scholarly journals The Gregoriev Ice Cap length changes derived by 2-D ice flow line model for harmonic climate histories

2009 ◽  
Vol 1 (1) ◽  
pp. 55-91
Author(s):  
Y. V. Konovalov ◽  
O. V. Nagornov
Keyword(s):  
Numerical Solution ◽  
Air Temperature ◽  
Equilibrium Equation ◽  
Flow Line ◽  
Mechanical Equilibrium ◽  
Surface Mass ◽  
Ice Cap ◽  
Ice Surface ◽  
Glacier Length ◽  
Length Changes

Abstract. Different ice thickness distributions along the flow line and the flow line length changes of the Gregoriev Ice Cap, Terskey Ala-Tau, Central Asia, were obtained for some surface mass balance histories which can be considered as possible surface mass balances in the future. The ice cap modeling was performed by solving of steady state hydrodynamic equations in the case of low Reynolds number in the form of the mechanical equilibrium equation in terms of stress deviator components coupled with the continuity equation for incompressible fluid. The numerical solution was obtained by the finite difference method. A compound approximation of the ice surface boundary condition based on the extending of the mechanical equilibrium equation to ice surface points was applied. The approximation is considered as a way to overcome the problem of diagnostic equations numerical solution stability in the full model. The basal sliding can arise in the glacier tongue at certain climatic conditions and was introduced both through linear and through non-linear friction laws. A possible glacier length history, that corresponds to the regional climate changes derived from the tree-rings data, was obtained by the model. The correlations between the glacier length changes and annual air temperature histories were investigated within the simplified equation introduced by J. Oerlemans in the form of linear dependence of annual air temperature versus glacier length and time derivative of the length. The parameters of the dependence were derived from modeled glacier length histories that correspond to harmonic climate histories. The parameters variations were investigated for different periodicities of harmonic climate histories and appropriate dependences are presented in the paper. The results of the modeling are in a good agreement with the J. Oerlemans climatic model.

scholarly journals The Gregoriev Ice Cap evolution according to the 2-D ice flowline model for various climatic scenarios in the future

2009 ◽  
Vol 3 (1) ◽  
pp. 77-115
Author(s):  
Y. V. Konovalov ◽  
O. V. Nagornov
Keyword(s):  
Air Temperature ◽  
Equilibrium Equation ◽  
Mechanical Equilibrium ◽  
Surface Mass ◽  
Prognostic Equation ◽  
Ice Cap ◽  
Ice Surface ◽  
The Future ◽  
Glacier Length ◽  
Length Changes

Abstract. Different flowline thickness distributions and flowline length changes of the Gregoriev Ice Cap were obtained for some surface mass balance histories which can be considered as possible surface mass balances in the future. The ice cap modeling was performed by solving full Stokes equations in the form of one mechanical equilibrium equation in terms of stress deviator components in couple with continuity equation for incompressible substance. The numerical solution was obtained by the finite-difference method. The problem of diagnostic equations stability was overcome by a~compound approximation of the ice surface boundary condition based on the extending of the mechanical equilibrium equation to ice surface points. The problem of stability in the prognostic equation can arise at relatively small grid size in horizontal direction in the case of steep velocity decreasing closely to the ice front and was overcome by introducing the artificial viscosity into the prognostic equation. The basal sliding can arise in the glacier tongue at certain climatic conditions and was introduced through the linear friction law. The correlations between glacier length changes and annual air temperature histories were investigated within the simplified equation in the form of linear dependence of annual air temperature versus the glacier length and time derivation of the length.

scholarly journals Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap

2017 ◽  
Vol 8 (2) ◽  
pp. 283-294
Author(s):  
Yuri V. Konovalov ◽  
Oleg V. Nagornov
Keyword(s):  
Mass Balance ◽  
Flow Line ◽  
Surface Mass Balance ◽  
Ice Streams ◽  
Surface Mass ◽  
Ice Cap ◽  
Ice Surface ◽  
Ice Surface Temperature ◽  
Severnaya Zemlya ◽  
Academy Of Sciences

