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A prudent planetary limit for geologic carbon storage
No full textGeologically storing carbon is a key strategy for abating emissions from fossil fuels and durably removing carbon dioxide (CO2) from the atmosphere1,2. However, the storage potential is not unlimited3,4. Here we establish a prudent planetary limit of around 1,460 (1,290–2,710) Gt of CO2 storage through a risk-based, spatially explicit analysis of carbon storage in sedimentary basins. We show that only stringent near-term gross emissions reductions can lower the risk of breaching this limit before the year 2200. Fully using geologic storage for carbon removal caps the possible global temperature reduction to 0.7 °C (0.35–1.2 °C, including storage estimate and climate response uncertainty). The countries most robust to our risk assessment are current large-scale extractors of fossil resources. Treating carbon storage as a limited intergenerational resource has deep implications for national mitigation strategies and policy and requires making explicit decisions on priorities for storage use
Supplemental data to: Artificial upwelling via Stommel-Pipe as a marine CDR option? A present to future performance assessment in an Earth system model
No full textAlkalinity enhancement in subduction regions and the global ocean: Efficiency, earth system feedbacks, and scenario sensitivity
No full textOcean Alkalinity Enhancement (OAE) refers to the addition of alkaline material to the surface ocean, which shifts carbonate chemistry towards more oceanic uptake of atmospheric CO2. This study compares global OAE with regionally focused deployment in subduction regions of the Southern Ocean, Northwest Atlantic, and Norwegian-Barents Sea. We conducted ensemble simulations using an emissions-driven Earth System Model (ESM) under high- (SSP3-7.0) and low-emissions (SSP1-2.6) scenarios. By 2100, subduction region OAE was nearly as efficient (SSP3-7.0: 0.71±0.03, SSP1-2.6: 0.60±0.04) as global deployments (SSP3-7.0: 0.73±0.01, SSP1-2.6: 0.64±0.03). However, the ESM simulations did not reproduce the efficient vertical carbon transport seen in a previous ocean-only study, as strong internal variability and climate feedbacks to OAE hampered deep ocean carbon storage. The excess ocean CO2 uptake and atmospheric CO2 reduction were scenario-dependent (15-19% and 22-41% lower under SSP1-2.6 compared to SSP3-7.0, respectively). The pathways of excess ocean CO2 uptake and atmospheric CO2 reduction diverged between the scenarios after the mid-2060s, when atmospheric CO2 peaked and then declined under SSP1-2.6, with a substantially larger relative land carbon loss in SSP1-2.6 than in SSP3-7.0 for regional OAE deployment. Furthermore, the emissions-driven ensemble simulations showed that climate feedbacks introduced substantial uncertainty in early decades of regional OAE efficiency, posing challenges for near-term Monitoring, Reporting, and Verification. Reviewing our and previous model experiments revealed a strong linear relationship between added alkalinity and oceanic CO2 uptake and atmospheric reduction, highlighting that first-order effects of OAE on carbonate chemistry are well understood and consistently represented, while the effects of carbon and climate feedbacks (13-20%) and scenario sensitivity are smaller but non-negligible. Overall, our study shows that subduction regions can be a viable option for OAE; however, their efficiency is limited by these feedbacks and scenario sensitivity, which must be accounted for in future regional OAE interventions
Marine Geophysical Practical Training 2025 Cruise No. AL641
No full text29.9.2025 – 10.10.2025
Kiel (Germany) - Kiel (Germany)
GEOSE
Supplementary data for Xu et al. (2025) "Robustness and mechanisms of the atmospheric response over the Southern Ocean to idealized freshwater input around Antarctica"
No full textContrasting marine phytoplankton responses to meltwater inputs from Arctic and Antarctic glaciers revealed by bioassay experiments
No full textAlong the coastal periphery of the Greenland and Antarctic Ice Sheets, global warming has increased freshwater discharge and associated fluxes of terrigenous material from the cryosphere into the ocean. Shifts in the availability of light and bio-accessible nitrogen, phosphorous, silica, iron, manganese, and cobalt can influence seasonal patterns of marine primary production. Yet the spatial and temporal scales of changes to these drivers from ocean-cryosphere interaction remain unclear. Using bioassay experiments, we tested the response of coastal phytoplankton from Antarctica and Greenland to freshening and changes in micronutrient availability. In both polar regions, additions of freshwater >2% by volume resulted in significant short-term negative responses by the primary producers, yet their responses to changing micronutrient stoichiometry diverged. In the Western and Northern Antarctic Peninsula, 7 of 8 bioassay experiments, which incubated the ambient microbial