Description: Agglutinated foraminifers from 4 box cores spanning the past ca. 140 years (maximum) taken from the southern flank of the Skagerrak (NE North Sea) were studied. Fourtyseven species were identified, among them Liebusella goesi, Eggerelloides spp., Rhabdammina discreta, and Haplophragmoides bradyi are the most common. The two more westerly locations reveal significantly higher amounts of agglutinated foraminifers, which may be caused by a better supply of suitable food provided by east headed bottom currents. Extremely high sedimentation rates and a higher degree of pollution suggest environmental stress that may be one reason for lower amounts of agglutinated foraminifers at the two more easterly stations close to the Skagerrak deep. Increasing numbers of specimens within the present century suggests a combination of instability of the tests and ecological controls.

Description: Calcareous benthic foraminifera from four cores from the southern flank of the Skagerrak (NE North Sea) were investigated in order to estimate the response of this fossil group to climate fluctuations during the upper part of the Holocene. Q-mode factor analyses were carried out for the most abundant taxa. The results reveal C. laeuigata, H. baltllica, M. barleeanus, G. turgida, B. mal;yirintn, and U. yeregrirtn as most conm~on/importantta xa. In the upper part of all cores B. skagerrakensis shows a significant increase and dominates the foraminifer fauna in cores from greater water depth. The data suggest no direct relation between the fluctuations of foraminifer assemblages and climate change. However, climate forced fluctuations in the strength of the water-circulation caused considerable changes in the foraminifer assemblages. Three major assemblages were used for environmental analysis: H. baltlticn dominated assemblages were identified as indicators for stagnant conditions. They characterize the oldest core sections, most probably the Holocene climate optimum. Cassidl~linala euigata assemblages seem to indicate increasing current strength, a process that is often associated with deteriorating climatic conditions. Briznlirtn skaCqcrrnkensis appears to have a certain relation to unstable water masses, and probably a tolerance for increasing polution of the North Sea since the advent of modern industrialization.

Description: Marine habitats of shelf seas are in constant dynam- ic change and therefore need regular assessment particularly in areas of special interest. In this study, the single-beam acoustic ground discrimination system RoxAnn served to as- sess seafloor hardness and roughness, and combine these pa- rameters into one variable expressed as RGB (red green blue) color code followed by k-means fuzzy cluster analysis (FCA). The data were collected at a monitoring site west of the island of Helgoland (German Bight, SE North Sea) in the course of four surveys between September 2011 and November 2014. The study area has complex characteristics varying from out- cropping bedrock to sandy and muddy sectors with mostly gradual transitions. RoxAnn data enabled to discriminate all seafloor types that were suggested by ground-truth informa- tion (seafloor samples, video). The area appears to be quite stable overall; sediment import (including fluid mud) was de- tected only from the NW. Although hard substrates (boulders, bedrock) are clearly identified, the signal can be modified by inclination and biocover. Manually, six RoxAnn zones were identified; for the FCA, only three classes are suggested. The latter classification based on ‘hard’ boundaries would sufficefor stakeholder issues, but the former classification based on ‘soft’ boundaries is preferred to meet state-of-the-art scientific objectives.

Description: To determine the spatial resolution of sediment properties and benthic macrofauna communities in acoustic backscatter, the suitability of four acoustic seafloor classification devices (single-beam echosounder with RoxAnn and QTC 5.5 seafloor classification system, sidescan sonar with QTC Swathview seafloor classification, and multi-beam echosounder with QTC Swathview seafloor classification) was compared in a study area of approx. 6 km2 northwest of the island of Helgoland in the German Bight, southern North Sea. This was based on a simple similarity index between simultaneous sidescan sonar, single-beam echosounder and multi-beam echosounder profiling spanning the period 2011–2014. The results show a high similarity between seafloor classifications based on sidescan sonar and RoxAnn single-beamsystems, in turn associated with a lower similarity for the multi-beam echosounder system. Analyses of surface sediment samples at 39 locations along four transects (0.1 m2 Van Veen grab) revealed the presence of sandy mud (southern and western parts), coarse sand, gravel and cobbles. Rock outcrops were identified in the north-eastern and eastern parts. A typical Nucula nitidosa–Abra alba community was found in sandy muds to muddy sands in the northern part, whereas the southern part is characterised by widespread occurrence of the ophiuroid brittle star Amphiura filiformis. A transitional N. nitidosa–A. filiformis community was detected in the central part. Moreover, the southern part is characterised by a high abundance of A. filiformis and its commensal bivalve Kurtiella bidentata. The high number of A. filiformis feeding arms (up to ca. 6,800 per m2) can largely explain the gentle change of backscatter intensity along the tracks, because sediment composition and/or seafloor structures showed no significant variability.

