scholarly journals The significance of vertical moisture diffusion on drifting Snow sublimation near snow surface

2017 ◽  
Author(s):  
Ning Huang ◽  
Guanglei Shi
Keyword(s):  
Ice Sheets ◽  
Moisture Diffusion ◽  
Polar Ice ◽  
Sublimation Rate ◽  
Saturation State ◽  
Near Surface ◽  
Drifting Snow ◽  
Polar Ice Sheets ◽  
Fresh Water Resource ◽  
Semi Arid

Abstract. Drifting snow sublimation is a physical process containing phase change and heat change of the drifting snow, which is not only an important parameter for the studying of polar ice sheets and glaciers, but a significant one for the ecology of arid and semi-arid lands, where snow cover is the main fresh water resource. However, in the previous studies drifting snow sublimation near surface was ignored. Herein, we built a drifting snow sublimation model containing vertical moisture diffusion equation and heat balance equation, to study drifting snow sublimation near surface. The results showed that though drifting snow sublimation near surface was strongly reduced by negative feedback effect, relative humidity near surface didn’t reach the saturation state caused by vertical moisture diffusion. Therefore, the sublimation near surface will not stop in drifting snow near surface. The sublimation rate near surface is 3–4 orders of magnitude higher than that at 10 m. And the mass of snow sublimation near surface accounts for even more than half of the total if the wind velocity is small. Therefore, drifting snow sublimation near surface can't be neglected.

scholarly journals The significance of vertical moisture diffusion on drifting snow sublimation near snow surface

2017 ◽  
Vol 11 (6) ◽  
pp. 3011-3021 ◽  
Author(s):  
Ning Huang ◽  
Guanglei Shi
Keyword(s):  
Ice Sheets ◽  
Moisture Diffusion ◽  
Blowing Snow ◽  
Polar Ice ◽  
Sublimation Rate ◽  
Near Surface ◽  
Drifting Snow ◽  
Polar Ice Sheets ◽  
Snow Model ◽  
Semi Arid

Abstract. Sublimation of blowing snow is an important parameter not only for the study of polar ice sheets and glaciers, but also for maintaining the ecology of arid and semi-arid lands. However, sublimation of near-surface blowing snow has often been ignored in previous studies. To study sublimation of near-surface blowing snow, we established a sublimation of blowing snow model containing both a vertical moisture diffusion equation and a heat balance equation. The results showed that although sublimation of near-surface blowing snow was strongly reduced by a negative feedback effect, due to vertical moisture diffusion, the relative humidity near the surface does not reach 100  %. Therefore, the sublimation of near-surface blowing snow does not stop. In addition, the sublimation rate near the surface is 3–4 orders of magnitude higher than that at 10 m above the surface and the mass of snow sublimation near the surface accounts for more than half of the total snow sublimation when the friction wind velocity is less than about 0.55 m s−1. Therefore, the sublimation of near-surface blowing snow should not be neglected.

Evolution in geometry of firn in ice sheets detected by dielectric anisotropy

2020 ◽  
Author(s):  
Shuji Fujita ◽  
Kotaro Fukui ◽  
Motohiro Hirabayashi ◽  
Yoshinori Iizuka ◽  
Sumito Matoba ◽  
...  
Keyword(s):  
Residence Time ◽  
Ice Core ◽  
Ice Sheets ◽  
Vertical Movement ◽  
Dielectric Anisotropy ◽  
Anisotropic Structure ◽  
Physical Processes ◽  
Polar Ice ◽  
Near Surface ◽  
Polar Ice Sheets

<p>Ice in polar ice sheets once experience a state of firn at near-surface depths. Therefore, it is important to understand physical processes of firn formation, metamorphism and deformation for ice core studies. We investigated firn through measurement of tensorial values of the dielectric permittivity at microwave and millimeter-wave frequencies. This method can detect presence and strength of anisotropic structure in the geometry of pore spaces and ice matrix. We applied the method to many firn cores drilled at both ice sheets. We find that firn that have shorter residence time at the near-surface depths does not form strong vertical anisotropy that is caused by vertical movement of moistures. In contrast, firn that have longer residence time at the near-surface depths tend to form vertical anisotropy. When density exceeds  ~600 kg/m<sup>3</sup>, a common feature of firn at many polar sites is that there are evolution of vertically elongated features of pore spaces in firn despite growth of vertical compression. We hypothesize an explanation as follows. As firn becomes denser, air within firn needs escape paths to upward directions as compared to sinking firn. In firn, porous structure tend to have vertically elongated structure because of this vertical escape movement of air. The observed phenomena of the grow th of the vertical dielectric anisotropy<br>can be understood by this vertical movement of the air w ithin firn.</p>

Shallow-Layers-Detection Ice Sounding Radar for Mapping of Polar Ice Sheets

2021 ◽  
pp. 1-10
Author(s):  
Bo Zhao ◽  
Yueyi Zhang ◽  
Shinan Lang ◽  
Yan Liu ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Polar Ice ◽  
Polar Ice Sheets

scholarly journals The response of fabric variations to simple shear and migration recrystallization

2015 ◽  
Vol 61 (227) ◽  
pp. 537-550 ◽  
Author(s):  
Joseph H. Kennedy ◽  
Erin C. Pettit
Keyword(s):  
Thermal Activation ◽  
Nearest Neighbor ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Polar Ice ◽  
Climatic Variations ◽  
Fabric Evolution ◽  
Polar Ice Sheets ◽  
Low Levels ◽  
And Migration

