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.

The purpose of this special issue is to illustrate the role of a sustainable coastal research infrastructure in supporting monitoring, sciences, and management of the coastal marine areas. As such the JERICO-RI research infrastructure is most suitable, gathering 34 partners in Europe with the same overarching objective: to strengthen and enlarge a solid and transparent European network of coastal observatories and to provide an operational service for the timely, continuous, and sustainable delivery of high-quality environmental (physical, biogeochemical, and biological) data and services related to the marine environment in European coastal seas. Six scientific areas are targeted, from the sensor development to the data analysis and the scientific results. These are the following:

1. the pelagic biodiversity with phytoplankton and harmful algal blooms;
2. the benthic biodiversity and habitats;
3. the contaminant transports;
4. the coastal transport and hydrology;
5. the carbonate systems and C cycle; and
6. the coastal operational oceanography and modelling.

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.

Despite their socio-economic and environmental impacts, extreme events in the marine environment are generally poorly understood, simulated, or predicted. In particular, the dynamics of these events involve multiple temporal and spatial scales and can be driven by different mechanics and complex feedback involving the ocean and its interaction with the other spheres of the climate system. In response to climate change, the frequency and magnitude of these events could dramatically change, resulting in significant impacts on human life and property as well as on marine ecosystems. Hence, advancing our understanding of the dynamics leading to extremes in marine environments is crucial for improving their predictability, which, in turn, will help to achieve environmental and social sustainability. With this rationale, the special issue will focus on marine extremes at multiple temporal and spatial scales. Studies discussing ocean dynamics and air–sea interactions that can influence the evolution of marine extremes are particularly welcome; the inclusion of work using techniques ranging from in situ to remote-sensing observations and from numerical models to innovative artificial intelligence techniques (e.g. machine learning) is also encouraged. This diversity of topics will make for a highly multidisciplinary special issue, open to multiple applications in the field of marine extremes. Contributions related to the investigation of marine heat waves, marine storminess, storm surge and sea level rise, dense-water formation, deep-ocean extreme events, etc. are other examples of potential topics. The special issue has been stimulated by the EGU General Assembly 2023, session OS4.6, but all submissions on this topic are welcome, regardless of whether authors participated in the conference.

The loss of mass from glaciers, ice caps, and polar ice sheets has accelerated over the last 3 decades as a result of climate change. This has made land ice the major contributor to sea level rise and the main cause of its acceleration. However, the evolution of the land-based cryosphere over the course of the 21st century and beyond adds considerable uncertainties to sea level rise projections, particularly if instability mechanisms are triggered, leading to rapid retreat of marine basins in Antarctica. Critical knowledge gaps pose challenges for predicting the land ice response to the evolution of climate and the resulting impact on sea level, from cryospheric process understanding, ice sheet and glacier modelling, and coupling with the atmosphere and ocean to bridging the gap with sea level and coastal-impact sciences. This special issue includes contributions related to the following:

• Earth observations that help to constrain glacier and ice sheet surface conditions, dynamics, or mass loss;
• theoretical or numerical modelling of cryospheric processes or coupling with the ocean and atmosphere;
• standalone or coupled projections of ice surface mass balance;
• Arctic and Antarctic ocean conditions promoting and/or responding to ice sheet loss;
• glacier or ice sheet dynamics and mass balance;
• approaches to analysing multi-model ensembles or computing global and regional sea level rise projections;
• coastal impacts of sea level rise and climate change, adaptation needs, and related climate services.

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.

Coastal oceanographic processes present important differences to deep-water oceanography, resulting in higher prediction errors, where bottom topography exerts a strong control on wave/current/turbulence fields. These fields are modified by many additional factors that include interactions with coastal infrastructure, stratification, river discharges, and many non-linear effects such as breaking waves or nearshore circulation typical of shallow-water domains.

The special issue invites papers tackling simulations, observations, and analyses of coastal interactions, supporting the combinations of coastal observations (in situ and remote) and new modelling approaches (structured or unstructured grids) to reduce predictive uncertainties or to include new processes (interactions with groundwater flows, damping by biotopes, etc.). The special issue welcomes aggregation of data sets (e.g. different Sentinels or combinations with other satellites); new land boundary formulations; advanced assimilation or error bounding techniques; and, in general, original papers that contribute to the advancement of coastal oceanography. Papers proposing criteria to enhance applications or addressing the multiple scales in coastal processes, from storm events to decadal or climatic scales, are also welcome.

The special issue invites papers from recent and ongoing research projects dealing with green engineering for coastal zones and from EGU sessions in coastal oceanography and which can provide advancements in facing the many challenges experienced by present and future coasts. The wide range of possible topics is open to the interaction of nature-based solutions with coastal processes, uncertainties in coastal decision-making, and the role of operational coastal systems in reducing the growing risks in these areas. Contributions exploring the potential and currently open issues of non-linear response functions, support from artificial intelligence, or downscaled oceanographic projections are also covered.

The special issue will build upon a number of recent EU and international projects dealing with green engineering for coastal zones. Among them, there are many H2020 projects (e.g. the REST-COAST project; https://rest-coast.eu/) and an increasing number of special sessions dedicated to these topics (e.g. EGU but also Coastal Sediments 2023). The special issue is open and welcomes contributions within its scope.

