By redistributing a large amount of heat and salt, the Atlantic Ocean significantly impacts regional and global climate over a wide range of time scales. In particular, the subpolar North Atlantic has seen strong variations in ocean heat and freshwater content over the past couple of decades, as well as in the uptake and storage of anthropogenic carbon, which has been attributed to changes in the large-scale Atlantic circulation. However, the mechanisms through which the ocean circulation changes and impacts the climate system and their feedback and predictability remain elusive. This session invites contributions that advance our understanding of Atlantic Ocean variability, the role it plays in the atmosphere–ocean–ice system, and its role in extreme weather events and abrupt climate change. It aims to bring together recent progress in understanding the circulation and climate variability in the Atlantic sector from paleoclimate, historical, and future perspectives. Studies utilizing observational, modeling, and/or theoretical frameworks are all welcome.

The importance of the ocean’s biological carbon pump (BCP), the process of exporting surface-produced organic matter (OM) into the deep ocean, and its role in alleviating the rising atmospheric carbon dioxide have long been recognized. Recent advances in the observational and modeling approaches have demonstrated multi-faceted export pathways and diverse biogeochemical processes that operate on wide-ranging temporal and spatial timescales, from days to years and from microscale (𝜇m) to mesoscale (km). New ship-based observational instruments (e.g., particle imaging and optics), analytical techniques (e.g., omics, biomarkers, isotopes), and modeling studies yield novel insights into the complex mechanisms of BCP, including the significance of zooplankton and microbial communities in altering sinking OM flux. Meanwhile, autonomous platforms (e.g., gliders, BGC-Argo floats) have been gathering data with unprecedentedly high spatiotemporal resolution. Integrating these fields leads to a more holistic understanding of the BCP. This session welcomes experimental-, field- and modeling-based studies that quantify and/or investigate mechanistic controls on the strength/processes of the BCP. Abstracts focusing on biological, chemical, and physical aspects of the BCP are all encouraged. We aim to identify gaps and challenges and discuss new directions and potential points of collaboration for future BCP research.

Ocean have responded to climate change in many different ways, including sea level rise, sea temperature/salinity change, ocean acidification, and ocean deoxygenation, which profoundly affect ocean circulation, productivity, nutrient cycling etc. These changes together could further threaten the biota in ocean and the health of marine system. Thus, it is critical to develop an improved understanding of the mechanisms driving long-term trends and variability in these key ocean elements. In addition, we need to document and predict how these ocean elements will change in the future under climate change, such that society can make informed decisions and understand costs and benefits trade-offs for mitigation, tourisms, and fisheries. How to reasonably use observations and modelling results to accurately reflect ocean changes is still a grand challenge. Improved observation coverage and quality, data processing techniques, and numerical modelling of the changes in ocean are critically needed. In addition, unravelling the causes and consequences of these changes is also a further challenge. The objective of this session is to bring together the efforts in observing and understanding historical and/or future changes in ocean under climate change, to explore the mechanisms behind these changes, and to examine the effects of these changes on ocean plants and animals. This session aims to discuss how we can achieve more reliable and accurate observational datasets and projection tools.

Corals are amazing marine invertebrates that are foci of tremendous amount of researches over several decades. Corals build up reefs that support shallow water ecosystem. They are one of the major calcifiers in the modern ocean that sequester CO₂ from Earth’s atmosphere. They are sensitive to environmental stresses (e.g. sea-surface temperature and pH of seawater) and their skeletons faithfully record ample environmental and biological information in modern and paleo-oceans. In this session, we welcome, but not limit to, the submission of researches focusing on 1) describing and characterizing the physiology and biology of corals, as well as the bio-mineralization processes, particularly using advanced biological and chemical techniques; 2) field and lab scale observations of coral ecology and the response of corals to extreme climate stress; 3) applying geochemical proxies documented in coral skeletons to understanding modern and paleo-climates over the world; and 4) advancing our understanding of the origin of the ‘vital effects’ (or biological effect) in coral skeletons.

In recent years, microplastics have become a major global environmental issue and have attracted worldwide attention due to their ubiquitous presence and potential threats to the ecosystem and human health. They can transport through riverine systems and eventually reach the ocean, even the polar regions. In the past years, much efforts have been paid on microplastic occurrence, mobility, bioaccumulation, and toxicity. However, it is still challenging to develop the andvanced analytical methods and technologies, understand well their fate and ecological risks, and regulate the management of microplastics. State-of-the-art information is urgently needed to i) improve and develop advanced sampling and monitoring methods and techniques; ii) explore source-and-sink processes; iii) evaluate the ecotoxicity; and iv) conduct efficient management of plastic pollution. This session welcomes contributions focused on various aspects of marine microplastics, but not limited to:

1) Novel sampling and monitoring methodologies of marine microplstics.

2) Transport, mixing, and fate of microplastics on their way from land to the ocean, including polar regions.

3) The interaction of microplastics with organic and inorganic pollutants and/or microorganisms.

4) Trophic transfer of microplastics through marine food webs and ecological impacts on marine organisms.

5) Recycling and regulation management for plastics from local to regional and international scales.

The global ocean is the largest reservoir of reactive nitrogen on Earth. Nitrogen is an important limiting nutrient that exerts significant control on ocean productivity, and the emission of atmospherically active trace gases nitric oxide and nitrous oxide from the oceans have profound impacts on ozone depletion and global warming associated climate change. Thus, as an essential element, nitrogen provides foundation to the function and stability of various marine ecosystems. The marine nitrogen cycle is driven and connected by complex microbial transformation processes, including nitrogen fixation, assimilation, nitrification, anammox, DNRA, and denitrification. Marine nitrogen-transforming microorganisms display extensive phylogenetic diversity and metabolic versatility and have evolved to efficiently access and use every form of nitrogen that spans a wide range of redox states, either for energy production or for biosynthesis. Recent advances in marine nitrogen cycle have come from diverse research fields, including novel physiology and metabolism, new molecular tools, enhanced isotopic labeling techniques, and global biogeochemical modeling. These emerging research directions are already contributing to urgent efforts to address the primary challenge facing marine scientists: the unprecedented onslaught of anthropogenic environmental change on the microbial nitrogen cycle. Ongoing ocean warming, acidification, deoxygenation, and seawater stratification have major effects on the microbial nitrogen cycle. In turn, the responses of marine nitrogen-transforming microbes to anthropogenic perturbation and global climate change will feed back to the cycle of major nutrients, micronutrients, and greenhouse gases.

In this session, we will focus on the wealth of new marine nitrogen cycle research spanning from molecular levels to global biogeochemical scales. We invite contributions that use diverse laboratory, field study, and modeling approaches to study dynamic marine nitrogen transformation processes in a vast range of environments from productive estuaries to oligotrophic pelagic waters, and from the sunlit ocean to the abyssal deep sea and sediments. This session aims for closer communications between marine scientists with different academic backgrounds for studying the marine nitrogen cycle.