Abstract. Prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap on Komsomolets Island, Severnaya Zemlya archipelago, were undertaken in this study. The experiments were based on inversions of basal friction coefficients using a two-dimensional flow-line thermocoupled model and Tikhonov's regularization method. The modeled ice temperature distributions in the cross sections were obtained using ice surface temperature histories that were inverted previously from borehole temperature profiles derived at the summit of the Academy of Sciences Ice Cap and the elevational gradient of ice surface temperature changes (about 6.5 °C km−1). Input data included interferometric synthetic aperture radar (InSAR) ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements, while the surface mass balance was adopted from previous investigations for the implementation of both the forward and inverse problems. The prognostic experiments revealed that both ice mass and ice stream extent declined for the reference time-independent surface mass balance. Specifically, the grounding line retreated: (a) along the B–B′ flow line from  ∼  40 to  ∼  30 km (the distance from the summit), (b) along the C–C′ flow line from  ∼  43 to  ∼  37 km, and (c) along the D–D′ flow line from  ∼  41 to  ∼  32 km, when considering a time period of 500 years and assuming a time-independent surface mass balance. Ice flow velocities in the ice streams decreased with time and this trend resulted in the overall decline of the outgoing ice flux. Generally, the modeled glacial evolution was in agreement with observations of deglaciation of the Severnaya Zemlya archipelago.

scholarly journals Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap: future modeled histories obtained for the reference surface mass balance

2015 ◽  
Vol 6 (2) ◽  
pp. 2211-2242 ◽  
Author(s):  
Y. V. Konovalov ◽  
O. V. Nagornov
Keyword(s):  
Mass Balance ◽  
Flow Line ◽  
The Arctic ◽  
Surface Mass Balance ◽  
Two Dimensional ◽  
Ice Streams ◽  
Surface Mass ◽  
Ice Cap ◽  
Ice Surface ◽  
Academy Of Sciences

Abstract. The prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago, are implemented in this study. These experiments are based on inversions of basal friction coefficients using a two-dimensional flow-line thermo-coupled model and the Tikhonov's regularization method. The modeled ice temperature distributions in the cross-sections were obtained using the ice surface temperature histories that were inverted previously from the borehole temperature profiles derived at the Academy of Sciences Ice Cap. Input data included InSAR ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements and the surface mass balance, were adopted from the prior investigations for the implementation of both the forward and inverse problems. The prognostic experiments reveal that both ice mass and ice stream extents decline for the reference time-independent surface mass balance. Specifically, the grounding line retreats (a) along the B–B' flow line from ~ 40 to ~ 30 km (the distance from the summit), (b) along the C–C' flow line from ~ 43 to ~ 37 km, and (c) along the D–D' flow line from ~ 41 to ~ 32 km considering a time period of 500 years and assuming time-independent surface mass balance. Ice flow velocities in the ice streams decrease with time and this trend results in the overall decline of the outgoing ice flux. Generally, the modeled histories are in agreement with observations of sea ice extent and thickness indicating a continual ice decline in the Arctic.

The formation of new glacial lakes at the Jostedalsbreen ice cap in southwest Norway and their future implications

2020 ◽  
Author(s):  
Katja Laute ◽  
Achim A. Beylich
Keyword(s):  
Current Trend ◽  
Glacial Lake ◽  
Glacier Area ◽  
Glacial Lakes ◽  
Economic Implications ◽  
Ice Cap ◽  
Western Norway ◽  
Outburst Floods ◽  
Glacier Length ◽  
Length Changes

