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Trends And Persistence In The Greenland Ice Sheet Mass
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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.
Book Synopsis Determining Greenland Ice Sheet Sensitivity to Regional Climate Change by : Nicole-Jeanne Schlegel
Download or read book Determining Greenland Ice Sheet Sensitivity to Regional Climate Change written by Nicole-Jeanne Schlegel and published by . This book was released on 2011 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Greenland Ice Sheet, which extends south of the Arctic Circle, is vulnerable to melt in a warming climate. Complete melt of the ice sheet would raise global sea level by about 7 meters. Prediction of how the ice sheet will react to climate change requires inputs with a high degree of spatial resolution and improved simulation of the ice-dynamical responses to evolving surface mass balance. No Greenland Ice Sheet model has yet met these requirements. A three-dimensional thermo-mechanical ice sheet model of Greenland was enhanced to address these challenges. First, it was modified to accept high-resolution surface mass balance forcings. Second, a parameterization for basal drainage (of the sort responsible for sustaining the Northeast Greenland Ice Stream) was incorporated into the model. The enhanced model was used to investigate the century to millennial-scale evolution of the Greenland Ice Sheet in response to persistent climate trends. During initial experiments, the mechanism of flow in the outlet glaciers was assumed to be independent of climate change, and the outlet glaciers' dominant behavior was to counteract changes in surface mass balance. Around much of the ice sheet, warming resulted in calving front retreat and reduction of total ice sheet discharge. Observations show, however, that the character of outlet glacier flow changes with the climate. The ice sheet model was further developed to simulate observed dynamical responses of Greenland's outlet glaciers. A phenomenological description of the relation between outlet glacier discharge and surface mass balance was calibrated against recent observations. This model was used to investigate the ice sheet's response to a hypothesized 21st century warming trend. Enhanced discharge accounted for a 60% increase in Greenland mass loss, resulting in a net sea level increment of 7.3 cm by year 2100. By this time, the average surface mass balance had become negative, and widespread marginal thinning had caused 30% of historically active calving fronts to retreat. Mass losses persisted throughout the century due to flow of dynamically responsive outlets capable of sustaining high calving rates. Thinning in these areas propagated upstream into higher elevation catchments. Large drainage basins with low-lying outlets, especially those along Greenland's west coast and those fed by the Northeast Greenland Ice Stream, were most susceptible to dynamic mass loss in the 21st century.
Book Synopsis Evolution of the W. Greenland Percolation Zone Over the Past 50 Years by : Karina A. Graeter
Download or read book Evolution of the W. Greenland Percolation Zone Over the Past 50 Years written by Karina A. Graeter and published by . This book was released on 2017 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Greenland Ice Sheet (GrIS) has been losing mass since at least the early 2000s, mostly due to enhanced surface melt from rising summer temperatures. Currently, approximately 40% of the surface melt generated on the GrIS percolates into the snow/firn and refreezes, where it has no immediate impact on GrIS mass changes. The majority of meltwater refreeze occurs in the percolation zone, a region of the accumulation zone where there is significant surface melt but little runoff. However, it remains unclear how the percolation zone is responding to changes in climate and whether it will continue to prevent a significant fraction of meltwater from contributing to surface runoff and sealevel rise. Here we analyze seven shallow firn cores collected from the W. Greenland percolation zone as part of the 2016 Greenland Traverse for Acculmulation and Climate Studies (GreenTrACS) and find that there have been significant changes in melt refreeze and density over the past 50 years. Meltwater refrozen as ice layers indicates a dramatic increase in meltwater refreeze in cores 1-5. Increases in meltwater refreeze correspond to similar increases in firn density over the past 18 years. In contrast, the cores indicate no trend in annual accumulation at any of the cores sites. Evaluation of the distribution of ice layers in the context of surface temperatures and climate circulation patterns shows that changes in meltwater refreeze and firn density are closely tied to trends in persistent summertime Greenland Blocking Events (GBEs) and N. Atlantic sea surface temperatures. Whether current rates of meltwater percolation and firn densification will continue depend on the future evolution and persistence of these phenomena. While trends in N. Atlantic SST are reasonably well understood for the twenty-first century, it remains unclear how GBE frequency and duration will evolve. Thus, a better understanding of the causes of N. Atlantic SST variability and GBEs as well as their future evolution under twenty-first century climate warming scenarios is imperative for predicting future GrIS meltwater retention and what impact this will have on Greenland's contribution to global sea-level rise.