Description: IMCOAST among a number of other initiatives investigates the modern and the late Holocene environmental de- velopment of south King George Island with a strong emphasis on Maxwell Bay and its tributary fjord Potter Cove (maximum water depth: about 200 m). In this part of the project we aim at reconstructing the modern sediment distribution in the inner part of Potter Cove using an acoustic ground discrimination system (RoxAnn) and more than136 ground-truth samples. Over the past 20 years the air temperatures in the immediate working area increased by more than 0.6 K (Schloss et al. 2012) which is less than in other parts of the West Antarctic Peninsula (WAP) but it is still in the range of the recovery of temperatures from the Little Ice Age maximum to the beginning of the 20th century. Potter Cove is a small fjord characterized by a series of moraine ridges produced by a tidewater glacier (Fourcade Glacier). Presumably, the farthest moraine is not much older than about 500 years (LIA maxi- mum), hence the sediment cover is rather thin as evidenced by high resolution seismic data. Since a few years at least the better part of the tidewater glacier retreated onto the island’s mainland. It is suggested that such a fun- damental change in the fjord’s physiography has also changed sedimentation patterns in the area. Potter Cove is characterized by silty-clayey sediments in the deeper inner parts of the cove. Sediments are coarser (fine to coarse sands and boulders) in the shallower areas; they also coarsen from the innermost basin to the mouth of the fjord. Textural structures follow the seabed morphology, i.e. small v-shaped passages through the moraine ridges. The glacier still produces large amounts of turbid melt waters that enter the cove at various places. We presume that very fine-grained sediments fall out from the meltwater plumes and are distributed by mid-depth or even bottom currents, thus suggesting an anti-estuarine circulation pattern. Older sediments that are more distal to the glacier front and sediments in shallower places (e.g. on top of the moraine ridges) become increasingly overprinted by coarser sediments from the shallow areas of the fjord. These areas are prone to wave induced winnowing effects as well as disturbances by ploughing icebergs. It can be concluded that coarsening of the fjord sediments will continue while the supply of fine-grained meltwater sediments might cease due to exhaustion of the reservoirs.

