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Measuring Recent Ice Mass Loss From The Margin Of The Greenland Ice Sheet Using Aster Derived Digital Elevation Models
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Book Synopsis Measuring Recent Ice Mass Loss from the Margin of the Greenland Ice Sheet Using Aster-derived Digital Elevation Models by : Tristan A. Rhodes
Download or read book Measuring Recent Ice Mass Loss from the Margin of the Greenland Ice Sheet Using Aster-derived Digital Elevation Models written by Tristan A. Rhodes and published by . This book was released on 2009 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Global Land Ice Measurements from Space by : Jeffrey S. Kargel
Download or read book Global Land Ice Measurements from Space written by Jeffrey S. Kargel and published by Springer. This book was released on 2014-07-08 with total page 936 pages. Available in PDF, EPUB and Kindle. Book excerpt: An international team of over 150 experts provide up-to-date satellite imaging and quantitative analysis of the state and dynamics of the glaciers around the world, and they provide an in-depth review of analysis methodologies. Includes an e-published supplement. Global Land Ice Measurements from Space - Satellite Multispectral Imaging of Glaciers (GLIMS book for short) is the leading state-of-the-art technical and interpretive presentation of satellite image data and analysis of the changing state of the world's glaciers. The book is the most definitive, comprehensive product of a global glacier remote sensing consortium, Global Land Ice Measurements from Space (GLIMS, http://www.glims.org). With 33 chapters and a companion e-supplement, the world's foremost experts in satellite image analysis of glaciers analyze the current state and recent and possible future changes of glaciers across the globe and interpret these findings for policy planners. Climate change is with us for some time to come, and its impacts are being felt by the world's population. The GLIMS Book, to be released about the same time as the IPCC's 5th Assessment report on global climate warming, buttresses and adds rich details and authority to the global change community's understanding of climate change impacts on the cryosphere. This will be a definitive and technically complete reference for experts and students examining the responses of glaciers to climate change. World experts demonstrate that glaciers are changing in response to the ongoing climatic upheaval in addition to other factors that pertain to the circumstances of individual glaciers. The global mosaic of glacier changes is documented by quantitative analyses and are placed into a perspective of causative factors. Starting with a Foreword, Preface, and Introduction, the GLIMS book gives the rationale for and history of glacier monitoring and satellite data analysis. It includes a comprehensive set of six "how-to" methodology chapters, twenty-five chapters detailing regional glacier state and dynamical changes, and an in-depth summary and interpretation chapter placing the observed glacier changes into a global context of the coupled atmosphere-land-ocean system. An accompanying e-supplement will include oversize imagery and other other highly visual renderings of scientific data.
Book Synopsis Improving a Priori Regional Climate Model Estimates of Greenland Ice Sheet Surface Mass Loss Through Assimilation of Measured Ice Surface Temperatures by : Mahdi Navari
Download or read book Improving a Priori Regional Climate Model Estimates of Greenland Ice Sheet Surface Mass Loss Through Assimilation of Measured Ice Surface Temperatures written by Mahdi Navari and published by . This book was released on 2015 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Greenland ice sheet has been the focus of climate studies due to its considerable impact on sea level rise. Accurate estimates of surface mass balance components - including precipitation, runoff, and evaporation - over the Greenland ice sheet would contribute to understanding the cause of the ice sheet's recent changes (i.e., increase in melt amount and duration, thickening of ice sheet interior, thinning at the ice sheet margins) and help to forecast future changes. Deterministic approaches provide a general trend of the surface mass fluxes, but they cannot characterize the uncertainty of estimates. The data assimilation method developed in this dissertation aimed to optimally merge the satellite-derived ice surface temperature into a snow/ice model while taking into account the uncertainty of input variables. Satellite-derived ice surface temperatures were used to improve the estimates of the Greenland ice sheet surface mass fluxes. Three studies were conducted on the Greenland ice sheet. The goal of the first study was to provide a proof of concept of the proposed methodology. A set of observing system simulation experiments was performed to retrieve