scholarly journals Neumayer III and Kohnen Station in Antarctica operated by the Alfred Wegener Institute

2016 ◽  
Vol 2 ◽  
Author(s):  
Christine Wesche ◽  
Rolf Weller ◽  
Gert König-Langlo ◽  
Tanja Fromm ◽  
Alfons Eckstaller ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Shelf ◽  
Deep Drilling ◽  
Research Activities ◽  
Starting Point ◽  
Air Chemistry ◽  
Dronning Maud Land ◽  
Core Project ◽  
The Antarctic

The Alfred Wegener Institute operates two stations in Dronning Maud Land, Antarctica. The German overwintering station Neumayer III is located on the Ekström Ice Shelf at 70°40’S and 08°16’W and is the logistics base for three long-term observatories (meteorology, air chemistry and geophysics) and nearby research activities. Due to the vicinity to the coast (ca. 20 km from the ice shelf edge), the Neumayer III Station is the junction for many German Antarctic expeditions, especially as the starting point for the supply traverse for the second German station Kohnen.The summer station Kohnen is located about 600 km from the coast and 750 km from Neumayer III Station on the Antarctic plateau at 75°S and 00°04’E. It was erected as the base for the deep-drilling ice core project, which took place between 2001 and 2006. Since then Kohnen Station is used as a logistics base for different research projects.

Synoptic situations causing high precipitation rates on the Antarctic plateau: observations from Kohnen Station, Dronning Maud Land

2006 ◽  
Vol 18 (2) ◽  
pp. 279-288 ◽  
Author(s):  
Gerit Birnbaum ◽  
Ralf Brauner ◽  
Hinnerk Ries
Keyword(s):  
Large Scale ◽  
Ice Core ◽  
Mean Value ◽  
Cloud Formation ◽  
Heavy Snowfall ◽  
Greenwich Meridian ◽  
Dronning Maud Land ◽  
High Precipitation ◽  
The Antarctic

Kohnen Station (75°S, 0°E, 2892 m) is one of the two drilling sites of the European Project for Ice Coring in Antarctica. Snow falls at Kohnen only a few times a year with comparatively high precipitation rates of 1 mm to over 5 mm water equivalent per event. These events contribute considerably to the total annual accumulation of which the long-term mean value is 62 mm water equivalent per year. For ice core interpretation, it is important to understand synoptic processes leading to such high precipitation rates. Our investigation is based on visually observed periods of heavy snowfall at Kohnen during summer campaigns since 2001/2002. The corresponding synoptic situations can be grouped into three categories. Category I is where occluding fronts of eastward-moving low pressure systems reach the plateau, a fairly frequent occurrence. Category II is where lows or secondary lows formed east of the Greenwich Meridian move to the west (retrograde movement), and frontal clouds influence the plateau. In Category III, large-scale lifting processes (due to an upper air low west of Kohnen Station) lead to cloud formation over the plateau of Dronning Maud Land.

scholarly journals Modelling the long-term response of the Antarctic ice sheet to global warming

1998 ◽  
Vol 27 ◽  
pp. 161-168 ◽  
Author(s):  
Roland C. Warner ◽  
W.Κ. Budd
Keyword(s):  
Global Warming ◽  
Mass Loss ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Basal Melting ◽  
The Antarctic ◽  
Term Response

The primary effects of global warming on the Antarctic ice sheet can involve increases in surface melt for limited areas at lower elevations, increases in net accumulation, and increased basal melting under floating ice. For moderate global wanning, resulting in ocean temperature increases of a few °C, the large- increase in basal melting can become the dominant factor in the long-term response of the ice sheet. The results from ice-sheet modelling show that the increased basal melt rates lead to a reduction of the ice shelves, increased strain rates and flow at the grounding lines, then thinning and floating of the marine ice sheets, with consequential further basal melting. The mass loss from basal melting is counteracted to some extent by the increased accumulation, but in the long term the area of ice cover decreases, particularly in West Antarctica, and the mass loss can dominate. The ice-sheet ice-shelf model of Budd and others (1994) with 20 km resolution has been modified and used to carry out a number of sensitivity studies of the long-term response of the ice sheet to prescribed amounts of global warming. The changes in the ice sheet are computed out to near-equilibrium, but most of the changes take place with in the first lew thousand years. For a global mean temperature increase of 3°C with an ice-shelf basal melt rate of 5 m a−1 the ice shelves disappear with in the first few hundred years, and the marine-based parts of the ice sheet thin and retreat. By 2000 years the West Antarctic region is reduced to a number of small, isolated ice caps based on the bedrock regions which are near or above sea level. This allows the warmer surface ocean water to circulate through the archipelago in summer, causing a large change to the local climate of the region.

