scholarly journals Effect Of Inversion Winds On Topographic Detail And Mass Balance On Inland Ice Sheets

1975 ◽  
Vol 14 (70) ◽  
pp. 85-90 ◽  
Author(s):  
I.M. Whillans
Keyword(s):  
Mass Balance ◽  
Air Flow ◽  
Ice Sheets ◽  
Blowing Snow ◽  
Ice Flow ◽  
Surface Mass ◽  
Topographic Features ◽  
Snow Drift ◽  
And Inversion ◽  
Inland Ice

Steady-state gravity flow of air (inversion wind) on sloping snow-covered ice sheets is analyzed for sensitivity to local topography. Topographic features of the order of a few kilometres or less in length are too small to affect the direction and speed of this air flow. Air flow on a longer scale should however conform cosely to topography. Surface roughness on ice sheets is consistent with these results. Features of length shorter than a few kilometers (drifts and sastrugi) are transient, but longer features (surface undulations) remain essentially unaltered for many years. On the longer scale, inversion wind speed and therefore the amount of drifting and blowing snow should vary with the surface slope even where slope changes by as little as 1/10%. Observed variations in surface mass balance (aceumulated snow) in upper Marie Byrd Land, Antarctica, support this hypothesis. Snow drift and inversion winds thus constitute a feed-back mechanism on the form of ice sheets and some of the topographic detail, formerly attributed to ice-flow character alone, may be in large part due to this mechanism.

scholarly journals Effect Of Inversion Winds On Topographic Detail And Mass Balance On Inland Ice Sheets

1975 ◽  
Vol 14 (70) ◽  
pp. 85-90 ◽  
Author(s):  
I. M. Whillans
Keyword(s):  
Mass Balance ◽  
Air Flow ◽  
Ice Sheets ◽  
Blowing Snow ◽  
Ice Flow ◽  
Surface Mass ◽  
Topographic Features ◽  
Snow Drift ◽  
And Inversion ◽  
Inland Ice

Steady-state gravity flow of air (inversion wind) on sloping snow-covered ice sheets is analyzed for sensitivity to local topography. Topographic features of the order of a few kilometres or less in length are too small to affect the direction and speed of this air flow. Air flow on a longer scale should however conform cosely to topography. Surface roughness on ice sheets is consistent with these results. Features of length shorter than a few kilometers (drifts and sastrugi) are transient, but longer features (surface undulations) remain essentially unaltered for many years. On the longer scale, inversion wind speed and therefore the amount of drifting and blowing snow should vary with the surface slope even where slope changes by as little as 1/10%. Observed variations in surface mass balance (aceumulated snow) in upper Marie Byrd Land, Antarctica, support this hypothesis.Snow drift and inversion winds thus constitute a feed-back mechanism on the form of ice sheets and some of the topographic detail, formerly attributed to ice-flow character alone, may be in large part due to this mechanism.

scholarly journals Snow Drift

1977 ◽  
Vol 19 (81) ◽  
pp. 123-139 ◽  
Author(s):  
U. Adok
Keyword(s):  
Mass Balance ◽  
Ice Sheets ◽  
Turbulence Theory ◽  
Windward Side ◽  
Alternative Theory ◽  
Height Range ◽  
Surface Mass ◽  
Snow Drift ◽  
Polar Ice Sheets

AbstractWind-blown snow represents an age-old problem in the applied glaciology of most higher-latitude regions, but its physical intricacies first received attention in esoteric discussions on the long-term mass balance of polar ice sheets (Loewe, 1933, 1956). Measurements on the uniform unlimited surface of such ice sheets have shown good agreement, at least over a limited height range, with estimates for the concentration and flux of drift snow as a function of height and wind velocity based on turbulence theory. An alternative theory, developed concurrently from wind-tunnel results and field observations in Siberia, is discussed on the basis of its most recent exposition (Dyunin, 1974). Basic questions requiring further study include drift-snow concentrations at considerable heights, drift evaporation, and electrical phenomena. The main practical aspects of snow drift relate to the prevention of excess accumulation on roads, railway lines, and avalanche slopes; and to the encouragement of accumulation in fields and forests, and other locations where frost protection and/or storage of water is desired. The methods used are reviewed; they are beginning to rely on physical concepts and theories rather than solely on empirical formulae derived from engineering experiments.In regions of positive surface mass balance, buildings and other structures tend to become obliterated by snow drift. An important factor of this process is the fall-out of snow in the retarded flow on the windward side of the structure. Some recent attempts to measure and calculate that fall-out are discussed.

