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Search Results: 1 - 10 of 4654 matches for " sea ice "
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An Overlooked Term in Assessment of the Potential Sea-Level Rise from a Collapse of the West Antarctic Ice Sheet  [PDF]
Diandong Ren, Mervyn Lynch, Lance M. Leslie
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.46090
Abstract:

As to sea level rise (SLR) contribution, melting and setting afloat make no difference for land based ice. Melting of West Antarctic Ice Sheet (WAIS) into water is impossible in the upcoming several centuries, whereas breaking and partially afloat is likely as long as sea waters find a pathway to the bottom of those ice sectors with basal elevation below sea level. In this sense WAIS may be disintegrated in a future warming climate. We reassess the potential contribution to eustatic sea level from a collapse of WAIS and find that previous assessments have overlooked a contributor: slope instability after the cementing ice is removed. Over loading ice has a buttressing effect on slope movements the same way ice shelves hinder the flow of non-floating coastal ice. A sophisticated landslide model estimates a 9-mm eustatic SLR contribution from subsequent landslides.

Improved Retrieval of Sea Ice Thickness and Density from Laser Altimeter  [PDF]
Vera Djepa
Atmospheric and Climate Sciences (ACS) , 2014, DOI: 10.4236/acs.2014.45080
Abstract: The sensitivity of weather and climate system to sea ice thickness (SIT) in the Arctic is recognised from various studies. Decrease of SIT will affect atmospheric circulation, temperature, precipitation and wind speed in the Arctic and remotely. Ice thermodynamics and dynamic properties depend strongly on ice and snow thickness. The heat transfer through ice critically depends on ice thickness. Long term accurate SIT records with corresponding uncertainties are required for improved seasonal weather forecast and estimate of the sea ice mass balance. Satellite radar and Laser Altimeter (LA) provide long term records of sea ice freeboard. Assuming isostatic equilibrium, SIT is retrieved from the freeboard, extracted from radar altimeter (RA) or LA, where the snow depth, density, ice and water density are input variables in the equation for hydrostatic equilibrium to derive SIT from LA or RA. Different input variables (snow depth, density, ice and water density) with unknown accuracy have been applied from various authors to retrieve SIT and Sea Ice Draft (SID) from RA or LA, leading to not comparative results. Sea ice density dependence on ice type, thermodynamic properties and freeboard is confirmed with different studies. Sensitivity analyses confirm the great impact of sea ice density, snow depth and density on accuracy of the retrieved SIT and the importance of inserting variable ice density (VID) in the equation for hydrostatic equilibrium for more accurate SIT retrieval, weather and climate forecast. The impact of sea ice density and snow depth and density on retrieved SIT from the freeboard derived from LA and RA have been analyzed in this study using the equation for hydrostatic equilibrium, statistical and sensitivity analyses. An algorithm is developed to convert the freeboard, derived from LA in SIT, inserting VID in the equation for hydrostatic equilibrium. The algorithm is validated with field, laboratory studies and collocated SIT retrieved from RA on board Envisat. The accuracy of the developed algorithm is analyzed, using statistical and uncertainty analyses. It is found that the uncertainty of the retrieved SIT from LA is decreased 7.6 times (from rhi = 59 cm for fixed ice density) if variable ice density is inserted in the equation for hydrostatic equilibrium. The SIT, which has been retrieved from the freeboard derived from LA is validated with collocated SIT derived from RA2 on Envisat, using variable ice density. The bias of the mean SIT derived from LA and RA has been reduced from -1.1 m to about one millimeter when VID is
Impacts of Changes in Sea Ice and Heat Flux on Arctic Warming  [PDF]
Yong Cao, Lingen Bian, Jinping Zhao
Atmospheric and Climate Sciences (ACS) , 2019, DOI: 10.4236/acs.2019.91006
Abstract: The reduction of Arctic sea ice has enhanced the sea-ice-air interaction in the Arctic atmospheric boundary layer, especially the increase in sea-air heat flux in autumn. Changes in radiation and heat flux and the role of sea-ice-air interactions in climate change in the central Arctic were analyzed and evaluated on the basis of the observation data of ice stations during the six Chinese Arctic Research Expeditions. The albedo is high in the Arctic sea-ice surface except the melting process. Overall, the Arctic sea-ice surface can absorb radiation energy, which is much lower than that absorbed by mid-latitude surfaces. Consequently, a relatively weak turbulence exchange occurred between the sea-ice surface and the atmosphere. Further estimates of the surface heat budget in the Arctic are obtained using eddy correlation and flux-profile method. The results are representative of the heat balance and ice-air interactions in the central Arctic Ocean. In the Arctic, changes in heat flux displayed notable interdecadal characteristics, similar to the change of sea-ice extent. The heat flux in September of each year in 2001-2014 was considerably higher compared with that in 1979-2000, particularly at the edges of the central Arctic Ocean. In September of each year in 1979-2014, the sea-ice extent was remarkably negatively correlated to the heat flux (sensible heat flux + latent heat flux), and the heat flux was considerably positively correlated to the atmospheric temperature at 2 m above sea level. This result demonstrates that a reduction of Arctic sea ice will lead to changes in heat flux, thereby warming the atmosphere and increasing the temperature of the atmospheric boundary layer over the Arctic. In addition, this impact is long-lasting.
Variations of sea ice temperature from CHINARE 2003 and its application on sea ice model evaluation
ZHANG Zhanhai,LIU Jiping,
ZHANG Zhanhai
,LIU Jiping

