scholarly journals Dynamics and mass balance of four large East Antarctic outlet glaciers

2011 ◽  
Vol 52 (59) ◽  
pp. 116-126 ◽  
Author(s):  
Leigh A. Stearns
Keyword(s):  
Remote Sensing ◽  
Mass Balance ◽  
Sea Level ◽  
Fresh Water ◽  
Ross Sea ◽  
Accumulation Rate ◽  
Accumulation Rates ◽  
Input Output ◽  
Ice Flow ◽  
Transantarctic Mountains

AbstractThe East Antarctic ice sheet (EAIS) is Earth’s largest reservoir of fresh water and has the potential to raise sea level by ~50 m. A significant amount of the ice sheet’s mass is discharged by outlet glaciers draining through the Transantarctic Mountains, the balance characteristics of which are largely unknown. Here the mass balance is estimated for four glaciers draining ice from the EAIS through the Transantarctic Mountains into the Ross Sea embayment: David, Mulock, Byrd and Nimrod glaciers. Remote-sensing observations are used to map changes in ice flow and surface elevation, and ultimately to compute the mass balance of each glacier using the input–output method and three separate estimates for accumulation rate. Results computed using this method indicate small positive balances for David (2.41±1.31 Gt a–1), Mulock (1.91±0.84 Gt a–1) and Nimrod (0.88±0.39 Gt a–1) glaciers, and a large positive imbalance for Byrd Glacier (21.67±4.04 Gt a–1). This large imbalance for Byrd Glacier is inconsistent with other observations, and is likely due to an overestimation of accumulation rates across large regions of the interior catchment.

scholarly journals A representative density profile of the North Greenland snowpack

2016 ◽  
Vol 10 (5) ◽  
pp. 1991-2002 ◽  
Author(s):  
Christoph Florian Schaller ◽  
Johannes Freitag ◽  
Sepp Kipfstuhl ◽  
Thomas Laepple ◽  
Hans Christian Steen-Larsen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Density Profile ◽  
Accumulation Rate ◽  
Sampling Technique ◽  
Data Sets ◽  
Accumulation Rates ◽  
The North ◽  
North Greenland ◽  
Good Agreement

Abstract. Along a traverse through North Greenland in May 2015 we collected snow cores up to 2 m depth and analyzed their density and water isotopic composition. A new sampling technique and an adapted algorithm for comparing data sets from different sites and aligning stratigraphic features are presented. We find good agreement of the density layering in the snowpack over hundreds of kilometers, which allows the construction of a representative density profile. The results are supported by an empirical statistical density model, which is used to generate sets of random profiles and validate the applied methods. Furthermore we are able to calculate annual accumulation rates, align melt layers and observe isotopic temperatures in the area back to 2010. Distinct relations of δ18O with both accumulation rate and density are deduced. Inter alia the depths of the 2012 melt layers and high-resolution densities are provided for applications in remote sensing.

The local Last Glacial Maximum in McMurdo Sound, Antarctica: Implications for ice-sheet behavior in the Ross Sea Embayment

2019 ◽  
Vol 132 (1-2) ◽  
pp. 31-47 ◽  
Author(s):  
Andrew J. Christ ◽  
Paul R. Bierman
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Significant Advance ◽  
Ice Flow ◽  
Mcmurdo Sound ◽  
Last Glacial ◽  
Transantarctic Mountains ◽  
Western Ross Sea

AbstractDuring the Last Glacial Maximum (LGM), a grounded ice sheet filled the Ross Sea Embayment in Antarctica and deposited glacial sediments on volcanic islands and peninsulas in McMurdo Sound and coastal regions of the Transantarctic Mountains. The flow geometry and retreat history of this ice are debated, with contrasting views yielding divergent implications for the interaction between and stability of the East and West Antarctic ice sheets during late Quaternary time. Here, we present terrestrial geomorphologic evidence and reconstruct former ice-marginal environments, ice sheet elevations, and ice-flow directions in McMurdo Sound. Fossil algae in ice-marginal sediments provide a coherent radiocarbon chronology of maximum ice extent and deglaciation. We integrate these data with marine records to reconstruct grounded ice dynamics in McMurdo Sound and the western Ross Sea. The combined data set suggests ice flow toward the Transantarctic Mountains in McMurdo Sound during peak glaciation, with thick, grounded ice at or near its maximum position between 19.6 and 12.3 ka. Persistent grounded ice in McMurdo Sound and across the western Ross Sea after Meltwater Pulse 1a (14.0–14.5 ka) suggests that this sector of Antarctica did not significantly contribute to this rapid sea-level rise event. Our data show no significant advance of locally derived ice from the Transantarctic Mountains into McMurdo Sound during the local LGM.