THE STUDIES OF SURFACE MASS BALANCE AND ICE FLOW ON GLACIERS AUSTRELOVéNBREEN AND PEDERSENBREEN, SVALBARD, ARCTIC

2010 ◽  
Vol 22 (1) ◽  
pp. 10-22 ◽  
Author(s):  
Mingxing Xu ◽  
Ming Yan ◽  
Jiawen Ren ◽  
Songtao Ai ◽  
Jiancheng Kang ◽  
...  
Keyword(s):  
Mass Balance ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass

Exploring the complex uncertainties in coupled climate-ice simulations of the Last Glacial Maximum

2021 ◽  
Author(s):  
Lauren Gregoire ◽  
Niall Gandy ◽  
Lachlan Astfalck ◽  
Robin Smith ◽  
Ruza Ivanovic ◽  
...  
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Sea Surface ◽  
Surface Mass ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Simulating the co-evolution of climate and ice-sheets during the Quaternary is key to understanding some of the major abrupt changes in climate, ice and sea level. Indeed, events such as the Meltwater pulse 1a rapid sea level rise and Heinrich, Dansgaard–Oeschger and the 8.2 kyr climatic events all involve the interplay between ice sheets, the atmosphere and the ocean. Unfortunately, it is challenging to simulate the coupled Climate-Ice sheet system because small biases, errors or uncertainties in parts of the models are strongly amplified by the powerful interactions between the atmosphere and ice (e.g. ice-albedo and height-mass balance feedbacks). This leads to inaccurate or even unrealistic simulations of ice sheet extent and surface climate. To overcome this issue we need some methods to effectively explore the uncertainty in the complex Climate-Ice sheet system and reduce model biases. Here we present our approach to produce ensemble of coupled Climate-Ice sheet simulations of the Last Glacial maximum that explore the uncertainties in climate and ice sheet processes.</p><p>We use the FAMOUS-ICE earth system model, which comprises a coarse-resolution and fast general circulation model coupled to the Glimmer-CISM ice sheet model. We prescribe sea surface temperature and sea ice concentrations in order to control and reduce biases in polar climate, which strongly affect the surface mass balance and simulated extent of the northern hemisphere ice sheets. We develop and apply a method to reconstruct and sample a range of realistic sea surface temperature and sea-ice concentration spatio-temporal field. These are created by merging information from PMIP3/4 climate simulations and proxy-data for sea surface temperatures at the Last Glacial Maximum with Bayes linear analysis. We then use these to generate ensembles of FAMOUS-ice simulations of the Last Glacial maximum following the PMIP4 protocol, with the Greenland and North American ice sheets interactively simulated. In addition to exploring a range of sea surface conditions, we also vary key parameters that control the surface mass balance and flow of ice sheets. We thus produce ensembles of simulations that will later be used to emulate ice sheet surface mass balance.  </p>

scholarly journals Temporally stable surface mass balance asymmetry across an ice rise derived from radar internal reflection horizons through inverse modeling

2016 ◽  
Vol 62 (233) ◽  
pp. 525-534 ◽  
Author(s):  
DENIS CALLENS ◽  
REINHARD DREWS ◽  
EMMANUEL WITRANT ◽  
MORGANE PHILIPPE ◽  
FRANK PATTYN
Keyword(s):  
Mass Balance ◽  
Large Scale ◽  
Optimization Technique ◽  
Internal Reflection ◽  
Asymmetric Distribution ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Atmospheric Flow ◽  
Surface Mass ◽  
Ice Shelves

ABSTRACTIce rises are locally grounded parts of Antarctic ice shelves that play an important role in regulating ice flow from the continent towards the ocean. Because they protrude out of the otherwise horizontal ice shelves, ice rises induce an orographic uplift of the atmospheric flow, resulting in an asymmetric distribution of the surface mass balance (SMB). Here, we combine younger and older internal reflection horizons (IRHs) from radar to quantify this distribution in time and space across Derwael Ice Rise (DIR), Dronning Maud Land, Antarctica. We employ two methods depending on the age of the IRHs, i.e. the shallow layer approximation for the younger IRHs near the surface and an optimization technique based on an ice flow model for the older IRHs. We identify an SMB ratio of 2.5 between the flanks and the ice divide with the SMB ranging between 300 and 750 kg m−2 a−1. The SMB maximum is located on the upwind side, ~4 km offset to today's topographic divide. The large-scale asymmetry is consistently observed in time until 1966. The SMB from older IRHs is less-well constrained, but the asymmetry has likely persisted for >ka, indicating that DIR has been a stable features over long time spans.

