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The climate intervention approach marine cloud brightening (MCB) would aim to reduce climate warming by injecting sea salt aerosol (iSSA) into the lower troposphere to increase cloud albedo, reflect more sunlight, and cool the surface. Due to the short atmospheric lifetime of tropospheric aerosol, MCB iSSA emissions and their resulting radiative forcing are regional by nature. This presents a significant challenge and opportunity, as there are many potential MCB implementation patterns that could produce widely varying climate responses. Previous modeling studies suggest that MCB implementation in the subtropical oceans can cause global cooling but often result in remote regional temperature and precipitation responses that may be considered undesirable. Here, we use three Earth system models (ESMs) to estimate the impact of MCB implementation in 14 different ocean regions, assessing MCB forcing and cooling efficiency in each region and examining the patterns of temperature response from each case. We find that iSSA emissions in the midlatitude oceans produce stronger cloud forcing, greater cooling efficiency, and more spatially uniform cooling. With this information, we evaluate a novel MCB emission strategy that emits iSSA in the midlatitude oceans. The ESMs show this iSSA emission pattern produces temperature and precipitation responses across all three ESMs that are quite similar in pattern (but of opposite sign) to the greenhouse gas (GHG) response. Thus, compared to previously tested iSSA injection patterns, midlatitude MCB implementations may be more suitable when intending to maintain climates close to present-day conditions.
Aquanauts—people who live and work underwater for extended periods—have anecdotally reported cognitive shifts in how they perceive the ocean environment and their role in it. This experience bears resemblance to the cognitive shift astronauts have experienced when first seeing our planet from space, dubbed “The Overview Effect.” This shift involves an intense feeling of awe that increases astronauts’ sense of connection to humanity and the entire planet. In this study, we used semi-structured interviews with aquanauts to document their experiences living underwater. Results show that aquanauts do indeed experience shifts in cognitive, affective, behavioral, perspectival, and relational areas that strengthen feelings of connectedness and commitment to the marine environment. However, the effects of the experience varied between aquanauts, indicating a potential “Underview Effect” that may occur on a spectrum of intensity with a number of core features.
Oxygen depletion in marine ecosystems, known as hypoxia, is an escalating form of marine pollution driven by eutrophication and climate-induced warming that threatens coastal ecosystems worldwide. Although the ecological impacts of hypoxia are well documented, its broader environmental consequences remain less understood, including how oxygen stress alters human use of marine habitats. Based on an extensive oxygen monitoring dataset integrated with bottom-trawl activity and catch records from the Western Baltic Sea (2010-2023), we assess how fisheries respond to varying levels of hypoxia as an indicator of ecosystem degradation and its consequences for fishing activities. Fishing activity declined to 20% of baseline levels under moderate hypoxia (2-4 mg/L) and to 10% under severe hypoxia (<2 mg/L). Fishers also delayed their return to previously hypoxic areas by an average of 1.9-2.7 weeks, respectively. These behavioral shifts mirror known ecological responses of demersal fish and benthic invertebrates to sublethal oxygen stress. While the resumption of fishing activity suggests some short-term recovery, likely reflecting the return of some fish species to affected areas, long-term degradation of benthic communities may further compromise habitat quality and fish stock productivity. Our findings highlight the importance of incorporating oxygen dynamics into environmental and fisheries management, pollution mitigation, and marine spatial planning, particularly as hypoxia intensifies under the combined pressures of climate change and nutrient loading.
Mantas exhibit graceful swimming postures and efficient propulsion mechanisms, making them an ideal reference for bionic autonomous underwater robots. When propelling, backward-streamwise waves cross the manta’s pectoral fins, one of the key mechanisms to its efficient propulsion. To investigate the effect of the traveling wave in the fin’s surface on the hydrodynamics, this paper builds a fluid solver based on the Immersed Boundary-Lattice Boltzmann Method (IB-LBM), on which the hydrodynamics and kinematics of a one-degree-of-freedom self-propelled model for the propulsion process of the manta ray robot are simulated when varying the dimensionless wave number (Nw). The thrust distribution on the fin surface with different Nw is also explored based on the manta robot’s motion equation. The results show that varying Nw significantly affects the thrust distribution of the pectoral fin surface, thereby resulting in an overall change in the hydrodynamic and kinematic characteristics of the manta ray robot. When Nw is small, the fluid force is distributed relatively uniformly on the pectoral fin surface, with a rather minimal thrust component of the robot’s resultant force. While Nw increases, the concentrating district of fluid force shifts towards the trailing edge, leading to a greater forward thrust. The stable cruising speed increases by 3.35 times, and the propulsion efficiency rises by 86.7
The vibration and noise radiation of submarine thrusters have become an important research object for the low-noise design of submarines. The unsteady force generated during the operation of the thruster caused by the incoming turbulence is one of the important sources of low-frequency vibration noise in submarines. In this paper, a high-fidelity numerical simulation model of pump-jet propulsion unsteady flow under submarine hull wake condition is constructed based on the improved delayed separation eddy simulation and large eddy simulation (LES) turbulence models. By comparing with the experimental data, it is found that the LES turbulence model forecasts the low-frequency unsteady broadband force with higher accuracy. A method for predicting the low-frequency unsteady broadband force of pump-jet propulsion is formed. Based on this method, the flow field characteristics and low-frequency unsteady broadband forces of the pump-jet thruster under three scaling scales and two advance ratios are calculated. Results indicate that the scaling effect of the pump-jet thruster cannot be neglected: the duct thrust coefficient KTd decreases with increasing scaling scale, while the stator drag coefficient KTs, rotor thrust coefficient KTr, rotor torque coefficient KQr, thruster efficiency, amplitude of unsteady force at the first-order lobe frequency, and amplitude of energy integral in the corresponding interval all increase accordingly. Additionally, at identical scaling scales, as inflow velocity rises, both the amplitude of unsteady forces on rotor blades and the amplitude of energy integrals grow significantly.
