scholarly journals Impact of frontal ablation on the ice thickness estimation of marine-terminating glaciers in Alaska

2019 ◽  
Vol 13 (10) ◽  
pp. 2657-2672 ◽  
Author(s):  
Beatriz Recinos ◽  
Fabien Maussion ◽  
Timo Rothenpieler ◽  
Ben Marzeion
Keyword(s):  
Sea Level ◽  
Thickness Distribution ◽  
Regional Scale ◽  
Ice Thickness ◽  
Potential Contribution ◽  
Volume Estimate ◽  
Tidewater Glaciers ◽  
Thickness Estimation ◽  
The Impact ◽  
Frontal Ablation

Abstract. Frontal ablation is a major component of the mass budget of calving glaciers, strongly affecting their dynamics. Most global-scale ice volume estimates to date still suffer from considerable uncertainties related to (i) the implemented frontal ablation parameterization or (ii) not accounting for frontal ablation at all in the glacier model. To improve estimates of the ice thickness distribution of glaciers, it is thus important to identify and test low-cost and robust parameterizations of this process. By implementing such parameterization into the ice thickness estimation module of the Open Global Glacier Model (OGGM v1.1.2), we conduct a first assessment of the impact of accounting for frontal ablation on the estimate of ice stored in glaciers in Alaska. We find that inversion methods based on mass conservation systematically underestimate the mass turnover and, therefore, the thickness of tidewater glaciers when neglecting frontal ablation. This underestimation can amount to up to 19 % on a regional scale and up to 30 % for individual glaciers. The effect is independent of the size of the glacier. Additionally, we perform different sensitivity experiments to study the influence of (i) a constant of proportionality (k) used in the frontal ablation parameterization, (ii) Glen's temperature-dependent creep parameter (A) and (iii) a sliding velocity parameter (fs) on the regional dynamics of Alaska tidewater glaciers. OGGM is able to reproduce previous regional frontal ablation estimates, applying a number of combinations of values for k, Glen's A and fs. Our sensitivity studies also show that differences in thickness between accounting for and not accounting for frontal ablation occur mainly at the lower parts of the glacier, both above and below sea level. This indicates that not accounting for frontal ablation will have an impact on the estimate of the glaciers' potential contribution to sea-level rise. Introducing frontal ablation increases the volume estimate of Alaska marine-terminating glaciers from 9.18±0.62 to 10.61±0.75 mm s.l.e, of which 1.52±0.31 mm s.l.e (0.59±0.08 mm s.l.e when ignoring frontal ablation) are found to be below sea level.

scholarly journals Impact of frontal ablation on the ice thickness estimation of marine-terminating glaciers in Alaska

2018 ◽  
Author(s):  
Beatriz Recinos ◽  
Fabien Maussion ◽  
Timo Rothenpieler ◽  
Ben Marzeion
Keyword(s):  
Sea Level ◽  
Thickness Distribution ◽  
Regional Scale ◽  
Ice Thickness ◽  
Potential Contribution ◽  
Tidewater Glaciers ◽  
Thickness Estimation ◽  
Volume Estimates ◽  
The Impact ◽  
Frontal Ablation

