Hannes Grobe’s research while affiliated with Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung and other places

Die magnetische Suszeptibilität von rezenten fluviatilen Sedimenten im Saale Einzugsgebiet wird mit derjenigen potentieller Liefergesteine verglichen. Liefergesteine mit hoher Suszeptibilität sind vor allem paläozoische Basaltoide und ihre metamorphen Produkte sowie stratiforme und gangförmige Vererzungen in Schiefergebirgsarealen. Dabei zeigt sich, dass geogene Quellen für die relativ hohe Suszeptibilität der fluviatilen Sedimente nicht allein verantwortlich sein können. Anthropogene Einträge, z.B. von Eisenabrieb des Straßen-und Schienenverkehrs und künstlich hergestellten Baumaterialien und Schlacken historischer Erzgewinnung, sind in vielen Proben nachweisbar. Vermutlich von besonderer Bedeutung sind Flugaschen, die aus Oberböden abgeschwemmt und in den Vorflutern transportiert und abgelagert werden. Dies dokumentiert, wie stark unsere Gesellschaft in fluviatile Systeme eingreift. Abstract Rock magnetic susceptibility in the catchment of River Thuringian Saale. Magnetic susceptibility of recent fluvial sediments of River Saale is compared to that of potential source rocks. Rocks with high susceptibility are especially palaeozoic basaltoids and their metamorphic products as well as stratiform and vein deposits in slate mountain areas. It is evident that geogenic sources alone cannot be responsible for the relatively high susceptibility values of fluvial sediments. Anthropogenic contributions by e.g. abrasion of metallic Fe from vehicles and trains, artificial building materials and scoria from historical ore mining are present in most samples. Fly ashes eroded from topsoils and transported and deposited within the drainage system are probably of high importance. This documents how strongly society impacts on fluvial systems. 36 M. PIRRUNG ET AL.

The Antarctic Peninsula’s Pacific margin is one of the best studied sectors of the Antarctic continental margin. Since the 1990s, several research cruises have targeted the continental rise with geophysical surveys, conventional coring and deep-sea drilling. The previous studies highlighted the potential of large sediment drifts on the rise as high-resolution palaeoenvironmental archives. However, these studies also suffered from chronological difficulties arising from the lack of calcareous microfossils, with initial results from geomagnetic relative palaeointensity (RPI) dating promising a possible solution. This paper presents data from new sediment cores recovered on cruise JR298 from seven continental rise sites west of the Antarctic Peninsula and in the Bellingshausen Sea with the objectives to (i) seek calcareous foraminifera, especially at shallow drift sites, to constrain RPI-based age models, and (ii) investigate the depositional history at these locations. We present the results of chronological and multi-proxy analyses on these cores and two cores previously collected from the study area. We establish new age models for the JR298 records and compare them with published RPI-based age models. In addition, we evaluate the reliability of different palaeoproductivity proxies and infer depositional processes. Planktic foraminifera are present in various core intervals. Although their stable oxygen isotope (δ¹⁸O) ratios, tephrochronological constraints and glacial-interglacial changes in sediment composition provide age models largely consistent with the RPI chronologies, we also observe distinct differences, predominantly in the Bellingshausen Sea cores. Enrichments of solid-phase manganese together with evidence for “burn-down” of organic carbon in late glacial and peak interglacial sediments document non-steady-state diagenesis that may have altered magnetic mineralogy and, thus, RPI proxies. This process may explain discrepancies between RPI-based age models and those derived from δ¹⁸O data combined with tephrochronology. The data also indicate that organic carbon is a much less reliable productivity proxy than biogenic barium or organically-associated bromine in the investigated sediments. In agreement with previous studies, sediment facies indicate a strong control of deposition on the rise by bottom currents that interacted with detritus supplied by meltwater plumes, gravitational down-slope transport processes and pelagic settling of iceberg-rafted debris (IRD) and planktic microfossils. Bottom-current velocities underwent only minor changes over glacial-interglacial cycles at the drift crests, with down-slope deposition only rarely affecting these shallow locations. Maximum concentrations of coarse IRD at the seafloor surfaces of the shallow sites result predominantly from upward pumping caused by extensive bioturbation. This process has to be taken into account when past changes in IRD deposition are inferred from quantifying clasts >1 mm in size.

Small changes in the radiation budget at the earth's surface can lead to large climatological responses when persistent over time. With the increasing debate on anthropogenic influences on climatic processes during the 1980s the need for accurate radiometric measurements with higher temporal resolution was identified, and it was determined that the existing measurement networks did not have the resolution or accuracy required to meet this need. In 1988 the WMO therefore proposed the establishment of a new international Baseline Surface Radiation Network (BSRN), which should collect and centrally archive high-quality ground-based radiation measurements in 1 min resolution. BSRN began its work in 1992 with 9 stations; currently (status 2018-01-01), the network comprises 59 stations (delivering data to the archive) and 9 candidates (stations recently accepted into the network with data forthcoming to the archive) distributed over all continents and oceanic environments. The BSRN database is the World Radiation Monitoring Center (WRMC). It is hosted at the Alfred Wegener Institute (AWI) in Bremerhaven, Germany, and now offers more than 10 300 months of data from the years 1992 to 2017. All data are available at 10.1594/PANGAEA.880000 free of charge.

