ALBERT

Description: Hotspot-influenced spreading axes are characterized by a shallow axis, thickened crust, and possibly by higher-than-normal eruption frequency, all signs of an excess of magma and heat being supplied to such ridges by the hotspot. Despite this, these ridges are also characterized by an apparently lower-than-average incidence of high-temperature hydrothermal venting, raising questions about their thermal budget. The type example for hotspot-ridge interaction is the Reykjanes Ridge south of Iceland, which shows abnormally shallow bathymetry between the Reykjanes Peninsula at ca. 63°N and the Charlie Gibbs Fracture Zone at 53°N.The seafloor surrounding the present spreading axis is also characterized by V-shaped bathymetric ridges, thoughtto be produced by regions of excess melting migrating along the axis through time. Cruise MSM75aimed to produce geological maps of four key areas along the ridge -one with thickened crust where a V-shaped ridge intersects the present-day axis, one with thickened crust but no on-axis V-shaped ridge anomaly, a third with more normal crustal thickness and an axial valley and a fourth at the only known, but up to present unsampled, Reykjanes hydrothermal site Steinaholl. This geological mapping is to be usedto investigate questions of variations in eruption size or frequency away from Iceland, the interplay between magmatism and tectonism, the axial volcanology of V-shaped ridges and how thick crust is cooled in the apparent paucity of high-temperature vent fields.

Description: The transit of RV SONNE from Las Palmas (departure: 11.12.2021) to Guayaquil, Ecuador (arrival: 11.01.2022) is directly related to the international collaborative project SO287-CONNECT of GEOMAR in cooperation with Hereon and the University of Bremen, supported by the German Federal Ministry of Education and Research (BMBF) between October 15 2021 and January 15 2024. The research expedition was conducted to decipher the coupling of biogeochemical and ecological processes and their influence on atmospheric chemistry along the transport pathway of water from the upwelling zones off Africa into the Sargasso Sea and further to the Caribbean and the equatorial Pacific. Nutrient-rich water rises from the deep and promotes the growth of plant and animal microorganisms, and fish at the ocean surface off West Africa. The North Equatorial Current water carries the water from the upwelling, which contains large amounts of organic material across the Atlantic to the Caribbean, supporting bacterial activity along the way. But how the nutritious remnants of algae and other substances are processed on their long journey, biochemically transformed, decomposed into nutrients and respired to carbon dioxide, has so far only been partially investigated. Air, seawater and particles were sampled in order to provide new details about the large cycles of carbon and nitrogen, but also of many other elements such as oxygen, iodine, bromine and sulfur. Inorganic and organic bromine and iodine compounds are generally emitted naturally from the ocean into the atmosphere, promote cloud formation and affect climate, and some even reach the stratosphere where they contribute to ozone depletion. We measured how much of these compounds are released from the ocean, and at what locations and how they are transformed in the ocean and in the atmosphere. Sargassum algae, which have become a nuisance on beaches in the western and eastern Atlantic, support life and contribute to carbon cycling in the middle of the Atlantic, the Sargasso Sea and in the Caribbean, while their contribution to halogen cycling and marine bromine and iodine emissions was previously unknown. We investigated the influence of various natural parameters such as temperature and solar radiation on the biogeochemical transformation processes in order to understand the influence of climate change on these processes in incubation experiments with seawater and algae. We investigated how anthropogenic signals such as shipping traffic influence the nitrogen and sulphur cycle in the ocean, as well as the impact of nitrogen oxides from ship exhaust and sulphurous, acidic and dirty water from purification systems on organisms and biochemical processes. Plastic debris was sampled from the surface waters to investigate its contribution to global biogeochemical transformation processes. The working hypotheses of the research program were:  Bioavailability of dissolved organic carbon in surface waters decreases along the productivity gradient and transport pathway from the Eastern to the Western Tropical North Atlantic.  Nutrient gradients from East to West constrain the microbial utilization of organic matter- contributing to an accumulation of C-rich organic matter due to a) limited mineralization and b) enhanced exudation- also leading to gel-like particles accumulation in the western tropical North Atlantic and Sargasso Sea.  Tropospheric and stratospheric ozone are strongly impacted by biogeochemical and ecological processes occurring around and in the NA gyre system related to marine iodine and bromine cycles.  The long-range transport of natural and anthropogenic organic matter in water and of gases and aerosols in the air impact carbon-export, biogeochemical cycles in the water column, and the release of gases and particles from the ocean significantly. 4 SONNE -Berichte, SO287, Las Palmas - Guayaquil, 11.12.2021 - 11.01.202 The data and samples obtained specifically target carbon, nutrient and halogen cycling, the composition of phytoplankton, bacteria, the transport and sequestration of macro algae and the air-sea exchange processes of climate relevant gases and aerosols. The influence of ecological and transport processes, as well as anthropogenic impacts on the North Atlantic gyre system, specifically in the Sargasso Sea and the influence of ship emissions throughout the Atlantic towards the west and into the Pacific will be investigated with the data.