Abstract. Frontal ablation is a major component of the mass budget of tidewater glaciers, strongly affecting their dynamics. Most global scale ice volume estimates to date still suffer from considerable uncertainties related to i) the implemented frontal ablation parameterisation or ii) for not accounting for frontal ablation at all in the glacier model. To improve estimates of the ice thickness distribution of glaciers it is thus important to identify and test low-cost and robust parameterisations of this fundamental process. By implementing such parameterisation into the ice-thickness estimation module of the Open Global Glacier Model (OGGM v1.0.1), we conduct a first assessment of the impact of accounting for frontal ablation on the estimate of ice stored in glaciers in Alaska. We find that inversion methods based on mass conservation systematically underestimate the mass turnover (and therefore the thickness) of tidewater glaciers when neglecting frontal ablation. This underestimation can rise up to 17 % on a regional scale and up to 47 % for individual glaciers. The effect strongly depends on the size of the glacier. Additionally, we perform different sensitivity experiments to study the influence of i) a constant of proportionality (k) used in the frontal ablation parameterisation, ii) Glen's temperature-dependent creep parameter (A) and iii) a sliding velocity parameter (fs) on the regional dynamics of Alaska marine-terminating glaciers. OGGM is able to reproduce previous regional frontal ablation estimates applying a number of combinations of values for k, Glen's A and fs. These different model configurations show that volume estimates after accounting for frontal ablation are 15 to 17 % higher than volume estimates ignoring frontal ablation. Our sensitivity studies also show that differences in thickness between accounting for and not accounting for frontal ablation occur mainly at the lower parts of the glacier, both above and below sea level. This indicates that not accounting for frontal ablation will have an impact on the estimate of the glaciers' potential contribution to sea-level rise. Introducing frontal ablation increases the volume estimate of Alaska marine-terminating glaciers from 9.01 ± 0.35 to 10.43 ± 0.44 mm. SLE, of which 1.41 ± 0.18 mm. SLE (0.58 ± 0.05 mm. SLE when ignoring frontal ablation) are found to be below sea level.

scholarly journals Calibration of a frontal ablation parameterisation applied to Greenland's peripheral calving glaciers

2021 ◽  
pp. 1-13
Author(s):  
Beatriz Recinos ◽  
Fabien Maussion ◽  
Brice Noël ◽  
Marco Möller ◽  
Ben Marzeion
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Mass Gain ◽  
Reference Period ◽  
Volume Estimate ◽  
Surface Mass ◽  
Ice Volume ◽  
Order Of Magnitude ◽  
The Impact ◽  
Frontal Ablation

Abstract We calibrate the calving parameterisation implemented in the Open Global Glacier Model via two methods (velocity constraint and surface mass balance (SMB) constraint) and assess the impact of accounting for frontal ablation on the ice volume estimate of Greenland tidewater peripheral glaciers (PGs). We estimate an average regional frontal ablation flux of 7.38±3.45 Gta−1 after calibrating the model with two different satellite velocity products, and of 0.69±0.49 Gta−1 if the model is constrained using frontal ablation fluxes derived from independent modelled SMB averaged over an equilibrium reference period (1961–90). This second method makes the assumption that most PGs during that time have an equilibrium between mass gain via SMB and mass loss via frontal ablation. This assumption serves as a basis to assess the order of magnitude of dynamic mass loss of glaciers when compared to the SMB imbalance. The differences between results from both methods indicate how strong the dynamic imbalance might have been for PGs during that reference period. Including frontal ablation increases the estimated regional ice volume of PGs, from 14.47 to 14.64±0.12 mm sea level equivalent when using the SMB method and to 15.84±0.32 mm sea level equivalent when using the velocity method.

scholarly journals Antarctic sea-ice thickness and volume estimates from ice charts between 1995 and 1998

2015 ◽  
Vol 56 (69) ◽  
pp. 383-393 ◽  
Author(s):  
E. Rachel Bernstein ◽  
Cathleen A. Geiger ◽  
Tracy L. Deliberty ◽  
Mary D. Lemcke-Stampone
Keyword(s):  
Sea Ice ◽  
Regional Scale ◽  
Weighted Average ◽  
Ice Thickness ◽  
Average Thickness ◽  
Sea Ice Thickness ◽  
Subjective Analysis ◽  
Stage Of Development ◽  
Volume Estimates ◽  
The Impact

