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Determining Greenland Ice Sheet Accumulation Rates From Radar Remote Sensing
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Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721263622 Total Pages :30 pages Book Rating :4.2/5 (636 download)
Book Synopsis Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing by : National Aeronautics and Space Administration (NASA)
Download or read book Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-16 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the snow accumulation and the ice discharge of the ice sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken throughout the ice sheet. The sparse data associated with ice cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations. Jezek, Kenneth C. Goddard Space Flight Center
Book Synopsis L-band InSAR Estimates of Greenland Ice Sheet Accumulation Rates by : Albert C. Chen
Download or read book L-band InSAR Estimates of Greenland Ice Sheet Accumulation Rates written by Albert C. Chen and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Greenland Ice Sheet contains nearly 3 million cubic kilometers of glacial ice. Were the ice to completely melt, that would cause the sea level to rise about 7 meters. Each year, the ice sheet gains ice from snowfall and loses ice through iceberg calving and other ablation mechanisms. Thus assessing the ice sheet's mass balance (annual net gain/loss of ice) requires accurate spatial mapping of accumulation rates (mean annual snowfall). In this thesis, we examine how recent satellite radar remote sensing data can be used to supplement in-situ accumulation rate estimates in the inner regions of the Greenland Ice Sheet. We present a method using interferometric synthetic aperture radar (InSAR) data to obtain estimates of snow accumulation in Greenland. InSAR is a technique that provides images of the Earth from radar data collected by a spacecraft. We show that the second-order phase statistics (coherence) of InSAR images is related to subsurface structure, which, in the inner dry-snow zone of the Greenland ice sheet, is related to accumulation rate. We have implemented software to form and geocode InSAR images of Greenland and correct for ionospheric inhomogeneity, which has limited the accuracy of longer-wavelength measurements of the Earth's polar regions. We developed a model to relate accumulation rate to InSAR measurements. By inverting the model we obtain estimates of Greenland ice sheet accumulation rates. We show a comparison of our results with in-situ measurements over a 1,400 km strip spanning the entire dry-snow zone, and demonstrate that they follow the in-situ measurements more accurately than state-of-the-art results derived from radar amplitude measurements alone.
Book Synopsis Estimating Snow Accumulation from InSAR Correlation Observations by : Shadi Oveisgharan
Download or read book Estimating Snow Accumulation from InSAR Correlation Observations written by Shadi Oveisgharan and published by . This book was released on 2007 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Snow accumulation in remote regions such as Greenland and Antarctica is a key factor for estimating Earth's ice mass balance. In situ data are sparse, hence it is useful to derive snow accumulation from remote sensing observations, such as from microwave thermal emission and from radar brightness. These data are usually interpreted using electromagnetic models in which volume scattering is the dominant mechanism. The main limitation of this approach is that microwave brightness is not well-related to backscatter if the ice sheet is layered. Because larger grain size and thicker annual layers both increase radar image brightness, the first corresponding to lower accumulation rate and the second to higher accumulation rate, models of radar brightness alone cannot accurately reflect accumulation. Consideration of interferometric radar correlation measurements also can resolve this ambiguity. Here we introduce an ice scattering model that relates InSAR correlation and radar brightness to both ice grain size and hoar layer spacing in the dry snow zone of Greenland. We use this model and ERS satellite radar observations to derive several parameters related to snow accumulation rates in a small area in the dry snow zone. These parameters show agreement with four in situ core accumulation rate measurements in this area, while models using only radar brightness data do not match the observed variation in accumulation rates.
Book Synopsis Satellite Remote Sensing for Ice Sheet Research by :
Download or read book Satellite Remote Sensing for Ice Sheet Research written by and published by . This book was released on 1985 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report assesses potential research applications of satellite data over the terrestrial ice sheets of Greenland and Antarctica and recommends actions required to ensure acquisition of relevant data and appropriate processing to a form suitable for research purposes. Relevant data include high-resolution visible and SAR imagery, infrared, passive-microwave and scatterometer measurements, and surface topography information from laser and radar altimeters.
