Age estimates of isochronous reflection horizons by combining ice core, survey, and synthetic radar data.

Ice core records and ice-penetrating radar data contain complementary information on glacial subsurface structure and composition, providing various opportunities for interpreting past and present environmental conditions. To exploit the full range of possible applications, accurate dating of internal radar reflection horizons and knowledge about their constituting features is required. On the basis of three ice core records from Dronning Maud Land, Antarctica, and surface-based radar profiles connecting the drilling locations, we investigate the accuracies involved in transferring age-depth relationships obtained from the ice cores to continuous radar reflections. Two methods are used to date five internal reflection horizons: (1) conventional dating is carried out by converting the travel time of the tracked reflection to a single depth, which is then associated with an age at each core location, and (2) forward modeling of electromagnetic wave propagation is based on dielectric profiling of ice cores and performed to identify the depth ranges from which tracked reflections originate, yielding an age range at each drill site. Statistical analysis of all age estimates results in age uncertainties of 5 10 years for conventional dating and an error range of 1 16 years for forward modeling. For our radar operations at 200 and 250 MHz in the upper 100 m of the ice sheet, comprising some 1000 1500 years of deposition history, final age uncertainties are 8 years in favorable cases and 21 years at the limit of feasibility. About one third of the uncertainty is associated with the initial ice core dating; the remaining part is associated with radar data quality and analysis

Polar aircraft Polar5 and Polar6 operated by the Alfred Wegener Institute

Due to the remoteness and difficulty to access the snow covered polar regions, ski-equipped aircraft are an indispensable tool for polar research. The Alfred Wegener Institute has a long tradition in airborne polar science – starting with the aircraft Polar1 and Polar2 in 1983. In 2007 the first Basler BT-67 (Polar5) and in 2011 the second Basler BT-67 (Polar6) were brought into service and replaced Polar2 and Polar4. They carry a variety of scientific equipment for investigation of the lithosphere, atmosphere and cryosphere and all their interactions. Beside being deployed for science missions, the aircraft are also part of the Dronning Maud Land Air Network (DROMLAN), a logistical partnership to transport equipment and personnel to various stations in Dronning Maud Land, Antarctica

Research Vessel HEINCKE Operated by the Alfred-Wegener-Institute

HEINCKE operated by the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, is a medium size multipurpose research vessel, which was designed for long-term cruises throughout the North Atlantic Sea up to Svalbard and the adjacent shelf seas. She offers work places and accommodation for 12 scientists and 12 crew members. The operating range of this low noise ship is about 7500 nautical miles (= 30 passage days). Four laboratories (wet, dry, constant temperature controlled and hydroacoustic/CTD) offer almost vibration-free work places. Additionally space is available for special containers. The ship is equipped with several winch systems, cranes, and sonar systems, which allow a wide range of biological, chemical, oceanographic, geological and geophysical research applications. The onboard science support equipment allows working in water depths of up to approximately 2000 meters

Electromagnetic wave speed in polar ice: Validation of the CMP technique with high resolution dielectric-profiling and gamma-density measurements

The accuracy of the traveltime-velocity and traveltime-depth profile derived from ground-penetrating radar (GPR) common-midpoint (CMP) surveys at different frequencies is investigated for the first time ever by direct comparison with the profile calculated from high resolution dielectric-profiling (DEP) ice core data.In addition, we compare two traveltime profiles calculated from ice core density data by means of different dielectrical mixture models with the DEP based profile.CMP surveys were carried out at frequencies of 25, 50, 100 and 200 MHz near the new European deep drilling site DML05 in Dronning Maud Land, Antarctica, during the 1998/99 field season.An improved scanning capacitor for high resolution DEP and a Gamma-densiometer for density measurements were used to determine thecomplex dielectric constant and the density at 5 mm increments along the ice core B32, retrieved in 1997/98 at DML05.The comparisons with DEP and density based velocity series show that the CMP velocity series are slightly higher, but asymptotically approach the core based velocities with depth.Root-mean-square differences of the DEP velocity series range between 8% for the 25 MHz CMP and 2% in the case of the 200 MHz survey.Density based velocities differ from the DEP velocities by less than 1%.The traveltime-depth series calculated from the interval velocities show a better agreement between all series than the velocity series.Differences are between 5.7 and 1.4% for the 25 and 200 MHz CMP measurements, and less than 0.6% for the density data.Based on these comparisons we evaluate the accuracy with which the depth of electromagnetic reflectors observed in common-offset profiles can be determined and discuss reasons for the observed differences between CMP- and core based profiles.Moreover, we compare the errors determined from the field measurements with those estimated from GPR system characteristics to provide a measure that can be used to estimate the accuracy of GPR analyses for the planning of GPR campaigns.Our results show that CMP surveys are a useful technique to determine the depth of radar reflectors in combination with common-offset measurements, especially on a region-wide basis