<p>In recent years, the number and size of glacial lakes in mountain regions have increased worldwide associated to the climate-induced glacier retreat and thinning. Glacial lakes can cause glacial lake outburst floods (GLOFs) which can pose a significant natural hazard in mountainous areas and can cause loss of human life as well as damage to infrastructure and property.</p><p>The glacial landscape of the Jostedalsbreen ice cap in south-western Norway is currently undergoing significant changes reflected by progressing glacier length changes of the outlet glaciers and the formation of new glacial lakes within the recently exposed glacier forefields. We present a new glacier area outline for the entire Jostedalsbreen ice cap and the first detailed inventory of glacial lakes which were formed within the newly exposed ice-free area at the Jostedalsbreen ice cap. In detail, we explore (i) the glacial lake characteristics and types and (ii) analyse their spatial distribution and hazard potential.</p><p>For the period from 1952-1985 to 2017/2018 the entire glacier area of the Jostdalsbreen ice cap experienced a loss of 79 km<sup>2</sup>. A glacier area reduction of 10 km<sup>2</sup> occurred since 1999-2006. Two percent of the recently exposed surface area (since 1952-1985) is currently covered with newly developed glacial lakes corresponding to a total number of 57 lakes. In addition, eleven lakes that already existed have enlarged in size. Four types of glacial lakes are identified including bedrock-dammed, bedrock- and moraine-dammed, moraine-dammed and ice-dammed lakes. Especially ice- or moraine-dammed glacial lakes can be the source of potentially catastrophic glacier lake outburst floods. According to the inventory of glacier-related hazardous events in Norway GLOFs represent the most common hazardous events besides ice avalanches and incidents related to glacier length changes. Around the Jostedalsbreen ice cap several historical but also recent events are documented. The majority of the events caused partly severe damage to farmland and infrastructure but fortunately no people have been harmed by today.</p><p>Due to the predicted increase in summer temperatures for western Norway until the end of this century, it is very likely that the current trend of an accelerated mass loss of Norwegian glaciers will continue. As one consequence of this development, further new lakes will emerge within the newly exposed terrain. The development of new glacial lakes has diverse regional and global socio-economic implications. Especially in mainland Norway, where glaciers and glacier-fed streams have a high importance for hydropower production, tourism and climate research it is essential to gain a better understanding of the possible impacts of glacial lakes for being prepared for risks but also advantages arising from these newly emerging landscape elements.</p>

scholarly journals Dynamics of the ice cap on King George Island, Antarctica: field measurements and numerical simulations

2010 ◽  
Vol 51 (55) ◽  
pp. 80-90 ◽  
Author(s):  
Martin Rückamp ◽  
Norbert Blindow ◽  
Sonja Suckro ◽  
Matthias Braun ◽  
Angelika Humbert
Keyword(s):  
Air Temperature ◽  
Water Layer ◽  
Climatic Conditions ◽  
King George Island ◽  
Differential Gps ◽  
Ice Flow ◽  
Climate Conditions ◽  
Ice Cap ◽  
Ice Surface ◽  
Mean Annual Air Temperature

AbstractKing George Island is located at the northern tip of the Antarctic Peninsula, which is influenced by maritime climate conditions. The observed mean annual air temperature at sea level is –2.4˚C. Thus, the ice cap is regarded as sensitive to changing climatic conditions. Ground-penetrating radar surveys indicate a partly temperate ice cap with an extended water layer at the firn/ice transition of the up to 700 m high ice cap. Measured firn temperatures are close to 0˚C at the higher elevations, and they differ considerably from the measured mean annual air temperature. The aim of this paper is to present ice-flow dynamics by means of observations and simulations of the flow velocities. During several field campaigns from 1997/98 to 2008/09, ice surface velocities were derived with repeated differential GPS measurements. Ice velocities vary from 0.7 m a−1 at the dome to 112.1 m a−1 along steep slopes. For the western part of the ice cap a three-dimensional diagnostic full-Stokes model was applied to calculate ice flow. Parameters of the numerical model were identified with respect to measured ice surface velocities. The simulations indicate cold ice at higher elevations, while temperate ice at lower elevations is consistent with the observations.

scholarly journals Response of the ice cap Hardangerjøkulen in southern Norway to the 20th and 21st century climates

2009 ◽  
Vol 3 (3) ◽  
pp. 947-993 ◽  
Author(s):  
R. H. Giesen ◽  
J. Oerlemans
Keyword(s):  
Mass Balance ◽  
21St Century ◽  
Meteorological Data ◽  
Coupled Model ◽  
Ice Dynamics ◽  
Change Models ◽  
Ice Cap ◽  
Glacier Length ◽  
Length Changes ◽  
Southern Norway

Abstract. Glacier mass balance changes lead to geometry changes and vice versa. To include this interdependence in the response of glaciers to climate change, models should include an interactive scheme coupling mass balance and ice dynamics. In this study, we couple a spatially distributed mass balance model to a two-dimensional ice-flow model and apply this coupled model to the ice cap Hardangerjøkulen in southern Norway. The available glacio-meteorological records, mass balance and glacier length change measurements were utilized for model calibration and validation. Driven with meteorological data from nearby synoptic weather stations, the coupled model realistically simulated the observed mass balance and glacier length changes during the 20th century. The mean climate for the period 1961–1990, computed from local meteorological data, was used as a basis to prescribe climate projections for the 21st century at Hardangerjøkulen. For a projected temperature increase of 3°C from 1961–1990 to 2071–2100, the modelled net mass balance soon becomes negative at all altitudes and Hardangerjøkulen disappears around the year 2100. The projected changes in the other meteorological variables could at most partly compensate for the effect of the projected warming.

