scholarly journals Climatic signals from 76 shallow firn cores in Dronning Maud Land, East Antarctica

2015 ◽  
Vol 9 (3) ◽  
pp. 925-944 ◽  
Author(s):  
S. Altnau ◽  
E. Schlosser ◽  
E. Isaksson ◽  
D. Divine
Keyword(s):  
Meteorological Data ◽  
Southern Annular Mode ◽  
Temporal Variations ◽  
East Antarctica ◽  
Positive Trend ◽  
Ice Shelf ◽  
Data Set ◽  
Surface Mass ◽  
Dronning Maud Land ◽  
Climatic Signals

Abstract. The spatial and temporal distribution of surface mass balance (SMB) and δ18O were investigated in the first comprehensive study of a set of 76 firn cores retrieved by various expeditions during the past 3 decades in Dronning Maud Land, East Antarctica. The large number of cores was used to calculate stacked records of SMB and δ18O, which considerably increased the signal-to-noise ratio compared to earlier studies and facilitated the detection of climatic signals. Considerable differences between cores from the interior plateau and the coastal cores were found. The δ18O of both the plateau and the ice shelf cores exhibit a slight positive trend over the second half of the 20th century. In the corresponding period, the SMB has a negative trend in the ice shelf cores, but increases on the plateau. Comparison with meteorological data from Neumayer Station revealed that for the ice shelf regions, atmospheric dynamic effects are more important than thermodynamics while on the plateau; the temporal variations of SMB and δ18O occur mostly in parallel, and thus can be explained by thermodynamic effects. The Southern Annular Mode (SAM) has exhibited a positive trend since the mid-1960s, which is assumed to lead to a cooling of East Antarctica. This is not confirmed by the firn core data in our data set. Changes in the atmospheric circulation that result in a changed seasonal distribution of precipitation/accumulation could partly explain the observed features in the ice shelf cores.

scholarly journals Climatic signals from 76 shallow firn cores in Dronning Maud Land, East Antarctica

2014 ◽  
Vol 8 (6) ◽  
pp. 5961-6005 ◽  
Author(s):  
S. Altnau ◽  
E. Schlosser ◽  
E. Isaksson ◽  
D. Divine
Keyword(s):  
Meteorological Data ◽  
Southern Annular Mode ◽  
Temporal Variations ◽  
East Antarctica ◽  
Positive Trend ◽  
Ice Shelf ◽  
Data Set ◽  
Surface Mass ◽  
Dronning Maud Land ◽  
Climatic Signals

Abstract. The spatial and temporal distribution of surface mass balance (SMB) and δ18O were investigated in the first comprehensive study of a set of 76 firn cores retrieved by various expeditions during the past three decades in Dronning Maud Land, East Antarctica. The large number of cores was used to calculate stacked records of SMB and δ18O, which considerably increased the signal-to-noise ratio compared to earlier studies and facilitated the detection of climatic signals. Considerable differences between cores from the interior plateau and the coastal cores were found. The δ18O of both the plateau and the ice shelf cores exhibit a slight positive trend over the second half of the 20th century. In the corresponding period, the SMB has a negative trend in the ice shelf cores, but increases on the plateau. Comparison with meteorological data from Neumayer Station revealed that for the ice shelf regions atmospheric dynamic effects are more important than thermodynamics, while on the plateau, the temporal variations of SMB and δ18O occur mostly in parallel, thus can be explained by thermodynamic effects. The Southern Annular Mode (SAM) exhibits a positive trend since the mid-1960s, which is assumed to lead to a cooling of East Antarctica. This is not confirmed by the firn core data in our data set. Changes in the atmospheric circulation that result in a changed seasonal distribution of precipitation/accumulation could partly explain the observed features in the ice shelf cores.

scholarly journals Accumulation variability and mass budgets of the Lambert Glacier-Amery Ice Shelf system, East Antarctica, at high elevations

2006 ◽  
Vol 43 ◽  
pp. 351-360 ◽  
Author(s):  
Jiahong Wen ◽  
Kenneth C. Jezek ◽  
Andrew J. Monaghan ◽  
Bo Sun ◽  
Jiawen Ren ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Accumulation Rate ◽  
Temporal Variations ◽  
High Elevation ◽  
East Antarctica ◽  
Ice Shelf ◽  
Surface Mass ◽  
Amery Ice Shelf ◽  
High Elevations ◽  
Lambert Glacier