Description: During the past decades Mg/Ca ratios have been increasingly used in order to calculate past temperature variations independent from faunal assemblages. Especially in the Fram Strait, the main pathway of heat flux to the Arctic, new temperature estimation tools are urgently needed to better understand past complex interaction of different water masses and the extent of Atlantic Water advection to the Arctic Ocean. The Holocene section of a sediment core from the western Svalbard margin has been studied at high-resolution for benthic proxy indicators to reconstruct deepwater sources and mixing in the Arctic Gateway since the last ca 10,000 years. Benthic stable isotope values and sortable silt mean grain size data are compared to a first, preliminary data set of Mg/Ca paleotemperatures established from the benthic foraminifer species Cibicidoides wuellerstorfi in the eastern Fram Strait. When compared to planktic proxy indicators, this reconstruction of past bottom water temperatures at a northernmost site allows to estimate the linkage between deepwater inflow and AW advection within the West Spitsbergen Current. Furthermore, benthic Mg/Ca temperatures can help unravelling the local impact (e.g., by brine-enriched waters) from general trends in bottom water circulation. Short-lived decreases in benthic carbon isotope values seem to correlate to cold surface water events in the area such as the 8.2 ka event. Similarly, decreases in benthic carbon isotope values in the Nordic Seas around 8 ka have been assigned to decreased bottom water ventilation possibly due to an entrainment of relatively fresh water into the thermohaline system (Bauch et al., 2001). While sluggish bottom current speeds have been found for the 8.2 ka event north of our site on the Yermak Plateau (Hass, 2002), during colder events on the Western Svalbard margin sediment data seem to anticorrelate to benthic carbon isotope data either suggesting a rather unexpected increase in bottom current velocity or an impact of brine-enriched winter waters from the fjord/trough system which might have generated increased lateral coarser-grained sediment injections (Sarnthein et al., 2003). A Late Holocene trend towards significantly higher benthic oxygen isotopes may be either related to a cooling or increasing salinity in bottom waters. Higher salinity of bottom waters may be again caused by dense water formation during winter sea-ice formation in southern and western Svalbard fjords (e.g., Quadfasel et al., 1988; Rudels et al., 2005). Bauch, H. A., H. Erlenkeuser, R. F. Spielhagen, U. Struck, J. Matthiessen, J. Thiede, and J. Heinemeier (2001a), A multiproxy reconstruction of the evolution of deep and surface waters in the subarctic Nordic seas over the last 30,000 yr, Quaternary Science Reviews, 20(4), 659-678. Hass, H. C. (2002), A method to reduce the influence of ice-rafted debris on a grain size record from northern Fram Strait, Polar Research, 21(2), 299-306. Quadfasel, D., B. Rudels, and K. Kurz (1988), Outflow of dense water from a Svalbard fjord into the Fram Strait, Deep Sea Research Part A. Oceanographic Research Papers, 35(7), 1143-1150. Rudels, B., G. Bjork, J. Nilsson, P. Winsor, I. Lake, and C. Nohr (2005), The interaction between waters from the Arctic Ocean and the Nordic Seas north of Fram Strait and along the East Greenland Current: results from the Arctic Ocean-02 Oden expedition, Journal of Marine Systems, 55(1-2), 1-30. Sarnthein, M., S. van Krefeldt, H. Erlenkeuser, P. M. Grootes, M. Kucera, U. Pflaumann, and M. Schulz (2003), Centennial-to-millennial-scale periodicities of Holocene climate and sediment injections off the western Barents shelf, 75◦N, Boreas, 32, 447-461.

Description: Climate fluctuations of the past two millennia such as the Little Ice Age and the Medieval Warm Period are reported mainly from the Northern Hemisphere. Evidence from Antarctica is comparably sparse and reveals regional and temporal differences, which are particularly evident at the western and eastern sides of the Antarctic Peninsula. High-resolution coastal-marine sediment cores from the northernmost tip of the West Antarctic Peninsula reveal periods dominated by finer sediments between periods that lack the finer sediment component. In Maxwell Bay this fine sediment (grain size mode around 16 μm) has been traced back to sediment related to the occurrence of glacial meltwater. It was found in sheltered places and meltwater creeks of Potter Cove, a small tributary fjord to Maxwell Bay. In the sediment core this sediment occurs predominantly between 600 and 1250 AD (Medieval Warm Period) whereas it is only sparsely affecting the record between 1450 and 1900 AD (Little Ice Age). The temporal pattern is very similar to global-temperature reconstructions and even resembles temperature reconstructions from the Northern Hemisphere. To avoid local effects that may occur in Maxwell Bay more sediment cores were taken from bays and straits further south of King George Island during Cruise PS97 of RV “Polarstern” in 2016. A core from English Strait reveals completely different sedimentary conditions with no detectable meltwater signal (16 μm). However, the mean grain size record resembles that of the cores from Maxwell Bay. The lack of a clear-cut meltwater sediment class as it occurs further north is likely the result of a much smaller hinterland (Greenwich and Robert islands) when compared to Maxwell Bay between Nelson Island and the much bigger King George Island where glaciers and ice sheets discharge large quantities of very turbid meltwater directly into the bay. It is concluded that during the warmer climate periods a large amount of meltwa- ter was released along the NW Antarctic Peninsula. The related plume sediments were distributed downstream to overprint coastal sediments even though the amount was likely not sufficient to produce a discrete sediment class.

