Description: Eastern Boundary Upwelling Ecosystems (EBUEs) are associated with high biological productivity, high fish catch and they highly contribute to marine carbon sequestration. Whether coastal upwelling has intensified or weakened under climate change in the past decades is controversially discussed and different approaches (e.g., time-series of chlorophyll, wind, sea surface temperature, modeling experiments) have been considered. We present a record of almost two decades of particle fluxes (1991–2009) from ca. 600 to 3100 m water depth in the Canary Basin at site ESTOC (European Station for Time series in the Ocean Canary Islands; ca. 29°N, 15°30.W, ca. 3600 m water depth), located in the offshore transition zone of the northern Canary Current-EBUE. We compare these flux records with those measured at a mesotrophic sediment trap site further south off Cape Blanc (Mauritania, ca. 21°N). The deep ocean fluxes at ESTOC in ca. 3 km recorded the evolution of the coastal Cape Ghir filament (30–32°N, 10–12°W) due to lateral advection of particles, whereas the upper water column sediment traps in ca. 1 km reflected the oligotrophic conditions in the overlying waters of ESTOC. We observed an increased emphasis in spring-time fluxes since 2005, associated with a change in particle composition, while satellite chlorophyll biomass did not show this pattern. Due to its northern location in the CC-EBUEs, spring biogenic fluxes at ESTOC provide a better relationship to the forcing of the North Atlantic Oscillation than those recorded further south off Cape Blanc. Off Cape Blanc, deep fluxes showed the best overlap with the deep ESTOC fluxes during the spring season before 2005. On the long-term, both chlorophyll and particle fluxes showed an increasing trend at ESTOC which was not observed further south at the mesotrophic Cape Blanc site. This might indicate that, depending on their location along the NW African margin, coastal upwelling systems react differently to global change.

Description: Calcium carbonate hexahydrate (ikaite) is a rare mineral that forms as metastable species in the organic-carbon-rich sediments of the King George Basin, Bransfield Strait, Antarctica, as a consequence of early diagenetic decomposition of organic matter under cold water (−1.4 °C) and high pressure (200 bar) conditions. Large crystals grow in the sediment immediately below the diagenetic transition between microbial sulfate reduction and methanogenesis at ~320 cm below sea floor (bsf). This process is reflected in the dissolved sulfate, total carbon dioxide, and methane concentrations, as well as in the carbon, hydrogen, and oxygen isotope chemistries of the interstitial fluids and dissolved gases of the host sediment. The ikaite crystal faithfully records in its zonal structure the changing carbon isotope ratio of the total dissolved carbon dioxide pool as it gradually diminishes during methanogenesis (δ13Cikaite = −17.5 to −21.4‰). These changes in the crystal’s host environment follow general Rayleigh carbon isotope fractionation. The oxygen isotopes of the ikaite carbonate (δ18Oikaite = 1.46 to 4.45‰) also show a strong zonal distribution, unrelated to temperature of formation, but perhaps controlled by the degree of recrystallization of ikaite to calcite. The crystal water of the ikaite is depleted 11‰ in 2H/1H (VSMOW) relative to the coexisting interstitial water, which is in excellent agreement with the isotope fractionation of other hydrated minerals. In addition to the in situ temperature and pressure, nucleation of the ikaite crystals in the Bransfield Basin sediments may be induced by the high alkalinity, high phosphate concentrations, and dissolved organic compounds. Intense microbial metabolism generates such compounds; of these, aspartic acid and glutamic acid may play an important role, as they do in biological and extracellular carbonate mineral precipitation. All indications are that low temperatures (such as of polar environments), high calcium carbonate supersaturation caused by interstitial methanogenesis, and a sufficiently large supply of dissolved phosphate and amino acids favor metastable ikaite formation. These conditions, modified by recrystallization, may be preserved in calcite glendonites, thinolites, and other calcitic pseudomorphs derived from ikaite and found throughout the ancient sedimentary record.