Implications of rapid sediment accumulation in a small New England salt marsh

1992 ◽  
Vol 29 (9) ◽  
pp. 2013-2017 ◽  
Author(s):  
R. Scott Anderson ◽  
H. W. Borns Jr. ◽  
D. C. Smith ◽  
C. Race
Keyword(s):  
Salt Marsh ◽  
New England ◽  
Sea Level ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Sediment Supply ◽  
Greenhouse Warming ◽  
Accumulation Rates ◽  
Marsh Sediment ◽  
England Salt Marsh

The sediment accumulation rate within a small Spartina alterniflora marsh in Maine has been determined by measuring the amount of peat accretion on top of human-produced boards protruding from an exposed face of the marsh. Boards are at depths of 50–140 cm, suggesting sediment accumulation rates of 6.2–7.0 mm/year. Based on these data and a review of other relevant studies, aggradation in small marshes such as Shipyard Cove should be able to keep pace marginally with the anticipated sea-level rise due to "greenhouse" warming, given sufficient sediment supply. Local 19th century land clearance and subsequent erosion, activities that are greatly reduced today, probably supplied the bulk of the inorganic marsh sediment.

scholarly journals Geometric changes and mass balance of the Austfonna ice cap, Svalbard

2010 ◽  
Vol 4 (1) ◽  
pp. 21-34 ◽  
Author(s):  
G. Moholdt ◽  
J. O. Hagen ◽  
T. Eiken ◽  
T. V. Schuler
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
Dynamic Equilibrium ◽  
Accumulation Rate ◽  
Laser Altimetry ◽  
Future Evolution ◽  
Annual Variations ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Elevation Changes

Abstract. The dynamics and mass balance regime of the Austfonna ice cap, the largest glacier on Svalbard, deviates significantly from most other glaciers in the region and is not fully understood. We have compared ICESat laser altimetry, airborne laser altimetry, GNSS surface profiles and radio echo-sounding data to estimate elevation change rates for the periods 1983–2007 and 2002–2008. The data sets indicate a pronounced interior thickening of up to 0.5 m y−1, at the same time as the margins are thinning at a rate of 1–3 m y−1. The southern basins are thickening at a higher rate than the northern basins due to a higher accumulation rate. The overall volume change in the 2002–2008 period is estimated to be −1.3±0.5 km3 w.e. y−1 (or −0.16±0.06 m w.e. y−1) where the entire net loss is due to a rapid retreat of the calving fronts. Since most of the marine ice loss occurs below sea level, Austfonna's current contribution to sea level change is close to zero. The geodetic results are compared to in-situ mass balance measurements which indicate that the 2004–2008 surface net mass balance has been slightly positive (0.05 m w.e. y−1) though with large annual variations. Similarities between local net mass balances and local elevation changes indicate that most of the ice cap is slow-moving and not in dynamic equilibrium with the current climate. More knowledge is needed about century-scale dynamic processes in order to predict the future evolution of Austfonna based on climate scenarios.

scholarly journals Regional Greenland accumulation variability from Operation IceBridge airborne accumulation radar

2017 ◽  
Vol 11 (2) ◽  
pp. 773-788 ◽  
Author(s):  
Gabriel Lewis ◽  
Erich Osterberg ◽  
Robert Hawley ◽  
Brian Whitmore ◽  
Hans Peter Marshall ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Drainage Basin ◽  
Function Analysis ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Accumulation Rates ◽  
Surface Mass

Abstract. The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge accumulation radar flights totaling  >  17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100–300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a−1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GrIS surface mass balance estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.

scholarly journals Large-Scale Numerical Modelling of the Antarctic Ice Sheet

1982 ◽  
Vol 3 ◽  
pp. 42-49 ◽  
Author(s):  
W.F. Budd ◽  
I.N. Smith
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Ice Thickness ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Flow Parameters ◽  
The Antarctic ◽  
Thinning Rate