Description: Swath-bathymetry, high-resolution seismics and lithological data from the Wijdefjorden-Austfjorden fjord system, the largest fjord system on northern Spitsbergen, have been analysed. The data indicate that multiple halts and/or readvances during the deglaciation of the study area at the end of the last glacial occurred. However, even though the study area and several west Spitsbergen fjords are fed by the same glacier source (the ice field Lomonosovfonna), the final deglaciation of Wijdefjorden-Austfjorden took place after 9300 cal. years BP, i.e. at least approx. 2000 years later than in the west. It is suggested that the retarded deglaciation of the study area is mainly related to the fjord bathymetry, i.e. a more than 35 km wide and up to 60 m high plateau in the central parts of the study area (approx. 45 km beyond the present fjord head). Multiple, relatively large and partly stacked moraine ridges and sediment wedges are suggested to reflect that the ice front retreated slowly across this shallow area and that repeated readvances occurred. The absence of larger sediment wedges in the deeper parts between the shallow area and the fjord head may indicate that the final retreat occurred rapidly.

Description: Swath bathymetry and seismic data reveal two slide scars providing evidence for large-scale mass-wasting on the continental slope off northwest Spitsbergen. The largest scar is approx. 35 km long, at least 16 km wide and located between 1300 and 3000 m water depth. The failure is assumed to be of a retrogressive nature, because it affected multiple stratigraphic levels up to at least 200 ms two-way-travel time (approx. 150 m) below the present seafloor. The second largest slope failure affected an area of at least 35 km length, up to 7 km width and 70 ms (approx. 55 m) thickness below 1400 m water depth. It cuts into the south-eastern sidewall of the largest scar between 2700 and 2800 m water depth and deposition of sediment lobes within the largest scar occurred. The bathymetry within this slide scar is relatively smooth compared to the largest scar, but single blocks are visible. These observations suggest a retrogressive configuration of this slide, too. Minor failures along the side walls occur. Both slide scars are filled in with approx. 15 m of acoustically stratified sediments, suggesting that the slope failures occurred almost synchronously. However, the sediment lobes beyond the lower limit of the second largest slide scar suggest that this slide occurred after the largest slide. The slides were most probably triggered by seismic activity leading to failure within contouritic sediments.

Description: The Western Antarctic Peninsula experiences a temperature increase that is higher than in other parts of Antarctica. Within the last 50 years the tidewater glaciers in the tributary fjords of Maxwell Bay (King George Island) have retreated landwards with increasing speed. Meltwaters mobilize fine-grained sediments and transport those in plumes out of the coves into Maxwell Bay. Our hypothesis is that meltwater sediments characterize warmer climate periods of the Holocene. Marine sediment cores recovered along a profile of the eastern slope of Maxwell Bay were studied. The cores were taken in high-accumulation areas at the entrances of Collins Harbor, Marian and Potter coves. We measured the grain-size distribution in 1-cm steps in each core with a Laser diffraction particle analyzer (range 0.04–2500 μm) in order to resolve shifts in grain size compositions in very high resolution. We undertook different approaches for reliable age determination of the sediments. Since marine biogenic carbonate suitable for radiocarbon age determination is sparse, radiocarbon dating of the extracted humic acid fraction of the bulk sediment was included. Unfortunately, these age determinations turned out to be not reliable, likely because they are overprinted by an unknown older radiocarbon source. Preliminary results suggest that the cores cover approximately the last 2000 years. The magnetic susceptibility (MS) parameter fluctuates throughout the cores. It is negatively correlated to the amount of total organic carbon (TOC) and biogenic opal, suggesting dilution of the MS signal through higher input of organic material. Together with the bathymetry data, sub-bottom profiles reveal information on the interior of the topography and the geometry of the deposited sediments. The profiles obtained in Potter Cove show almost no sediment penetration suggesting either a very thin sediment cover and/or highly reworked unsorted sediments. The sub-bottom profiles from Maxwell Bay penetrate approximately 30 m beneath seafloor and show clearly stratified sediment layers in water depths 〉250 m. In conclusion we observe fluctuations in grain size, MS, TOC and biogenic opal that are most likely the result of tidewater glacier and ice sheet dynamics, the presence or absence of meltwater sediments and the variations in bioproductivity. Thus the cores reveal the history of climate-controlled sedimentation in Maxwell Bay including the history of deglaciation from adjacent coves of the upper Holocene.