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Global climate is regulated by the ocean, which stores, releases, and transports large amounts of mass, heat, carbon, and oxygen. Understanding, monitoring, and predicting the exchanges of these quantities across the ocean’s surface, their interactions with the atmosphere, and their horizontal and vertical pathways through the global oceans, are key for advancing fundamental knowledge and improving forecasts and longer-term projections of climate, weather, and ocean ecosystems. The existing global observing system provides immense value for science and society in this regard by supplying the data essential for these advancements. The tropical ocean observing system in particular has been developed over decades, motivated in large part by the far-reaching and complex global impacts of tropical climate variability and change. However, changes in observing needs and priorities, new challenges associated with climate change, and advances in observing technologies demand periodic evaluations to ensure that stakeholders’ needs are met. Previous reviews and assessments of the tropical observing system have focused separately on individual basins and their associated observing needs. Here we provide a broader perspective covering the tropical observing system as a whole. Common gaps, needs, and recommendations are identified, and interbasin differences driven by socioeconomic disparities are discussed, building on the concept of an integrated pantropical observing system. Finally, recommendations for improved observations of tropical basin interactions, through oceanic and atmospheric pathways, are presented, emphasizing the benefits that can be achieved through closer interbasin coordination and international partnerships. 

Abstract Marine heatwaves have profoundly impacted marine ecosystems over large areas of the world oceans, calling for improved understanding of their dynamics and predictability. Here, we critically review the recent substantial advances in this active area of research, including the exploration of the three-dimensional structure and evolution of these extremes, their drivers, their connection with other extremes in the ocean and over land, future projections, and assessment of their predictability and current prediction skill. To make progress on predicting and projecting marine heatwaves and their impacts, a more complete mechanistic understanding of these extremes over the full ocean depth and at the relevant spatial and temporal scales is needed, together with models that can realistically capture the leading mechanisms at those scales. Sustained observing systems, as well as measuring platforms that can be rapidly deployed, are essential to achieve comprehensive event characterizations while also chronicling the evolving nature of these extremes and their impacts in our changing climate. 

The UN Decade of Ocean Science for Sustainable Development (Ocean Decade) challenges marine science to better inform and stimulate social and economic development while conserving marine ecosystems. To achieve these objectives, we must make our diverse methodologies more comparable and interoperable, expanding global participation and foster capacity development in ocean science through a new and coherent approach to best practice development. We present perspectives on this issue gleaned from the ongoing development of the UNESCO Intergovernmental Oceanographic Commission (IOC) Ocean Best Practices System (OBPS). The OBPS is collaborating with individuals and programs around the world to transform the way ocean methodologies are managed, in strong alignment with the outcomes envisioned for the Ocean Decade. However, significant challenges remain, including: (1) the haphazard management of methodologies across their lifecycle, (2) the ambiguous endorsement of what is “best” and when and where one method may be applicable vs. another, and (3) the inconsistent access to methodological knowledge across disciplines and cultures. To help address these challenges, we recommend that sponsors and leaders in ocean science and education promote consistent documentation and convergence of methodologies to: create and improve context-dependent best practices; incorporate contextualized best practices into Ocean Decade Actions; clarify who endorses which method and why; create a global network of complementary ocean practices systems; and ensure broader consistency and flexibility in international capacity development. 

Abstract. Over the past decade, our understanding of the IndianOcean has advanced through concerted efforts toward measuring the oceancirculation and air–sea exchanges, detecting changes in water masses, andlinking physical processes to ecologically important variables. Newcirculation pathways and mechanisms have been discovered that controlatmospheric and oceanic mean state and variability. This review bringstogether new understanding of the ocean–atmosphere system in the IndianOcean since the last comprehensive review, describing the Indian Oceancirculation patterns, air–sea interactions, and climate variability.Coordinated international focus on the Indian Ocean has motivated theapplication of new technologies to deliver higher-resolution observationsand models of Indian Ocean processes. As a result we are discovering theimportance of small-scale processes in setting the large-scale gradients andcirculation, interactions between physical and biogeochemical processes,interactions between boundary currents and the interior, and interactions between thesurface and the deep ocean. A newly discovered regional climate mode in thesoutheast Indian Ocean, the Ningaloo Niño, has instigated more regionalair–sea coupling and marine heatwave research in the global oceans. In thelast decade, we have seen rapid warming of the Indian Ocean overlaid withextremes in the form of marine heatwaves. These events have motivatedstudies that have delivered new insight into the variability in ocean heatcontent and exchanges in the Indian Ocean and have highlighted the criticalrole of the Indian Ocean as a clearing house for anthropogenic heat. Thissynthesis paper reviews the advances in these areas in the last decade.