Southern Ocean Sentinel: The Vital Role of Antarctic Sea Ice in a Warming World PDF Download

Author: James
Publisher:
ISBN: 9783384260994
Category :
Languages : en
Pages : 0

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Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309456037
Category : Science
Languages : en
Pages : 83

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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: Douglas G. Martinson
Publisher:
ISBN:
Category :
Languages : en
Pages : 6

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The seasonal sea ice field of the Southern Ocean strongly modulates climate through its insulating effect and high albedo. Consequently, it plays a significant role in global climate and must be adequately parameterized for inclusion in large-scale circulation models attempting to predict the nature of global change. Recent field studies and modeling work show that the ice field is highly sensitive to the static stability and vertical fluxes in the Southern Ocean water column. Given the marginal stability and strong fluxes of the present-day water column, relatively small changes in the ocean/atmosphere may lead to significant changes in the stability or fluxes and thus the nature of the sea ice cover. These interactions link the local- and regional-scale processes to the global-scale processes, forming a Southern Ocean/climate feedback loop. The local-scale processes operate at sub-grid scales in most climate models; therefore the results of a local process-oriented model are reviewed to examine the nature of the local-regional interactions which are critical to this system. The model scalings, which describe the system parameter dependence, indicate the direction and magnitude of change of the key external parameters which will drive the system toward a more stable or more unstable state. They also allow a computationally efficient means of monitoring the key elements of the ocean/sea ice system in large-scale models. The main external parameters include: (1) depth of the pycnocline; (2) ratio of heat to salt through the pycnocline; (3) strength of the pycnocline; and (4) magnitude of atmospheric cooling. The divergence of the ice field also plays an important role.

Author: Joseph O. Fletcher
Publisher:
ISBN:
Category : Climatology
Languages : en
Pages : 124

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Author: Earle Wilson
Publisher:
ISBN:
Category :
Languages : en
Pages : 106

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This dissertation explores key physical mechanisms that control upper ocean and sea ice variability in the Southern Ocean. The first portion of this work presents an observational analysis of wintertime upper ocean stability and pycnocline heat availability in the Antarctic sea ice zone. This analysis reveals that the southern Weddell Sea region, which features a weak upper ocean stratification and relatively strong thermocline, is preconditioned for exceptionally high rates of winter ventilation. In other open-ocean regions, such as the northern Ross Sea, the stronger winter stratification greatly limits the efficiency with which heat may be extracted from the pycnocline. The coupling between winter ice growth and upper ocean ventilation is further explored using an idealized 1D sea ice-ocean model. This model is used to simulate winter ice growth in different regions under identical surface forcing. Consistent with the observational analysis, these simulations show that the unique thermohaline structure of the Weddell Sea, specifically that near Maud Rise, facilitates a strong negative feedback to winter sea ice growth. For this region, the entrainment of heat into the mixed layer can maintain a near-constant ice thickness over much of winter. However, these simulations also reveal that this quasi-equilibrium is attained when the pycnocline is thin and supports a large vertical temperature gradient. Further experimentation demonstrates that the surface stress imparted by a powerful storm may upset this balance and lead to substantial ice melt. In simulations initialized with profiles from more strongly stratified regions, such as near the sea ice edge of the major polar gyres, the entrainment of heat into the mixed layer had weak impact on winter ice growth---even during periods of strong wind forcing. Thus, a key takeaway is that the thermodynamic coupling between winter sea ice growth and ocean ventilation has significant regional variability. This regionality must be considered when evaluating the response of the Antarctic ice-ocean system to future changes in ocean stratification and surface forcing. In the final portion of this dissertation, focus is shifted to variations in Southern Ocean sea surface temperature (SST) and sea ice extent (SIE) on seasonal timescales. This work is motivated by the abrupt reversal of Southern Ocean SST and SIE trends that occurred in 2016 and 2017. The first half of this chapter examines the role of surface winds in the initiation of the anomalous sea ice retreat that occurred in late 2016. This is done via a simple regression analysis that quantifies the linear relationship between seasonal SIC anomalies and near-instantaneous local wind anomalies, using observations and reanalysis. With this empirical relationship, we demonstrate that surface wind anomalies can largely explain the SIC anomalies observed in the winter and spring of 2016. In the Weddell Sea, some of this preconditioning was associated with the winter polynyas that appeared that year. These events are linked to strong upwelling in the Weddell Sea and the passage of powerful winter storms. Lastly, we construct an updated seasonal mixed layer heat budget for the Southern Ocean, which is then used to explain the near-record Southern Ocean SSTs that occurred in the summer of 2016--2017. This analysis reveals that the warming maximum was the combined effect of enhanced air-sea heating, reduced northward Ekman transport, and shallower than normal mixed layer depths. From these results, we conclude that the 2016--2017 Southern Ocean SST and SIE anomalies were primarily caused by a serendipitous sequence of anomalous atmospheric and oceanic conditions. These anomalies coincided with an unusual synchronization of tropical and extratropical modes of climate variability.

Author:
Publisher:
ISBN:
Category : Microwave remote sensing
Languages : en
Pages : 228

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Data from the Electrically Scanning Microwave Radiometer (ESMR) on the Nimbus 5 satellite are used to determine the extent and distribution of Antarctic sea ice. The characteristics of the southern ocean, the mathematical formulas used to obtain quantitative sea ice concentrations, the general characteristics of the seasonal sea ice growth/decay cycle and regional differences, and the observed seasonal growth/decay cycle for individual years and interannual variations of the ice cover are discussed. The sea ice data from the ESMR are presented in the form of color-coded maps of the Antarctic and the southern oceans. The maps show brightness temperatures and concentrations of pack ice averaged for each month, 4-year monthly averages, and month-to-month changes. Graphs summarizing the results, such as areas of sea ice as a function of time in the various sectors of the southern ocean are included. The images demonstrate that satellite microwave data provide unique information on large-scale sea ice conditions for determining climatic conditions in polar regions and possible global climatic changes.