Description: Fracture zones were recognized to be an integral part of the seabed long before plate tectonics was established. Later, plate tectonics linked fracture zones to oceanic transform faults (OTF), suggesting that they are the inactive and hence fossil trace of transforms. Yet, scientists spend little time surveying them in much detail. Recent evidence suggests that the traditional concept of transform faults as being conservative (non-accretionary) plate boundary faults might be wrong. Instead, numerical modelling results suggest that transform faults seem to suffer from extensional tectonics below their strike-slip surface fault zone, and a global compilation of legacy bathymetric data suggest that ridge-transform intersections seem to be settings of magmatic activity, modifying the lithosphere and burying the transform valley before it passes into the fracture zone region. During M170 we tested those hypotheses by collecting a suite of new data from the Oceanographer and Hayes transform faults offsetting the Mid-Atlantic Ridge to the south of the Azores near 35°N and hence conducted a pilot study revealing the state-of-stress derived from micro-earthquakes and bathymetry as well as geological sampling to evaluate magmatic and tectonic processes shaping transform faults. Preliminary analysis of 10-days of seismicity data recorded at hydrophone stations showed 10-15 local earthquakes per day and bathymetric data supports that ridge-transform intersections support indeed a second phase of magmatic accretion.

Description: The coastal and open oceans represent a major, but yet unconstrained, sink for plastics. It is likely that plastic-biota interactions are a key driver for the fragmentation, aggregation, and vertical transport of plastic litter from surface waters to sedimentary sinks. Cruise SO279 conducted sampling to address core questions of microplastic distribution in the open ocean water column, biota, and sediments. Seven stations were sampled between the outer Bay of Biscay and the primary working area south of the Azores. Additional samples were collected from surface waters along the cruise track to link European coastal and shelf waters with the open ocean gyre. Microplastic samples coupled with geochemical tracer analyses will build a mechanistic understanding of MP transport and its biological impact reaching from coastal seas to the central gyre water column and sinks at the seabed. Furthermore, floating plastics were sampled for microbial community and genetic analyses to investigate potential enzymatic degradation pathways. Cruise SO279 served as the third cruise of a number of connected research cruises to build an understanding of the transport pathways of plastic and microplastic debris in the North Atlantic from the input through rivers and air across coastal seas into the accumulation spots in the North Atlantic gyre and the vertical export to its sink at the seabed. The cruise was an international effort as part of the JPI Oceans project HOTMIC (“HOrizontal and vertical oceanic distribution, Transport, and impact of MICroplastics”) and the BMBF funded project PLASTISEA (‘Harvesting the marine Plastisphere for novel cleaning concepts’), and formed a joint effort of HOTMIC and PLASTISEA researchers from a range of countries and institutes.

Description: Summary Cruise MSM96 sailed to assess small-and large-scale geochemical and seafloor substrate heterogeneity across the NE Atlantic basin. Weemployed a hierarchical surveying strategy at three spatial scales: local, regional, and basin,to investigatetrace metaland Rare Earth Element and Yttrium concentrationsand patterns. At each of the survey sitesPorcupine Abyssal Plain and Iberian Abyssal Plain, we sampledcovering three data resolution scales: centimeter (TV-MUC), meter (OFOS), and kilometer scale (MBES). Our objective was to quantify the impact of topography on the geochemistry within and between regions and to establish the link –across resolution scales –between geochemistry, imagery,and bathymetrytofacilitate spatial extrapolation of seafloor geochemical dataand substrate characteristics to kilometer-scale.We studied three topography types: valleys, plains,and hills. Theirlocation was objectively chosen bya geomorphons terrain classification.By studying heterogeneity on the local and regional scales, we focused on topographic heterogeneity because spatial heterogeneity with respect to particle and organic matter flux from the sea surface can be expected to be minimal.As a basis, solid-phase and pore-watersamples were taken for on-shore lab analyses of porosity, major elements,total organic carbon, nitrate, anddissolved Mn and Fe.This basic data helps to assess REY controls in the solid phase and pore water. All geochemical parameters together will be used to assess local-to basin-scale heterogeneity and how it is linked to topography.In the future, this should be extended to also incorporate, e.g., oceanography, minerology, microbiology, and eventually link all these parameters across scales.

Description: The MSM89 expedition of Maria S Merian was a contribution to the international research initiative EUREC4A (www.eurec4a.eu). The cruise was carried out in concert with the M161 campaign on RV METEOR (Germany) and the EUREC4A-OA campaign on NO L’ATALANTE (France). Airplane and drone operations as well as well as continuous observations from the ground-based site on the Island of Barbados (BCO) were considered during the MSM89 campaign. Moreover, the cruise was coordinated with ships and Saildrone© operations in the context of the US American ATOMIC project. The overall goal of the EUREC4A field campaign was to collect observational data that will enable research on dynamic and thermodynamic processes in the atmosphere and ocean that will bring the understanding of the role of clouds in the climate system to a new level. MSM89 had its focus on the ocean/atmosphere coupling across ocean mesoscale vortices. For this purpose, both ocean and atmosphere profile measurements were carried out to observe the temporal evolution and spatial heterogeneity of the atmospheric and oceanic boundary layer. Autonomous observing platforms (underwater glider) and a ship towed platform (Cloudkite) augmented the ship-based observations. Incubation experiments were performed to determine Nitrogen fixation rates, the gas exchange for carbon dioxide and oxygen uptake.