Description: Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. Based on new hydroacoustic data, we propose that the most recent hot spot volcanic activity occurs west of the island. We surveyed relatively young intraplate volcanic fields and scattered, probably monogenetic, submarine volcanoes with multibeam echosounders and sub-bottom profilers. Structural and zonal GIS analysis of bathymetric and backscatter results, based on habitat mapping algorithms to discriminate seafloor features, revealed numerous previously-unknown volcanic structures. South of Tristan da Cunha, we discovered two large seamounts. One of them, Isolde Seamount, is most likely the source of a 2004 submarine eruption known from a pumice stranding event and seismological analysis. An oceanic core complex, identified at the intersection of the Tristan da Cunha Transform and Fracture Zone System with the Mid-Atlantic Ridge, might indicate reduced magma supply and, therefore, weak plume-ridge interaction at present times.

Description: The Walvis Ridge-Rio Grande Rise System is the only seamount chain in the Atlantic that is known being continuously active since the Cretaceous (130 Ma) and one of very few worldwide, that links an active hotspot (Tristan-Gough) with a continental flood basalt province (the Paraná-Etendeka province in South America and Africa). Previous work has documented age-progressive volcanism along at least parts of the Walvis Ridge and several initiatives acquired new geophysical and petrological data from seamounts of the Walvis Ridge and its southerly neighbours over the last decade. The youngest stretch of the Walvis Ridge, the islands of Tristan da Cunha, was the focus of the ISOLDE project within the DFG priority program SPP1375 „South Atlantic Margin Processes and Links with onshore Evolution (SAMPLE)”. Temporary seismological and magneto-telluric measurements were carried out to characterize the upper mantle in the search for evidence of a mantle plume. Two expeditions with R/V MARIA S. MERIAN headed towards this remote area to install and dismantle ocean-bottom stations in 2012 and 2013, respectively. Hydroacoustic data were collected along the tracks and around the islands, allowing a first detailed bathymetric insight to the area, underpinned by backscatter and sediment echo sounder observations. One unexpected outcome was the discovery of a new submarine volcano, Isolde Seamount, at the eastern flanks of Nightingale Island. Isolde lies very close to the assumed site of a submarine eruption in 2004, known only from floating pumice and seismicity. Further submarine volcanic centres could be mapped around the islands. Of interest are two volcanic fields, each about 20 x 40 km across, to the NW of Inaccessible Island, where small monogenetic volcanic cones and young lava flows were mapped. Young volcanic activity seems to extend up to 250 km westwards from the Tristan group to about 14.8 W, where we mapped a small volcanic cone on top of old abyssal hills only 130 km east of the Mid-Atlantic Ridge. Further westward, normal seafloor fabric, with clearly defined abyssal hills, dominates the seafloor. Scattered volcanic activity is visible along and in close vicinity to the Tristan da Cunha Fracture Zone. The intraplate volcanic fields as well as the scattered probably monogenetic submarine volcanoes could indicate that the Tristan mantle plume (or at least part of it) currently sits to the west/southwest of Tristan da Cunha.

Description: Biodiversity is expected to change in response to future global warming. However, it is difficult to predict how species will track the ongoing climate change. Here we use the fossil record of planktonic foraminifera to assess how biodiversity responded to climate change with a magnitude comparable to future anthropogenic warming. We compiled time series of planktonic foraminifera assemblages, covering the time from the last ice age across the deglaciation to the current warm period. Planktonic foraminifera assemblages shifted immediately when temperature began to rise at the end of the last ice age and continued to change until approximately 5,000 years ago, even though global temperature remained relatively stable during the last 11,000 years. The biotic response was largest in the mid latitudes and dominated by range expansion, which resulted in the emergence of new assemblages without analogues in the glacial ocean. Our results indicate that the plankton response to global warming was spatially heterogeneous and did not track temperature change uniformly over the past 24,000 years. Climate change led to the establishment of new assemblages and possibly new ecological interactions, which suggests that current anthropogenic warming may lead to new, different plankton community composition.