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 Simulation of the Antarctic ice sheet with a three-dimensional polythermal ice-sheet model, in support of the EPICA project

1998 ◽  
Vol 27 ◽  
pp. 201-206 ◽  
Author(s):  
R. Calov ◽  
A. Savvin ◽  
R. Greve ◽  
I. Hansen ◽  
K. Hutter
Keyword(s):  
Shear Deformation ◽  
Ice Core ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Climate Forcing ◽  
Drilling Process ◽  
Antarctic Ice Sheet ◽  
Atlantic Sector ◽  
Dronning Maud Land ◽  
The Antarctic

The three-dimensional polythermal ice-sheet model SICOPOLIS is applied to the entire Antarctic ice sheet in support of the European Project for Ice Coring in Antartica (EPICA). in this study, we focus on the deep ice core to be drilled in Dronning Maud Land (Atlantic sector of East Antarctica) as part of EPICA. It has not yel been decided where the exact drill-site will be situated. Our objective is to support EPICA during its planning phase as well as during the actual drilling process. We discuss a transient simulation with a climate forcing derived from the Vostok ice core and the SPECMAP sea-level record. This simulation shows the range of accumulation, basal temperature, age and shear deformation to be expected in the region of Dronning Maud Land. Based on these results, a possible coring position is proposed, and the distribution of temperature, age, horizontal velocity and shear deformation is shown for this column.

scholarly journals Long-term changes in the acid and salt concentrations of the Greenland Ice Core Project ice core from electrical stratigraphy

1995 ◽  
Vol 100 (D8) ◽  
pp. 16249 ◽  
Author(s):  
Eric W. Wolff ◽  
John C. Moore ◽  
Henrik B. Clausen ◽  
Claus U. Hammer ◽  
Josef Kipfstuhl ◽  
...  
Keyword(s):  
Ice Core ◽  
Long Term Changes ◽  
Core Project

scholarly journals Antarctic climate variability at regional and continental scales over the last 2,000 years

2017 ◽  
Author(s):  
Barbara Stenni ◽  
Mark A. J. Curran ◽  
Nerilie J. Abram ◽  
Anais Orsi ◽  
Sentia Goursaud ◽  
...  
Keyword(s):  
Working Group ◽  
Ice Core ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Temperature Reconstructions ◽  
Temperature Scaling ◽  
Antarctic Continent ◽  
Cooling Trend ◽  
The Antarctic

Abstract. Climate trends in the Antarctic region remain poorly characterised, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica 2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5 and 10-year resolution, for 7 climatically-distinct regions covering the Antarctic continent. Following earlier work of the Antarctica 2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica, and the whole continent. We use three methods for our temperature reconstructions: i) a temperature scaling based on the δ18O-temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data; ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and iii) a composite-plus-scaling approach used in a previous continental scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0–1900 CE we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000-years. However, projected warming of the Antarctic continent during the 21st Century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica 2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data-model comparison and assessments of past, present and future driving factors of Antarctic climate.

scholarly journals Antarctic Atmospheric River Climatology and Impacts

2020 ◽  
Author(s):  
Jonathan Wille ◽  
Vincent Favier ◽  
Irina V. Gorodetskaya ◽  
Cécile Agosta ◽  
Jai Chowdhry Beeman ◽  
...  
Keyword(s):  
Mass Balance ◽  
Surface Mass Balance ◽  
Ice Shelf ◽  
Surface Mass ◽  
Atmospheric Rivers ◽  
Atmospheric River ◽  
Dronning Maud Land ◽  
Antarctic Continent ◽  
Surface Melt ◽  
The Antarctic

<p>Atmospheric rivers, broadly defined as narrow yet long bands of strong horizontal vapor transport typically imbedded in a low level jet ahead of a cold front of an extratropical cyclone, provide a sub-tropical connection to the Antarctic continent and are observed to significantly impact the affected region’s surface mass balance over short, extreme events. When an atmospheric river makes landfall on the Antarctic continent, their signature is clearly observed in increased downward longwave radiation, cloud liquid water content, surface temperature, snowfall, surface melt, and moisture transport.</p><p>Using an atmospheric river detection algorithm designed for Antarctica and regional climate simulations from MAR, we created a climatology of atmospheric river occurrence and their associated impacts on surface melt and snowfall. Despite their rarity of occurrence over Antarctica (maximum frequency of ~1.5% over a given point), they have produced significant impacts on melting and snowfall processes. From 1979-2017, atmospheric rivers landfalls and their associated radiative flux anomalies and foehn winds accounted for around 40% of the total summer surface melt on the Ross Ice Shelf (approaching 100% at higher elevations in Marie Byrd Land) and 40-80% of total winter surface melt on the ice shelves along the Antarctic Peninsula. On the other side of the continent in East Antarctica, atmospheric rivers have a greater influence on annual snowfall variability. There atmospheric rivers are responsible for 20-40% of annual snowfall with localized higher percentages across Dronning Maud Land, Amery Ice Shelf, and Wilkes Land.</p><p>Atmospheric river landfalls occur within a highly amplified polar jet pattern and often are found in the entrance region of a blocking ridge. Therefore, atmospheric river variability is connected with atmospheric blocking variability over the Southern Ocean. There has been a significant increase in atmospheric river activity over the Amundsen-Bellingshausen sea and coastline and into Dronning Maud Land region from 1980-2018. Meanwhile, there is a significant decreasing trend in the region surrounding Law Dome. Our results suggest that atmospheric rivers play a significant role in the Antarctic surface mass balance, and that any future changes in atmospheric blocking or tropical-polar teleconnections may have significant impacts on future surface mass balance projections.</p>

scholarly journals Ice flux of Plogbreen, a small ice stream in Dronning Maud Land, Antarctica