the true surface mass fluxes of the Greenland ice sheet. The data assimilation framework was able to reduce the RMSE of the prior estimates of runoff, sublimation/evaporation, surface condensation, and surface mass loss fluxes by 61%, 64%, 76%, and 62%, respectively, over the nominal prior estimates from the regional climate model. In the second study, satellite-derived ice surface temperatures were assimilated into a snow/ice model. The results show that the data assimilation framework was capable of retrieving ice surface temperatures with a mean spatial RMSE of 0.3 K which was 69% less than that of the prior estimate without conditioning on satellite-derived ice surface measurements. Evaluation of surface mass fluxes is a critical part of the study; however, it is limited by the spare amount of independent data sets. Several data sets were used to investigate the feasibility of verification of results. It was found that predicted melt duration is in agreement with melt duration from passive microwave measurements; however, more efforts are needed to further verify the results. In the third study, the feasibility of microwave radiance assimilation was investigated by characterizing the error and uncertainty in predicted passive microwave brightness temperature from the radiative transfer model. We found significant uncertainty between the predicted measurement and satellite-derived passive microwave brightness temperature due to error in snow states, coarse resolution of the passive microwave and also an imperfect coupled snow/ice and radiative transfer model. Based on our findings, radiance assimilation requires more accurate snow grain size parameterization to take into account temporal and spatial variability of snow grain size. Furthermore, coarse resolution of both passive microwave brightness temperature and snow/ice model and attribute uncertainties of both predicted and measured brightness temperature make the radiance assimilation unattractive. This research demonstrates that ice surface temperature measurements have valuable information that can be extracted by a data assimilation technique to improve the estimates of the Greenland ice sheet surface mass fluxes.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721533107 Total Pages :26 pages Book Rating :4.5/5 (331 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 2018-06-20 with total page 26 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 areally Integrated snow accumulation and the net 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 from isolated spots across the ice sheet. The sparse data associated with ice cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland Ice Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area. Jezek, Kenneth C. Goddard Space Flight Center
Book Synopsis Analysis of Antarctic Crustal Motion Using Remote Sensing and GPS Data by : Stephanie Ann Konfal
Download or read book Analysis of Antarctic Crustal Motion Using Remote Sensing and GPS Data written by Stephanie Ann Konfal and published by . This book was released on 2012 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Tilted paleoshorelines and GPS data from the Dry Valleys and surrounding region of Victoria Land, Antarctica are analyzed. Paleoshorelines of proglacial lakes were mapped utilizing a multisensor approach, and tilts were derived from elevations along strandlines digitized from high-resolution airborne Light Detection and Ranging (LiDAR) digital elevation models (DEMs). Resulting tilts were combined with shoreline age data to determine long-term patterns of crustal deformation. Modern rates of horizontal crustal motion and crustal tilting were derived from GPS stations within the Transantarctic Mountain Deformation (TAMDEF) network and the Antarctic Network (ANET) component of the Polar Earth Observing Network (POLENET). Patterns of crustal motion observed from both GPS and paleoshoreline records are interpreted to document GIA-induced crustal deformation since the Last Glacial Maximum (LGM). A change in earth deformation pattern with time suggests that the weak earth profile beneath the study region permitted successive responses to multiple phases of ice mass change since the LGM. Shoreline tilt directions suggest ice unloading associated with Talos Dome in the northern Victoria Land and Wilkes Land sectors of East Antarctica. Unloading in this region is not represented in models of GIA for Antarctica, suggesting current GIA models underpredict ice mass loss and resultant rates of rebound for northern Victoria Land and Wilkes Land sectors of East Antarctica. Significantly, such an underprediction of GIA rebound rates indicates that estimates of East Antarctic ice mass balance derived from the Gravity Recovery and Climate Experiment (GRACE) satellite-based studies, which are strongly dependent on GIA model corrections, have underestimated ice mass loss from the East Antarctic ice sheet.
