[PDF] Melt Water Retention Processes In Snow And Firn On Ice Sheets And Glaciers Observations And Modeling eBook

Author : W. Tad Pfeffer
Publisher : Frontiers Media SA
Page : 160 pages
File Size : 30,63 MB
Release : 2018-11-08
Category :
ISBN : 2889456196

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Melt takes place where the surface of glaciers or ice sheets interacts with the atmosphere. While the processes governing surface melt are fairly well understood, the pathways of the meltwater, from its origin to the moment it leaves a glacier system, remain enigmatic. It is not even guaranteed that meltwater leaves a glacier or ice sheet. On Greenland, for example, only slightly more than 50% of the meltwater runs off. The remainder mostly refreezes within the so-called firn cover of the ice sheet. This eBook contains 11 studies which tackle the challenge of understanding meltwater retention in snow and firn from various angles. The studies focus both on mountain glaciers and on the Greenland ice sheet and address challenges such as measuring firn properties, quantifying their influence on meltwater retention, modelling firn processes and meltwater refreezing as well as unravelling the mechanisms within the recently discovered Greenland firn aquifers.

Author : Daqing Yang
Publisher : Springer Nature
Page : 914 pages
File Size : 36,35 MB
Release : 2020-08-28
Category : Science
ISBN : 3030509303

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This book provides a comprehensive, up-to-date assessment of the key terrestrial components of the Arctic system, i.e., its hydrology, permafrost, and ecology, drawing on the latest research results from across the circumpolar regions. The Arctic is an integrated system, the elements of which are closely linked by the atmosphere, ocean, and land. Using an integrated system approach, the book’s 30 chapters, written by a diverse team of leading scholars, carefully examine Arctic climate variability/change, large river hydrology, lakes and wetlands, snow cover and ice processes, permafrost characteristics, vegetation/landscape changes, and the future trajectory of Arctic system evolution. The discussions cover the fundamental features of and processes in the Arctic system, with a special focus on critical knowledge gaps, i.e., the interactions and feedbacks between water, permafrost, and ecosystem, such as snow pack and permafrost changes and their impacts on basin hydrology and ecology, river flow, geochemistry, and energy fluxes to the Arctic Ocean, and the structure and function of the Arctic ecosystem in response to past/future changes in climate, hydrology, and permafrost conditions. Given its scope, the book offers a valuable resource for researchers, graduate students, environmentalists, managers, and administrators who are concerned with the northern environment and resources.

Author :
Publisher :
Page : pages
File Size : 49,82 MB
Release : 2009
Category :
ISBN :

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The temporal variability in surface snow and glacier melt flux and runoff were investigated for the ablation area of lakobshavn Isbrae, West Greenland. High-resolution meteorological observations both on and outside the Greenland Ice Sheet (GrIS) were used as model input. Realistic descriptions of snow accumulation, snow and glacier-ice melt, and runoff are essential to understand trends in ice sheet surface properties and processes. SnowModel, a physically based, spatially distributed meteorological and snow-evolution modeling system was used to simulate the temporal variability of lakobshavn Isbrre accumulation and ablation processes for 2000/01-2006/07. Winter snow-depth observations and MODIS satellite-derived summer melt observations were used for model validation of accumulation and ablation. Simulations agreed well with observed values. Simulated annual surface melt varied from as low as 3.83 x 109 m3 (2001/02) to as high as 8.64 x 109 m3 (2004/05). Modeled surface melt occurred at elevations reaching 1,870 m a.s.l. for 2004/05, while the equilibrium line altitude (ELA) fluctuated from 990 to 1,210 m a.s.l. during the simulation period. The SnowModel meltwater retention and refreezing routines considerably reduce the amount of meltwater available as ice sheet runoff; without these routines the lakobshavn surface runoff would be overestimated by an average of 80%. From September/October through May/June no runoff events were simulated. The modeled interannual runoff variability varied from 1.81 x 109 m3 (2001/02) to 5.21 x 109 m3 (2004/05), yielding a cumulative runoff at the Jakobshavn glacier terminus of ≈2.25 m w.eq. to ≈4.5 m w.eq., respectively. The average modeled lakobshavn runoff of ≈3.4 km3 y−1 was merged with previous estimates of Jakobshavn ice discharge to quantify the freshwater flux to Illulissat Icefiord. For both runoff and ice discharge the average trends are similar, indicating increasing (insignificant) influx of freshwater to the Illulissat Icefiord for the period 2000/01-2006/07. This study suggests that surface runoff forms a minor part of the overall Jakobshavn freshwater flux to the fiord: around 7% (≈3.4 km3 y−1) of the average annual freshwater flux of ≈51.0 km3 y−1 originates from the surface runoff.

Author : Matthew Cooper
Publisher :
Page : 230 pages
File Size : 42,50 MB
Release : 2020
Category :
ISBN :