Download or read book Vogel, Manfred, 1946- written by and published by . This book was released on 1961 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The folder may include clippings, announcements, small exhibition catalogs, and other ephemeral items.
Book Synopsis Seasonal to Multidecadal Drivers of Variability at Greenland Outlet Glaciers by : Michalea D. King
Download or read book Seasonal to Multidecadal Drivers of Variability at Greenland Outlet Glaciers written by Michalea D. King and published by . This book was released on 2020 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Chapter 3, we extend our 2000-2016 discharge time series to the period 1985-2018, combining more than three decades of GrIS-wide observational products of outlet glacier velocity, elevation, and front position changes, and compare decadal variability in discharge with calving front position. We find that the close relationship between frontal change and ice discharge identified over the 2000-2016 record holds true for the 34-year record, and that increased glacier discharge can be attributed almost entirely to the retreat of glacier fronts, rather than inland ice sheet processes, such as changes in meltwater runoff. Discharge sensitivity to retreat is remarkably consistent across the ice sheet, with all main regions showing an increase in discharge of 4-5% per km of retreat. Most importantly, we show that widespread retreat between 2000 and 2005 resulted in a step-increase in discharge and a switch to a new dynamic state of sustained mass loss. The increase in discharge was large enough to alone ensure persistent negative ice sheet mass balance, even before including more recent negative trends in surface mass balance. This study is published in Nature Communications Earth & Environment (King et al., 2020).
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 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.
Book Synopsis Estimating and Reducing the Uncertainty in the Future Behaviour of the Greenland Ice Sheet by : Peter Fitzgerald
Download or read book Estimating and Reducing the Uncertainty in the Future Behaviour of the Greenland Ice Sheet written by Peter Fitzgerald and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study carries out a comprehensive ensemble experiment investigating previously unexplored combinations of model uncertainty in an attempt to quantify and attribute the response uncertainty of future Greenland ice sheet twenty first century simulation. The inclusion of multiple uncertainty sources facilitates the construction of the first ever probability density function (PDF) of Greenland ice sheet surface mass balance (5MB) behaviour over the 21st century. The use of an {insolation temperature' 5MB model permits the inclusion of important ice sheet feedbacks not accounted for in more parameterized models traditionally used in such uncertainty analysis. The lower sensitivity of 'this model (compared to temperature only parameterised models) results in the zi" century 5MB being in the lower end of previously reported ranges. The experiment includes a number of novel methods for downscaling climate data and incorporating new uncertainties such as climate model internal variability. This study also presents a new Bayesian inference method based on summary statistics of present day ice sheet behaviour. The inclusion of internal variability is shown to be crucially important in the Bayesian inference method so that realisations are not highly weighted due to coincidence of random climate fluctuations. Further to this, the long term climate signal is shown to produce too little warming to explain all of the recent runoff trends over the ice sheet, with internal variability accounting for the remainder. Caution must therefore be exercised when extrapolating present ice sheet trends into the future. The application of sensitivity analysis techniques facilitates the identification of important regions that dominate uncertainty, which help to constrain parameter ranges in future sampling within similar models. Climate model uncertainty is shown to dominate zi'' century uncertainty, with the models showing the largest zi" century warming producing the best reconstruction of present day runoff.