Book Synopsis Remote Sensing of the Cryosphere by : Marco Tedesco
Download or read book Remote Sensing of the Cryosphere written by Marco Tedesco and published by John Wiley & Sons. This book was released on 2015-01-27 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cryosphere, that region of the world where water is temporarily or permanently frozen, plays a crucial role on our planet. Recent developments in remote sensing techniques, and the acquisition of new data sets, have resulted in significant advances in our understanding of all components of the cryosphere and its processes. This book, based on contributions from 40 leading experts, offers a comprehensive and authoritative overview of the methods, techniques and recent advances in applications of remote sensing of the cryosphere. Examples of the topics covered include: • snow extent, depth, grain-size and impurities • surface and subsurface melting • glaciers • accumulation over the Greenland and Antarctica ice sheets • ice thickness and velocities • gravimetric measurements from space • sea, lake and river ice • frozen ground and permafrost • fieldwork activities • recent and future cryosphere-oriented missions and experiments All figures are in color and provide an excellent visual accompaniment to the technical and scientific aspect of the book. Readership: Senior undergraduates, Masters and PhD Students, PostDocs and Researchers in cryosphere science and remote sensing. Remote Sensing of the Cryosphere is the significant first volume in the new Cryosphere Science Series. This new series comprises volumes that are at the cutting edge of new research, or provide focussed interdisciplinary reviews of key aspects of the science.
Book Synopsis A Correlation-based Approach to Modeling Interferometric Radar Observations of the Greenland Ice Sheet by : E. Weber Hoen
Download or read book A Correlation-based Approach to Modeling Interferometric Radar Observations of the Greenland Ice Sheet written by E. Weber Hoen and published by . This book was released on 2001 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Interferometric synthetic aperture radar (InSAR) phase observations have greatly increased our understanding of the topography and motion of ice sheets, but yield little information on the sub-surface structure, a needed description for mass-balance estimates. Inversion of a diffuse volume scatter model shows that InSAR correlation values, p, can be related to radiowave penetration depths, d, which depend on characteristics of the snow/ice volume. Application to European Research Satellite (ERS) images (VV, 5.6 cm, 23 ̊incidence angle) of the Greenland ice sheet imply C-band d of 0 m along the rocky coast, 10-20 m in the bare ice zone, and 20-35 m in the percolation zone and dry snow zone, consistent with in situ results. Moreover, volume scattering reduces the ERS critical baseline from about 1100 m to 300 m. Correlation and backscatter power (ơ0) observations can be combined for further understanding of the snow/ice volume. In particular, p and ơ0 data of 15 km-long, 50 m-high topographic undulations in the dry snow zone arc minimum on the windward side and maximum on the lee side, with 1 to 3 dB variation typical. These spatial variations in the scattering medium appear to follow from differences in snow accumulation due to prevailing winds. Assuming that snow-grains are the dominant source of backscatter, the classical independent-scatterer model is physically implausible at firn densities; a second-order dense-medium radiative transfer model also is unable to explain both the observed d and ơ0. A modified Born approach provides a better match to ơ0 and p separately, but leads to different grain size solutions for each measurement type. A buried layer model based on the incoherent addition of echoes from hoar layer interfaces, in which scattering from a single layer is derived from small-perturbation methods, reconciles the ERS ơ0 and p data, with variations in hoar layer spacing of 12-17 cm providing the needed structural fluctuations for the observed range of ơ0 and p. Translation of layer spacing into accumulation rates predicts a 40% variability in accumulation rate from the windward to lee side and, more importantly, addresses high-resolution mapping of continental accumulation rates"--Leaves iv-v.
