Improving A Priori Regional Climate Model Estimates Of Greenland Ice Sheet Surface Mass Loss Through Assimilation Of Measured Ice Surface Temperatures

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Improving a Priori Regional Climate Model Estimates of Greenland Ice Sheet Surface Mass Loss Through Assimilation of Measured Ice Surface Temperatures

Author : Mahdi Navari
Publisher :
ISBN 13 :
Total Pages : 189 pages
Book Rating : 4.:/5 (17 download)

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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.

Greenland Ice Sheet Change: Surface Climate Variability and Glacier Dynamics

Author : Lei Yang
Publisher :
ISBN 13 :
Total Pages : 160 pages
Book Rating : 4.:/5 (637 download)

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Book Synopsis Greenland Ice Sheet Change: Surface Climate Variability and Glacier Dynamics by : Lei Yang

Download or read book Greenland Ice Sheet Change: Surface Climate Variability and Glacier Dynamics written by Lei Yang and published by . This book was released on 2007 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: The co-variability of glacier ice discharges and climate variability is also examined by using Polar MM5 V1 modeled summer temperature and April-September Positive Degree Day (PDD) anomalies. Ice discharges from south Greenland glaciers are found to be sensitive to temperature change. Based on sensitivities of ice discharge to melt index anomalies, time series of total ice discharge from 28 major glaciers since 1958 are modeled. The global sea level rise contribution from Greenland ice sheet during past 50 years is estimated be ∼0.6 mm yr-1 in average.

Assessing the Impact in Using Reanalysis Products to Simulate Surface Mass Balance Over the Greenland Ice Sheet

Author : Jessica Dawn Kromer
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.6/5 (625 download)

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Book Synopsis Assessing the Impact in Using Reanalysis Products to Simulate Surface Mass Balance Over the Greenland Ice Sheet by : Jessica Dawn Kromer

Download or read book Assessing the Impact in Using Reanalysis Products to Simulate Surface Mass Balance Over the Greenland Ice Sheet written by Jessica Dawn Kromer and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Greenland ice sheet (GrIS) surface mass balance (SMB), and processes which influence its behavior remain an active area of research, particularly for understanding the current sea-level budget and future projections of ice sheet mass loss. Currently, various methods are employed to model the surface mass balance of the contemporary GrIS, with methodologies ranging from the use of simple positive degree day models (PDD) to computationally intensive energy balance models (EBM's) and regional climate models (RCM's). Many of these methodologies rely on either direct forcing's (EBM's and PDD) or boundary conditions (RCM's) from atmospheric reanalysis products. Over time atmospheric reanalysis products have continued to improve with respect to horizontal resolution, allowing for direct use of fields critical for modeling and understanding the surface mass balance. Here we use a PDD model forced by temperature and precipitation from 3 atmospheric reanalysis products (ERA 5, Arctic System Reanalysis, and MERRA 2) at varying mesh resolution (30 km, 15 km, ~55 km respectively) to simulate the surface mass balance across the GrIS during the period 2000-2016. As higher resolution reanalysis products can help to better understand the contemporary GrIS surface mass balance, we highlight how variables important to the estimation of SMB vary amongst these reanalysis products and how these differences affect the SMB.

Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

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)

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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

Thriving on Our Changing Planet

Author : National Academies of Sciences, Engineering, and Medicine
Publisher : National Academies Press
ISBN 13 : 0309467578
Total Pages : 717 pages
Book Rating : 4.3/5 (94 download)

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Book Synopsis Thriving on Our Changing Planet by : National Academies of Sciences, Engineering, and Medicine

Download or read book Thriving on Our Changing Planet written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-01-20 with total page 717 pages. Available in PDF, EPUB and Kindle. Book excerpt: We live on a dynamic Earth shaped by both natural processes and the impacts of humans on their environment. It is in our collective interest to observe and understand our planet, and to predict future behavior to the extent possible, in order to effectively manage resources, successfully respond to threats from natural and human-induced environmental change, and capitalize on the opportunities â€" social, economic, security, and more â€" that such knowledge can bring. By continuously monitoring and exploring Earth, developing a deep understanding of its evolving behavior, and characterizing the processes that shape and reshape the environment in which we live, we not only advance knowledge and basic discovery about our planet, but we further develop the foundation upon which benefits to society are built. Thriving on Our Changing Planet presents prioritized science, applications, and observations, along with related strategic and programmatic guidance, to support the U.S. civil space Earth observation program over the coming decade.

The Ocean and Cryosphere in a Changing Climate

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)

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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.

Determining Greenland Ice Sheet Sensitivity to Regional Climate Change

Author : Nicole-Jeanne Schlegel
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (816 download)

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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 0 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.