Book Synopsis Ice Sheet Mass Balance Simulations for Greenland and Tibetan Plateau by : Tânia Gil Duarte Casal
Download or read book Ice Sheet Mass Balance Simulations for Greenland and Tibetan Plateau written by Tânia Gil Duarte Casal and published by . This book was released on 2003 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Using Sea-Level Data to Constrain the Contribution of the Greenland Ice Sheet to Contemporary and Recent Sea-Level Change by : Leanne Mary Wake
Download or read book Using Sea-Level Data to Constrain the Contribution of the Greenland Ice Sheet to Contemporary and Recent Sea-Level Change written by Leanne Mary Wake and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the potentially wide-reaching impacts on climate and sea-level change of a declining Greenland Ice Sheet (GrIS), the mass balance of the past decade has caused concern that the ice sheet is reacting to increased temperatures of the industrial era and that the ice sheet is in the initial stages of deglaciation. Global mean sea-level has been rising at a rate of 1.8 +/- 0.5 mm/yr over the past 50 years (Bindoff et al. 2007), and this has accelerated to 3.1 +/-0.1mm/yr (Cazenave et al., 2008) over the past decade. This study shows that although the surface mass balance of the GrIS can react quickly to changes in temperature, overall the ice sheet is in near balance over the period 1866-2005. During 1866-2005, the contribution from the GrIS to eustatic sea-level change is not larger than the error attached to current estimates of global mean sea-level rise. A novel type of relative sea-level data gathered from salt marshes in the south west of Greenland cover the period from ~1200 to 1800AD and show that a major slowdown in local sea-level rise from ~3mm/yr to ~0mm/yr occurred around 1500-1600 AD, with no significant departure from a 0mm/yr trend thereafter. Large contributions to sea-level change from steric changes and cryospheric sources outside of Greenland are ruled out as major drivers of this deceleration in sea-level fall. Modelling results indicate that the slowdown in relative sea-level is most likely due to the combined contribution of dynamic-related ice loss from Jakobshavn Isbrae and a delayed earth response to mass loss during a period of elevated temperatures from ~1000-1500AD. When considering the saltmarsh sea-level data for the 20th century within the context of the complete time series, the magnitude of ice loss in west Greenland for the past decade does not appear to be anomalous. This analysis suggests that similar mass loss has been sustained for several centuries prior to 1500AD.
Download or read book Vanishing Ice written by Vivien Gornitz and published by Columbia University Press. This book was released on 2019-06-11 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Arctic is thawing. In summer, cruise ships sail through the once ice-clogged Northwest Passage, lakes form on top of the Greenland Ice Sheet, and polar bears swim farther and farther in search of waning ice floes. At the opposite end of the world, floating Antarctic ice shelves are shrinking. Mountain glaciers are in retreat worldwide, unleashing flash floods and avalanches. We are on thin ice—and with melting permafrost’s potential to let loose still more greenhouse gases, these changes may be just the beginning. Vanishing Ice is a powerful depiction of the dramatic transformation of the cryosphere—the world of ice and snow—and its consequences for the human world. Delving into the major components of the cryosphere, including ice sheets, valley glaciers, permafrost, and floating ice, Vivien Gornitz gives an up-to-date explanation of key current trends in the decline of ice mass. Drawing on a long-term perspective gained by examining changes in the cryosphere and corresponding variations in sea level over millions of years, she demonstrates the link between thawing ice and sea-level rise to point to the social and economic challenges on the horizon. Gornitz highlights the widespread repercussions of ice loss, which will affect countless people far removed from frozen regions, to explain why the big meltdown matters to us all. Written for all readers and students interested in the science of our changing climate, Vanishing Ice is an accessible and lucid warning of the coming thaw.
Book Synopsis The Mass Balance of the Greenland Ice Sheet by : J. Oerlemans
Download or read book The Mass Balance of the Greenland Ice Sheet written by J. Oerlemans and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mass Balance and Ice Dynamics of the North-East Greenland Ice Sheet Margin by : Niels Reeh
Download or read book Mass Balance and Ice Dynamics of the North-East Greenland Ice Sheet Margin written by Niels Reeh and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Greenland Ice Sheet Surface Mass-balance Modeling in a 131-year Perspective, 1950-2080 by :
Download or read book Greenland Ice Sheet Surface Mass-balance Modeling in a 131-year Perspective, 1950-2080 written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluctuations in the Greenland Ice Sheet (GrIS) surface mass-balance (SMB) and freshwater influx to the surrounding oceans closely follow climate fluctuations and are of considerable importance to the global eustatic sea level rise. SnowModel, a state-of-the-art snow-evolution modeling system, was used to simulate variations in the GrIS melt extent, surface water balance components, changes in SMB, and freshwater influx to the ocean. The simulations are based on the IPCC scenario AlB modeled by the HIRHAM4 RCM (using boundary conditions from ECHAM5 AOGCM) from 1950 through 2080. In-situ meteorological station (GC-Net and WMO DMI) observations from inside and outside the GrIS were used to validate and correct RCM output data before it was used as input for SnowModel. Satellite observations and independent SMB studies were used to validate the SnowModel output and confirm the model's robustness. We simulated a ≈90% increase in end-of-summer surface melt extent (0.483 x 106 km2) from 1950 to 2080, and a melt index (above 2,000-m elevation) increase of 138% (1.96 x 106 km2 x days). The greatest difference in melt extent occured in the southern part of the GrIS, and the greatest changes in the number of melt days was seen in the eastern part of the GrIS (≈50-70%) and was lowest in the west (≈20-30%). The rate of SMB loss, largely tied to changes in ablation processes, lead to an enhanced average loss of 331 km3 from 1950 to 2080, an average 5MB level of -99 km3 for the period 2070-2080. GrIS surface freshwater runoff yielded an eustatic rise in sea level from 0.8 ± 0.1 (1950-1959) to 1.9 ± 0.1 mm (2070-2080) sea level equivalent (SLE) y−1. The accumulated GrIS freshwater runoff contribution from surface melting equaled 160 mm SLE from 1950 through 2080.