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

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

Expedtion program ANT-Land 2018/19 - Land activities and flight missions

The season ANT-Land 2018/19 is scheduled for the period from 31 October 2017 until 28 February 2019. Most of personnel will be flown into the Antarctic and back via the air link from Cape Town within the frame of Dronning Maud Land Air Network (DROMLAN). Ship calls are scheduled for RV POLARSTERN between 5th and 7st January 2019, to supply the majority of cargo for NEUMAYER STATION III and aircraft operations. A further ship call is MARY ARCTICA between 17th and 18th January 2019. Logistics will focus on two periods of lifting of the station. Furthermore a construction team will be onsite for maintenance of the station facilities. In the vicinity of NEUMAYER STATION III geophysical, glaciological, geological, biological and atmospheric projects are planned during the summer season. Medical studies of the Berlin Centre for Space Medicine (ZWMB) and University of Munich (LMU) will be continued and extended by the station staff during the winter period. In parallel, station facilities will be used to operate the Basler BT-67 aircraft POLAR 6. The regular weather forecast service (AWI/DWD) will be provided to all aircraft operations within the Dronning Maud Land region, in particular as a contribution to DROMLAN. KOHNEN STATION will be visited by the participants of six scientific projects and maintenance work such as lifting up the station and construction work. A traverse to KOHNEN STATION including supply goods will start from NEUMAYER STATION III will start mid of November. The DALLMANN LABORATORY at Base CARLINI (Argentina) will be opened at the beginning of November 2018. It is operated in cooperation with the Instituto Antártico Argentino (IAA). During the season 2018/19 German and international scientists (one scientific group) will work at the Potter Cove and the station area

Joint AWI-NIPR airborne operations in the past and the future

The Alfred Wegener Institute for Polar and Marine Research (AWI) has in the past operated two ski equipped aircraft (Dornier Do228-101) for scientific and logistic purposes in polar regions-called POLAR 2 and POLAR 4. Both aircraft are easily able to be adapted to different science programs. Aero-geophysical instrumentation and various atmospheric systems are available. In recent years, a long and fruitful cooperation with the National Institute of Polar Research (NIPR), Tokyo, has been established, whereby so far three joint airborne campaigns have been already performed in the Arctic, namely ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation), AAMP 2002 (Arctic Airborne Measurement Program), and ASTAR 2004. The ANTSYO (Antarctic flight missions at Syowa region: Airborne Geophysical, Glaciological, and Atmospheric Research in East Antarctica) operations of the AWI research aircraft, POLAR 2, started in the season 2005/06, from S17, near Syowa Station in December 2005. Running such surveys presents a logistical challenge that can only be met with the combined support of Alfred Wegener Institute, Bremerhaven, and the NIPR, Tokyo. Therefore, both national Antarctic programs put their logistical capabilities together in order to perform the first extensive airborne missions in this area over a period of three Antarctic summer seasons (2005/06 till 2007/08)

The MOSAiC ice floe: sediment-laden survivor from the Siberian shelf

In September 2019, the research icebreaker Polarstern started the largest multidisciplinary Arctic expedition to date, the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift experiment. Being moored to an ice floe for a whole year, thus including the winter season, the declared goal of the expedition is to better understand and quantify relevant processes within the atmosphere–ice–ocean system that impact the sea ice mass and energy budget, ultimately leading to much improved climate models. Satellite observations, atmospheric reanalysis data, and readings from a nearby meteorological station indicate that the interplay of high ice export in late winter and exceptionally high air temperatures resulted in the longest ice-free summer period since reliable instrumental records began. We show, using a Lagrangian tracking tool and a thermodynamic sea ice model, that the MOSAiC floe carrying the Central Observatory (CO) formed in a polynya event north of the New Siberian Islands at the beginning of December 2018. The results further indicate that sea ice in the vicinity of the CO (<40 km distance) was younger and 36 % thinner than the surrounding ice with potential consequences for ice dynamics and momentum and heat transfer between ocean and atmosphere. Sea ice surveys carried out on various reference floes in autumn 2019 verify this gradient in ice thickness, and sediments discovered in ice cores (so-called dirty sea ice) around the CO confirm contact with shallow waters in an early phase of growth, consistent with the tracking analysis. Since less and less ice from the Siberian shelves survives its first summer (Krumpen et al., 2019), the MOSAiC experiment provides the unique opportunity to study the role of sea ice as a transport medium for gases, macronutrients, iron, organic matter, sediments and pollutants from shelf areas to the central Arctic Ocean and beyond. Compared to data for the past 26 years, the sea ice encountered at the end of September 2019 can already be classified as exceptionally thin, and further predicted changes towards a seasonally ice-free ocean will likely cut off the long-range transport of ice-rafted materials by the Transpolar Drift in the future. A reduced long-range transport of sea ice would have strong implications for the redistribution of biogeochemical matter in the central Arctic Ocean, with consequences for the balance of climate-relevant trace gases, primary production and biodiversity in the Arctic Ocean