Copepods are often the predominant taxa in marine zooplankton and play an important role in the food web as intermediators between primary producers, the microbial loop and higher trophic levels. Due to their short life cycles and their rapid response to changing environments they are good indicators for ecosystem health and status. Investigating the effects of environmental change on planktonic copepods and thus the pelagic ecosystem requires data on species abundance and distribution. Here, we present 33 data sets with abundance and occurrence of planktonic copepods from 20 expeditions to the Southern Ocean (Weddell Sea, Scotia Sea, Amundsen Sea, Bellingshausen Sea, Antarctic Peninsula), one expedition to the Magellan region, one latitudinal transect in the Eastern Atlantic Ocean, one expedition to the Great Meteor Bank and one expedition to the northern Red Sea and Gulf of Aqaba. In this data compilation a total of 349 stations between 1985 and 2005 were archived. These data sets are now freely available at PANGAEA via the persistent identifier doi:10.1594/PANGAEA.884619. During most expeditions depth-stratified samples were taken with a Hydrobios multinet with 5 or 9 nets. On few occasions a Nansen or Bongo net was deployed. The deepest sample reached down to 2880 meter. As metadata sampling date and date/time, latitude, longitude, bottom depth, sampling depth interval, volume of filtered water and information of the net type and mesh size were recorded. Abundance and distribution data for 284 calanoid copepod species and 28 taxa of other copepod orders are provided. The taxonomic concept was consistent throughout the data sets. The density of calanoid copepod species was separately counted for females, males and copepodites. For selected species also the individual copepodite stages were counted.

Small changes in the radiation budget at the earth’s surface can lead to large climatological responses when persistent over time. With the increasing debate on anthropogenic influences on climatic processes during the 1980s the need for accurate radiometric measurements with higher temporal resolution was identified, and it was determined that the existing measurement networks did not have the resolution or accuracy required to meet this need. In 1988 the WMO therefore proposed the establishment of a new international Baseline Surface Radiation Network (BSRN), which should collect and centrally archive high quality ground-based radiation measurements in 1-minute resolution. BSRN began its work in 1992 with 9 stations, currently (status 2018-01-01), the network comprises 59 stations (with data) and 9 candidates (stations recently accepted into the network with data forthcoming to the archive) distributed over all continents. The BSRN database is the World Radiation Monitoring Center. It is hosted at the Alfred Wegener Institute in Bremerhaven, Germany and now offers more than 10 300 months of data from the years 1992 to 2017. All data are available at https://doi.pangaea.de/10.1594/PANGAEA.880000 free of charge.

The GIK-Archive of radiographs is a collection of X-ray negative and photographic images of sediment cores based on exposures taken since the early 1960s. During four decades of marine geological work at the University of Kiel, Germany, several thousand hours of sampling, careful preparation and X-raying were spent on producing a unique archive of sediment radiographs from several parts of the World Ocean. The archive consists of more than 18 500 exposures on chemical film that were digitized, geo-referenced, supplemented with metadata and archived in the data library PANGAEA®. With this publication, the images have become available open-access for use by the scientific community at https://doi.org/10.1594/PANGAEA.854841.

Previous reconstructions of ice-sheet changes in Antarctica's Weddell Sea sector since the Last Glacial Maximum (LGM) at 19-23 cal. (calibrated) kyr B.P. suffered from large uncertainties and were partly contradictory. As a consequence, the contribution of this sector to the LGM sea-level lowstand and post-LGM sea-level rise was unclear. Furthermore, whether and how precursor water masses for Antarctic Bottom Water (AABW) were formed in the Weddell Sea Embayment under glacial conditions is unknown, as this today requires the existence of the floating Filchner-Ronne Ice Shelf. Here we present new marine geophysical and marine geological data from the outer shelf section of the Filchner paleo-ice stream trough documenting that grounded ice had advanced onto and retreated from the outer shelf prior to 27.5 cal. kyr B.P., i.e., > 4500 yr before the LGM. The data reveal the presence of a stacked grounding-zone wedge (GZW) just south of 75°30'S. This GZW was formed during two episodes of grounding-line re-advance onto the outer shelf after 11.8 cal. kyr B.P., with data further inshore implying paleo-ice stream retreat from the GZW location prior to 8.7 cal. kyr B.P. Our findings show that (1) ice-sheet buildup in the Weddell Sea sector made only limited contributions to the LGM sea-level lowstand, (2) ice-ocean interaction below an ice shelf in outer Filchner Trough could have contributed to AABW production at the LGM, and (3) numerical models need to take into account a highly dynamic ice-sheet behavior in regions of the West Antarctic Ice Sheet and East Antarctic Ice Sheet confluence.