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 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 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 Quantifying and Characterizing Mass Loss from Icefields Using Remote Sensing by : Andrew K. Melkonian
Download or read book Quantifying and Characterizing Mass Loss from Icefields Using Remote Sensing written by Andrew K. Melkonian and published by . This book was released on 2015 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt: Glaciers outside the icesheets currently supply roughly the same amount of water to sea level rise (SLR) as Antarctica and Greenland and will likely constitute a significant fraction of SLR through 2100. SLR is one of the biggest challenges facing humanity, and much uncertainty remains regarding the contribution of glacier mass loss to SLR. Here we examine glaciers in the Patagonia region of southern Chile/Argentina, the Russian High Arctic (RHA) and Alaska, which have all contributed disproportionately to SLR, a trend that is expected to continue through 2100. The RHA is projected to be among the largest contributors, with total mass loss exceeding Alaska for 2006-2100 despite its smaller ice volume. We focus on several icefields, including two that have received relatively little attention, the Cordillera Darwin Icefield (CDI, 69.6? W, 54.6? S, 2,600 km2 of glaciated area) in the Patagonia region of southern Chile, and the Novaya Zemlya Icefield (NovZ, 65? W, 76? N, 22,100 km2 of glaciated area) in the Russian High Arctic. We also examine the Juneau Icefield (JIF, 58.3? N to 59.7? N, 3,830 km2) and Stikine Icefield (56.75? N to 58.5? N, 5,800 km2) in southeast Alaska. We produce high-resolution maps of surface elevation change rates (dh) and dt velocities for these icefields. dh dt are calculated by applying a weighted lin- ear regression to horizontally- and vertically-aligned digital elevation models (DEMs), revealing thinning patterns for individual glacier basins and allowing us to estimate total mass loss for each icefield. To our knowledge, the work presented here includes the first published study to use the technique of DEM time series to study mass loss of entire icefields. Velocities are measured by pixel-tracking applied to satellite image pairs, helping constrain the dynamic component of mass loss and detect acceleration. We provide a brief overview of the impact of changing various pixel-tracking parameters on velocity measurements, demonstrating, for example, how the ability to adjust parameters helps maximize coverage compared to working with fixed parameter values. We find an average mass loss rate at the CDI of -3.9"1.5 Gt yr-1 between 2000 and 2011, the first produced for this icefield. Three marine-terminating glaciers that cover 12% of the icefield area account for 31% of mass loss. Velocity measurements at the largest of these, the rapidly retreating Marinelli Glacier, constrain the lower bound on the annual calving flux as approximately 82"41% of the average mass loss rate for the glacier. The disproportionate mass loss contribution of the three tidewater glaciers, coupled with the high calving flux and retreat at Marinelli Glacier, provide evidence that dynamic mass loss is an important component of thinning at the CDI. At NovZ, we extend estimates of mass loss back to 1952 and up to the present. We find that the recent average thinning rate of -0.41"0.10 m water equivalent yr-1 (m w.e. yr-1, or elevation change at density of 1000 kg m-3) from 2012-2013/2014 is higher than the long-term average of -0.24"0.04 m w.e. yr-1 from 1952-2013/2014. Some of the increase is likely due to warming in the region, as recent thinning is higher than the long-term average at both land- and marine-terminating glaciers. There is also evidence of a dynamic component, because recent thinning, retreat and front velocities are all substantially greater at tidewater-terminating glaciers than land-terminating glaciers. The impact of ice dynamics is particularly apparent at Inostrantseva Glacier (INO), which ac- celerated at some point after 2006, leading to rapid retreat and thinning there. We compare our results at the CDI and NovZ with our dh dt and velocities for the JIF and Stikine in southeast Alaska. We explore how variations in climate, hypsometry and dynamics all contribute to the different magnitudes and patterns of mass loss at each icefield. The methods presented here for the assessment of icefield mass loss will help better constrain their contributions to SLR over the coming century.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721568406 Total Pages :24 pages Book Rating :4.5/5 (684 download)
Book Synopsis Understanding Recent Mass Balance Changes of the Greenland Ice Sheet by : National Aeronautics and Space Administration (NASA)
Download or read book Understanding Recent Mass Balance Changes of the Greenland Ice Sheet written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-20 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ultimate goal of this project is to better understand the current transfer of mass between the Greenland Ice Sheet, the world's oceans and the atmosphere, and to identify processes controlling the rate of this transfer, to be able to predict with greater confidence future contributions to global sea level rise. During the first year of this project, we focused on establishing longer-term records of change of selected outlet glaciers, reevaluation of mass input to the ice sheet and analysis of climate records derived from ice cores, and modeling meltwater production and runoff from the margins of the ice sheet. vanderVeen, Cornelius Goddard Space Flight Center
Book Synopsis Multi-Year Elevation Changes Near the West Margin of the Greenland Ice Sheet from Satellite Radar Altimetry by : Craig S. Lingle
Download or read book Multi-Year Elevation Changes Near the West Margin of the Greenland Ice Sheet from Satellite Radar Altimetry written by Craig S. Lingle and published by . This book was released on 1992 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mean changes in the surface elevation near the west margin of the Greenland ice sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations are also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.