Coupling a Regional Climate Model with a Greenland Ice Sheet Model for 21st Century Climate Change

Author : Jeroen Gerlo
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (98 download)

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Book Synopsis Coupling a Regional Climate Model with a Greenland Ice Sheet Model for 21st Century Climate Change by : Jeroen Gerlo

Download or read book Coupling a Regional Climate Model with a Greenland Ice Sheet Model for 21st Century Climate Change written by Jeroen Gerlo and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Effect of Modeled Pre-industrial Greenland Ice Sheet Surface Mass Balance Bias on Uncertainty in Sea Level Rise Projections in 2100

Author : Gail Ruth Gutowski
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (865 download)

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Book Synopsis Effect of Modeled Pre-industrial Greenland Ice Sheet Surface Mass Balance Bias on Uncertainty in Sea Level Rise Projections in 2100 by : Gail Ruth Gutowski

Download or read book Effect of Modeled Pre-industrial Greenland Ice Sheet Surface Mass Balance Bias on Uncertainty in Sea Level Rise Projections in 2100 written by Gail Ruth Gutowski and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Changes to ice sheet surface mass balance (SMB) are going to play a significant role in future sea level rise (SLR), particularly for the Greenland ice sheet. The Coupled Model Intercomparison Project Phase 5 (CMIP5) found that Greenland ice sheet (GIS) response to changes in SMB is expected to contribute 9 ± 4 cm to sea level by 2100 (Fettweis et al 2013), though other estimates suggest the possibility of an even larger response. Modern ice sheet geometry and surface velocities are common metrics for determining a model's predictability of future climate. However, care must be taken to robustly quantify prediction uncertainty because errors in boundary conditions such as SMB can be compensated by (and therefore practically inseparable from) errors in other aspects of the model, complicating calculations of total uncertainty. We find that SMB calculated using the Community Earth System Model (CESM) differs from established standards due to errors in the CESM SMB boundary condition. During the long ice sheet initialization process, small SMB errors such as these have an opportunity to amplify into larger uncertainties in GIS sensitivity to climate change. These uncertainties manifest themselves in ice sheet surface geometry changes, ice mass loss, and subsequent SLR. While any bias in SMB is not desirable, it is not yet clear how sensitive SLR projections are to boundary condition forcing errors. We explore several levels of SMB forcing bias in order to analyze their influence on future SLR. We evaluate ensembles of ice sheets forced by 4 different levels of SMB forcing error, covering a range of errors similar to SMB biases between CESM and RACMO SMB. We find that GIS SMB biases on the order of 1 m/yr result in 7.8 ± 3.4 cm SLR between 1850 and 2100, corresponding to 100% uncertainty at the 2[sigma] level. However, we find unexpected feedbacks between SMB and surface geometry in the northern GIS. We propose that the use of elevation classes may be incorrectly altering the feedback mechanisms in that part of the ice sheet.

Remote Sensing Observations of Modern-Day Regional Ice Sheet Change

Author : Tyler Clark Sutterley
Publisher :
ISBN 13 : 9781339784113
Total Pages : 132 pages
Book Rating : 4.7/5 (841 download)

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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.

Past to Future and Land to Sea: Constraining Global Glacier Models by Observations and Exploring Ice-ocean Interactions

Author : Jan-Hendrik Malles
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (138 download)

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Book Synopsis Past to Future and Land to Sea: Constraining Global Glacier Models by Observations and Exploring Ice-ocean Interactions by : Jan-Hendrik Malles

Download or read book Past to Future and Land to Sea: Constraining Global Glacier Models by Observations and Exploring Ice-ocean Interactions written by Jan-Hendrik Malles and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Glacier mass loss is an iconic process induced by anthropogenic climate change. It threatens human livelihood at coasts affected by the rising sea level and in glacierized hydrological basins where the glacial runoff is essential for water availability. Moreover, as glacier mass loss adds large amounts of freshwater to the oceans, it might alter ocean circulation in a way that affects marine ecosystems and the climate system. Only recently, satellite-data processing revealed mass changes on an individual glacier level (outside the large ice sheets), but only for the last two decades. Glacier mass change observations become increasingly sparse going back in time. Therefore, the glaciers' past contribution to global mean sea level rise can only be reconstructed using numerical models. Since glacier mass change will continue during this century, it is vital to understand how this will affect global mean sea level, ocean circulation, and regional hydrology. Again, this is only possible using numerical models. Hence, it is essential to improve these models by incorporating previously neglected processes of glacier mass change into them, mainly in the form of parametrizations, and by constraining them using observations. Moreover, it is crucial to understand the uncertainties of results produced by numerical models, as they can never fully represent the natural world, which also hinges on the amount and quality of observational data. This work will tackle aspects of three issues in numerically modeling glacier mass changes: past glacier mass change reconstructions' uncertainties, future mass change projections' uncertainties, specifically regarding marine-terminating glaciers, and ice-ocean interactions in the northern hemisphere outside the Greenland ice sheet. All three issues are relevant in addressing the question of how glaciers respond to changes in their mass balance due to climatic changes and what consequences such changes have for the Earth system and, ultimately, human livelihood. It is found that the further outside the glaciological and meteorological observations' spatial and temporal domain a numerical model is applied, the more uncertain reconstructed glacier mass changes become. Similarly, one primary source of uncertainty in future glacier mass change projections is the difference in climate models' outputs of near-surface temperatures and precipitation. More accurately describing marine-terminating glacier dynamics and considering volume changes below sea level reduces estimates of future glacier contribution to global mean sea level rise systematically. However, significant uncertainties due to uncertainty about appropriate values for parameters involved in modeling (marine-terminating) glaciers' dynamics are detected. Concerning ice-ocean interactions, it was found that including the freshwater input from glacier mass loss in the northern hemisphere (outside the Greenland ice sheet) in an ocean general circulation model significantly impacts the simulated high-latitude ocean circulation. Finally, a first estimate of the ice mass glaciers lose due to melting directly into the ocean was produced.