Recent advances in underwater imaging technology allow for the gathering of invaluable scientific information on seafloor ecosystems, such as direct in situ views of seabed habitats and quantitative data on the composition, diversity, abundance, and distribution of epibenthic fauna. The imaging approach has been extensively used within the research project DynAMo (Dynamics of Antarctic Marine Shelf Ecosystems) at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Bremerhaven (AWI), which aimed to comparatively assess the pace and quality of the dynamics of Southern Ocean benthos. Within this framework, epibenthic spatial distribution patterns have been comparatively investigated in two regions in the Atlantic sector of the Southern Ocean: the shelf areas off the northern tip of the Antarctic Peninsula, representing a region with above-average warming of surface waters and sea-ice reduction, and the shelves of the eastern Weddell Sea as an example of a stable high-Antarctic marine environment that is not (yet) affected by climate change. The AWI Ocean Floor Observation System (OFOS) was used to collect seabed imagery during two cruises of the German research vessel Polarstern, ANT-XXIX/3 (PS81) to the Antarctic Peninsula from January to March 2013 and ANT-XXXI/2 (PS96) to the Weddell Sea from December 2015 to February 2016. Here, we report on the image and data collections gathered during these cruises. During PS81, OFOS was successfully deployed at a total of 31 stations at water depths between 29 and 784 m. At most stations, series of 500 to 530 pictures (> 15 000 in total, each depicting a seabed area of approximately 3.45 m2 or 2.3 × 1.5 m) were taken along transects approximately 3.7 km in length. During PS96, OFOS was used at a total of 13 stations at water depths between 200 and 754 m, yielding series of 110 to 293 photos (2670 in total) along transects 0.9 to 2.6 km in length. All seabed images taken during the two cruises, including metadata, are available from the data publisher PANGAEA via the two persistent identifiers at 10.1594/PANGAEA.872719 (for PS81) and 10.1594/PANGAEA.862097 (for PS96).

The GIK-Archive of radiographs is a collection of X-ray negative images from sediment cores, prepared and exposed since the early 1960s. During four decades of marine geological work at the University of Kiel, Germany, some thousand hours of sampling, careful preparation and x-raying were spent to produce a unique archive of sediment 10 radiographs from several parts of the world ocean. The archive consists of more than 18 500 exposures on chemical film that were digitized, geo-referenced, supplemented with metadata and archived in the data library PANGAEA®. With this publication, the images become available in Open Access for use by the scientific community at https://doi.pangaea.de/10.1594/PANGAEA.854841.

Recent advances in underwater imaging technology allow for gathering invaluable scientific information on sea- floor ecosystems, such as direct in-situ views of seabed habitats and quantitative data on composition, diversity, abundance and distribution of epibenthic fauna. The imaging approach has been extensively used within the research project Dynamics of Antarctic Marine Shelf Ecosystems (DynAMo) of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Bremerhaven (AWI), which aimed to comparatively assess the pace and quality of the dynamics of Southern Ocean benthos. Within this framework, epibenthic spatial distribution patterns have been comparatively investigated in two regions of the Atlantic sector of the Southern Ocean, the shelf areas off the northern tip of the Antarctic Peninsula, representing a region with above-average warming of surface waters and sea-ice reduction, and the shelves of the eastern Weddell Sea, as an example of a stable high-Antarctic marine environment that is not (yet) affected by climate change. The Ocean Floor Observation System (OFOS) of the AWI was used to collect seabed imagery during two cruises of the German research vessel Polarstern, ANT-XXIX/3 (PS81) to the Antarctic Peninsula in January–March 2013 and ANT-XXXI/2 (PS96) to the Weddell Sea from December 2015 to February 2016. Here, we report on the image and data collections gathered during these cruises. During PS81, OFOS was successfully deployed at a total of 31 stations at water depths between 29 and 784 m. At most stations, series of 500 to 530 pictures (> 15,000 in total, each depicting a seabed area of approx. 3.45 m² (= 2.3 m × 1.5 m)) were taken along transects of approx. 3.7 km length. During PS96, OFOS was used at a total of 13 stations at water depths between 200 and 754 m, yielding series of 110 to 293 photos (2,670 in total) along transects of 0.9 to 2.6 km length. All seabed images taken during the two cruises, including metadata, are available from the data publisher PANGAEA via the two persistent identifiers doi:10.1594/PANGAEA.872719 (for PS81) and doi:10.1594/PANGAEA.862097 (for PS96).