AbstractThis work evaluates two distinct calculations of central tendency for sea-ice thickness and quantifies the impact such calculations have on ice volume for the Southern Ocean. The first calculation, area-weighted average thickness, is computed from polygonal ice features and then upscaled to regions. The second calculation, integrated thickness, is a measure of the central value of thickness categories tracked across different scales and subsequently summed to chosen regions. Both methods yield the same result from one scale to the next, but subsequent scales develop diverging solutions when distributions are strongly non-Gaussian. Data for this evaluation are sea-ice stage-of-development records from US National Ice Center ice charts from 1995 to 1998, as proxy records of ice thickness. Results show regionally integrated thickness exceeds area-weighted average thickness by as much as 60% in summer with as few as five bins in thickness distribution. Year-round, the difference between the two calculations yields volume differences consistently >10%. The largest discrepancies arise due to bimodal distributions which are common in ice charts based on current subjective-analysis protocols. We recommend that integrated distribution be used for regional-scale sea-ice thickness and volume estimates from ice charts and encourage similar testing of other large-scale thickness data archives.

scholarly journals New insight from CryoSat-2 sea ice thickness for sea ice modelling

2018 ◽  
Author(s):  
David Schröder ◽  
Danny L. Feltham ◽  
Michel Tsamados ◽  
Andy Ridout ◽  
Rachel Tilling
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Arctic Sea Ice ◽  
Ice Thickness ◽  
Atmospheric Conditions ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
Ice Growth ◽  
Melt Pond ◽  
The Impact

Abstract. Estimates of Arctic sea ice thickness are available from the CryoSat-2 (CS2) radar altimetry mission during ice growth seasons since 2010. We derive the sub-grid scale ice thickness distribution (ITD) with respect to 5 ice thickness categories used in a sea ice component (CICE) of climate simulations. This allows us to initialize the ITD in stand-alone simulations with CICE and to verify the simulated cycle of ice thickness. We find that a default CICE simulation strongly underestimates ice thickness, despite reproducing the inter-annual variability of summer sea ice extent. We can identify the underestimation of winter ice growth as being responsible and show that increasing the ice conductive flux for lower temperatures (bubbly brine scheme) and accounting for the loss of drifting snow results in the simulated sea ice growth being more realistic. Sensitivity studies provide insight into the impact of initial and atmospheric conditions and, thus, on the role of positive and negative feedback processes. During summer, atmospheric conditions are responsible for 50 % of September sea ice thickness variability through the positive sea ice and melt pond albedo feedback. However, atmospheric winter conditions have little impact on winter ice growth due to the dominating negative conductive feedback process: the thinner the ice and snow in autumn, the stronger the ice growth in winter. We conclude that the fate of Arctic summer sea ice is largely controlled by atmospheric conditions during the melting season rather than by winter temperature. Our optimal model configuration does not only improve the simulated sea ice thickness, but also summer sea ice concentration, melt pond fraction, and length of the melt season. It is the first time CS2 sea ice thickness data have been applied successfully to improve sea ice model physics.

Vulnerability of coastal areas to increased aquifer saturation due to climate change

2021 ◽  
Author(s):  
Alexandre Gauvain ◽  
Ronan Abhervé ◽  
Jean-Raynald de Dreuzy ◽  
Luc Aquilina ◽  
Frédéric Gresselin
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Large Scale ◽  
Regional Scale ◽  
Drainage System ◽  
Hydrological Regime ◽  
Coastal Areas ◽  
Western Coast ◽  
Study Sites ◽  
The Impact

<p>Like in other relatively flat coastal areas, flooding by aquifer overflow is a recurring problem on the western coast of Normandy (France). Threats are expected to be enhanced by the rise of the sea level and to have critical consequences on the future development and management of the territory. The delineation of the increased saturation areas is a required step to assess the impact of climate change locally. Preliminary models showed that vulnerability does not result only from the sea side but also from the continental side through the modifications of the hydrological regime.</p><p>We investigate the processes controlling these coastal flooding phenomena by using hydrogeological models calibrated at large scale with an innovative method reproducing the hydrographic network. Reference study sites selected for their proven sensitivity to flooding have been used to validate the methodology and determine the influence of the different geomorphological configurations frequently encountered along the coastal line.</p><p>Hydrogeological models show that the rise of the sea level induces an irregular increase in coastal aquifer saturations extending up to several kilometers inland. Back-littoral channels traditionally used as a large-scale drainage system against high tides limits the propagation of aquifer saturation upstream, provided that channels are not dominantly under maritime influence. High seepage fed by increased recharge occurring in climatic extremes may extend the vulnerable areas and further limit the effectiveness of the drainage system. Local configurations are investigated to categorize the influence of the local geological and geomorphological structures and upscale it at the regional scale.</p>

scholarly journals Replacing Fossil Fuels and Nuclear Power with Renewable Energy: Utopia or Valid Option? A Swiss Case Study of Bioenergy