AbstractThe temporal and spatial variability of the annual accumulation rate and the mass budgets of five sub-basins of the Lambert Glacier-Amery Ice Shelf system (LAS), East Antarctica, at high elevations are assessed using a variety of datasets derived from field measurements and modeling. The annual temporal variations of the accumulation rate for four cores from the west and east sides of the LAS are around ±34%. Decadal fluctuation of the accumulation from the DT001 firn core drops to ±10%, and the 30 year fluctuation to ±5%, which is assumed to contain the information about the regional and long-term trend in accumulation. The 15-point running mean of the annual accumulation rate derived from stake measurements can remove most of the high-frequency spatial variation so as to better represent the local accumulation. Model simulations show that the spatial variability of erosion/ deposition of snow by the wind has a noticeable impact on the surface mass balance at the higher parts of the LAS. Mass-budget estimates at high-elevation sub-basins of the LAS suggest drainage 9 has a negative imbalance of −0.7 ± 0.4 Gta-1, Lambert and Mellor Glaciers have a positive imbalance of 3.9 ± 2.1 and 2.1 ±2.4 Gta-1 respectively, and Fisher Glacier and drainage 11 are approximately in balance. The higher-elevation region as a whole has a positive mass imbalance of 4.4 ± 6.3 Gta-1, which is consistent with the most recent radar altimetry assessment that shows an overall thickening over this region.

scholarly journals Spatial and temporal variations in basal melting at Nivlisen ice shelf, East Antarctica, derived from phase-sensitive radars

2019 ◽  
Author(s):  
Katrin Lindbäck ◽  
Geir Moholdt ◽  
Keith W. Nicholls ◽  
Tore Hattermann ◽  
Bhanu Pratap ◽  
...  
Keyword(s):  
Deep Ocean ◽  
Temporal Variations ◽  
East Antarctica ◽  
Spatial And Temporal Variations ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Deep Ocean Water ◽  
Dronning Maud Land ◽  
Phase Sensitive ◽  
Basal Melting

Abstract. Thinning rates of ice shelves vary widely around Antarctica and basal melting is a major component in ice shelf mass loss. In this study, we present records of basal melting, at unique spatial and temporal resolution for East Antarctica, derived from autonomous phase-sensitive radars. These records show spatial and temporal variations of ice shelf basal melting in 2017 and 2018 at Nivlisen, central Dronning Maud Land. The annually averaged melt rates are in general moderate (~ 0.8 m yr-1). Radar profiling of the ice-shelf shows variable ice thickness from smooth beds to basal crevasses and channels. The highest melt rates (3.9 m yr-1) were observed close to a grounded feature near the ice shelf front. Daily time-varying measurements reveal a seasonal melt signal 4 km from the ice shelf front, at an ice draft of 130 m, where the highest daily melt rates occurred in summer (up to 5.6 m yr-1). This seasonality indicates that summer-warmed ocean surface water was pushed by wind beneath the ice shelf front. We observed a different melt regime 35 km into the ice-shelf cavity, at an ice draft of 280 m, with considerably lower melt rates (annual average of 0.4 m yr-1) and no seasonality. We conclude that warm deep ocean water at present has limited effect on the basal melting of Nivlisen. On the other hand, a warming in surface waters, as a result of diminishing sea-ice cover has the potential to increase basal melting near the ice-shelf front. Many ice shelves like Nivlisen are stabilized by pinning points at their ice fronts and these areas may be vulnerable to future change.

scholarly journals Physical properties of the seasonal snow cover in Dronning Maud Land, East Antarctica

2002 ◽  
Vol 34 ◽  
pp. 89-94 ◽  
Author(s):  
Eija Kärkäs ◽  
Hardy B. Granberg ◽  
Kimmo Kanto ◽  
Kai Rasmus ◽  
Chantale Lavoie ◽  
...  
Keyword(s):  
Snow Cover ◽  
Austral Summer ◽  
Research Programme ◽  
Temporal Variations ◽  
East Antarctica ◽  
Ice Shelf ◽  
Edge Zone ◽  
Snow Stratigraphy ◽  
Dronning Maud Land ◽  
Seaward Edge

