scholarly journals Could promontories have restricted sea-glacier penetration into marine embayments during Snowball Earth events?

2017 ◽  
Vol 11 (3) ◽  
pp. 1141-1148
Author(s):  
Adam J. Campbell ◽  
Betzalel Massarano ◽  
Edwin D. Waddington ◽  
Stephen G. Warren
Keyword(s):  
Flow Model ◽  
Narrow Range ◽  
Global Ocean ◽  
Snowball Earth ◽  
Ice Flow ◽  
Climate Conditions ◽  
Eukaryotic Algae ◽  
Extreme Cold ◽  
Glacier Flow

Abstract. During the Neoproterozoic (∼  1000–550 Ma), Earth experienced several climate excursions of extreme cold, often referred to as the Snowball Earth events. During these periods, thick flowing ice, referred to as sea glaciers, covered the entire planet's oceans. In addition, there is evidence that photosynthetic eukaryotic algae survived during these periods. With thick sea glaciers covering the oceans, it is uncertain where these organisms survived. One hypothesis is that these algae survived in marine embayments hydrologically connected to the global ocean, where the flow of sea glacier could be resisted. In order for an embayment to act as a refugium, the invading sea glacier must not completely penetrate the embayment. Recent studies have shown that straight-sided marine embayments could have prevented full sea-glacier penetration under a narrow range of climate conditions suitable for the Snowball Earth events. Here we test whether promontories, i.e., headlands emerging from a side shoreline, could further restrict sea-glacier flow. We use an ice-flow model, suitable for floating ice, to determine the flow of an invading sea glacier. We show that promontories can expand the range of climate conditions allowing refugia by resisting the flow of invading sea glaciers.

scholarly journals Could promontories have restricted sea-glacier penetration into marine embayments during Snow ball Earth events?

2016 ◽  
Author(s):  
Adam J. Campbell ◽  
Betzalel Massarano ◽  
Edwin D. Waddington ◽  
Stephen G. Warren
Keyword(s):  
Flow Model ◽  
Narrow Range ◽  
Global Ocean ◽  
Snowball Earth ◽  
Ice Flow ◽  
Climate Conditions ◽  
Eukaryotic Algae ◽  
Extreme Cold ◽  
Glacier Flow

Abstract. During the Neoproterozoic, Earth experienced several climate excursions of extreme cold, often referred to as the Snowball Earth events. During these periods, thick flowing ice, referred to as sea glaciers, covered the entire planet’s oceans. In addition, there is evidence that photosynthetic eukaryotic algae survived during these periods. With thick sea glaciers covering the oceans, it is uncertain where these organisms survived. One hypothesis is that these algae survived in marine embayments hydrologically connected to the global ocean, where the flow of sea glacier could be resisted. In order for an embayment to act as a refugium, the invading sea glacier must not completely penetrate the embayment. Recent studies have shown that straight-sided, marine embayments could have prevented full sea-glacier penetration under a narrow range of climate conditions suitable for the Snowball Earth events. Here we test whether promontories, i.e. headlands emerging from a side shoreline, could further restrict sea-glacier flow. We use an ice-flow model, suitable for floating ice, to determine the flow of an invading sea glacier. We show that promontories can expand the range of climate conditions allowing refugia by resisting the flow of invading sea glaciers.

Modelling the deformation and movement of an ice tunnel in Langjökull ice cap, Iceland

2020 ◽  
Author(s):  
Guðfinna Aðalgeirsdóttir
Keyword(s):  
Deformation Temperature ◽  
Flow Model ◽  
Tourist Attraction ◽  
Ice Flow ◽  
Model Simulations ◽  
Ice Cap ◽  
Tunnel Floor ◽  
Glacier Flow ◽  
Deformation Measurements ◽  
Tunnel Entrance

