties of Regime 4 to that of Regime 1 and 2. The influence of cloud base temperature on downwelling longwave flux is noted when comparing cloud optical depth properties of Regime 2 to that of Regime 1.
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309467578
Category : Science
Languages : en
Pages : 717
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Book Description
We live on a dynamic Earth shaped by both natural processes and the impacts of humans on their environment. It is in our collective interest to observe and understand our planet, and to predict future behavior to the extent possible, in order to effectively manage resources, successfully respond to threats from natural and human-induced environmental change, and capitalize on the opportunities â€" social, economic, security, and more â€" that such knowledge can bring. By continuously monitoring and exploring Earth, developing a deep understanding of its evolving behavior, and characterizing the processes that shape and reshape the environment in which we live, we not only advance knowledge and basic discovery about our planet, but we further develop the foundation upon which benefits to society are built. Thriving on Our Changing Planet presents prioritized science, applications, and observations, along with related strategic and programmatic guidance, to support the U.S. civil space Earth observation program over the coming decade.
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: Intergovernmental Panel on Climate Change (IPCC)
Publisher: Cambridge University Press
ISBN: 9781009157971
Category : Science
Languages : en
Pages : 755
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Book Description
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309209196
Category : Science
Languages : en
Pages : 153
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Book Description
There is little dispute within the scientific community that humans are changing Earth's climate on a decadal to century time-scale. By the end of this century, without a reduction in emissions, atmospheric CO2 is projected to increase to levels that Earth has not experienced for more than 30 million years. As greenhouse gas emissions propel Earth toward a warmer climate state, an improved understanding of climate dynamics in warm environments is needed to inform public policy decisions. In Understanding Earth's Deep Past, the National Research Council reports that rocks and sediments that are millions of years old hold clues to how the Earth's future climate would respond in an environment with high levels of atmospheric greenhouse gases. Understanding Earth's Deep Past provides an assessment of both the demonstrated and underdeveloped potential of the deep-time geologic record to inform us about the dynamics of the global climate system. The report describes past climate changes, and discusses potential impacts of high levels of atmospheric greenhouse gases on regional climates, water resources, marine and terrestrial ecosystems, and the cycling of life-sustaining elements. While revealing gaps in scientific knowledge of past climate states, the report highlights a range of high priority research issues with potential for major advances in the scientific understanding of climate processes. This proposed integrated, deep-time climate research program would study how climate responded over Earth's different climate states, examine how climate responds to increased atmospheric carbon dioxide and other greenhouse gases, and clarify the processes that lead to anomalously warm polar and tropical regions and the impact on marine and terrestrial life. In addition to outlining a research agenda, Understanding Earth's Deep Past proposes an implementation strategy that will be an invaluable resource to decision-makers in the field, as well as the research community, advocacy organizations, government agencies, and college professors and students.