AbstractSnow stratigraphy was analyzed in the Maudheimvidda area of western Dronning Maud Land, East Antarctica, during austral summer 1999/2000 as a part of the Finnish Antarctic Research Programme (FINNARP). Measurements were made in shallow (1–2m) snow pits along a 350 km transect from the coast to the polar plateau, covering at least one annual cycle and an elevation range from sea level to about 2500 m. The aim of the study is to document spatial and temporal variations in snow-cover properties, with the further aim of relating these variations to environmental factors and to patterns observable by remote sensing. The measurements suggest five principal snow zones: (i) sea ice, (ii) the seaward edge zone of the ice shelf, (iii) the inner parts of the ice shelf, (iv) the snow cover above the grounding line and (v) the local topographic highs. Local topographic highs such as ice domes and ice rises differ from other snow environments: the snow is less densely packed, possibly an indication of locally reduced speed of the katabatic outflow. Fewer and thinner crusts on the topographic highs are consistent with RADARSAT backscatter variations.

scholarly journals Surface melt magnitude retrieval over Ross Ice Shelf, Antarctica using coupled MODIS near-IR and thermal satellite measurements

2009 ◽  
Vol 3 (3) ◽  
pp. 1069-1107 ◽  
Author(s):  
D. J. Lampkin ◽  
C. C. Karmosky
Keyword(s):  
Meteorological Data ◽  
Temporal Variations ◽  
Katabatic Wind ◽  
Ice Shelf ◽  
Water Fraction ◽  
Ross Ice Shelf ◽  
Near Ir ◽  
Coarse Spatial Resolution ◽  
Surface Melt ◽  
The Antarctic

Abstract. Surface melt has been increasing over recent years, especially over the Antarctic Peninsula, contributing to disintegration of shelves such as Larsen. Unfortunately, we are not realistically able to quantify surface snowmelt from ground-based methods because there is sparse coverage of automatic weather stations. Satellite based assessments of melt from passive microwave systems are limited in that they only provide an indication of melt occurrence and have coarse spatial resolution. An algorithm was developed to retrieve surface melt magnitude using coupled near-IR/thermal surface measurements from MODIS were calibrated by estimates of liquid water fraction (LWF) in the upper 1 cm of the firn derived from a one-dimensional physical snowmelt model (SNTHERM89). For the modeling phase of this study, SNTHERM89 was forced by hourly meteorological data from automatic weather station data at reference sites spanning a range of melt conditions across the Ross Ice Shelf during a relatively intense melt season (2002). Effective melt magnitude or LWF<eff> were derived for satellite composite periods covering the Antarctic summer months at a 4 km resolution over the entire Ross Ice Shelf, ranging from 0–0.5% LWF<eff> in early December to areas along the coast with as much as 1% LWF<eff> during the time of peak surface melt. Spatial and temporal variations in the magnitude of surface melt are related to both katabatic wind strength and advection during onshore flow.

scholarly journals Dynamic influence of pinning points on marine ice-sheet stability: a numerical study in Dronning Maud Land, East Antarctica

2016 ◽  
Vol 10 (6) ◽  
pp. 2623-2635 ◽  
Author(s):  
Lionel Favier ◽  
Frank Pattyn ◽  
Sophie Berger ◽  
Reinhard Drews
Keyword(s):  
Data Assimilation ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
East Antarctica ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Outlet Glacier ◽  
Ice Shelves ◽  
Dronning Maud Land

Abstract. The East Antarctic ice sheet is likely more stable than its West Antarctic counterpart because its bed is largely lying above sea level. However, the ice sheet in Dronning Maud Land, East Antarctica, contains marine sectors that are in contact with the ocean through overdeepened marine basins interspersed by grounded ice promontories and ice rises, pinning and stabilising the ice shelves. In this paper, we use the ice-sheet model BISICLES to investigate the effect of sub-ice-shelf melting, using a series of scenarios compliant with current values, on the ice-dynamic stability of the outlet glaciers between the Lazarev and Roi Baudouin ice shelves over the next millennium. Overall, the sub-ice-shelf melting substantially impacts the sea-level contribution. Locally, we predict a short-term rapid grounding-line retreat of the overdeepened outlet glacier Hansenbreen, which further induces the transition of the bordering ice promontories into ice rises. Furthermore, our analysis demonstrated that the onset of the marine ice-sheet retreat and subsequent promontory transition into ice rise is controlled by small pinning points, mostly uncharted in pan-Antarctic datasets. Pinning points have a twofold impact on marine ice sheets. They decrease the ice discharge by buttressing effect, and they play a crucial role in initialising marine ice sheets through data assimilation, leading to errors in ice-shelf rheology when omitted. Our results show that unpinning increases the sea-level rise by 10 %, while omitting the same pinning point in data assimilation decreases it by 10 %, but the more striking effect is in the promontory transition time, advanced by two centuries for unpinning and delayed by almost half a millennium when the pinning point is missing in data assimilation. Pinning points exert a subtle influence on ice dynamics at the kilometre scale, which calls for a better knowledge of the Antarctic margins.

