Description: During the last season and ongoing planning, pre-site surveys are operated at the Ekströmisen, Dronning Maud Land, close to the Neumayer-Station III, with the primary target to build a stratigraphic age framework of the under-shelf-ice-sediments. These sediments are overlying the Explora Wedge [1], [2], a syn- or postrift volcanic deposit, and dipping north- to north-eastward. Expected ages could range from Late Mesozoic to Quaternary. From new vibroseismic profiles we will select sites for short core seafloor sampling of the oldest and of the youngest sediment sequences to confine their age time span. After that, we could select one or several sites for potential deep drillings (several hundred-meter-deep) with the support of international partner, if we could rise interest. The deep drillings should recover the sediments overlying the Explora Escarpment, and should discover the nature of the Explora Wedge as well. We expect that the overlying sediment sequences could reveal the history of polar amplification and climate changes in this part of Antarctica, the build-up of the East Antarctic Ice Sheet during past warmer climates and its Cenozoic and future dynamic and variability. The plan for seasons 2017/18 and 2018/19 are the testing of different sea floor sampling techniques through Hot Water Drill (HWD) holes. To select the drill sites for this shallow coring additional high resolution seismic will be acquired as well. Having holes through the shelf ice and sampling the sea floor will provide the unique opportunity for further piggy bag experiments consisting of multi-disciplinary nature. Experiments and measuring setup for oceanography, sea and shelf ice physics, geophysics, geology, hydrography, and biogeochemistry could be planned to characterize the sea-ice and shelf ice system, underlying water column, and the sediments. Video characterization underneath the shelf ice and at the seafloor, sediment trap deployment, seafloor mapping with an AUV (Leng, DFKI, ROBEX) could lead as well to innovative new interdisciplinary observations and discoveries of the sub-ice environment and ecosystem [3]. References: [1] Eisen, O., Hofstede, C., Diez, A., Kristoffersen, Y., Lambrecht, A., Mayer, C., Blenkner, R. & Hilmarsson, S., (2015), On-ice vibroseis and snowstream¬er systems for geoscientific research, Polar Science, 51-65, 9, http://dx.doi.org/10.1016/j.polar.2014.10.003. [2] Kristoffersen, Y., Hofstede, C., Diez, A., Blenkner, R., Lambrecht, A., Mayer, C. & Eisen, O., (2014), Reassembling Gondwana: A new high quality constraint from vibroseis exploration of the sub-ice shelf geology of the East Antarctic continental margin, J. Geophys. Res. Solid Earth, 9171-9182, 119 [3] Kuhn, G. & Gaedicke, C., (2015), A plan for interdisciplinary process-studies and geoscientific observations beneath the Ekström Ice Shelf (Sub-EIS-Obs), Polarforschung, 99-102, 84

Description: Sedimentary architecture and late Holocene development of a polar bay-mouth gravel spit system are presented based on ground-penetrating radar data, historical aerial images and radiocarbon dating. The spit is situated at the mouth of a tributary fjord formed by a tide water glacier and developed under the circumstances of an overall sea level fall. The system comprises two distinct marine terraces, situated below 0.8 m and at 3 to 5.7 m above present mean sea level. The upper terrace developed around 0.4 ka cal BP. It comprises several beach ridges formed by packages of seaward-dipping beds delimited by erosional unconformities. Beach ridges situated towards the more exposed western part of the spit facing the main fjord are internally characterized by convex aggradational bedding pattern. The lower terrace is located inside the bay in a more sheltered situation and comprises several curved beach ridges internally characterized by seaward-dipping beds delimited by erosional unconformities. The upper terrace is nowadays subjected to erosion and an up to 5 m high cliff developed towards the main fjord. There is a distinct shift in the direction of spit progradation through time, which we see as a reaction to intensified wave action at the beach and the retreat of the adjacent tide-water glacier. Furthermore, the lower terrace showed accelerated progradation during the last decades, probably in reaction to a reduction in annual sea-ice coverage, a lowering of the rate of glacioisostatic uplift and the subsequent stabilization of sea level, and an increased sediment availability.

Description: The MARUM-MeBo (abbreviation for Meeresboden-Bohrgerät, the German expression for seafloor drill rig) is a robotic drilling system that is developed since 2004 at the MARUM Center for Marine Environmental Sciences at the University of Bremen in close cooperation with Bauer Maschinen GmbH and other industry partners. The MARUM-MeBo drill rigs can be deployed from multipurpose research vessel like, RV MARIA S. MERIAN, RV METEOR, RV SONNE and RV POLARSTERN and are used for getting long cores both in soft sediments as well as hard rocks in the deep sea. The first generation drill rig, the MARUM-MeBo70 is dedicated for drilling depths of more than 70 m (Freudenthal and Wefer, 2013). Between 2005 and 2017 it was deployed on 18 research expeditions and drilled more than. 3 km into different types of lithologies including carbonate and crystalline rocks, gas hydrates, sands and gravel, glacial till and hemipelagic mud with an average recovery rate of 67 %. In February and March 2017 the MeBo70 was used on the West Antarctic continental shelf in the Amundsen Sea Embayment for the first time. The goal of the deployment on RV Polarstern expedition PS104 was to recover a series of sediment cores from different ages that will provide material for investigating the glaciation history of this area known as the most dynamic drainage area of the West Antarctic Ice Sheet. In this presentation we will focus on the operational experiences of this first deployment of a multi-barrel sea floor drill rig on the Antarctic continental shelf. References: Freudenthal, T and Wefer, G (2013) Drilling cores on the sea floor with the remote-controlled sea floor drilling rig MeBo. Geoscientific Instrumentation, Methods and Data Systems, 2(2). 329-337. doi:10.5194/gi-2-329-2013