Book Synopsis Reconstructing Surface Elevation Changes for the Greenland Ice Sheet (1993-2013) and Analysis of Zachariæ Isstrøm, Northeast Greenland by : Kyle Duncan
Download or read book Reconstructing Surface Elevation Changes for the Greenland Ice Sheet (1993-2013) and Analysis of Zachariæ Isstrøm, Northeast Greenland written by Kyle Duncan and published by . This book was released on 2015 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous studies investigating the velocity and elevation change records of the Greenland Ice Sheet (GrIS) revealed rapid and complex changes. It is therefore imperative to determine changes with both high spatial and temporal resolutions. By fusing multiple laser altimetry data sets, the Surface Elevation Reconstruction and Change (SERAC) program is capable of reconstructing surface elevation changes with high spatial and temporal resolution over the entire GrIS. The input data include observations from NASA's Ice, Cloud and land Elevation Satellite (ICESat) mission (2003-2009) as well as data collected by NASA's Airborne Topographic Mapper (ATM) (1993-2013) and Land, Vegetation and Ice Sensor (LVIS) (2007-2012) airborne laser altimetry systems. This study extends the record of surface elevation changes over the GrIS by adding 2012 and 2013 laser altimetry data to the previous 1993-2011 record. Extending the record leads to a new, more accurate and detailed altimetry record for 1993-2013. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Digital Elevation Models (DEMs) are fused with laser altimetry data over Zachariæ Isstrøm, northeast Greenland to analyze surface elevation changes and associated thinning rates during 1978-2014. Little to no elevation change occurred over Zachariæ Isstrøm from 1978-1999, however, from 1999-2014 elevation changes near the calving front became increasingly negative and accelerated. Calving front position showed steady retreat and grounding line position has been retreating towards the interior of the ice sheet at an increasing rate from 2010-2014 when compared to the 1996-2010 period. The measured elevation changes near the calving front have brought a large portion of the glacier close to the height of flotation. If the current thinning trend continues this portion of the glacier will reach flotation within the next 2-5 years allowing for further retreat and increased vulnerability to retreat for sections of the glacier further upstream.
Book Synopsis A New Model to Construct Ice Stream Surface Elevation Profiles and Calculate Contributions to Sea-Level Rise by : Yosuke Adachi
Download or read book A New Model to Construct Ice Stream Surface Elevation Profiles and Calculate Contributions to Sea-Level Rise written by Yosuke Adachi and published by . This book was released on 2012 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sea-level rise is a problem that affects regions worldwide - from the marshlands of the San Francisco Bay Area to the farmlands in coastal Bangladesh. Three-dimensional ice sheet models are the principle tools to evaluate mass loss from ice sheets that contribute to sea-level rise. We recognize that given the current limitations in representing the full extent of dynamical processes that affect ice sheet mass loss in 3-D ice sheet models, we cannot make reliable forecasts of sea-level rise from melting polar land ice. Thus, we take a completely different approach to gaining insight about the potential effects of climate change-induced perturbations on ice sheets. We build a flowline model that resolves the fast-flowing portions of ice sheets (i.e., ice streams). We express the dynamics along the flowline with (a) vertical shear deformation, (b) horizontal shear deformation, and (c) basal slip. Knowledge accumulated from prior force balance analyses performed on some polar ice streams allows us to form relations between (a) and (c), and between (a) and (c) combined and (b). Based on these relationships, we numerically construct surface elevation profiles along flowlines centered on ten select ice streams in Greenland and Antarctica, by prescribing three climate change-induced perturbations: grounding line retreat, ice stream widening, and surface mass balance increase. Comparing these constructed profiles to the current observed ones allows us to quantify the effect of these perturbations on the various characteristics that these ten ice streams possess. Pine Island Glacier, which flows over a long overdeepening, will lose more than half of its stored ice volume that is contributable to sea-level rise before it reaches a possible steady state. Recovery Ice Stream, with its slippery base, long stretch of streaming-flow, and longest flowline among those we examined, loses the most mass (812 km3/km width). Jutulstraumen, which has little room to widen and a short stretch of streaming-flow, experiences more mass gain due to surface mass balance increase than mass loss due to grounding line retreat and widening. The broad range of ice streams and their diverse responses to prescribed perturbations is a convincing message that an accurate assessment of the contribution of ice sheets to future sea-level rise can only be obtained by raising the resolution of models to resolve the fast-flowing features and looking at their mass changes individually over time.