AbstractThe observable microstructures in ice are the result of many dynamic and competing processes. These processes are influenced by climate variables in the firn. Layers deposited in different climate regimes may show variations in fabric which can persist deep into the ice sheet; fabric may ‘remember’ these past climate regimes. We model the evolution of fabric variations below the firn–ice transition and show that the addition of shear to compressive-stress regimes preserves the modeled fabric variations longer than compression-only regimes, because shear drives a positive feedback between crystal rotation and deformation. Even without shear, the modeled ice retains memory of the fabric variation for 200 ka in typical polar ice-sheet conditions. Our model shows that temperature affects how long the fabric variation is preserved, but only affects the strain-integrated fabric evolution profile when comparing results straddling the thermal-activation-energy threshold (∼−10°C). Even at high temperatures, migration recrystallization does not eliminate the modeled fabric’s memory under most conditions. High levels of nearest-neighbor interactions will, however, eliminate the modeled fabric’s memory more quickly than low levels of nearest-neighbor interactions. Ultimately, our model predicts that fabrics will retain memory of past climatic variations when subject to a wide variety of conditions found in polar ice sheets.

New Space Observation of the Global Cryosphere

2021 ◽  
Author(s):  
Zhitong Yu ◽  
Luojia Hu ◽  
Yan Huang ◽  
Rong Ma ◽  
Peng Xiao ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Rapid Change ◽  
Ice Sheets ◽  
Dynamic Monitoring ◽  
Observation System ◽  
Polar Ice ◽  
Polar Ice Sheets ◽  
New Space ◽  
Wide Swath

<p>Quantifying changes in Earth’s ice sheets and identifying the climate drivers are central to improving sea level projections. But it is a pity that the future sea level is difficult to predicted. Space observation can provide global multiscale long-term continuous monitoring data. And it is very important for understanding intrinsic mechanisms, improve models and projections and analyze the impacts on human civilization.</p><p>Several satellites are applied for Global Cryosphere Watch, including sea ice extent and concentration, ice sheet elevation, glacier area and velocity. Although there are many variable can be measured by satellite sensors. But several variables need to improve the observing capability and developing new methods. Such as snow depth on ice, ice sheets thickness, and permafrost parameters. China has established high-resolution earth observation system to realize stereopsis and dynamic monitoring of the lands, the oceans and the atmosphere.</p><p>Currently, Qian Xuesen Laboratory working together with Sun Yat-sen University, is trying to design a new space observation system to support Three Poles Environment and Climate Changes project. We are conceptualizing two series satellites including FluxSats and BingSats for carbon/water cycle and cryosphere observations, respectively. To clarify the mechanism of the cryosphere carbon release and carbon sink effects of the oceans and ecosystems. We are developing a new lidar system for detecting the concentration and wind speed, and then atmospheric boundary layer flux exchange can be estimated. To understand the rapid change of the sea ice, such as drift, fragmentation and freeze. We need a short revisit and wide swath system capabilities. InSAR technology gives the digitial elevation of the ice surface. And temporal difference InSAR (DInSAR) shows the changes of elevation. BingSAT-Tomographic Observation of Polar Ice Sheets (TOPIS) achieves the tomographic observation of polar ice sheets with a wide swath and short revisit time. Over the polar regions, the CubeSats form a large cross-track baseline with the master satellite to realize the high two-dimensional spatial resolution with the along-track synthetic aperture. The MirrorSAR technology is utilized in BingSat-TOPIS to achieve time and phase synchronization more economically than the traditional bistatic radar. Sparse array and digital beamforming are also considered to significantly reduce the number of microsatellites, and achieve tomographic images of polar ice sheets.</p>

Modeling the Interconnectivity of Non-stationary Polar Ice Sheets

2021 ◽  
Author(s):  
Luke Jackson ◽  
Katarina Juselius ◽  
Andrew Martinez ◽  
Felix Pretis
Keyword(s):  
Ice Sheets ◽  
Polar Ice ◽  
Polar Ice Sheets

scholarly journals Layer echoes in polar ice sheets

1975 ◽  
Vol 15 (73) ◽  
pp. 95-101 ◽  
Author(s):  
Gudmandsen Preben
Keyword(s):  
Stable Isotope ◽  
Ice Sheets ◽  
Polar Ice ◽  
Last Glaciation ◽  
Polar Ice Sheets ◽  
Isotope Profile

AbstractA multitude of extensive layers have been observed by radio-echo soundings in Greenland. By comparison with the stable isotope profile from Camp Century it is found that layering in the lop of the ice has been formed in the period since the last glaciation. Radio-echo layers observed at greater depths in central Greenland may have been created in the period of the interstadials and further down possibly in the period prior to the last glaciation. Further investigations are needed to prove this.

scholarly journals Layer echoes in polar ice sheets

1975 ◽  
Vol 15 (73) ◽  
pp. 95-101 ◽  
Author(s):  
Gudmandsen Preben
Keyword(s):  
Stable Isotope ◽  
Ice Sheets ◽  
Polar Ice ◽  
Last Glaciation ◽  
Polar Ice Sheets ◽  
Isotope Profile

AbstractA multitude of extensive layers have been observed by radio-echo soundings in Greenland. By comparison with the stable isotope profile from Camp Century it is found that layering in the lop of the ice has been formed in the period since the last glaciation. Radio-echo layers observed at greater depths in central Greenland may have been created in the period of the interstadials and further down possibly in the period prior to the last glaciation. Further investigations are needed to prove this.

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