community, suggested that phytoplankton experienced conditions replete with macro- and micronutrients and growth was light-limited during austral summer. Conversely, at one Antarctic incubation site upstream of local micronutrient sources, results indicated a novel cobalt and iron co-limitation with serial manganese limitation of phytoplankton growth. In contrast, bioassay results from West Greenland evidenced a more variable situation: phytoplankton responses suggested a combination of light limitation, nitrogen limitation with and without serial silica limitation, and phosphorous limitation. Phosphorous limitation is not thought to be common in polar marine waters yet increasingly may be plausible in Arctic fjords subject to increased freshening and stratification. Future responses of primary producers to increasing freshwater discharge around the Antarctic Peninsula and West Greenland may therefore diverge. Around Greenland, runoff may drive inshore communities increasingly towards nitrogen and possibly phosphorous limitation, while alleviating serial silica limitation for siliceous microalgae. Conversely, around the Antarctic Peninsula increasing runoff may alleviate light limitation via stratification and result in more efficient macronutrient drawdown
How Subduction Margin Processes and Properties Influence the Hikurangi Subduction Zone
No full textThe Hikurangi margin has been an important global focus for subduction zone research for the last decade. International Ocean Discovery Program drilling and geophysical investigations have advanced our understanding of megathrust slip behavior. Along and across the margin, detailed imaging reveals that the megathrust structure varies spatially and evolves over time. Heterogeneous properties of the plate boundary zone and overriding plate are impacted by the evolving nature of regional tectonics and inherited overriding plate structure. Along-strike variability in thickness of subducting sediment and northward increasing influence of seamount subduction strongly influence mega-thrust lithologies, fluid pressure, and permeability structure. Together, these exert strong control on spatial variations in coupling, slow slip, and seismicity distribution. Thicker incoming sediment, combined with a compressional upper plate, influences deeper coupling at southern Hikurangi, where paleoseismic investigations reveal recurring great ( M w > 8.0) earthquakes.
▪ The Hikurangi Subduction Zone is marked by large-scale changes in the subducting Pacific Plate and the overlying plate, with varied tectonic stress, crustal thickness, and sediment cover.
▪ The roughness of the lower plate influences the variability in megathrust slip behavior, particularly where seamounts enhance subduction of fluid-rich sediments.
▪ Variations in sediment composition impact the strength of the subduction interface, with the southern Hikurangi Subduction Zone exhibiting a more uniform megathrust fault.
▪ Properties of the upper plate influence fluid pressures and contribute to the observed along-strike variations in Hikurangi plate coupling and slip behavior
Exploring the potential of Baltic macroalgae for food preservation
No full textHighlights:
• Comparison of ASE and SFE extractions of Baltic macroalgae for food preservation
• The highest antibacterial, antioxidative effect and total phenol content by Fucus spp.
• Untargeted metabolomics by UPLC-MS/MS on bioactive extracts of Baltic macroalgae
Abstract
Despite all technological developments, food spoilage still remains a major economic, environmental and health concern. This study aimed to assess the potential of eight Baltic macroalgae for food preservation, specifically for antimicrobial and antioxidant active food packaging applications. Three brown, three red and two green macroalgae species were extracted automatically by Accelerated Solvent Extraction (ASE) and Supercritical Fluid Extraction (SFE) and evaluated for their antimicrobial effect against nine foodborne pathogens, antioxidant capacity and total phenolic content (TPC). The ASE and SFE extracts of brown algae (Fucus spp.) showed the highest antimicrobial and antioxidative activities and the greatest TPCs. Fucus distichus subsp. evanescens exhibited the highest inhibition against Staphylococcus aureus with IC50 values of 2.1 μg/mL (ASE, H2O:ethanol (50:50) extract) and 4.4 μg/mL (SFE, CO2:Ethanol (50:50). The ethanolic (100 %) ASE and CO2:Ethanol (20:80) SFE extracts of Fucus serratus showed the best antioxidant capacity (IC50s 37.9 μg/mL (ASE) and 24.6 μg/mL (SFE)) and the highest TPCs (158 mg GAE/g (ASE) and 297.41 mg GAE/g (SFE)). Bioactive extracts were further analyzed by UPLC-MS/MS-based untargeted metabolomics. The main components of all extracts were polar lipids (galactolipids and betaine lipids), along with carotenoids, phlorotannins and chlorophylls. These results provide insights into the bioactivity and chemical diversity of Baltic macroalgae, highlighting the potential of Fucus spp. for food preservation