scholarly journals Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

2020 ◽  
Vol 66 (260) ◽  
pp. 1064-1078
Author(s):  
Vikram Goel ◽  
Kenichi Matsuoka ◽  
Cesar Deschamps Berger ◽  
Ian Lee ◽  
Jørgen Dall ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Cores ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Shelves ◽  
The Past ◽  
Dronning Maud Land ◽  
The Antarctic

AbstractIce rises and rumples, locally grounded features adjacent to ice shelves, are relatively small yet play significant roles in Antarctic ice dynamics. Their roles generally depend upon their location within the ice shelf and the stage of the ice-sheet retreat or advance. Large, long-stable ice rises can be excellent sites for deep ice coring and paleoclimate study of the Antarctic coast and the Southern Ocean, while small ice rises tend to respond more promptly and can be used to reveal recent changes in regional mass balance. The coasts of Dronning Maud Land (DML) and Enderby Land in East Antarctica are abundant with these features. Here we review existing knowledge, presenting an up-to-date status of research in these regions with focus on ice rises and rumples. We use regional datasets (satellite imagery, surface mass balance and ice thickness) to analyze the extent and surface morphology of ice shelves and characteristic timescales of ice rises. We find that large parts of DML have been changing over the past several millennia. Based on our findings, we highlight ice rises suitable for drilling ice cores for paleoclimate studies as well as ice rises suitable for deciphering ice dynamics and evolution in the region.

scholarly journals Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica

2012 ◽  
Vol 6 (4) ◽  
pp. 841-857 ◽  
Author(s):  
W. Thiery ◽  
I. V. Gorodetskaya ◽  
R. Bintanja ◽  
N. P. M. Van Lipzig ◽  
M. R. Van den Broeke ◽  
...  
Keyword(s):  
Mass Balance ◽  
East Antarctica ◽  
Lower Probability ◽  
Research Station ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Drifting Snow ◽  
Dronning Maud Land ◽  
Meteorological Observations ◽  
Strong Winds

Abstract. In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation – either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS) near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance during 2009 and 2010. Comparison to three other AWSs in Dronning Maud Land with 11 to 13 yr of observations shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10–23% of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (17 mm w.e. yr−1 compared to 42 mm w.e. yr−1 at Svea Cross and 52 mm w.e. yr−1 at Wasa/Aboa). This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and, therefore, on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. This wind speed class turns out to contribute most to the total snowdrift sublimation mass flux, given its ability to lift a high number of particles while still allowing for considerable undersaturation.

scholarly journals Radar characterization of the basal interface across the grounding zone of an ice-rise promontory in East Antarctica

2012 ◽  
Vol 53 (60) ◽  
pp. 29-34 ◽  
Author(s):  
Kenichi Matsuoka ◽  
Frank Pattyn ◽  
Denis Callens ◽  
Howard Conway
Keyword(s):  
East Antarctica ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Temperature Dependent ◽  
Flow Models ◽  
Radar Method ◽  
Dronning Maud Land ◽  
Dependent Model ◽  
Temperature Dependent Model

AbstractRadar power returned from the basal interface along a 42 km long profile over an ice-rise promontory and the adjacent Roi Baudouin ice shelf, Dronning Maud Land, East Antarctica, is analyzed to infer spatial variations in basal reflectivity and hence the basal environment. Extracting basal reflectivity from basal returned power requires an englacial attenuation model. We estimate attenuation in two ways: (1) using a temperature-dependent model with input from thermomechanical ice-flow models; and (2) using a radar method that linearly approximates the geometrically corrected returned power with ice thickness. The two methods give different results. We argue that attenuation calculated using a modeled temperature profile is more robust than the widely used radar method, especially in locations where depth-averaged attenuation varies spatially or where the patterns of basal reflectivity correlate with the patterns of the ice thickness.

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