Book Synopsis The Influence of Meltwater on the Thermal Structure and Flow of the Greenland Ice Sheet by : Kristin Poinar
Download or read book The Influence of Meltwater on the Thermal Structure and Flow of the Greenland Ice Sheet written by Kristin Poinar and published by . This book was released on 2015 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the climate has warmed over the past decades, the amount of melt on the Greenland Ice Sheet has increased, and areas higher on the ice sheet have begun to melt regularly. This increase in melt has been hypothesized to enhance ice flow in myriad ways, including through basal lubrication and englacial refreezing. By developing and interpreting thermal ice-sheet models and analyzing remote sensing data, I evaluate the effect of these processes on ice flow and sea-level rise from the Greenland Ice Sheet. I first develop a thermal ice sheet model that is applicable to western Greenland. Key components of this model are its treatment of multiple phases (solid ice and liquid water) and its viscosity-dependent velocity field. I apply the model to Jakobshavn Isbræ, a fast-flowing outlet glacier. This is an important benchmark for my model, which I next apply to the topics outlined above. I use the thermal model to calculate the effect of englacial latent-heat transfer (meltwater refreezing within englacial features such as firn and crevasses) on ice dynamics in western Greenland. I find that in slow-moving areas, this can significantly warm the ice, but that englacial latent heat transfer has only a minimal effect on ice motion (10%). By contrast, in fast-flowing regions, which contribute most (60%) of the ice flux into the ocean, evidence of deep englacial warming is virtually absent. Thus, the effects of englacial latent heat transfer on ice motion are likely limited to slow-moving regions, which limits its importance to ice-sheet mass balance. Next, I couple a model for ice fracture to a modified version of my thermal model to calculate the depth and shape evolution of water-filled crevasses that form in crevasse fields. At most elevations and for typical water input volumes, crevasses penetrate to the top ~200–300 meters depth, warm the ice there by ~10°C, and may persist englacially, in a liquid state, for multiple decades. The surface hydrological network limits the amount of water that can reach most crevasses. We find that the depth and longevity of such crevasses is relatively robust to realistic increases in melt volumes over the coming century, so that we should not expect large changes in the englacial hydrological system under near-future climate regimes. These inferences put important constraints on the timescales of the Greenland supraglacial-to-subglacial water cycle. Finally, I assess the likelihood that higher-elevation surface melt could deliver water to regions where the bed is currently frozen. This hypothetical process is important because it could potentially greatly accelerate the seaward motion of the ice sheet. By analyzing surface strain rates and comparing them to my modeled basal temperature field, I find that this scenario is unlikely to occur: the conditions necessary to form surface-to-bed conduits are rarely found at higher elevations (~1600 meters) that may overlie frozen beds.
Author :Intergovernmental Panel on Climate Change (IPCC) Publisher :Cambridge University Press ISBN 13 :9781009157971 Total Pages :755 pages Book Rating :4.1/5 (579 download)
Book Synopsis The Ocean and Cryosphere in a Changing Climate by : Intergovernmental Panel on Climate Change (IPCC)
Download or read book The Ocean and Cryosphere in a Changing Climate written by Intergovernmental Panel on Climate Change (IPCC) and published by Cambridge University Press. This book was released on 2022-04-30 with total page 755 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Book Synopsis Ice Sheets and Climate by : Johannes Oerlemans
Download or read book Ice Sheets and Climate written by Johannes Oerlemans and published by Springer. This book was released on 1984-02-29 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discusses the specific role ice sheets play in the climate system, at a level suitable for post-graduate courses. Includes mathematical models.