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.

Despite their socio-economic and environmental impacts, extreme events in the marine environment are generally poorly understood, simulated, or predicted. In particular, the dynamics of these events involve multiple temporal and spatial scales and can be driven by different mechanics and complex feedback involving the ocean and its interaction with the other spheres of the climate system. In response to climate change, the frequency and magnitude of these events could dramatically change, resulting in significant impacts on human life and property as well as on marine ecosystems. Hence, advancing our understanding of the dynamics leading to extremes in marine environments is crucial for improving their predictability, which, in turn, will help to achieve environmental and social sustainability. With this rationale, the special issue will focus on marine extremes at multiple temporal and spatial scales. Studies discussing ocean dynamics and air–sea interactions that can influence the evolution of marine extremes are particularly welcome; the inclusion of work using techniques ranging from in situ to remote-sensing observations and from numerical models to innovative artificial intelligence techniques (e.g. machine learning) is also encouraged. This diversity of topics will make for a highly multidisciplinary special issue, open to multiple applications in the field of marine extremes. Contributions related to the investigation of marine heat waves, marine storminess, storm surge and sea level rise, dense-water formation, deep-ocean extreme events, etc. are other examples of potential topics. The special issue has been stimulated by the EGU General Assembly 2023, session OS4.6, but all submissions on this topic are welcome, regardless of whether authors participated in the conference.

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.

Coastal oceanographic processes present important differences to deep-water oceanography, resulting in higher prediction errors, where bottom topography exerts a strong control on wave/current/turbulence fields. These fields are modified by many additional factors that include interactions with coastal infrastructure, stratification, river discharges, and many non-linear effects such as breaking waves or nearshore circulation typical of shallow-water domains.

The special issue invites papers tackling simulations, observations, and analyses of coastal interactions, supporting the combinations of coastal observations (in situ and remote) and new modelling approaches (structured or unstructured grids) to reduce predictive uncertainties or to include new processes (interactions with groundwater flows, damping by biotopes, etc.). The special issue welcomes aggregation of data sets (e.g. different Sentinels or combinations with other satellites); new land boundary formulations; advanced assimilation or error bounding techniques; and, in general, original papers that contribute to the advancement of coastal oceanography. Papers proposing criteria to enhance applications or addressing the multiple scales in coastal processes, from storm events to decadal or climatic scales, are also welcome.

The special issue invites papers from recent and ongoing research projects dealing with green engineering for coastal zones and from EGU sessions in coastal oceanography and which can provide advancements in facing the many challenges experienced by present and future coasts. The wide range of possible topics is open to the interaction of nature-based solutions with coastal processes, uncertainties in coastal decision-making, and the role of operational coastal systems in reducing the growing risks in these areas. Contributions exploring the potential and currently open issues of non-linear response functions, support from artificial intelligence, or downscaled oceanographic projections are also covered.

The special issue will build upon a number of recent EU and international projects dealing with green engineering for coastal zones. Among them, there are many H2020 projects (e.g. the REST-COAST project; https://rest-coast.eu/) and an increasing number of special sessions dedicated to these topics (e.g. EGU but also Coastal Sediments 2023). The special issue is open and welcomes contributions within its scope.

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.

The loss of mass from glaciers, ice caps, and polar ice sheets has accelerated over the last 3 decades as a result of climate change. This has made land ice the major contributor to sea level rise and the main cause of its acceleration. However, the evolution of the land-based cryosphere over the course of the 21st century and beyond adds considerable uncertainties to sea level rise projections, particularly if instability mechanisms are triggered, leading to rapid retreat of marine basins in Antarctica. Critical knowledge gaps pose challenges for predicting the land ice response to the evolution of climate and the resulting impact on sea level, from cryospheric process understanding, ice sheet and glacier modelling, and coupling with the atmosphere and ocean to bridging the gap with sea level and coastal-impact sciences. This special issue includes contributions related to the following:

• Earth observations that help to constrain glacier and ice sheet surface conditions, dynamics, or mass loss;
• theoretical or numerical modelling of cryospheric processes or coupling with the ocean and atmosphere;
• standalone or coupled projections of ice surface mass balance;
• Arctic and Antarctic ocean conditions promoting and/or responding to ice sheet loss;
• glacier or ice sheet dynamics and mass balance;
• approaches to analysing multi-model ensembles or computing global and regional sea level rise projections;
• coastal impacts of sea level rise and climate change, adaptation needs, and related climate services.

The purpose of this special issue is to illustrate the role of a sustainable coastal research infrastructure in supporting monitoring, sciences, and management of the coastal marine areas. As such the JERICO-RI research infrastructure is most suitable, gathering 34 partners in Europe with the same overarching objective: to strengthen and enlarge a solid and transparent European network of coastal observatories and to provide an operational service for the timely, continuous, and sustainable delivery of high-quality environmental (physical, biogeochemical, and biological) data and services related to the marine environment in European coastal seas. Six scientific areas are targeted, from the sensor development to the data analysis and the scientific results. These are the following:

1. the pelagic biodiversity with phytoplankton and harmful algal blooms;
2. the benthic biodiversity and habitats;
3. the contaminant transports;
4. the coastal transport and hydrology;
5. the carbonate systems and C cycle; and
6. the coastal operational oceanography and modelling.