Description: The first Holocene marine transgression reached the inner fiords of King George Island approximately at 9.5 ka BP according to Sugden and John (1973). This age marks today the minimum age of the end of the last glacial period obtained on land and the start of the Holocene in this Antarctic sector. Following the first Holocene marine transgression, Watcham et al. (2011) reconstructed a relative sea level curve for the South Shetland Islands with a relative sea level rise of 15.5 m amsl for Fildes Peninsula between 8 and 7 ka BP. The curve shows that a delay occurred in the isostatic uplift after 7.2 ka BP related to a glacier still-stand resulting in a relative sea level rise. This is followed by a drop of the relative sea level after 7 ka BP due to the rate of glacial unloading and isostatic rebound exceeding the rate of eustatic sea level rise. The aim of this presentation is to show new evidence, which will help to understand the postglacial paleoenvironmental changes on King George Island. Our chrono-stratigraphical and geomorphological studies in Potter Peninsula suggest, that the Holocene post-glacial marine transgression was not just initiated before 7.7 ka BP but also reached 14 m amsl, and was locally interrupted by a glacier advance after 7.3 ka BP. This glacier advance can be correlated to Watcham´s et al (2011) curve, showing a drop of relative sea level between 7.2 and 7 ka BP. In conclusion, we consider that a glacier readvance took place between 7.2 and 7 ka BP in the Southern sector of King George Island. Additionally our findings show that the age of 9.5 ka BP as a minimum age of the onset of the Holocene transgression in the South Shetland Islands has to be reconsidered. References Sugden, D. and John, B., 1973. The age of glacier fluctuations in the South Shetland Islands,Antarctica. In: van Zinderen Bakker, E.M. (Ed.), Palaeoecology of Africa, the Surrounding Islands, and Antarctica. A.A. Balkema, 139-159 p., Cape Town. Watcham, E. P., Bentley, M. J., Hodgson, D. A., Roberts, S. J., Fretwell, P. T., Lloyd, J. M., Larter, R. D., Whitehouse, P. L., Leng, M. J., Monien, P. and Moreton, S. G., 2011. A new Holocene relative sea level curve for the South Shetland Islands, Antarctica. Quaternary Science Reviews 30, 3152–3170.

Description: Recent findings of outcrops of the so-called "Explora Wedge" and overlying younger sediments below the Ekström Ice Shelf initiated discussion about discovering this area in more detail. The Ekström Ice Shelf is a characteristic ice shelf and one out of numerous small to medium scale ice shelves around East Antarctica. It is bordered by ice rises and ridges, has only a small catchment area and a slow flowing central ice stream. Nevertheless, this region is of critical importance to water-mass preconditioning in the Weddell Sea, and like other ice shelves in that area particularly susceptible to future environmental changes. We have learned about sub-ice-shelf melting and freezing processes as well as the formation of supercool water and ice platelets mostly through modelling. Observations from land-fast sea ice are still very rare. Ikaite and related inorganic carbonate precipitation, processes probably observed in the ANDRILL sediment cores, may be associated with freezing processes and brine formation in this type of environment. Hardly any measurements exist regarding oceanographic and glaciological seasonal cycles and associated processes below an ice shelf, close to its calving, or at the grounding zones. Observations and detailed spatial mapping of seafloor morphology and composition are difficult and can only be done with the aid of AUVs or ROVs diving below the ice shelf. "Deep SCINI", a ROV that can be lowered through an ice hole, discovered a school of fish hidden under 740 m of ice and 850 km away from the coast and light, living at the grounding zone of the Ross Ice Shelf (WISSARD project). It also discovered a community of sea anemones (Edwardsiella andrillae), a new species, which lives in high densities upside down on the underside of the ice shelf and is part of an unknown system of biogeochemical processes. These are two more examples for living at the edge on Planet Earth. Evidence of these biological, oceanographic and glaciological processes could have been archived in sedimentary deposits. With detailed seafloor mapping and high-resolution reflection seismic we hope to find postglacial and Holocene sediments. A sequence of more than 1000 m thick sediments has been detected lying on top of the "Explora Wedge" in an area between the ice shelf calving line and about 40 km inland below the Ekström Ice Shelf. Up to now, its age is relatively unknown but could range from Cretaceous to Pleistocene. Therefore, this area would be predestined for exploring East Antarctica\'s development from a greenhouse environment after the Gondwana breakup to a Cenozoic icehouse environment, thus enabling us to possibly reconstruct the history and variability of the East Antarctic Ice Sheet. We will present various sites for drill holes and would like to raise awareness and interest within the community of polar researchers. Due to the proximity to the Neumayer III Station, the logistics of possible future investigations will be easier and will have less of an environmental impact than if started elsewhere in Antarctica.