Description: Palaeoclimate data hold the unique promise of providing a long-term perspective on climate change and as such can serve as an important benchmark for climate models. However, palaeoclimate data have generally been archived with insufficient standardisation and metadata to allow for transparent and consistent uncertainty assessment in an automated way. Thanks to improved computation capacity, transient palaeoclimate simulations are now possible, calling for data products containing multi-parameter time series rather than information on a single parameter for a single time slice. Efforts are underway to simulate a complete glacial–interglacial cycle using general circulation models (https://www.palmod.de/, last access: 6 May 2020), and to confront these simulations with palaeoclimate data, we have compiled a multi-parameter marine palaeoclimate data synthesis that contains time series spanning 0 to 130 000 years ago. We present the first version of the data product that focuses exclusively on time series for which a robust chronology based on benthic foraminifera δ18O and radiocarbon dating is available. The product contains 896 time series of eight palaeoclimate parameters from 143 individual sites, each associated with rich metadata, age–depth model ensembles, and information to refine and update the chronologies. This version contains 205 time series of benthic foraminifera δ18O; 169 of benthic foraminifera δ13C; 131 of seawater temperature; 174 and 119 of planktonic foraminifera δ18O and δ13C; and 44, 38 and 16 of carbonate, organic carbon and biogenic silica content, respectively. The data product is available in three formats (R, LiPD and netCDF) facilitating use across different software and operating systems and can be downloaded at https://doi.org/10.1594/PANGAEA.908831 (Jonkers et al., 2019). This data descriptor presents our data synthesis strategy and describes the contents and format of the data product in detail. It ends with a set of recommendations for data archiving.

Description: Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. Based on new hydroacoustic data, we propose that the most recent hot spot volcanic activity occurs west of the island. We surveyed relatively young intraplate volcanic fields and scattered, probably monogenetic, submarine volcanoes with multibeam echosounders and sub-bottom profilers. Structural and zonal GIS analysis of bathymetric and backscatter results, based on habitat mapping algorithms to discriminate seafloor features, revealed numerous previously-unknown volcanic structures. South of Tristan da Cunha, we discovered two large seamounts. One of them, Isolde Seamount, is most likely the source of a 2004 submarine eruption known from a pumice stranding event and seismological analysis. An oceanic core complex, identified at the intersection of the Tristan da Cunha Transform and Fracture Zone System with the Mid-Atlantic Ridge, might indicate reduced magma supply and, therefore, weak plume-ridge interaction at present times.

Description: Sub bottom profiler (SBP) aka sediment echosounder data. Sediment echosounder measurements were conducted continuously by means of Teledyne PARASOUND DS3 (P70) parametric sediment echosounder during both R/V MARIA S. MERIAN cruises, MSM20-2 (Jegen et al., 2015) and MSM24, until the shutdown of the system due to technical reasons on cruise MSM24. The system's beam width is 4.5° along-track and 5.0° across-track. The primary high frequency signal (PHF) with a frequency of about 18 kHz was recorded for water-column investigations while the secondary low frequency signal (SLF) with a frequency of 4 kHz is used to image the shallow sub-seafloor. This selection of four PARASOUND profiles were converted into SEG-Y data by using the PS32segy tool (Hanno Keil, University of Bremen, Germany). Afterwards, the ReflexW software57 (Sandmeier, 2012) was used to low-pass filter the data and to mute the water column.

Description: Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. Based on new hydroacoustic data, we propose that the most recent hot spot volcanic activity occurs west of the island. We surveyed relatively young intraplate volcanic fields and scattered, probably monogenetic, submarine volcanoes with multibeam echosounders and sub-bottom profilers. Structural and zonal GIS analysis of bathymetric and backscatter results, based on habitat mapping algorithms to discriminate seafloor features, revealed numerous previously-unknown volcanic structures. South of Tristan da Cunha, we discovered two large seamounts. One of them, Isolde Seamount, is most likely the source of a 2004 submarine eruption known from a pumice stranding event and seismological analysis. An oceanic core complex, identified at the intersection of the Tristan da Cunha Transform and Fracture Zone System with the Mid-Atlantic Ridge, might indicate reduced magma supply and, therefore, weak plume-ridge interaction at present times.