Author: Neloy Khare
Publisher: CRC Press
ISBN: 1000554597
Category : Science
Languages : en
Pages : 338

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This is the first book to provide a comprehensive overview of climate change–related investigations carried out by Indian researchers through initiatives in southern high latitude regions. It explains climate variability over the Southern Ocean and Antarctica; air, sea, ice, and atmosphere interactions; and the impact of climate variability on sea ice and the polar atmosphere. The data were gathered at two Indian research bases, Maitri and Bharti, which are ideal sites to study and understand climatic evolution in Antarctic in the past and recent changes. This book helps to understand climatological perspectives and to evaluate some of the most pressing issues in the south polar region. FEATURES Highlights the achievements of India in the contemporary field of Antarctic climatology Presents four decades of research by Indian scientists in Antarctica, which is now shared for the first time with the global community Includes case studies on climatological and environmental conditions of natural archives to shed light on climate scenarios in the Southern Ocean and Antarctic regions Covers various aspects of climate variability and induced air-sea-ice-atmosphere interactions This book is edited by one of the top scientists and researchers of India in the field of paleoclimatology, and the contributors are experts in the Antarctic region.

Author: Martin O. Jeffries
Publisher: American Geophysical Union
ISBN:
Category : Science
Languages : en
Pages : 416

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Published by the American Geophysical Union as part of the Antarctic Research Series, Volume 74. In a 1971 Scientific Committee on Antarctic Research report that reviewed polar contrasts in sea ice, Lyn Lewis and Willy Weeks made the following observation: "People who study sea ice in the Arctic Basin are commonly asked if they have ever studied ice in Antarctica, and they answer 'why bother, it's the same old stuff." Noting this was "fortunately true to a considerable extent," they added "It is clear that future work will depend critically on the logistics facilities available to allow surface observations beyond the fast ice edge at all seasons of the year. Of almost equal importance will be the development of instruments and recording equipment suited for use in the polar environment" (Lewis, E. L., and W. F. Weeks, Sea Ice: Some Polar Contrasts, in, Antarctic Ice and Water Masses, edited by G. Deacon, Scientific Committee on Antarctic Research, Cambridge, 23-34, 1971). Lewis and Weeks made no specific mention of Earth-orbiting satellites, on which the first passive microwave sensor became operational in December 1972. Less than a year later the giant Weddell Polynya was observed for the first time. Perhaps more than any other development, this unexpected feature illustrated the potential to greatly expand our knowledge of sea ice through the application of spaceborne remote sensing. Simultaneously, it acted as a catalyst for a significant increase in the level of research.

Author: Peter Wadhams
Publisher: Penguin UK
ISBN: 0241009421
Category : Science
Languages : en
Pages : 317

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'Utterly extraordinary ... the starkest book I've read on the impacts of accelerating climate change for a very long time ... if we're not listening to the likes of Peter Wadhams, then we too are in denial' Jonathon Porritt Most of the scientific establishment predict that the North Pole will be free of ice around the middle of this century. As Peter Wadhams, the world's leading expert on sea ice, demonstrates in this book, even this assessment of the future is optimistic. Wadhams has visited the Polar Regions more often than any other living scientist - 50 times since he was on the first ship to circumnavigate the Americas in 1970 - and has a uniquely authoritative perspective on the changes they have undergone and where those changes will lead. From his observations and the latest scientific research, he describes how dramatically sea ice has diminished over the past three decades, to the point at which, by the time this book is published, the Arctic may be free of ice for the first time in 10,000 years. Wadhams shows how sea ice is the 'canary in the mine' of planetary climate change. He describes how it forms and the vital role it plays in reflecting solar heat back into space and providing an 'air conditioning' system for the planet. He shows how a series of rapid feedbacks in the Arctic region are accelerating change there more rapidly than almost all scientists - and political authorities - have previously realised, and the dangers of further acceleration are very real. A Farewell to Ice is a report from the frontline of planetary change in the Arctic and Antarctic by a leading authority, presenting incontrovertible scientific data, but always in clear language which the layman can easily understand. It is one of the most important books published in recent years about the existential challenge which human civilization now faces.

Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309373700
Category : Science
Languages : en
Pages : 161

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Antarctic and Southern Ocean scientific research has produced a wide array of important and exciting scientific advances. Spanning oceanography to tectonics, microbiology to astrophysics, the extreme Antarctic environment provides unique opportunities to expand our knowledge about how our planet works and even the very origins of the universe. Research on the Southern Ocean and the Antarctic ice sheets is becoming increasingly urgent not only for understanding the future of the region but also its interconnections with and impacts on many other parts of the globe. The U.S. National Science Foundation (NSF) provides U.S. researchers with broad access to the continent and its surrounding ocean. A Strategic Vision for NSF Investments in Antarctic and Southern Ocean Research identifies priorities and strategic steps forward for Antarctic research and observations for the next decade. This survey presents a decadal vision for strategic investments in compelling research and the infrastructure most critical for supporting this research. This report makes recommendations for high-priority, larger-scale, community-driven research initiatives that address questions poised for significant advance with the next decades. This report also outlines a roadmap through which the vision and these priorities can be met.