Analysis of Surface Melting and Snow Accumulation Over the Greenland Ice Sheet from Spaceborne Microwave Sensors

Author : Indrajit Bhattacharya
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (768 download)

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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.

Temporal History of Ice Dynamics Contribution to Volume Changes of the Southeast Greenland Ice Sheet

Author : Soroush Rezvanbehbahani
Publisher :
ISBN 13 :
Total Pages : 102 pages
Book Rating : 4.:/5 (845 download)

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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.

Assessing the Uncertainties of Future Changes in Ice Sheets and Polar Climate Related to Internal Climate Variability and Climate Model Structural Uncertainties

Download Assessing the Uncertainties of Future Changes in Ice Sheets and Polar Climate Related to Internal Climate Variability and Climate Model Structural Uncertainties PDF Online Free

Author : Chii-yun Tsai
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (15 download)

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Book Synopsis Assessing the Uncertainties of Future Changes in Ice Sheets and Polar Climate Related to Internal Climate Variability and Climate Model Structural Uncertainties by : Chii-yun Tsai

Download or read book Assessing the Uncertainties of Future Changes in Ice Sheets and Polar Climate Related to Internal Climate Variability and Climate Model Structural Uncertainties written by Chii-yun Tsai and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Both Greenland and Antarctic ice sheets (hereafter, GrIS and AIS) have potential to be major contributors to future sea-level rise (SLR) and pose a major risk to human societies and coastal habitats. Current projections of polar climate and future SLR due to ice sheet mass loss remain highly uncertain and the sources of associated uncertainties are complex. In this dissertation, we seek to understand uncertainty of internal and forced variabilities within the climate system, and their impacts on polar climate variability and ice sheet disintegration. Three broad scientific questions are addressed in this dissertation: (1) How internal climate variability affects projections of polar climate? (2) What is the role of internal climate variability in affecting the GrIS and AIS evolution? (3) How does polar climate respond to anomalous sea surface temperature (SST) patterns and how would the responses differ across different climate model structures? Internal climate variability, which is inherently generated within the climate system due to natural processes, has shown to be one of the major contributors to uncertainty in future climate projections. Typically, the uncertainty in future climate due to internal climate variability can be estimated by conducting a large ensemble (LE) of model simulations with same external forcing but different initial conditions. To examine the impact of internal climate variability on polar climate and ice sheet evolutions, we use climate fields from two Community Earth System Model (CESM) LE experiments to force a three-dimensional ice sheet model. We investigate and quantify the impact of internal climate variability on influencing projections of the GrIS and AIS mass losses as well as their contributions to future SLR. Based on our simulations, internal climate variability can cause about 35 mm differences in the the GrIS contribution to SLR from 2000 to 2100, and for the AIS, the differences can be up to 80 mm, which is about 20% of the total change. Moreover, using ensemble-mean climate fields as the forcing in an ice sheet model significantly underestimates the GrIS and AIS mass losses and their contributions to SLR by about 12% and 29%, respectively. On estimating polar climate sensitivity to anomalous SSTs using a suite of large-ensemble model simulations with different configurations of atmospheric models, we identify that recent summer temperature changes over Greenland are sensitive to the north Atlantic SSTs and the sensitivity patters are consistent across different atmospheric model configurations. In addition, the recent summer Greenland temperature changes can be captured by a multi-linear model based on the associated sensitivity and SST information. However, sensitivity of polar climate over the Antarctic regions to anomalous SST patterns is model-dependent and its variability cannot be fully captured using a Green's function based model driven by SST information. Overall, this dissertation aims to highlight (1) the importance of internal climate variability in projecting ice sheet mass loss over the next few centuries and (2) the estimates of sensitivity of polar climate to anomalous SSTs can be strongly model-dependent over most of the polar regions due to climate model structural uncertainty. Thus, these two types of uncertainty should be considered and further investigated when estimating the future changes in polar climate and their impact on ice sheet contribution to future SLR.

Measuring Recent Ice Mass Loss from the Margin of the Greenland Ice Sheet Using Aster-derived Digital Elevation Models

Author : Tristan A. Rhodes
Publisher :
ISBN 13 :
Total Pages : 174 pages
Book Rating : 4.:/5 (8 download)

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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:

Greenland Ice Sheet Surface Mass-balance Modeling in a 131-year Perspective, 1950-2080

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (727 download)

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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.

Estimating and Reducing the Uncertainty in the Future Behaviour of the Greenland Ice Sheet

Author : Peter Fitzgerald
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (835 download)

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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.