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2051 ◽  
Author(s):  
Renato Lemm ◽  
Raphael Haymoz ◽  
Astrid Björnsen Gurung ◽  
Vanessa Burg ◽  
Tom Strebel ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Energy Demand ◽  
Renewable Energy Sources ◽  
Regional Scale ◽  
Energy Sources ◽  
Potential Contribution ◽  
Swiss Canton ◽  
Future System ◽  
Conversion Technologies ◽  
The Impact

The transition towards a reliable, sustainable, low-carbon energy system is a major challenge of the 21st century. Due to the lower energy density of many renewable energy sources, a future system is expected to be more decentralized, leading to significant changes at the regional scale. This study analyzes the feasibility of the energy transition in the Swiss canton of Aargau as an illustrative example and explores different strategies to satisfy the local demand for electricity, heat, and fuel by 2035. In particular, we assess the potential contribution of biomass. Four scenarios demonstrate what energy demand proportion could be covered by bioenergy if different priorities were given to the provision of heat, electricity, and fuel. The impact of improved conversion technologies is also considered. The results show that the sustainably available renewable energy sources in canton Aargau will probably not be sufficient to cover its forecasted energy demand in 2035, neither with present nor future biomass conversion technologies. At best, 74% of the energy demand could be met by renewables. Biomass can increase the degree of autarky by a maximum of 13%. Depending on the scenario, at least 26–43% (2500–5700 GWh) of total energy demand is lacking, particularly for mobility purposes.

scholarly journals Application of remote sensing and GIS for assessing the level of change of land use status in the coast of Ngoc Hien district (Ca Mau province) due to the impact of sea level rise

2019 ◽  
Vol 19 (3B) ◽  
pp. 227-237
Author(s):  
Pham Viet Hong ◽  
Tran Anh Tuan ◽  
Nguyen Thi Anh Nguyet
Keyword(s):  
Climate Change ◽  
Remote Sensing ◽  
Land Use ◽  
Natural Disasters ◽  
Sea Level Rise ◽  
Sea Level ◽  
Human Life ◽  
Regional Scale ◽  
Great Influence ◽  
The Impact

Today, environmental hazards and challenges are no longer confined to the national or regional scale but on the global scale. One of the biggest challenges for humanity is the natural disasters, global warming and sea level rise. The natural disasters causing serious consequences for human life, such as: Storms, floods, earthquakes, tsunamis, desertification, high tides... increase in frequency, intensity and scale. In recent years, Ca Mau province as well as coastal provinces of Vietnam is under great influence due to the impacts of climate change. One of the most affected districts in Ca Mau province is Ngoc Hien district. The district has a geographic location with three sides bordering the sea, one side bordering the river, a completely isolated terrain. The terrain is flat, strongly divided by the system of natural rivers and canals and intertwined canals, so it is constantly flooded by the sea. Ngoc Hien district is characterized by a sub-equatorial monsoon climate, directly affected by irregular semi-diurnal regime. The main purpose of the paper is to assess coastal vulnerability due to the impact of climate change over time with GIS-based remote sensing images. Remote sensing data with multi-time characteristics, collected in many periods and covering a wide area is an effective tool for monitoring shoreline fluctuations in particular and land use status of the study area in general.

scholarly journals Major improvement of altimetry sea level estimations using pressure derived corrections based on ERA-interim atmospheric reanalysis