Book Synopsis Deriving Snow Accumulation Rates of Greenland and the Antarctic Ice Sheet from Microwave Remote Sensing Data by : Stefanie Linow
Download or read book Deriving Snow Accumulation Rates of Greenland and the Antarctic Ice Sheet from Microwave Remote Sensing Data written by Stefanie Linow and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Glaciological Observations Using Phase-sensitive Radar by : Ole Zeising
Download or read book Glaciological Observations Using Phase-sensitive Radar written by Ole Zeising and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The large ice sheets in Greenland and Antarctica are losing mass due to global warming. In particular, the acceleration of ice streams and thus the increased discharge into the ocean contributes significantly to global sea-level rise. The floating extensions of the ice streams counteract this, but intense basal melting can destabilise the ice shelves. In this thesis, a contribution is made to determine the melt rates of two ice shelves, which are crucial for the future mass losses of the respective ice sheets. In the north, the focus is on the Northeast Greenland Ice Stream (NEGIS) that feeds the Nioghalvfjerdsbrae (79°N Glacier). My analysis of phase-sensitive radar measurements indicates high melt rates near the onset of the ice stream and thus the presence of subglacial melt water, which is associated with the formation of the ice flow. An extensive study in my thesis reveals that the 79°N Glacier has been thinned out considerably in recent years due to extreme melt rates and that large channels have been formed. Melt rates of the Filchner Ice Shelf, Antarctica, which I also determined using phase-sensitive radar measurements, are comparatively low. I was able to attribute significant deviations from remote sensing-derived melt rates to inaccuracies in the used ice flow velocity field. Furthermore, I show that the use of newer velocity fields improves the determination of the melt rates from remote sensing. My analysis of melt rate time series in the vicinity of a channel indicates higher melt rates in the summer as well as several melt events spread over the entire measurement period. Another study combines measurements and numerical modelling and shows that higher melt rates must have occurred in the past than those that were measured. These would lead to the closure of the channel within 250 years. Thus, neither the channel itself nor the present day melt rates endanger the stability of one of the largest Antarctic ice shelves at present.
Book Synopsis Polar Environments and Global Change by : Roger G. Barry
Download or read book Polar Environments and Global Change written by Roger G. Barry and published by Cambridge University Press. This book was released on 2018-08-09 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surveys atmospheric, oceanic and cryospheric processes, present and past conditions, and changes in polar environments.
Book Synopsis Comprehensive Remote Sensing by : Shunlin Liang
Download or read book Comprehensive Remote Sensing written by Shunlin Liang and published by Elsevier. This book was released on 2017-11-08 with total page 3183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive Remote Sensing, Nine Volume Set covers all aspects of the topic, with each volume edited by well-known scientists and contributed to by frontier researchers. It is a comprehensive resource that will benefit both students and researchers who want to further their understanding in this discipline. The field of remote sensing has quadrupled in size in the past two decades, and increasingly draws in individuals working in a diverse set of disciplines ranging from geographers, oceanographers, and meteorologists, to physicists and computer scientists. Researchers from a variety of backgrounds are now accessing remote sensing data, creating an urgent need for a one-stop reference work that can comprehensively document the development of remote sensing, from the basic principles, modeling and practical algorithms, to various applications. Fully comprehensive coverage of this rapidly growing discipline, giving readers a detailed overview of all aspects of Remote Sensing principles and applications Contains ‘Layered content’, with each article beginning with the basics and then moving on to more complex concepts Ideal for advanced undergraduates and academic researchers Includes case studies that illustrate the practical application of remote sensing principles, further enhancing understanding
Book Synopsis Polar Remote Sensing by : Robert Massom
Download or read book Polar Remote Sensing written by Robert Massom and published by Springer Science & Business Media. This book was released on 2006-08-31 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polar Remote Sensing is a two-volume work providing a comprehensive, multidisciplinary discussion of the applications of satellite sensing. Volume 2 focuses on the ice sheets, icebergs, and interactions between ice sheets and the atmosphere and ocean. It contains information about the applications of satellite remote sensing in all relevant polar related disciplines, including glaciology, meteorology, climate and radiation balance and oceanogaraphy. It also provides a brief review of the state-of-the-art of each discipline, including current issues and questions. Various passive and active remote sensor types are discussed, and the book then concentrates on specific geophysical applications. Its interdisciplinary approach means that major advances and publications are highlighted. Polar Remote Sensing: Ice Sheets summarizes fundamental principles of detectors, imaging and geophysical product retrieval includes a chapter on the important new field of satellite synthetic-aperture radar interferometry is a "one stop shop" for polar remote sensing information contains significant new information on the Earth's polar regions describes sophisticated groundbased remote sensing applications with specific reference to their use in polar regions.