scholarly journals Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

2017 ◽  
Vol 11 (1) ◽  
pp. 281-302 ◽  
Author(s):  
Henning Åkesson ◽  
Kerim H. Nisancioglu ◽  
Rianne H. Giesen ◽  
Mathieu Morlighem
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
Ice Age ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Surface Mass ◽  
Ice Caps ◽  
Ice Cap ◽  
Length Changes

Abstract. Understanding of long-term dynamics of glaciers and ice caps is vital to assess their recent and future changes, yet few long-term reconstructions using ice flow models exist. Here we present simulations of the maritime Hardangerjøkulen ice cap in Norway from the mid-Holocene through the Little Ice Age (LIA) to the present day, using a numerical ice flow model combined with glacier and climate reconstructions. In our simulation, under a linear climate forcing, we find that Hardangerjøkulen grows from ice-free conditions in the mid-Holocene to its maximum extent during the LIA in a nonlinear, spatially asynchronous fashion. During its fastest stage of growth (2300–1300 BP), the ice cap triples its volume in less than 1000 years. The modeled ice cap extent and outlet glacier length changes from the LIA until today agree well with available observations. Volume and area for Hardangerjøkulen and several of its outlet glaciers vary out-of-phase for several centuries during the Holocene. This volume–area disequilibrium varies in time and from one outlet glacier to the next, illustrating that linear relations between ice extent, volume and glacier proxy records, as generally used in paleoclimatic reconstructions, have only limited validity. We also show that the present-day ice cap is highly sensitive to surface mass balance changes and that the effect of the ice cap hypsometry on the mass balance–altitude feedback is essential to this sensitivity. A mass balance shift by +0.5 m w.e. relative to the mass balance from the last decades almost doubles ice volume, while a decrease of 0.2 m w.e. or more induces a strong mass balance–altitude feedback and makes Hardangerjøkulen disappear entirely. Furthermore, once disappeared, an additional +0.1 m w.e. relative to the present mass balance is needed to regrow the ice cap to its present-day extent. We expect that other ice caps with comparable geometry in, for example, Norway, Iceland, Patagonia and peripheral Greenland may behave similarly, making them particularly vulnerable to climate change.

scholarly journals Response of the ice cap Hardangerjøkulen in southern Norway to the 20th and 21st century climates

2010 ◽  
Vol 4 (2) ◽  
pp. 191-213 ◽  
Author(s):  
R. H. Giesen ◽  
J. Oerlemans
Keyword(s):  
Mass Balance ◽  
21St Century ◽  
Meteorological Data ◽  
Coupled Model ◽  
Ice Dynamics ◽  
Linear Temperature ◽  
Ice Cap ◽  
Glacier Length ◽  
Length Changes ◽  
Southern Norway

Abstract. Glaciers respond to mass balance changes by adjusting their surface elevation and area. These properties in their turn affect the local and area-averaged mass balance. To incorporate this interdependence in the response of glaciers to climate change, models should include an interactive scheme coupling mass balance and ice dynamics. In this study, a spatially distributed mass balance model, comprising surface energy balance calculations, was coupled to a vertically integrated ice-flow model based on the shallow ice approximation. The coupled model was applied to the ice cap Hardangerjøkulen in southern Norway. The available glacio-meteorological records, mass balance and glacier length change measurements were utilized for model calibration and validation. Forced with meteorological data from nearby synoptic weather stations, the coupled model realistically simulated the observed mass balance and glacier length changes during the 20th century. The mean climate for the period 1961–1990, computed from local meteorological data, was used as a basis to prescribe climate projections for the 21st century at Hardangerjøkulen. For a linear temperature increase of 3 °C from 1961–1990 to 2071–2100, the modelled net mass balance soon becomes negative at all altitudes and Hardangerjøkulen disappears around the year 2100. The projected changes in the other meteorological variables could at most partly compensate for the effect of the projected warming.

scholarly journals Effects of surface roughness and light-absorbing impurities on glacier surface albedo, August-one ice cap, Qilian Mountains, China

2020 ◽  
Author(s):  
Junfeng Liu ◽  
Rensheng Chen ◽  
Yongjian Ding ◽  
Chuntan Han ◽  
Yong Yang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Large Scale ◽  
Surface Albedo ◽  
Flow Line ◽  
Glacier Surface ◽  
Negative Power ◽  
Mountain Glaciers ◽  
Ice Cap ◽  
Ice Surface ◽  
Exciting Potential