大气和海洋科学快报 , 2009,
Abstract: Variations of vertical profiles of sea ice temperature, and adjacent atmosphere and ocean temperatures were measured by ice drifting buoys deployed in the northeast Chukchi Sea, as part of the 2003 Chinese Arctic Research Expedition. The buoy observations (September 2003 to February 2005) show that the cooling of the ice began in late September, propagated down through the ice, reaching the bottom of the ice in December, and continued throughout the winter. In winter 2003/2004, some obvious warmings were observed in the upper portion of the ice in response to major warmings in the overlying atmosphere associated with the periodicity of storms in the northeast Chukchi Sea. It is found that the melt season at the buoy site in 2004 was about 15% longer than normal. The buoy observed vertical ice temperature profiles were also used as a diagnostic for sea ice model evaluation. The results show that the simulated ice temperature profiles have large discrepancies as compared to the observations.
Storfjorden (Svalbard): Modeling of the Polynya Development and the Sea Ice Ridging Process
Denis Zyryanov,J?rg Haarpaintner,Reinert Korsnes
Modeling, Identification and Control , 2003, DOI: 10.4173/mic.2003.1.4
Abstract: Remote sensing observations of Storfjorden ice cover described the persistence and evolution of latent heat polynyas during winter 1997/1998. The induced important ice production was quantitatively estimated by simple modeling of the sea ice dynamics and growth. In the present work we used mathematical modeling to qualitatively simulate the polynya open and developing. First, we estimate the values of internal stresses appeared in Storfjorden ice sheet due to the wind stress and used them in the model calibration algorithm. Then, we model the polynya open and developing in simple quasi-static approach. The sea ice ridging process is modeled last and the maximum of ice ridges height is estimated. The results of the simulations are compared to satellite observations from ERS-2. They show that the equilibrium stages of the model developing coincide in common with in-situ data of satellite observations. From another side, the estimations show that the ice ridge keel can achieve height up to 8m along the eastern shore of Spitsbergen.
Antarctic Sea Ice—A Polar Opposite?
Ted Maksym,Sharon E. Stammerjohn,Stephen Ackley,Rob Massom
Oceanography , 2012,
Abstract: As the world's ice diminishes in the face of climate change—from the dramatic decline in Arctic sea ice, to thinning at the margins of both the Greenland and Antarctic ice sheets, to retreating mountain glaciers the world over—Antarctic sea ice presents something of a paradox. The trend in total sea ice extent in the Antarctic has remained steady, or even increased slightly, over the past three decades, confounding climate model predictions showing moderate to strong declines. This apparent intransigence masks dramatic regional trends; declines in sea ice in the Bellingshausen Sea region that rival the high-profile decline in the Arctic have been matched by opposing increases in the Ross Sea. Much of the explanation lies in the unique nature of the Antarctic sea ice zone. Its position surrounding the continent and exposure to the high-energy wind and wave fields of the open Southern Ocean shape both its properties and its connection to the atmosphere and ocean in ways very different from the Arctic. Sea ice extent and variability are strongly driven by large-scale climate variability patterns such as the El Ni o-Southern Oscillation and the Southern Annular Mode. Because many of these patterns have opposing effects in different regions around the continent, decreases in one region are often accompanied by similar, opposing increases in another. Yet, the failure of climate models to capture either the overall or regional behavior also reflects, in part, a poor understanding of sea ice processes. Considerable insight has been gained into the nature of these processes over the past several decades through field expeditions aboard icebreakers. However, much remains to be discovered about the nature of Antarctic sea ice; its connections with the ocean, atmosphere, and ecosystem; and its complex response to present and future climate change.
Thermal convection in ice sheets: New data, new tests  [PDF]
Terence J. Hughes
Natural Science (NS) , 2012, DOI: 10.4236/ns.2012.47056
Abstract: Thermal convection in the Antarctic Ice Sheet was proposed in 1970. Demonstrating its existence proved to be elusive. In 2009, tributaries to ice streams were postulated as the surface expression of underlying thermal convection rolls aligned in directions of advective ice flow. Two definitive tests of this hypothesis are now possible, using highly accurate ice elevations and velocities provided by the European, Japanese, and Canadian Space Agencies that allow icestream tributaries and their velocities to be mapped. These tests are 1) measuring lowering of tributary surfaces to see if lowering is due only to advective ice thinning, or also requires lowering en masse in the broad descending part of convective flow, and 2) measuring transverse surface ice velocities to see if ice entering tributaries from the sides increases while crossing lateral shear zones, as would be required if this flow is augmented by convective flow ascending in the narrow side shear zones and diverted into tributaries by advective ice flow. If (1) and (2) are applied to tributaries converging on Byrd Glacier, the same measurements can be conducted when tributaries pack together to become “flow stripes” down Byrd Glacier and onto the Ross Ice Shelf to see if (2) is reduced when lateral advection stops. This could determine if thermal convection remains active or shuts down as ice thins. Thermal convection in the Antarctic Ice Sheet would raise three questions. Can it cause the ice sheet to self-destruct as convective flow turns on and off? Does it render invalid climate records extracted at depth from ice cores? Can the ice sheet be studied as a miniature mantle analogous in some respects to Earth’s mantle?
Sea Ice Observations in Polar Regions: Evolution of Technologies in Remote Sensing  [PDF]
Praveen Rao Teleti, Alvarinho J. Luis
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.47097
Abstract:

Evolution of remote sensing sensors technologies is presented, with emphasis on its suitability in observing the polar regions. The extent of influence of polar regions on the global climate and vice versa is the spearhead of climate change research. The extensive cover of sea ice has major impacts on the atmosphere, oceans, and terrestrial and marine ecosystems of the polar regions in particular and teleconnection on other processes elsewhere. Sea ice covers vast areas of the polar oceans, ranging from ~18 × 106 km2 to ~23 × 106 km2, combined for the Northern and Southern Hemispheres. However, both polar regions are witnessing contrasting rather contradicting effects of climate change. The Arctic sea ice extent is declining at a rate of 0.53 × 106 km2·decade–1, whereasAntarcticaexhibits a positive trend at the rate of 0.167 × 106 km2·decade–1. This work reviews literature published in the field of sea ice

Holes in Progressively Thinning Arctic Sea Ice Lead to New Ice Algae Habitat
Sang Heon Lee |,C. Peter McRoy,Hyoung Min Joo,Rolf Gradinger
Oceanography , 2011,
Abstract: The retreat and thinning of Arctic sea ice associated with climate warming is resulting in ever-changing ecological processes and patterns. One example is our discovery of myriad new "marine aquaria" formed by melt holes in the perennial sea ice. In previous years, these features were closed, freshwater melt ponds on the surface of sea ice. Decreased ice thickness now allows these ponds to melt through to the underlying ocean, thus creating a new marine habitat and concentrating a food source for the ecosystem through accumulation of algae attached to refreezing ice in late summer. This article describes the formation of these late-season algal masses and comments on their overall contribution to Arctic ecosystems and the consequences of a continued decline in sea ice.
Land Ice and Sea Level Rise: A Thirty-Year Perspective
W. Tad Pfeffer
Oceanography , 2011,
Abstract: The present-day assessment of contributions to sea level rise from glaciers and ice sheets depends to a large degree on new technologies that allow efficient and precise detection of change in otherwise inaccessible polar regions. The creation of an overall research strategy, however, was set in early collaborative efforts nearly 30 years ago to assess and project the contributions of glaciers and ice sheets to sea level rise. Many of the research objectives recommended by those early collaborations were followed by highly successful research programs and led to significant accomplishments. Other objectives are still being pursued, with significant intermediate results, but have yet to mature into fully operational tools; among them is the fully deterministic numerical ice sheet model. Recognized as a crucial tool in 1983 by the first formal working group to be convened to quantitatively evaluate glaciers and ice sheet contributions to sea level in a CO2-warmed future environment, the deterministic numerical model of glacier and ice sheet behavior has been the ultimate prognostic tool sought by the glaciological research community ever since. Progress toward this goal has been thwarted, however, by lack of knowledge of certain physical processes, especially those associated with interactions of ice with the bedrock it rests on, and interactions of ice with the ocean and calving of icebergs. Over the last decade, when mass loss rates from Greenland and Antarctica started to accelerate, some means of projecting glacier and ice sheet changes became increasingly necessary, and alternatives to deterministic numerical models were sought. The result was a variety of extrapolation schemes that offer partial constraints on future glacier and ice sheet losses, but also contain significant uncertainties and rely on assumptions that are not always clearly expressed. This review examines the history of assessments of glacier and ice sheet contributions to sea level rise, and considers how questions asked 30 years ago shaped the nature of the research agenda being carried out today.
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