Book Synopsis Seasonal and Interannual Variations of Ice Sheet Surface Elevation at the Summit of Greenland by : H. Jay Zwally
Download or read book Seasonal and Interannual Variations of Ice Sheet Surface Elevation at the Summit of Greenland written by H. Jay Zwally and published by BiblioGov. This book was released on 2013-08 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observed seasonal and interannual variations in the surface elevation over the summit of the Greenland ice sheet are modeled using a new temperature-dependent formulation of firn-densification and observed accumulation variations. The observed elevation variations are derived from ERS (European Remote Sensing)-1 and ERS-2 radar altimeter data for the period between April 1992 and April 1999. A multivariate linear/sine function is fitted to an elevation time series constructed from elevation differences measured by radar altimetry at orbital crossovers. The amplitude of the seasonal elevation cycle is 0.25 m peak-to-peak, with a maximum in winter and a minimum in summer. Inter-annually, the elevation decreases to a minimum in 1995, followed by an increase to 1999, with an overall average increase of 4.2 cm a(exp -1) for 1992 to 1999. Our densification formulation uses an initial field-density profile, the AWS (automatic weather station) surface temperature record, and a temperature-dependent constitutive relation for the densification that is based on laboratory measurements of crystal growth rates. The rate constant and the activation energy commonly used in the Arrhenius-type constitutive relation for firn densification are also temperature dependent, giving a stronger temperature and seasonal amplitudes about 10 times greater than previous densification formulations. Summer temperatures are most important, because of the strong non-linear dependence on temperature. Much of firn densification and consequent surface lowering occurs within about three months of the summer season, followed by a surface build-up from snow accumulation until spring. Modeled interannual changes of the surface elevation, using the AWS measurements of surface temperature and accumulation and results of atmospheric modeling of precipitation variations, are in good agreement with the altimeter observations.
Book Synopsis Remote Sensing Observations of Modern-Day Regional Ice Sheet Change by : Tyler Clark Sutterley
Download or read book Remote Sensing Observations of Modern-Day Regional Ice Sheet Change written by Tyler Clark Sutterley and published by . This book was released on 2016 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Earth's great ice sheets are losing mass at accelerating levels, rising global sea levels and posing a significant problem to society. The ice sheets contain enough water to raise sea level by 65 meters, and are the largest reservoirs of freshwater on the planet. Measurements of current ice sheet mass change are important in order to assess their current contribution to sea level rise, and to constrain future projections. There are three general approaches for measuring the current mass balance of ice sheets: the gravimetric method using time-variable gravity measurements, the altimetric method combining surface elevation change measurements with estimates of the density change, and the mass budget method combining rates of mass input from snow and rain with rates of mass output from meltwater runoff, ice discharge and other processes. In this dissertation, we use multiple independent measurements to assess the current uncertainties in mass balance efforts, and to create new estimates of current ice sheet mass change. We investigate key regions of Antarctica, where changes in the ice sheet velocity structure have led to accelerating mass losses. We compile new assessments of the mass change of the Greenland ice sheet, where increased rates of surface runoff and losses from ice sheet dynamics have dramatically shifted the mass balance regime. The work helps constrain estimation errors from GRACE, provides new constraints to ice sheet and glacial isostatic adjustment models, and helps improve our general understanding of the mechanisms driving current ice sheet mass change.