scholarly journals Basal Sliding Relations Deduced from Ice-Sheet Data

1984 ◽  
Vol 30 (105) ◽  
pp. 131-139 ◽  
Author(s):  
L. W. Morland ◽  
G. D. Smith ◽  
G. S. Boulton
Keyword(s):  
Boundary Condition ◽  
Mass Balance ◽  
Large Scale ◽  
Ice Sheet ◽  
Lower Boundary ◽  
Tangential Velocity ◽  
Greenland Ice Sheet ◽  
Overburden Pressure ◽  
Ice Flow ◽  
Surface Mass

AbstractThe sliding law is defined as a basal boundary condition for the large-scale bulk ice flow, relating the tangential tractionτb, overburden pressurepb, and tangential velocityubon a smoothed-out mean bed contour. This effective bed is a lower boundary viewed on the scale of the bulk ice flow and is not the physical ice/rock or sediment interface. The sliding relation reflects on the same scale the complex motion taking place in the neighbourhood of the physical interface. The isothermal steady-state ice-sheet analysis of Morland and Johnson (1980, 1982) is applied to known surface profiles from the Greenland ice sheet and Devon Island ice cap, with their corresponding mass-balance distributions, to determineτb,pb, andubfor each case. These basal estimates are used in turn to construct, using least-squares correlation, polynomial representations for an overburden dependenceλ(pb) in the adopted form of sliding lawτb═λ(pb)ub1/mwithm ≥1.The two different data sets determine functionsλ(pb) of very different magnitudes, reflecting very different basal conditions. A universal sliding law must therefore contain more general dependence on basal conditions, but the two relations determined appear to describe the two extremes. Hence use of both relations in turn to determine profiles compatible with given mass-balance distributions can be expected to yield extremes of the possible profiles, and further to show the sensitivity of profile form to variation of the sliding relation. The theory is designed as a basis for reconstruction of former ice sheets and their dynamics which are related to the two fundamental determinants of surface mass balance and basal boundary condition.

Impact of solar forcing on the surface mass balance of northern ice sheets for glacial conditions

2012 ◽  
Vol 335-336 ◽  
pp. 18-24 ◽  
Author(s):  
Marie-Noëlle Woillez ◽  
Gerhard Krinner ◽  
Masa Kageyama ◽  
Gilles Delaygue
Keyword(s):  
Mass Balance ◽  
Ice Sheets ◽  
Surface Mass Balance ◽  
Solar Forcing ◽  
Surface Mass

Trends and projections in ice sheet mass balance

2020 ◽  
Author(s):  
Andrew Shepherd ◽  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Sea Levels ◽  
Global Sea Level

<p>In recent decades, the Antarctic and Greenland Ice Sheets have been major contributors to global sea-level rise and are expected to be so in the future. Although increases in glacier flow and surface melting have been driven by oceanic and atmospheric warming, the degree and trajectory of today’s imbalance remain uncertain. Here we compare and combine 26 individual satellite records of changes in polar ice sheet volume, flow and gravitational potential to produce a reconciled estimate of their mass balance. <strong>Since the early 1990’s, ice losses from Antarctica and Greenland have caused global sea-levels to rise by 18.4 millimetres, on average, and there has been a sixfold increase in the volume of ice loss over time. Of this total, 41 % (7.6 millimetres) originates from Antarctica and 59 % (10.8 millimetres) is from Greenland. In this presentation, we compare our reconciled estimates of Antarctic and Greenland ice sheet mass change to IPCC projection of sea level rise to assess the model skill in predicting changes in ice dynamics and surface mass balance.  </strong>Cumulative ice losses from both ice sheets have been close to the IPCC’s predicted rates for their high-end climate warming scenario, which forecast an additional 170 millimetres of global sea-level rise by 2100 when compared to their central estimate.</p>

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