Abstract. Surface albedo is the main influence on surface melt for Qilian mountain glaciers. Fluctuations in surface albedo are due primarily to variations in micro scale surface roughness (ξ) and light-absorbing impurities (LAIs) in this region. However, combined ξ and LAIs effects over glacier surface albedo are rarely studied and surface roughness rarely considered in the albedo parameterization methods in this region. The present study was conducted in tandem with an intensive photogrammetric survey of glacier surface roughness, LAIs samples and albedo observations along the main flow-line of August-one ice cap during the 2018 melt season. Automatic photogrammetry of surface roughness and automatic observation of glacier surface albedo was conducted at middle of the ice cap in 2018. Detailed analysis indicates a negative power function and positive linear relationship exist between ξ and albedo for snow and ice surface, respectively. ξ could explain 68% of snow surface albedo and 38 % of ice surface albedo variation in melt season. Effective LAIs concentration (Cξ) calculated by consider ξ effect over LAIs deposition account for more than 63 % of albedo variation at ice surface. Using either ξ or Cξ to estimate ice surface albedo would be a great improvement over some current parameterization methods, such as assuming a constant mean ice surface albedo. A finer resolution of above 50 mm and above 100 mm is recommended for ice and snow ξ calculations, which explain more albedo variation than coarse resolutions below it. With advances in topographic surveys to improve the resolution, extent and availability of topographic datasets and surface roughness, appropriate parameterizations of albedo based on ξ have exciting potential to be applied over large scale snow cover and glacier.

scholarly journals Simulating asymmetric growth and retreat of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene

2016 ◽  
Author(s):  
Henning Åkesson ◽  
Kerim H. Nisancioglu ◽  
Rianne H. Giesen ◽  
Mathieu Morlighem
Keyword(s):  
Mass Balance ◽  
Ice Age ◽  
Dynamical Response ◽  
Surface Mass Balance ◽  
Outlet Glacier ◽  
Surface Mass ◽  
Ice Caps ◽  
Ice Cap ◽  
Length Changes ◽  
Southern Norway

Abstract. Changes to the volume of glaciers and ice caps currently amount to half of the total cryospheric contribution to sea-level rise and are projected to remain substantial throughout the 21st century. To simulate glacier behavior on centennial and longer time scales, models rely on simplified dynamics and tunable parameters for processes not well understood. Model calibration is often done using present-day observations, even though the relationship between parameters and parametrized processes may be altered for significantly different glacier states. In this study, we simulate the evolution of the Hardangerjøkulen ice cap in southern Norway from the mid-Holocene through the Little Ice Age (LIA) to the present-day. For both the calibration and transient experiments, we run an ensemble using a two-dimensional ice flow model with local mesh refinement. For the Holocene, we apply a simple surface mass balance forcing based on climate reconstructions. For the LIA until 1962, we use geomorphological evidence and measured outlet glacier positions to find a mass balance history, while from 1963 until today we use direct mass balance measurements. Given a linear climate forcing, we find that Hardangerjøkulen grew from ice-free conditions in the mid-Holocene, to its maximum LIA extent in a highly non-linear fashion. During the fastest stage of growth (2200-1200 BP), the ice cap tripled its ice volume over only 1000 years. We also reveal an intriguing spatial asymmetry during advance and retreat; the western ice cap and the northern outlet glacier Midtdalsbreen grow first and disappear first. In contrast, the eastern part, including the northeastern outlet glacier Blåisen, grows last and disappears last. Furthermore, volume and area of several outlet glaciers, as well as of the entire ice cap, vary out-of-phase for multiple centuries during the late Holocene, before varying in-phase approaching the LIA. We relate this to bed topography and the mass balance-altitude feedback, and challenge canonical linear assumptions between ice cap extent and glacier proxy records. Thus, we provide new insight into long-term dynamical response of ice caps to climate change, relevant for paleoglaciological studies and future predictions. Our model simulates ice cap extent and outlet glacier length changes from the LIA until today that are close to observations. We show that present-day Hardangerjøkulen is extremely sensitive to surface mass balance changes, mainly due to a strong mass balance-altitude feedback for the gently sloping surface topography of the ice cap.

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