A large-scale dynamic numerical model of the Antarctic ice sheet has been developed to study its present state of ice flow and mass balance as well as its response to long-term changes of climate or sea-level.The flow of ice over a two-dimensional grid is determined from the ice thickness, the basal shear stress, the bedrock depth, and ice flow parameters derived from velocities of existing ice sheets. The change in ice thickness with time is governed by the continuity equation involving the ice flux divergence and the ice accumulation or ablation. At the ice sheet seaward boundary, a floating criterion and floating ice thinning rate apply. Bedrock depression with a time-delayed response dependent on the history of the ice load is also included.A 61 × 61 point grid with 100 km spacing has been used to represent the ice-sheet surface, bedrock, and accumulation rate. The model has been used to simul a te the growth of the present ice sheet and i ts reaction to changes of sea-level, bedrock depression, accumulation rate, ice flow parameters, and the iceshelf thinning rate.Preliminary results suggest that the present ice sheet is not in equilibrium but rather is still adjusting to changes of these parameters.

Modelling ice rise englacial temperature profiles to constrain past ice-sheet dynamics

2020 ◽  
Author(s):  
Aleksandr Montelli ◽  
Jonathan Kingslake
Keyword(s):  
Heat Flux ◽  
Boundary Conditions ◽  
Ross Sea ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Thickness Change

<p>Present-day englacial temperatures are the product of the millennial-scale histories of ice flow and thermal boundary conditions experienced by an ice sheet. Vertical englacial temperature profiles extracted from boreholes drilled at ice divides record past ice dynamics and changing external forcings. Bindschadler (1990) estimated the timing of grounding of Crary Ice Rise, Ross Sea, by minimizing the mismatch between modelled and measured temperature profiles. This approach has huge potential if future boreholes are drilled at Antarctic ice rises in locations suspected of undergoing significant dynamics change. Yet, the uncertainties inherent in this approach must be carefully assessed to target and maximize the utility of borehole drilling. Here, using a 1D vertical heat flux model, we simulate the evolution of temperature as a function of depth in six locations with slow-flowing, cold-based ice in the Weddell and Ross Sea sectors of the West Antarctic Ice Sheet. The locations were chosen using output from the Parallel Ice Sheet Model (PISM) as which are most likely to have ungrounded and regrounded during the last deglaciation (i.e., through last 20 k.y.). We use the shallow ice approximation assuming horizontally isothermal ice and no basal sliding. Several parameters, accounting for timing and duration of grounding/ungrounding events, surface temperature evolution, accumulation rate, ice-thickness change, geothermal heat flux and vertical velocity, are varied to generate a range of different temperature profile outputs. Uncertainties associated with each parameter are then evaluated using a Monte-Carlo approach, yielding a statistical account of model sensitivity to key variables. We highlight that the precision needed to infer timing of grounding increases with the duration of grounded ice flow. Results presented here can help in choosing future ice drilling sites, and provide useful constraints on inferring past forcings and changing boundary conditions from in-situ temperature-depth measurements.</p>

scholarly journals TALDICE-1 age scale of the Talos Dome deep ice core, East Antarctica

2011 ◽  
Vol 7 (1) ◽  
pp. 1-16 ◽  
Author(s):  
D. Buiron ◽  
J. Chappellaz ◽  
B. Stenni ◽  
M. Frezzotti ◽  
M. Baumgartner ◽  
...  
Keyword(s):  
Inverse Method ◽  
Ross Sea ◽  
Accumulation Rate ◽  
A Priori ◽  
Ice Core ◽  
East Antarctica ◽  
Last Deglaciation ◽  
Ice Flow ◽  
Climate Record ◽  
The Last Deglaciation

Abstract. A new deep ice core drilling program, TALDICE, has been successfully handled by a European team at Talos Dome, in the Ross Sea sector of East Antarctica, down to 1620 m depth. Using stratigraphic markers and a new inverse method, we produce the first official chronology of the ice core, called TALDICE-1. We show that it notably improves an a priori chronology resulting from a one-dimensional ice flow model. It is in agreement with a posteriori controls of the resulting accumulation rate and thinning function along the core. An absolute uncertainty of only 300 yr is obtained over the course of the last deglaciation. This uncertainty remains lower than 600 yr over Marine Isotope Stage 3, back to 50 kyr BP. The phasing of the TALDICE ice core climate record with respect to the central East Antarctic plateau and Greenland records can thus be determined with a precision allowing for a discussion of the mechanisms at work at sub-millennial time scales.