2004 ◽  
Vol 39 ◽  
pp. 409-416
Author(s):  
Jim Hedfors ◽  
Veijo Allan Pohjola
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Austral Summer ◽  
Snow Accumulation ◽  
Surface Velocity ◽  
Cross Sectional ◽  
Ice Surface ◽  
Dronning Maud Land ◽  
Using Data

AbstractAs part of a long-term mass-balance program run by SWEDARP since 1988, a detailed study on Plogbreen, Dronning Maud Land, Antarctica, was undertaken during the austral summer of 2003 to investigate the long-term mass balance. We compare ice outflux, φout, through a cross-sectional gate with ice influx, φin, from the upstream catchment area. The φin is based on calculations of snow accumulation upstream of the gate using data available from published ice-core records. The φout is based on Glen’s flow law aided by thermodynamic modeling and force-budget calculations. Input data from the field consist of measurements of ice surface velocity and ice geometry. The ice surface velocity was measured using repeated differential global positioning system surveying of 40 stakes over a period of 25 days. The ice geometry was determined by 174 km of ground-penetrating radar profiling using ground-based 8MHz dipole antennas. This study presents the collected velocity and geometry data as well as the calculated ice flux of Plogbreen. The results show a negatively balanced system within the uncertainty limits; φout = 0.55 ± 0.05 km3 a–1 and φin = 0.4 ± 0.1 km3 a–1. We speculate that the negative balance can be explained by recent eustatic increase reducing resistive stresses and inducing accelerated flow.

scholarly journals Multidecadal warming of Antarctic waters

Science ◽  
2014 ◽  
Vol 346 (6214) ◽  
pp. 1227-1231 ◽  
Author(s):  
Sunke Schmidtko ◽  
Karen J. Heywood ◽  
Andrew F. Thompson ◽  
Shigeru Aoki
Keyword(s):  
Continental Shelf ◽  
Large Scale ◽  
Bottom Water ◽  
Heat Content ◽  
Ice Shelf ◽  
Antarctic Continental Shelf ◽  
Antarctic Waters ◽  
Core Depth ◽  
The Antarctic

Decadal trends in the properties of seawater adjacent to Antarctica are poorly known, and the mechanisms responsible for such changes are uncertain. Antarctic ice sheet mass loss is largely driven by ice shelf basal melt, which is influenced by ocean-ice interactions and has been correlated with Antarctic Continental Shelf Bottom Water (ASBW) temperature. We document the spatial distribution of long-term large-scale trends in temperature, salinity, and core depth over the Antarctic continental shelf and slope. Warming at the seabed in the Bellingshausen and Amundsen seas is linked to increased heat content and to a shoaling of the mid-depth temperature maximum over the continental slope, allowing warmer, saltier water greater access to the shelf in recent years. Regions of ASBW warming are those exhibiting increased ice shelf melt.

scholarly journals Potential mechanisms for anisotropy in ice-penetrating radar data

2012 ◽  
Vol 58 (209) ◽  
pp. 613-624 ◽  
Author(s):  
R. Drews ◽  
O. Eisen ◽  
D. Steinhage ◽  
I. Weikusat ◽  
S. Kipfstuhl ◽  
...  
Keyword(s):  
Ice Core ◽  
Impurity Content ◽  
Radar Data ◽  
Surface Strain ◽  
Center Frequency ◽  
Dronning Maud Land ◽  
Principal Directions ◽  
Drilling Site ◽  
Antenna Polarization ◽  
The Antarctic

AbstractRadar data (center frequency 150 MHz) collected on the Antarctic plateau near the EPICA deep-drilling site in Dronning Maud Land vary systematically in backscattered power, depending on the azimuth antenna orientation. Backscatter extrema are aligned with the principal directions of surface strain rates and change with depth. In the upper 900m, backscatter is strongest when the antenna polarization is aligned in the direction of maximal compression, while below 900 m the maxima shift by 90° pointing towards the lateral flow dilatation. We investigate the backscatter from elongated air bubbles and a vertically varying crystal-orientation fabric (COF) using different scattering models in combination with ice-core data. We hypothesize that short-scale variations in COF are the primary mechanism for the observed anisotropy, and the 900 m boundary between the two regimes is caused by ice with varying impurity content. Observations of this kind allow the deduction of COF variations with depth and are potentially also suited to map the transition between Holocene and glacial ice.

Sign in / Sign up

Export Citation Format

Share Document