Book Synopsis IEEE International Geoscience and Remote Sensing Symposium Proceedings by :
Download or read book IEEE International Geoscience and Remote Sensing Symposium Proceedings written by and published by . This book was released on 2003 with total page 790 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Remote Sensing in Northern Hydrology by : Claude R. Dugua
Download or read book Remote Sensing in Northern Hydrology written by Claude R. Dugua and published by American Geophysical Union. This book was released on 2005-01-14 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 163. The North, with its vast and varied landscapes, sparse population, and cold climate has always challenged its explorers: physically, mentally, logistically, and technically. The scientific community in particular has known such challenges in the past and does so today, especially in light of the projected intensification of climate change at high latitudes. Indeed, there are clear signs that change is already ongoing in many environmental variables: Air temperature and annual precipitation (including snowfall) are increasing in many regions; spring snow cover extent is decreasing; lake and river ice freeze-up dates are occurring later and breakup dates earlier; glaciers are retreating rapidly; permafrost temperatures are increasing and, in many cases, the permafrost is thawing; and sea-ice extent is at record minimums and thinning.
Book Synopsis Radioglaciology by : V.V. Bogorodsky
Download or read book Radioglaciology written by V.V. Bogorodsky and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt: Antarctica, the sixth continent, was discovered more than 160 years ago. Since then this large, mysterious continent of ice and penguins has attracted world interest. Scientific expeditions from various countries have begun to study the geographical and natural conditions of the icy continent. Systematic and comprehensive inves tigations in the Antarctic started in the middle of our century. In 1956 the First Soviet Antarctic Expedition headed to the coast of Antarctica. Their program included studies of the atmosphere, hydrosphere and cryosphere. Thirty years have since passed. Scientists have unveiled many secrets of Antarctica: significant geophysical processes have been investigated, and a large body of new information on the Antarctic weather, Southern Ocean hydrology and Antarctic glaciers has been obtained. We can now claim that the horizons of polar geo physics, oceanology, and particularly glaciology, have expanded. Scientific inves tigators have obtained new information about all Antarctic regions and thus have created the opportunity to use the Antarctic in the interests of mankind.
Book Synopsis Analysis of Surface Melting and Snow Accumulation Over the Greenland Ice Sheet from Spaceborne Microwave Sensors by : Indrajit Bhattacharya
Download or read book Analysis of Surface Melting and Snow Accumulation Over the Greenland Ice Sheet from Spaceborne Microwave Sensors written by Indrajit Bhattacharya and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuous monitoring of changes in the Greenland ice sheet from both space and air borne sensors has been conducted since the early 1970's. Since the mid-1990's dramatic changes occurring on the Greenland ice sheet have been observed both from space borne sensors and field work. These changes, primarily mass loss from the ice sheet, are related to the observed trend of earth's warmer climate in recent decades both in peer reviewed journals and in popular media. This dissertation addresses two parameters that contribute to Greenland ice sheet mass balance estimates. The first factor is characterization of surface melting of the Greenland ice sheet from satellite-based passive and active microwave sensors. We use a wavelet based edge detection technique to delineate surface melt from brightness temperature measured by passive microwave sensors. Along with brightness temperature data, we also use normalized backscatter data from the Quick Scatterometer (QuikSCAT) as an independent sensor for comparison with the radiometer derived results. We use a semi-empirical threshold based method for surface melt detection from QuikSCAT. Our results show a step-like, consistent increase in melt area of the Greenland ice sheet since 1995. This step-like increase is also observed in the mean summer air temperature along portions of the Greenland coast. The 1995 step-like increase of melt area (and melt index, a measure of melt intensity) is correlated with a distinct change of the North Atlantic Oscillation (NAO) index (from positive to negative) after 1995. The second factor is mass accumulation in the upper reaches of the ice-sheet. We use an empirical model that correlates mean annual brightness temperature to annual accumulation rate. We apply a microwave emission model for the dry snow region of Greenland to show that 37 GHz vertically polarized brightness temperature data are better suited to capture the inter-annual variability of snow accumulation. Using our model we estimate a snow accumulation time series from brightness temperature for 150 km x 150 km area around Summit Camp in central Greenland. Using measured surface velocities and ice thickness we calculate the surface mass balance for our study area. We find a positive mass balance of 3.18 ± 6.0 cm/yr. Our mass balance derived elevation change is in agreement with satellite altimeter data and published results of other researchers.