<p>In winter 2014-2015 a long tunnel was dug into the ice cap Langjökull at about 1260 m a.s.l., close to the ELA. The tunnel was opened for tourists in spring 2015 (https://intotheglacier.is/) and has since then become a popular tourist attraction.  Before the tunnel was opened in winter 2015 and in the subsequent two years measurements of the tunnel deformation, temperature and density along the tunnel has been measured.  The tunnel is both closing because of ice deformation and it deforms with the glacier flow, which causes the entrance into the ice tunnel to become gradually steeper.  We use a full-Stokes ice flow model to compute the evolution of the tunnel floor and the closure of the tunnel. The deformation measurements are used to constrain the ice viscosity and the floor measurements to validate the modeled glacier flow. The model simulations are then used to predict the movement of the tunnel in the coming few years, which is useful for the planning of the tunnel entrance renovations.</p>

scholarly journals Assessing Controls on Ice Dynamics at Crane Glacier, Antarctic Peninsula Using a Numerical Ice Flow Model

2021 ◽  
Author(s):  
Rainey Aberle
Keyword(s):  
Antarctic Peninsula ◽  
Flow Model ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Climate Conditions ◽  
Ice Shelves ◽  
Tidewater Glacier ◽  
Mass Discharge

The widespread retreat of glaciers and the collapse of ice shelves along the Antarctic Peninsula has been attributed to atmospheric and oceanic warming, which promotes mass loss. However, several glaciers on the eastern peninsula that were buttressed by the Larsen A and B ice shelves prior to collapse in 1995 and 2002, respectively, have been advancing in recent years. This asymmetric pattern of rapid retreat and long-term re-advance is similar to the tidewater glacier cycle, which can occur largely independent of climate forcing. Here, I use a width- and depth-integrated numerical ice flow model to investigate glacier response to ice shelf collapse and the influence of changing climate conditions at Crane Glacier, formerly a tributary of the Larsen B ice shelf, over the last ~10 years. Sensitivity tests to explore the influence of perturbations in surface mass balance and submarine melt (up to 10 m a-1) and fresh water impounded in crevasses (up to 10 m) on glacier dynamics reveal that by 2100, the modeled mass discharge ranges from 0.53-98 Gt a-1, with the most substantial changes due to surface melt-induced thinning. My findings suggest that the growth of a floating ice tongue can hinder enhanced flow, allowing the grounding zone to remain steady for many decades, analogous to the advancing stage of the tidewater glacier cycle. Additionally, former tributary glaciers can take several decades to geometrically adjust to ice shelf collapse at their terminal boundary while elevated glacier discharge persists.

scholarly journals A full-Stokes ice flow model for the vicinity of Dome Fuji, Antarctica, with induced anisotropy and fabric evolution

2009 ◽  
Vol 3 (1) ◽  
pp. 1-31 ◽  
Author(s):  
H. Seddik ◽  
R. Greve ◽  
T. Zwinger ◽  
L. Placidi
Keyword(s):  
Flow Model ◽  
Stokes Equations ◽  
Melting Rate ◽  
Induced Anisotropy ◽  
Geothermal Heat ◽  
Ice Flow ◽  
Climate Conditions ◽  
Anisotropic Flow ◽  
Drill Site ◽  
Basal Melting

Abstract. A three-dimensional, thermo-mechanically coupled ice flow model with induced aniso-tropy has been applied to a ~200×200 km domain around the Dome Fuji drill site, Antarctica. The model ("Elmer/Ice") is based on the open-source multi-physics package Elmer (http://www.csc.fi/elmer/) and solves the full-Stokes equations. Flow-induced anisotropy in ice is accounted for by an implementation of the Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor ("CAFFE model"). Steady-state simulations for present-day climate conditions are conducted. The main findings are: (i) the flow regime at Dome Fuji is a complex superposition of vertical compression, horizontal extension and bed-parallel shear; (ii) for a geothermal heat flux of 60 mW m−2 the basal temperature at Dome Fuji reaches the pressure melting point and the basal melting rate is ~1 mm a−1; (iii) the fabric shows a weak single maximum at Dome Fuji, which increases the age of the ice compared to an isotropic scenario; (iv) as a consequence of spatially variable basal melting conditions, and contrary to intuition, the basal age is smaller where the ice is thicker and larger where the ice is thinner. The latter result is of great relevance for the consideration of a future drill site in the area.

scholarly journals The response of Petermann Glacier, Greenland, to large calving events, and its future stability in the context of atmospheric and oceanic warming