Description: A multi-proxy study including sedimentological, mineralogical, biogeochemical and micropaleontological methods was conducted on sediment core PS69/849-2 retrieved from Burton Basin, MacRobertson Shelf, East Antarctica. The goal of this study was to depict the deglacial and Holocene environmental history of the MacRobertson Land–Prydz Bay region. A special focus was put on the timing of ice-sheet retreat and the variability of bottom-water formation due to sea ice formation through the Holocene. Results from site PS69/849-2 provide the first paleo-environmental record of Holocene variations in bottom-water production probably associated to the Cape Darnley polynya, which is the second largest polynya in the Antarctic. Methods included end-member modeling of laser-derived high-resolution grain size data to reconstruct the depositional regimes and bottom-water activity. The provenance of current-derived and ice-transported material was reconstructed using clay-mineral and heavy-mineral analysis. Conclusions on biogenic production were drawn by determination of biogenic opal and total organic carbon. It was found that the ice shelf front started to retreat from the site around 12.8 ka BP. This coincides with results from other records in Prydz Bay and suggests warming during the early Holocene optimum next to global sea level rise as the main trigger. Ice-rafted debris was then supplied to the site until 5.5 cal. ka BP, when Holocene global sea level rise stabilized and glacial isostatic rebound on MacRobertson Land commenced. Throughout the Holocene, three episodes of enhanced bottom-water activity probably due to elevated brine rejection in Cape Darnley polynya occured between 11.5 and 9 cal. ka BP, 5.6 and 4.5 cal. ka BP and since 1.5 cal. ka BP. These periods are related to shifts from warmer to cooler conditions at the end of Holocene warm periods, in particular the early Holocene optimum, the mid-Holocene warm period and at the beginning of the neoglacial. In contrast, between 7.7 and 6.7 cal. ka BP, brine rejection shut down, maybe owed to warm conditions and pronounced open-water intervals.

Description: With this project, we want to enhance our knowledge of the global carbon cycle on glacial/ interglacial time-scales. To achieve this objective, it is of crucial importance to understand the role of the Southern Ocean on the release and uptake of greenhouse gases. As the southern Indian Ocean is currently fundamentally underrepresented in paleoceanographic reconstructions, it is our aim to reconstruct the contribution of this ocean to the atmospheric pattern of CO2. Therefore, we plan to use a novel multiproxy-approach, combining stable (δ13C) and radiogenic (d14C) isotope reconstructions with analyses of B/Ca-derived carbonate ion concentrations on a sediment core depth transect of the Kerguelen Islands. These analyses will provide a detailed insight into the history of water mass ventilation in the Indian Ocean on glacial/interglacial timescales. Ultimately, we want to combine the findings of this project with other water mass ventilation studies (e.g. Skinner et al., 2010; Sarnthein et al., 2013; Ronge et al., under review) and Earth System Modeling. These findings, in combination with previous studies from the Atlantic and Pacific Oceans will for the first time allow a comprehensive reconstruction of CO2-enriched deep-water during the last glacial, the ventilation throughout the deglaciation and the contribution to the atmospheric CO2-level.

Description: Sea floor morphology plays an important role in many scientific disciplines such as ecology, hydrology and sedimentology since geomorphic features can act as physical controls for e.g. species distribution, oceanographically flow-path estimations or sedimentation processes. In this study, we provide a terrain analysis of the Weddell Sea based on the 500 m × 500 m resolution bathymetry data provided by the mapping project IBCSO. Seventeen seabed classes are recognized at the sea floor based on a fine and broad scale Benthic Positioning Index calculation highlighting the diversity of the glacially carved shelf. Beside the morphology, slope, aspect, terrain rugosity and hillshade were calculated and supplied to the data archive PANGAEA. Applying zonal statistics to the geomorphic features identified unambiguously the shelf edge of the Weddell Sea with a width of 45–70 km and a mean depth of about 1200 m ranging from 270 m to 4300 m. A complex morphology of troughs, flat ridges, pinnacles, steep slopes, seamounts, outcrops, and narrow ridges, structures with approx. 5–7 km width, build an approx. 40–70 km long swath along the shelf edge. The study shows where scarps and depressions control the connection between shelf and abyssal and where high and low declination within the scarps e.g. occur. For evaluation purpose, 428 grain size samples were added to the seabed class map. The mean values of mud, sand and gravel of those samples falling into a single seabed class was calculated, respectively, and assigned to a sediment texture class according to a common sediment classification scheme.