Over the last 2 decades, studies have shown that the sea-surface microlayer covers large areas of the global ocean and, under certain conditions, can even form biofilm-like (and thus unique) habitats between the ocean and the atmosphere. Due to its recurrent biofilm-like features and unique position at the atmosphere–ocean interface, the microlayer is central to a range of global biogeochemical and climate-related processes, including marine carbon cycling, air–sea gas exchange, physical surface processes, and aerosol production. Despite the fact that processes occurring in and across the microlayer have received increasing attention during recent years, our knowledge about the microlayer remains rudimentary. New approaches and technologies have been developed to understand the formation and function of the microlayer on a mechanistic level. For example, the BASS (Biogeochemical processes and Air–sea exchange in the Sea-Surface microlayer; https://uol.de/en/bass) group has been funded to explore the significance of the microlayer as a bio- and photochemical reactor in an unprecedented comprehensive and interdisciplinary approach, and BASS findings will contribute to this special issue (SI). The purpose of the SI is twofold: (1) to present outcomes of a BASS mesocosm study and (2) to present further contributions on the microlayer from the wider research community based on field, mesocosm, modelling, and laboratory studies. This SI will bring together the latest scientific studies to describe the microlayer as an interface between the ocean and atmosphere across different disciplines.

Marine extreme events, encompassing phenomena such as storm surges, marine heatwaves, biogeochemical extremes, harmful algal blooms, jellyfish blooms, extreme storms, and even unique occurrences like medicanes (Mediterranean hurricanes), are becoming more common. These events have profound consequences for marine ecosystems, coastal communities, and global economies. Extreme sea level events, driven by intense storms and rising sea levels, can inundate coastlines, leading to devastating flooding and erosion. Marine heatwaves, fuelled by climate change, can trigger mass coral bleaching events, disrupting delicate marine ecosystems and jeopardizing the biodiversity that they support. Harmful algal blooms and jellyfish blooms, exacerbated by nutrient pollution and warmer waters, can lead to oxygen depletion, cause mass mortality events in various species, and pose risks to human health. The concurrence of oceanic and atmospheric extremes, marine and atmospheric heat waves, wind and wave extremes, harmful algal blooms, hypoxic conditions, and high-acidity events may lead to a nonlinear increase in environmental stress.

Addressing the impacts of these events requires a comprehensive approach, involving measures to mitigate climate change, improve coastal resilience, and promote sustainable marine management practices. A crucial aspect of addressing and mitigating the impacts of marine extreme events lies in deepening our scientific understanding of these phenomena and in establishing solid methodologies for defining climatological baselines and for extreme analyses in a changing climate. Scientific research plays a pivotal role in unravelling the intricate mechanisms behind these events, predicting their occurrence, and formulating effective strategies to manage and adapt to their consequences. By exploring the underlying causes, interactions, and feedback loops, scientists can provide invaluable insights that guide policymakers, communities, and industries in making informed decisions.

Over the past 25 years autonomous underwater gliders have progressed from experimental vehicles through scientific instruments to operational tools. Observations from gliders are now enhancing our understanding of physical, biogeochemical, and biological oceanographic processes. They represent a mature technology and complement traditional ocean sampling capabilities, especially for sustained real-time oceanographic measurements. They are now used as standard research tools in sustainable ocean observations and process studies, collecting measurements of physical, chemical, and bio-optical ocean variables. Underwater gliders have unique capacities to connect open-ocean and coastal processes and to sample the ocean at regional scales during multi-month missions. Gliders have been routinely deployed to monitor the ocean, for example monitoring continental shelves, boundary currents, and polar regions including in under-ice operations. More recently gliders have contributed to environmental hazard detection such as in the detection of marine heat waves and hurricane prediction.

This special issue has been stimulated by the International Underwater Glider Conference (IUGC) that was held in Gothenburg in June 2024, but submissions are open to everyone regardless of participation in the conference.

We invite papers advancing knowledge on the ocean's physical, biogeochemical, and ecosystem properties and processes by using underwater gliders and/or by their combined use with other observing platforms or numerical models. Contributions on technological aspects such as the development of glider sensors are welcome provided they include some ocean science advance.

In 2024–2025 Ocean Science will be 20 years old, during which time it has been internationally at the forefront of high-quality, open-access, and open-peer-review publishing in our field of science. To celebrate this jubilee, we are publishing a special collection of “reviews and perspectives” papers, looking back at how ocean sciences have advanced over the last 20 years and looking forward to how they might advance over the next 20 years. The Ocean Science Jubilee special issue will be a compilation of influential papers across the broad range of ocean science topics covered by the journal. Accepted reviews and perspectives papers may also be included in the https://encyclopedia-of-geosciences.net/.

Submission of reviews and perspectives papers is open to everyone. We welcome the perspectives of early-career scientists. You do not have to be invited to submit a paper to the special issue. Reviews and perspectives papers are welcome on any topic and discipline within ocean sciences, as with any paper in Ocean Science. Manuscripts will undergo the usual rigorous and open peer review.

This special issue describes efforts establishing high-resolution regional ocean and biogeochemical modelling capabilities for Modular Ocean Model 6 (MOM6) and selected initial applications. MOM is amongst the most widely used ocean models for global climate and earth system applications, with a lineage of scientific contributions exceeding 50 years. MOM6 represents an ambitious evolution of previous MOM formulations, embracing numerous recent modelling advances and an open development approach. MOM6 and its associated biogeochemical components have been successfully deployed for the Sixth Coupled Model Intercomparison Project (CMIP6) and other international global climate and ocean prediction efforts. The resolution and regional optimality of global simulations, however, are inevitably limited by the computational, forcing, and parameterization demands of global climate-scale simulations. Ocean modelling frameworks capable of simulating and connecting physical, biogeochemical, and ecosystem processes from ocean basins to coasts and estuaries are needed to understand the role of oceans in global change and to anticipate global change impacts on marine ecosystems and coastal communities. Development of robust regional modelling capabilities for MOM6 (i.e. regional MOM6) creates such a framework, but the extension of MOM6 to high-resolution regional applications presents many challenges.

The papers in this collection present the overall design and implementation of regional MOM6, describe new parameterizations intended for regional applications, present a first generation of regional MOM6 configurations from across the global ocean, and offer select initial applications in ocean science. Advances in horizontal grid generation and boundary condition formulation are highlighted, including those enabling a more seamless transmission of physical and biogeochemical information from global to regional scales and those required to handle flexible Lagrangian vertical coordinates. The robustness of physical and biogeochemical configurations and parameterizations – many of which were developed for global applications – is explored in higher-resolution implementations spanning environments from the Arctic to equatorial waters. Analysis of tradeoffs between model skill and computational cost highlights algorithmic improvements critical for producing decision-relevant ensembles that span a range of ocean futures. The collected works provide a foundation for the expanded application of regional MOM6 to understand and predict ocean conditions across scales.

This is a traditional style special issue open to all papers within the topic. We anticipate that contributions will be primarily to GMD initially but that there will be a growing number of applications suitable for OS once the core development papers have been published. The indefinite ending date will allow for a greater number of initial applications to be published in OS and enable eventual documentation of generational updates planned for some configurations.