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The Greenland Ice Sheet is a major contributor to global sea level rise, with recent mass loss dominated by meltwater runoff from the ablation zone, i.e. areas of the ice sheet where annual mass losses exceed gains. In this zone, the winter snowpack melts entirely each summer exposing bare glacier ice. Observations of Greenland's ablation zone suggest the exposed bare ice surface is comprised of low-density ice termed "weathering crust" that may store meltwater, potentially reducing meltwater runoff export to surrounding oceans. Climate models are the primary tools used to forecast future Greenland mass loss, but these models treat the ablation zone as impermeable high-density ice with no meltwater retention capacity. Recent evidence suggests that climate models overpredict meltwater runoff from the ablation zone, which may be linked to weathering crust presence, but diagnosing climate model predictions is difficult because observations of meltwater runoff on the ice sheet surface are extremely rare and weathering crust presence is undocumented. This dissertation presents the results of four investigations that address this problem by pairing field observations of hydrologic and radiative properties of bare ice collected in Greenland's ablation zone with numerical modeling and analysis of climate model output. The results of these investigations reveal the presence of low-density weathering crust on Greenland's bare ice ablation zone surface and the potential for non-trivial meltwater runoff retention within weathering crust on Greenland's bare ice ablation zone surface. New estimates of spectral radiation attenuation coefficients are quantified and directly applied to a numerical model of spectral and thermodynamic heat transfer in bare ice. This model successfully simulates meltwater runoff from a supraglacial catchment on Greenland's southwest ablation zone surface. Model results suggest that nocturnal refreezing of meltwater stored within weathering crust occurs in Greenland's ablation zone, potentially reducing runoff up to 32% on annual timescales. These findings imply a reinterpretation of refreezing on bare ice as an important control on Greenland's ablation zone surface mass balance and the need to represent this process in climate model predictions of future Greenland mass loss.

Author : Roger G. Barry
Publisher : Cambridge University Press
Page : 445 pages
File Size : 35,74 MB
Release : 2018-08-09
Category : History
ISBN : 1108423167

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Surveys atmospheric, oceanic and cryospheric processes, present and past conditions, and changes in polar environments.

Author : Intergovernmental Panel on Climate Change (IPCC)
Publisher : Cambridge University Press
Page : 2410 pages
File Size : 46,98 MB
Release : 2023-07-26
Category : Science
ISBN : 1009175351

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The Working Group I contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive assessment of the physical science basis of climate change. It considers in situ and remote observations; paleoclimate information; understanding of climate drivers and physical, chemical, and biological processes and feedbacks; global and regional climate modelling; advances in methods of analyses; and insights from climate services. It assesses the current state of the climate; human influence on climate in all regions; future climate change including sea level rise; global warming effects including extremes; climate information for risk assessment and regional adaptation; limiting climate change by reaching net zero carbon dioxide emissions and reducing other greenhouse gas emissions; and benefits for air quality. The report serves policymakers, decision makers, stakeholders, and all interested parties with the latest policy-relevant information on climate change. Available as Open Access on Cambridge Core.

Author : Daniel J. Sturgis
Publisher :
Page : 80 pages
File Size : 48,68 MB
Release : 2009
Category : Ice sheets
ISBN : 9781109532845

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Surface meltwater generated in the accumulation zone of the Greenland Ice Sheet (GrIS) will either be retained by refreezing or connect to the glacial drainage system and contribute to annual runoff. The fate of this meltwater is controlled by the infiltration process, which occurs in the presence of subfreezing snow/firnpack temperatures and ice layers. Ice layers are typically treated as impermeable horizons. However, dye-trace observations suggest ice layers do not impede flow but rather accelerate flow by destabilizing the wetting-front, forming preferential flow paths termed pipes. Until the 2008 field season, the permeability of ice layers formed in the snow/firnpack on GrIS was unmeasured. Air permeameter measurements show ice layer permeability to range from 10 -15 m 2 to 10 -12 m 2 and firn to be approximately 10 -11 m 2 . Temperature profile measurements of the snow/firnpack were recorded every 30 min during the 2007 melt season. Temperature profile data confirms piping as a mechanism for meltwater delivery to 10+ m depths at T1 without increasing the full snow/firnpack temperature to 0°C. Meltwater that is piped to the glacier-ice surface can connect to the glacial drainage system and runoff. Current models used to estimate annual runoff from GrIS do not consider the infiltration process; possibly underestimating the actual runoff.

Author : P. Singh
Publisher : Springer Science & Business Media
Page : 764 pages
File Size : 18,46 MB
Release : 2001-02-28
Category : Science
ISBN : 9780792367673

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This book provides an updated discussion of snow and glacier hydrology, drawing on the results of recent investigations. It serves as a source of reference at the senior undergraduate or beginning graduate level and stimulates further interest in this important part of the hydrologic cycle.

Author : Avirup Sen Gupta
Publisher :
Page : pages
File Size : 21,92 MB
Release : 2014
Category :
ISBN :

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The Hindu-Kush Himalayan region possesses a large resource of snow and ice, which acts as a freshwater reservoir for irrigation, domestic water consumption or hydroelectric power for billions of people in South Asia. Monitoring hydrologic resources in this region is challenging because of the difficulty of installing and maintaining a climate and hydrologic monitoring network, limited transportation and communication infrastructure and difficult access to glaciers. As a result of the high, rugged topographic relief, ground observations in the region are extremely sparse. Reanalysis data offer the potential to compensate for the data scarcity, which is a barrier in hydrological modeling and analysis for improving water resources management. Reanalysis weather data products integrate observations with atmospheric model physics to produce a spatially and temporally complete weather record in the post-satellite era. This dissertation creates an integrated hydrologic modeling system that tests whether streamflow prediction can be improved by taking advantage of the National Aeronautics and Space Administration (NASA) remote sensing and reanalysis weather data products in physically based energy balance snow melt and hydrologic models. This study also enhances the energy balance snowmelt model by adding capability to quantify glacier melt. The novelty of this integrated modeling tool resides in allowing the user to isolate various components of surface water inputs (rainfall, snow and glacier ice melt) in a cost-free, open source graphical-user interface-based system that can be used for government and institutional decision-making. Direct, physically based validation of this system is challenging due to the data scarcity in this region, but, to the extent possible, the model was validated through comparison to observed streamflow and to point measurements at locations in the United States having available data