Description: Over the last two decades sea bed drilling technology has proven to provide a valuable complement to the services of classical drill ships. Especially for shallow drillings up to 200 mbsf and when working in remote areas difficult to access, sea bed drill rigs are a cost-effective alternative. Recent developments especially concerning borehole logging techniques add to the capabilities of sea bed drilling technology. The MARUM-MeBo is a robotic drilling system that is developed since 2004 at the MARUM Center for Marine Environmental Sciences at the University of Bremen (Freudenthal and Wefer, 2013). The drill rig is deployed on the sea bed and remotely controlled from the vessel. It is used for core drilling in soft sediments as well as hard rocks in the deep sea. Especially since an upgrade in 2007/2008 for the use of wireline drilling technique, the first-generation drill rig MARUM-MeBo70 with a drilling capacity of about 70 m was successfully deployed on more than 15 research expeditions. Since 2014 the second-generation drill rig MARUM-MeBo200 with an increased drilling capacity of up to 200 m below sea floor is successfully in operation. In this presentation we focus on results of three recent drilling campaigns, exemplifying the exploitation of the potential of the sea bed drilling technology: In early 2017 the MeBo70 was deployed from the ice breaking vessel RV POLARSTERN on the West Antarctic shelf (Gohl et al., 2017), an area difficult to access by a drill ship. We were able to recover a sedimentary sequence of the upper Cretaceous time period as one of the very few terrigenous records from this time in Antarctica. This sequence indicates that about 92 to 83 Mio years ago at a paleolatitude of about 82°S this area was covered by a temperate coastal rain forest, making any Antarctic ice sheet formation at this time period unlikely (Klages et al., in press). Also, in 2017 the MeBo70 was deployed in the Arctic off Svalbard. Next to coring a temperature probe was used to assess in situ temperatures and local geothermal gradients (Riedel et al. 2018). Combining these temperature data with the porewater geochemistry of the drilled cores Wallmann et al (2018) were able to prove the effect of isostatic rebound after deglaciation on gas hydrate dissociation. In late 2017 the MeBo200 was deployed in the Black Sea. Geophysical borehole log data of P-wave velocity, electrical resistivity, and spectral gamma ray were combined with core-derived physical properties of porosity, magnetic susceptibility, and bulk density and compared with seismic data of the region (Riedel et al., in press). This study shows the potential of core-log seismic integration for shallow drilling campaigns conducted with a sea bed drill rig. References: Freudenthal, T and Wefer, G (2013) Geoscientific Instrumentation, Methods and Data Systems, 2(2). 329-337. doi:10.5194/gi-2-329-2013 Gohl, K, et al. (2017) Geochemistry, Geophysics, Geosystems, 18, 4235–4250. https://doi.org/10.1002/2017GC007081 Klages, JP et al. (in press) Nature, 2019-10-14805B Riedel, M et al. (2018) Geochemistry, Geophysics, Geosystems, 19, 1165–1177. doi:10.1002/2017GC007288 Riedel, M et al. (in press) Marine and Petroleum Geology, doi.org/10.1016/j.marpetgeo.2019.104192 Wallmann, K et al. (2018) Nature Communications, 9:83, DOI: 10.1038/s41467-017-02550-9

Description: The data set compiles gamma-ray wet bulk density, magnetic susceptibility (MS), and XRF core scans of the three cores GeoB16433-1 (38° 07.843'N, 144° 00.135'E, 7,525 m water depth), GeoB16431-1 (38° 00.177'N, 143° 59.981'E, 7,542 m water depth), and GeoB16444-1 (37° 42.017'N, 143° 52.377'E, 7,529 m water depth) retrieved from the central Japan Trench during Sonne Cruise SO219A in 2012. Gamma-ray wet bulk density and MS were measured by using the Geotek multi-sensor core logger at MARUM, University of Bremen. XRF core scans (elements: Al, Si, S, K, Ca, Ti, Mn, Fe, Br, Rb, Sr, Zr) were analyzed by using the Avaatech XRF core scanner at MARUM, University of Bremen.

Description: Shallow sediment cores were collected with gravity cores from sites in the Japan Trench during cruise SO219A with R/V SONNE. In order to determine ex-situ concentrations of methane dissolved in pore water, sediment samples were taken from the sediment cores with cut-off syringes and transferred into glass vials. Methane concentrations in the headspace gas were used to calculate concentrations of methane dissolved in pore water (uncorrected for sediment porosity and Bunsen coefficient).

Description: Shallow sediment cores were collected with gravity cores from sites in the Japan Trench during cruise SO219A with R/V SONNE. In order to determine ex-situ concentrations of methane dissolved in pore water, sediment samples were taken from the sediment cores with cut-off syringes and transferred into glass vials. Methane concentrations in the headspace gas were used to calculate concentrations of methane dissolved in pore water (uncorrected for sediment porosity and Bunsen coefficient).

Description: Shallow sediment cores were collected with gravity cores from sites in the Japan Trench during cruise SO219A with R/V SONNE. In order to determine ex-situ concentrations of methane dissolved in pore water, sediment samples were taken from the sediment cores with cut-off syringes and transferred into glass vials. Methane concentrations in the headspace gas were used to calculate concentrations of methane dissolved in pore water (uncorrected for sediment porosity and Bunsen coefficient).