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Rapid burial and intense degradation of organic matter drive active silicate weathering in the subsurface sediments of the ocean’s deepest realm
No full textHadal trenches (>6000 m water depth) have been revealed as hotspots of organic carbon burial and microbial respiration in the ultradeep ocean environment. However, understanding of the anaerobic metabolic pathways and rates, as well as carbon-silicon cycling, in the hadal trench sediments remains very fragmentary because of the shallow nature of traditional coring penetration. Using materials collected during International Ocean Discovery Program (IODP) Expedition 386 in the Japan Trench and a reaction-transport model, we provide a regional quantitative assessment of organic carbon turnover by sulfate reduction, anaerobic oxidation of methane, and methanogenesis in addition to silicate weathering and authigenic carbonate and clay formation. We show that rapid burial of relatively labile organic carbon resulting from subduction earthquakes triggers organic carbon and methane turnover at rates comparable to those in continental margin sediments, thereby stimulating active silicate weathering and authigenic carbonate formation. Despite vigorous organic carbon turnover, the vast majority of organic carbon is buried, implying an important role of tectonic-associated events in translocating and preserving organic carbon in the deepest part of the ocean. These results quantitatively demonstrate, for the first time, active coupled carbon-silicon cycling in hadal trench sediments and have implications for the subduction zone carbon budget
Temperature-based Diagnosis of the Gulf Stream Path Overestimates a Northward Shift in a Warming Ocean
No full textA northward shift in the Gulf Stream (GS) path is considered a fingerprint of a weakening Atlantic Meridional Overturning Circulation (AMOC) and has been linked to recent ecosystem alterations in the northwest Atlantic Ocean. Temperature-based criteria, widely used as proxies for GS location, suggest a northward shift. This study uses high-resolution climate models to show that these criteria, especially those based on the North Wall, overestimate the shift under high-emission scenarios by a factor of two to three. In contrast, a sea surface height (SSH)-based criterion remains more closely aligned with the true GS path, providing a more reliable estimate. The rising seawater temperature biases isotherm-based assessments, creating a misleading indication of a GS migration. These results call into question the notion that warming in the northwest North Atlantic is causally related to a northward migration of the GS and emphasize the need for more robust indicators of its position
Navigating the challenges of data management in the DAM research missions
No full textThe research missions of the German Marine Research Alliance (DAM) focus on highly relevant topics for society and support science-based decisions for the sustainable use and management of coastal areas and oceans. In these large-scale, transdisciplinary and cross-institutional projects, effective data management is an important prerequisite to ensure the long-term preservation and reusability of research data. Our working group supports scientists involved in the DAM research missions to make their research data FAIR - Findable, Accessible, Interoperable and Reusable. We regularly discuss various challenges in research data management such as reservation towards data sharing, or a lack of knowledge, personnel and resources to implement sustainable data management. Consequently, we develop and offer solutions, formulate recommendations and organize informational and training events. We highlight the advantages of FAIR data handling, promote the connection to DAM-related activities such as the project “Underway” Research Data and the Marine Data Portal, and support data publishing and archiving e.g. in PANGAEA - Data Publisher for Earth & Environmental Science. We found that existing and dedicated data managers, good communication and training, as well as practical technical solutions are key to supporting scientists to manage their data FAIRly
1. Wochenbericht AL635
No full text1st weekly report (30.06-06.07.2025), R/V Alkor AL63 5PlastTrackBalt, Western Baltic Sea, Kiel-Kie
ERC Synergy Project T-SECTOR: Testing Solid Earth Climate Connections Through mid Ocean Ridge Time Series
No full textPre-Rift Orogenic Erosion Facilitates the Exhumation of Lower Crust at Rifted Margins
No full textDuring the late-stage of continental rifting, lower crustal rocks can be exhumed to the Earth's surface. Such exposure has been identified especially in rifts that developed within former orogens. These rifts exploited zones of lithospheric weakness created during previous mountain-building events. Here we investigate whether lower crustal exhumation during rifting could result directly from structural inheritance of prior orogeny. To this aim we use Wilson-Cycle numerical models where we impose a prior shortening and subsequent extension. Our models incorporate the effects of thermal and structural inheritance as well as surface processes. We find that the erosion of mountain belts thins the upper crust, reducing the upper-to-lower crustal ratio prior to rifting. This process facilitates the exhumation of lower crustal material during extension, exposing them at the Earth's surface along the footwall of normal faults. We suggest a new conceptual model to explain lower crustal exhumation observed at rifted margins worldwide.