2012 ◽  
Vol 58 (208) ◽  
pp. 229-239 ◽  
Author(s):  
F.M. Nick ◽  
A. Luckman ◽  
A. Vieli ◽  
C.J. Van Der Veen ◽  
D. Van As ◽  
...  
Keyword(s):  
Flow Model ◽  
Temperature Variability ◽  
Satellite Observations ◽  
Ice Flow ◽  
Mass Budget ◽  
Lateral Resistance ◽  
Speed Up ◽  
Resistive Forces ◽  
Glacier Flow ◽  
The Impact

AbstractThis study assesses the impact of a large 2010 calving event on the current and future stability of Petermann Glacier, Greenland, and ascertains the glacier’s interaction with different components of the climate and ocean system. We use a numerical ice-flow model that captures the major aspects of the glacier’s mass budget, the resistive forces controlling glacier flow, and includes dynamic calving. Satellite observations and model results show that the recent break-off of 25% of the floating tongue did not result in a significant glacier speed-up due to the low lateral resistance of this relatively wide and thin ice tongue. We demonstrate that seasonal speed-up at Petermann Glacier is mainly driven by meltwater lubrication rather than freeze-up conditions in the fjord. Results also show that sub-shelf ocean melt may have a profound effect on the future stability of Petermann Glacier, emphasizing the urgent need for more observations, and a better understanding of fjord temperature variability and circulation.

scholarly journals A full Stokes ice flow model for the vicinity of Dome Fuji, Antarctica, with induced anisotropy and fabric evolution

2011 ◽  
Vol 5 (2) ◽  
pp. 495-508 ◽  
Author(s):  
H. Seddik ◽  
R. Greve ◽  
T. Zwinger ◽  
L. Placidi
Keyword(s):  
Flow Model ◽  
Stokes Equations ◽  
Melting Rate ◽  
Induced Anisotropy ◽  
Geothermal Heat ◽  
Ice Flow ◽  
Climate Conditions ◽  
Anisotropic Flow ◽  
Drill Site ◽  
Basal Melting

Abstract. A three-dimensional, thermo-mechanically coupled ice flow model with induced anisotropy has been applied to a ~200 × 200 km domain around the Dome Fuji drill site, Antarctica. The model ("Elmer/Ice") is based on the open-source multi-physics package Elmer (http://www.csc.fi/elmer/) and solves the full Stokes equations. Flow-induced anisotropy in ice is accounted for by an implementation of the Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor ("CAFFE model"). Steady-state simulations for present-day climate conditions are conducted. The main findings are: (i) the flow regime at Dome Fuji is a complex superposition of vertical compression, horizontal extension and bed-parallel shear; (ii) for an assumed geothermal heat flux of 60 mW m−2 the basal temperature at Dome Fuji reaches the pressure melting point and the basal melting rate is ~0.35 mm a−1; (iii) in agreement with observational data, the fabric shows a strong single maximum at Dome Fuji, and the age of the ice is decreased compared to an isotropic scenario; (iv) as a consequence of spatially variable basal melting conditions, the basal age tends to be smaller where the ice is thicker and larger where the ice is thinner. The latter result is of great relevance for the consideration of a future drill site in the area.

scholarly journals Dilation of subglacial sediment governs incipient surge motion in glaciers with deformable beds

2020 ◽  
Vol 476 (2238) ◽  
pp. 20200033 ◽  
Author(s):  
B. M. Minchew ◽  
C. R. Meyer
Keyword(s):  
Pore Water ◽  
Flow Model ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Slip Rate ◽  
Effective Pressure ◽  
Ice Flow ◽  
History Of ◽  
Glacier Surges ◽  
Geographical Clustering