scholarly journals Greenland ice sheet contribution to sea-level rise from a new-generation ice-sheet model

2012 ◽  
Vol 6 (6) ◽  
pp. 1561-1576 ◽  
Author(s):  
F. Gillet-Chaulet ◽  
O. Gagliardini ◽  
H. Seddik ◽  
M. Nodet ◽  
G. Durand ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass ◽  
Continental Scale ◽  
New Generation

Abstract. Over the last two decades, the Greenland ice sheet (GrIS) has been losing mass at an increasing rate, enhancing its contribution to sea-level rise (SLR). The recent increases in ice loss appear to be due to changes in both the surface mass balance of the ice sheet and ice discharge (ice flux to the ocean). Rapid ice flow directly affects the discharge, but also alters ice-sheet geometry and so affects climate and surface mass balance. Present-day ice-sheet models only represent rapid ice flow in an approximate fashion and, as a consequence, have never explicitly addressed the role of ice discharge on the total GrIS mass balance, especially at the scale of individual outlet glaciers. Here, we present a new-generation prognostic ice-sheet model which reproduces the current patterns of rapid ice flow. This requires three essential developments: the complete solution of the full system of equations governing ice deformation; a variable resolution unstructured mesh to resolve outlet glaciers and the use of inverse methods to better constrain poorly known parameters using observations. The modelled ice discharge is in good agreement with observations on the continental scale and for individual outlets. From this initial state, we investigate possible bounds for the next century ice-sheet mass loss. We run sensitivity experiments of the GrIS dynamical response to perturbations in climate and basal lubrication, assuming a fixed position of the marine termini. We find that increasing ablation tends to reduce outflow and thus decreases the ice-sheet imbalance. In our experiments, the GrIS initial mass (im)balance is preserved throughout the whole century in the absence of reinforced forcing, allowing us to estimate a lower bound of 75 mm for the GrIS contribution to SLR by 2100. In one experiment, we show that the current increase in the rate of ice loss can be reproduced and maintained throughout the whole century. However, this requires a very unlikely perturbation of basal lubrication. From this result we are able to estimate an upper bound of 140 mm from dynamics only for the GrIS contribution to SLR by 2100.

scholarly journals Shore Evidences of a High Antarctic Ocean Wave Event: Geomorphology, Event Reconstruction and Coast Dynamics through a Remote Sensing Approach

2021 ◽  
Vol 13 (3) ◽  
pp. 518
Author(s):  
Stefano Ponti ◽  
Mauro Guglielmin
Keyword(s):  
Remote Sensing ◽  
Sea Level ◽  
Storm Surge ◽  
Sea Water ◽  
Ross Sea ◽  
Average Rate ◽  
Field Measurements ◽  
Water Infiltration ◽  
Wave Event ◽  
High Wave Energy

Remote sensing can be helpful in defining the dynamic of a high-latitude coastal environment where the role of cryogenic processes like sea-ice or permafrost are the main drivers together with storm surge and wind action. Here we examined the geomorphological dynamics of a beach located at Edmonson Point (74° S) not far from the Italian Antarctic Station “Mario Zucchelli” between 1993 and 2019 using different remote sensing techniques and field measurements. Our data demonstrate that the average rate of surficial increase of the beach (0.002 ± 0.032 m yr−1) was slightly higher than the uplift rate determined by previous authors (0–1 cm yr−1) in case of pure isostatic rebound. However, we suggest that the evolution of EPNB is likely due to the couple effect of vertical uplift and high wave-energy events. Indeed, the coastline accumulation could be related to the subsurface sea water infiltration and annually freezing at the permafrost table interface as aggradational ice as suggested by the ERT carried out in 1996. This ERT suggests the occurrence of saline frozen permafrost or hypersaline brines under the sea level while permafrost with ice occurred above the sea level. The beach also revealed areas that had quite high subsidence values (between 0.08 and 0.011 m yr−1) located in the area where ice content was higher in 1996 and where the active layer thickening and wind erosion could explain the measured erosion rates. Here, we also dated at the late morning of 15 February 2019 coastal flooding and defined a significant wave height of 1.95 m. During the high oceanic wave event the sea level increased advancing shoreward up to 360 m, three times higher than the previous reported storm surge (81 m) and with a sea level rise almost five times higher than has been previously recorded in the Ross Sea.

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