Description: Content The attached raster-files are saved in the formats PDF and georeferenced PNG. The shapefile "VolcanicCones_Tristan", including its auxiliary files, as well as all other georeferenced files are shown in the projected coordinate system UTM28S with geodetic datum WGS84 (EPSG # 32728). The two Excel files contain a, the volume calculation of the volcanic cones and b, the decision table for the BPI classification. 1. Rugosity/Ruggedness raster & Benthic Terrain Modeler: To investigate the structural complexity of the study area, a rugosity (surface roughness) raster was created using the arc-chord ratio (ACR) index after Du Preez (2015). The ACR method is defined as the contoured area of the surface divided by the area of the surface orthogonally projected onto a plane of best fit. In this way, it effectively decouples rugosity from the slope. To reduce artefacts in the rugosity raster caused by the underlying bathymetry data, the ACR rugosity raster was calculated from the three-fold resampled bathymetry data. The benthic terrain of Tristan da Cunha was analyzed using ESRIs ArcGIS™ with the aid of the ArcGIS application's Benthic Terrain Modeler (BTM) v. 3.0 (Lundblad et al., 2006; Wright et al., 2012) which classifies bathymetry data and analyses seafloor characteristics. The most important derivative for this analysis is the Bathymetric Position Index (BPI). The BPI is modified from the Topographic Position Index, which is used in terrestrial environments (Weiss, 2001). It compares the elevation of each cell in the bathymetry raster with the mean elevation of a defined neighborhood around that cell. In this analysis, an annulus neighborhood with an inner and outer radius is used. To identify both fine and broad features on the seafloor, two BPI grids were created using an inner radius of 15 km and an outer radius of 22.5 km for the broad-scale BPI raster and 1.5 km and 3 km, respectively, for the fine-scale BPI raster. Since the bathymetric position tends to be auto-correlated (Erdey-Heydorn, 2008), the BPI grids were standardized. The overall structural analysis was based on a classification dictionary (Supplementary Material Table S2) which defines several geomorphological structures by their broad and fine scale BPI and their slope. The transition from flat areas to broad slopes was set to 3° and from broad to steep slopes to 25°. 2. Slope & Aspect Slope and aspect are first order derivates of the bathymetry. They are both shown in colored categories. 3. Backscatter The beam time series are shown as a mosaic in stretched greyscale from black & white and in color white to brown. For analysis the dataset was separated in categories and shown in colors from dark green to light brown. 4. Volume calculations of volcanic cones: We utilized the GIS software GlobalMapper v18.2 for volume calculations of the volcanic cones, though the prework to generate the volcanic cone polygons was conducted with ESRIs ArcGIS™. The result of the BTM classification was used to extract the four classes that represent outcrops or local ridges (see Supplementary Material Table S2: Class 6, 11, 13 and 14). This outcrop raster was then converted into polygon features. Areas smaller than 0.1 km² were excluded from further analyses. Since it is not possible to select polygons by their shape, a manual selection of the polygon features was necessary to remove all polygons that do not represent circular cone-shaped morphologies (e.g., elongated ridges or parts of the main islands). Furthermore, all polygons were buffered as the outcrop classes from the BTM classification result do not extend to the approximate base of the outcrops, which is due to the functionality of the BPI. The best buffer distance was measured exemplarily (here we buffered with 200 m). Finally, the polygons were smoothed by a Bezier Interpolation and exported as a shapefile. The actual volume calculation was conducted with GlobalMapper's analysis & measurement tool "Pile Volume" and exported as a .CSV file (Supplementary Material Table S1). Mean backscatter values were calculated for each volcanic cone by using the ArcGIS tool "Zonal Statistics". Very low (〈-68 dB) and very high (〉-8 dB) backscatter values were excluded beforehand using the "Extract by Attribute tool" as they mainly occur near the outer beams and the nadir and, therefore, most likely represent erroneous dB values.