Description: Abstract The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica's continental ice volume. Over the last few decades, studies on glacial–geological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23–19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on the Weddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different ice-sheet models have reconstructed conflicting {LGM} ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the {LGM} sea-level low-stand of ~130 m vary considerably. In this paper, we summarise and review the geological records of past ice-sheet margins and past ice-sheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the {LGM} ice-sheet configuration, including time-slice reconstructions for post-LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacial–geological datasets on Antarctic Ice-Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical ice-sheet models.

Description: The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica’s continental ice volume. Over the last few decades, studies on glacialegeological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23e19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on theWeddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different icesheet models have reconstructed conflicting LGM ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the LGM sealevel low-stand of w130 m vary considerably. In this paper, we summarise and review the geological records of past ice-sheet margins and past icesheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the LGM ice-sheet configuration, including time-slice reconstructions for post- LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacialegeological datasets on Antarctic Ice- Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical icesheet models

Description: This poster presents results and performance of an operational vibroseis system used in Antarctica on the Ekströmisen and its catchment area. The about 500 km long overland traverse covered very different surface regimes in the elevation range from sea level up to 1000 m in the austral season 2013/14. The presentation is the successful culmination of a six-year effort to develop an operational vibroseis system for Antarctica and Greenland. Over three weeks the campaign acquired: • 407 km of seismic profiles in total, thereof • 110 km in 6-fold resolution with 125 m shot spacing • 25 km in 3-fold resolution with 250 m shot spacing. The remaining distance was covered in single-fold with 750 m shot spacing. The traverse used a well-established 60 channel 1.5 km streamer and a new setup with a vibroseis Buggy “EnviroVibe” with Mattracks on a polyethylen sled. The sled had a hole in the center to lower the vibrator pad directly onto the snow surface. With this setup data production varied between 20 km/day for 6-fold and 40 km/day for single fold for a decent 9h day of measurements. The combination of Mattracks with the PE-sled was especially advantageous on hard and rough surfaces because of the flexibility of each and the relatively lose mounting by cargo straps and wooden blocks. Production speeds were limited by the snow streamer, which had an increasing damage rate of geophone groups for velocities above 6 km/h. The source system itself could easily accommodate transfer velocities of 15 km/h. In combination with the streamer winch mounted in front of the source on a separate freight sled the channel spacing could be reduced to fractions of the 25 m spacing interval by combining several sweeps at the same location, thus increasing spatial resolution. The vibrator source was operated with a 10-250 Hz sweep over 10 s with 80% of the peak force of 66 kN. On soft surfaces a setup-sweep was utilized. Preliminary data analysis shows that sea floor geomorphology, subglacial sedimentary layering and englacial layering can be clearly imaged in the respective resolution of the source’s bandwidth. Interestingly, the ration of p-wave to s-wave energy varied considerably depending on the surface characteristics. In comparison to airborne and ground-based radar surveys, the system was able to image very steep sidewalls of subglacial trenches because of the large offset aperture where radar systems did not provide any reflections. Such system will help to considerably improve the future characterisation of sublglacial and englacial environments.

Description: The breakup of Gondwana is manifested by coeval early Jurassic Karoo magmatism in South Africa and East Antarctica. In South Africa, the large volumes of volcanic rocks of the adjoining Lebombo and Mwenetzi-Save monoclines represent a volcanic rift margin, and in East Antarctica, a corresponding feature, the Explora Wedge is buried below sediments and floating ice shelves on the continental margin of Dronning Maud Land. We use the seismic vibrator source to explore the sub-ice geology in Antarctica, and the new seismic reflection and available regional aeromagnetic data enable us to outline a dogleg landward extent of the Explora Wedge in Dronning Maud Land. The congruent inboard wedge geometries on the two continents define a high quality constraint, which facilitate for the first time, a geologically consistent and tight reconstruction of Africa relative to East Antarctica within Gondwana. The uncertainties in correlations of major geological features (mobile belts) from one continent to the other may now be of the order of ten’s of kilometers rather than hundreds of kilometers.

Description: We present a record encompassing marine isotope stages 7-1 from a hitherto unexplored and heavily ice-covered area of the Arctic Ocean, the Lomonosov Ridge off the northern Greenland-Canada continental margin, using nannofossil and benthic foraminifera stratigraphy. Planktic foraminifera assemblages are used as a key paleoceanographic proxy, and a surprisingly large variability is found for an interior Arctic Ocean site. Abundant small (63-125 µm) subpolar Turborotalita quinqueloba occur in two sections, possibly representing substages 5e (last interglacial) and 5a (warm interstadial). However, the present-day circulation pattern and the very distant location of high productive regions cannot explain such high abundances of subpolar specimens in the interior, perennially sea ice-covered Arctic Ocean. Hence our proxy record indicates that last interglacial sea ice concentrations were reduced off some areas of northern Greenland-Canada. Whether this was part of a larger regional pattern or it represents the influence of polynya areas with locally increased productivity remains to be solved. With respect to glacial conditions, increased ice-rafted debris (IRD) deposition in the area appears to be associated with glacial stages 6, 4, and late 3. Stage 2 sediments (including the Last Glacial Maximum) are condensed with a sparse IRD content only.