Glacier surges are quasi-periodic episodes of rapid ice flow that arise from increases in slip rate at the ice–bed interface. The mechanisms that trigger and sustain surges are not well understood. Here, we develop a new model of incipient surge motion for glaciers underlain by sediments to explore how surges may arise from slip instabilities within a thin layer of saturated, deforming subglacial till. Our model represents the evolution of internal friction, porosity and pore water pressure within the till as functions of the rate and history of shear deformation, and couples the till mechanics to a simple ice-flow model. Changes in pore water pressure govern incipient surge motion, with less permeable till facilitating surging because dilation-driven reductions in pore water pressure slow the rate at which till tends towards a new steady state, thereby allowing time for the glacier to thin dynamically. The reduction of overburden (and thus effective) pressure at the bed caused by dynamic thinning of the glacier sustains surge acceleration in our model. The need for changes in both the hydromechanical properties of the till and the thickness of the glacier creates restrictive conditions for surge motion that are consistent with the rarity of surge-type glaciers and their geographical clustering.

scholarly journals Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

2015 ◽  
Vol 11 (10) ◽  
pp. 1395-1416 ◽  
Author(s):  
S. Fujita ◽  
F. Parrenin ◽  
M. Severi ◽  
H. Motoyama ◽  
E. W. Wolff
Keyword(s):  
Age Differences ◽  
Flow Model ◽  
Ice Cores ◽  
Ice Flow ◽  
Surface Mass ◽  
The Past ◽  
The One ◽  
Mis 5E ◽  
Age Constraints ◽  
Mis 5

Abstract. Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d–6. Therefore, we hypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d–6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, −230 years (minimum) at MIS 7a and +60 to +126 years on average.

scholarly journals At what depth is the Eemian layer expected to be found at NEEM?

2008 ◽  
Vol 48 ◽  
pp. 100-102 ◽  
Author(s):  
Susanne L. Buchardt ◽  
Dorthe Dahl-Jensen
Keyword(s):  
Flow Model ◽  
Accumulation Rate ◽  
Ice Core ◽  
Monte Carlo Analysis ◽  
Interglacial Period ◽  
Ice Flow ◽  
North West ◽  
Flow Parameters ◽  
Drill Site ◽  
Radio Echo Sounding

AbstractNo continuous record from Greenland of the Eemian interglacial period (130–115 ka BP) currently exists. However, a new ice-core drill site has been suggested at 77.449˚ N, 51.056˚Win north-west Greenland (North Eemian or NEEM). Radio-echo sounding images and flow model investigations indicate that an undisturbed Eemian record may be obtained at NEEM. In this work, a two-dimensional ice flow model with time-dependent accumulation rate and ice thickness is used to estimate the location of the Eemian layer at the new drill site. The model is used to simulate the ice flow along the ice ridge leading to the drill site. Unknown flow parameters are found through a Monte Carlo analysis of the flow model constrained by observed isochrones in the ice. The results indicate that the Eemian layer is approximately 60m thick and that its base is located approximately 100m above bedrock.

scholarly journals Sensitivity of Greenland Ice Sheet Projections to Model Formulations

2013 ◽  
Vol 59 (216) ◽  
pp. 733-749 ◽  
Author(s):  
H. Goelzer ◽  
P. Huybrechts ◽  
J.J. Fürst ◽  
F.M. Nick ◽  
M.L. Andersen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Sea Level ◽  
Flow Model ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Glacier Dynamics

AbstractPhysically based projections of the Greenland ice sheet contribution to future sea-level change are subject to uncertainties of the atmospheric and oceanic climatic forcing and to the formulations within the ice flow model itself. Here a higher-order, three-dimensional thermomechanical ice flow model is used, initialized to the present-day geometry. The forcing comes from a high-resolution regional climate model and from a flowline model applied to four individual marine-terminated glaciers, and results are subsequently extended to the entire ice sheet. The experiments span the next 200 years and consider climate scenario SRES A1B. The surface mass-balance (SMB) scheme is taken either from a regional climate model or from a positive-degree-day (PDD) model using temperature and precipitation anomalies from the underlying climate models. Our model results show that outlet glacier dynamics only account for 6–18% of the sea-level contribution after 200 years, confirming earlier findings that stress the dominant effect of SMB changes. Furthermore, interaction between SMB and ice discharge limits the importance of outlet glacier dynamics with increasing atmospheric forcing. Forcing from the regional climate model produces a 14–31 % higher sea-level contribution compared to a PDD model run with the same parameters as for IPCC AR4.

Sign in / Sign up

Export Citation Format

Share Document