Key Points
We use numerical models to assess the influence of pre-rift orogenic inheritance on subsequent rifted margin formation
Syn-orogenic erosion removes upper crustal material, reducing the pre-rift ratio between upper and lower crust
This process explains lower crust exhumation at rifted margins of the South China Sea, Gulf of Lion, Aegean, Mid-Norway, and South Atlantic
Plain Language Summary
Continents often break apart where mountains used to be. Continental rifting is hence affected by geological structures that result from prior mountain building. In this study, we use numerical models that incorporate both mountain building and continental rifting, accounting for the influence of surface processes. Our models allow for quantifying by how much the upper layer of the crust becomes thinner due to erosion. As the thickness of the upper crust decreases, the lower crust becomes uplifted to shallower depths during mountain building. When tectonic shortening ceases and extension eventually takes over, the lower crust is finally exhumed to the surface along normal faults
Late Pliocene growth of the West Antarctic Ice Sheet to near-modern configuration
No full textAccurate prediction of a West Antarctic Ice Sheet (WAIS) collapse and its impact on sea level in a future warmer climate remains uncertain. Here, we provide evidence for the transition from a smaller-sized WAIS during the warm Pliocene to an expanded ice sheet closer to its modern configuration during the Pleistocene based on geochemical records from the proximity to the current maximum ice loss in the Amundsen Sea. In contrast to Pliocene ice sheet dynamics, the WAIS exhibited a relatively muted response throughout the Pleistocene despite substantial glacial-interglacial variations in atmospheric CO₂ levels, temperature, and orbital forcing. Our data suggest that critical tipping points for WAIS growth occurred under atmospheric-oceanic conditions of the Pliocene–Pleistocene transition. These findings highlight the importance of the Pliocene–Pleistocene transition in establishing the modern configuration of the WAIS and its importance as a key interval for understanding ice sheet stability under the changing climate
Sartori mud volcano of the Calabrian accretionary prism (Mediterranean Sea) and the architecture of its mudflows over the last 56 ka
No full textMud volcanoes (MVs) are surface structures typically formed by the episodical expulsion of fluids and solids, and are often associated with accretionary prisms at convergent plate boundaries. Previous studies have focused on the distribution, structure and activity of MVs, but often lacked in differentiation of individual mudflow eruption phases and the calculation of total erupted volume of mudflows. This study combines a high-resolution multi-parameter analysis of mudflows to reconstruct the chronology of the eruption history of Sartori MV over the past 56 ka. The multi-parameter analysis includes ship- and AUV-based hydroacoustic surveys, sub-bottom profiler, 3D seismic investigations, and sediment core data. Sediment cores were used to validate geophysical results and to estimate the relative age of mudflows based on prominent marker horizons. The results show a steady decrease in the volume of erupted mud breccia from 56 ka ago to the present. The largest volumes erupted contained > 18.2 × 10 6 m 3 of material. The presence of mass transport deposits at the same sediment depth as buried mudflows suggests the occurrence of a common trigger event, which resulted in mass movement of the MV eruption and slope destabilization. This study represents an advance in the ability to distinguish individual, and sometimes very small-scale, mudflows over a time span of ~ 56 ka. The inclusion of age-dated sediment core information provides a robust framework of the temporal evolution of these mudflows. Consequently, this study makes a significant contribution to the general understanding of changes in the mud breccia eruption history of MVs
Gärtnern unter Wasser: Wie Taucher mit Seegras das Klima retten wollen
No full textEchter Öko-Joker: Seegraswiesen sind wichtig beim Kampf gegen die globale Erwärmung. Deshalb werden die grünen Halme auch in der Ostsee gepflanzt. Das Projekt lebt von Ehrenamtlern – die schon erste Erfolge erkennen