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 Temporal History of Ice Dynamics Contribution to Volume Changes of the Southeast Greenland Ice Sheet by : Soroush Rezvanbehbahani
Download or read book Temporal History of Ice Dynamics Contribution to Volume Changes of the Southeast Greenland Ice Sheet written by Soroush Rezvanbehbahani and published by . This book was released on 2013 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current estimations of the contribution of ice sheets to future sea level rise are solely based on changes in Surface Mass Balance (SMB) of Antarctic and Greenland Ice Sheets. However, the reported SMB changes over the Greenland Ice Sheet explain only about 50% of the observed total mass loss of the Greenland Ice Sheet (GrIS). The other 50% is caused by ice dynamic processes, which have not been included in most sea level rise predictions. The goal of this study was to investigate surface elevation changes of the entire GrIS in 2003-2009. In addition to the total elevation changes, elevation changes due to ice dynamics were also estimated by computing the difference between surface elevation changes measured by laser altimetry and those caused by SMB processes. I applied the Surface Elevation And Change Detection (SERAC) approach to derive surface elevation changes from laser altimetry observations. By fusing satellite laser altimetry (Ice, Cloud, and land Elevation Satellite (ICESat)) and airborne laser altimetry (Airborne Topographic Mapper (ATM) and Land, Vegetation, and Ice Sensor (LVIS)) data, I have reconstructed the elevation and volume change history of the GrIS at more than 55,000 locations. To estimate elevation changes due to SMB, SMB anomalies from RACMO2/GR were converted into height changes using a simple firn-densification model. To facilitate the visualization of elevation changes and the computation of volume changes I interpolated the irregularly distributed observations of ice sheet elevation changes into regular grids. Finally, I partitioned the ice sheet elevation and volume changes into SMB-related and ice dynamics-related changes and computed the contributions of major drainage basins. I have shown that the southeast GrIS was the main contributor of ice loss in Greenland inx2003-2009. The Kangerlussuaq Glacier drainage basin exhibited the largest ice-dynamics related volume loss from the twelve major drainage basins of southeast Greenland. The regions below 2000 m elevation, despite constituting only about 28% of the southeast GrIS, contribute to more than 92% to its ice-dynamics related volume loss. Ice sheet elevation changes, as well as annual volume changes of the twelve major southeast Greenland drainage basins, show a complex spatial and temporal pattern. Finally, the effect of ocean and air temperature changes as external forcing mechanisms on the observed volume change patterns is also discussed. I have shown that the trend of ocean temperatures anomalies along the southeast coast of the GrIS shows a close similarity to the estimated ice-dynamics related volume change pattern.
Book Synopsis Trends and Persistence in the Greenland Ice Sheet Mass by : Guglielmo Maria Caporale
Download or read book Trends and Persistence in the Greenland Ice Sheet Mass written by Guglielmo Maria Caporale and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper examines trends and persistence in the Greenland ice sheet mass by applying fractional integration methods to a dataset constructed by Mankoff et al. (2020) on ice discharge for seven different regions of Greenland. The adopted empirical framework encompasses a wide range of stochastic processes and is informative about their dynamic and long-run properties. The main finding is that significant changes have occurred in the behaviour of the series of interest in recent years; more specifically, although a deterministic trend is not present, ice discharge in the various regions of Greenland has become a non-stationary, explosive process, with shocks having permanent effects. It appears that, as a result of global warming, the ice mass loss in Greenland has already reached a tipping point and become an irreversible process.
Download or read book SeaRISE written by Robert A. Bindschadler and published by . This book was released on 1990 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of a workshop on the possibility of a rapid rise in sea level following the response of the West Antarctic ice sheet to global warming, and outline of a project to study the phenomenon, called SEARISE : Sea Level Response to Ice Sheet Evolution.