2016 ◽  
Author(s):  
L. Carrere ◽  
Y. Faugère ◽  
M. Ablain
Keyword(s):  
Shallow Water ◽  
Sea Level ◽  
Positive Impact ◽  
Regional Scale ◽  
Atmospheric Correction ◽  
Deep Ocean ◽  
Global Ocean ◽  
Strong Impact ◽  
Residual Variance ◽  
The Impact

Abstract. New Dynamic Atmospheric Correction (DAC) and Dry Tropospheric (DT) correction derived from the ERA-Interim meteorological reanalysis have been computed on the 1992-2013 altimeter period. Using these new corrections improves significantly sea-level estimations for short temporal signals (< 2 months); the impact is stronger if considering old altimeter missions (ERS-1, ERS-2, TP), for which DAC_ERA allows reducing the residual variance at crossovers by more than 10 cm2 in the Southern Ocean and in some shallow water regions. The impact of DT_ERA is also significant in the southern high latitudes for these missions. Using the ERA-interim forcing has the greatest positive impact on the first decade of altimetry, then this impact diminishes until giving similar results as the operational forcing from year 2002. Concerning more recent missions (Jason-1, Jason-2, and Envisat), results are very similar between ERA-Interim and ECMWF based corrections: on average on global ocean, the operational DAC becomes slightly better than DAC_ERA only from year 2006, likely due to the switch to a higher resolution of operational forcing. At regional scale, both DACs are similar in deep ocean but DAC_ERA raises the residual crossovers variance in some shallow water regions. On the second decade of altimetry, unexpectedly DT_ERA still gives better results compared to the operational DT. Concerning climate signals, both DAC_ERA and DT_ERA have a low impact on global MSL trend, but they can have a strong impact on long-term regional trends estimation, until several mm/yr locally.

scholarly journals A combined approach of remote sensing and airborne electromagnetics to determine the volume of polynya sea ice in the Laptev Sea

2013 ◽  
Vol 7 (1) ◽  
pp. 441-473 ◽  
Author(s):  
L. Rabenstein ◽  
T. Krumpen ◽  
S. Hendricks ◽  
C. Koeberle ◽  
C. Haas ◽  
...  
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Growth Conditions ◽  
Ice Age ◽  
The Arctic ◽  
Ice Thickness ◽  
Laptev Sea ◽  
Volume Estimate ◽  
Sea Ice Thickness ◽  
Level Ice

Abstract. A combined interpretation of synthetic aperture radar (SAR) satellite images and helicopter electromagnetic (HEM) sea-ice thickness data has provided an estimate of sea-ice volume formed in Laptev Sea polynyas during the winter of 2007/08. The evolution of the surveyed sea-ice areas, which were formed between late December 2007 and middle April 2008, was tracked using a series of SAR images with a sampling interval of 2–3 days. Approximately 160 km of HEM data recorded in April 2008 provided sea-ice thicknesses along profiles that transected sea-ice varying in age from 1–116 days. For the volume estimates, thickness information along the HEM profiles was extrapolated to zones of the same age. The error of areal mean thickness information was estimated to be between 0.2 m for younger ice and up to 1.55 m for older ice, with the primary error source being the spatially limited HEM coverage. Our results have demonstrated that the modal thicknesses and mean thicknesses of level ice correlated with the sea-ice age, but that varying dynamic and thermodynamic sea-ice growth conditions resulted in a rather heterogeneous sea-ice thickness distribution on scales of tens of kilometers. Taking all uncertainties into account, total sea-ice area and volume produced within the entire surveyed area were 52 650 km2 and 93.6 ± 26.6 km3. The surveyed polynya contributed 2.0 ± 0.5% of the sea-ice produced throughout the Arctic during the 2007/08 winter. The SAR-HEM volume estimate compares well with the 112 km3 ice production calculated with a high resolution ocean sea-ice model. Measured modal and mean-level ice thicknesses correlate with calculated freezing-degree-day thicknesses with a factor of 0.87–0.89, which was too low to justify the assumption of homogeneous thermodynamic growth conditions in the area, or indicates a strong dynamic thickening of level ice by rafting of even thicker ice.

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