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While the field of hydrography is crucial for maritime navigation and other maritime applications, oceanography is the field that provides the relevant data and knowledge for predicting climate change, monitoring marine resources, and exploring marine life. Digital ocean twins combine these two exciting fields and combine ocean observations and ocean models to establish virtual representations of a real world system, in this case the ocean or an ocean area, as well as assets in the ocean and processes within ocean industries or the natural environment. They have the potential to play a critical role in optimising and supporting sustainable ocean development. Digital Twins are synchronised with their real-world counterparts at a specific frequency and fidelity. They can provide valuable insights into the ocean's state and its evolution over time, which can be used to support decision-making in ocean governance and various ocean-related industries. Digital ocean twins can transform human ocean interactions by accelerating holistic understanding, optimal decision-making, and effective interventions. Digital twins of the ocean use ocean observations, historical and forecast data to represent the past and present and simulate possible future scenarios. They are motivated by outcomes, tailored to use cases, powered by integration, built on data, guided by domain knowledge, and implemented in IT systems. In this article, we explore the benefits of digital twins for the ocean, the challenges in developing them, and the current state of the art in ocean digital twin technology. One of the main benefits of digital ocean twins is their ability to provide accurate predictions of ocean conditions under expected interventions. Their information can be used to support decision- making in various applications including ocean-related industries, such as fishing, shipping, and offshore energy production. Additionally, digital twins can help to improve our understanding of the ocean's complex processes and their interactions with human activities, such as climate change, pollution, resource extraction and overfishing. Researchers and IT companies are combining various technologies and data sources, such as the Internet of Things for ocean observations, state of the art data science, artificial intelligence and machine learning, data spaces and vocabularies into digital ocean twins to contextualise data, improve the accuracy of ocean models and make ocean knowledge more accessible to a wide range of users.

Digital twins are fine-grained digital replicas of physical objects and systems which have been widely applied in the engineering realm for tasks such as engine optimization and port management. Recently, digital twins have also caught the attention of marine scientists as a solution to socio-environmental problems. By bundling and providing access to observational data, models, and simulations, digital twins allow users to explore current and future ‘what-if’ scenarios, especially related to human interactions with the ocean. High-value application areas include fisheries and mariculture, marine protected areas, ocean-based tourism, ecological forecasting, nature-based solutions, marine infrastructure development, and the interactions between all of these with an ever-growing collection of data streams.In the context of the UN Decade of Ocean Science for Sustainable Development, we launched the international programme “DITTO - The Digital Twins of the Ocean“ (ditto-oceandecade.org) in May 2022. DITTO’s mission is to develop and share a common understanding of Digital Twins of the Ocean, to establish best practice examples and to advance a digital framework to empower ocean professionals to effectively create their own application-focused digital twin. This powerful framework will enable users to visualize and explore ocean knowledge and empower ocean professionals and models, forecasts, citizen scientists, policymakers, and the general public alike.A successful regional implementation of a Digital Twin depends on four aspects: A) a capable ocean observing system B) An innovative ocean modeling and prediction capability C) An interoperable, shared and easily accessible data environment. D) An interactive user interface. International cooperation will be key for success., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

In recognition of the Ocean’s importance “to an equitable and sustainable planet”, the United Nations have pronounced 2021-2030 as the Decade of Ocean Science for Sustainable Development. What will “the Ocean we need for the future we want” look like? And how can we transform human behavior to become more sustainable? And what are the expected impacts on the ocean. Realizing that the ocean dimension of sustainable development should be underpinned by inclusive knowledge, the Ocean Decade identifies ten challenges to deliver “the science we need for the Ocean we want”.The UN Ocean Decade recognises seven societal outcomes and ten challenges. In order to facilitate progress the community is asked to proposed global decade programmes which themselves are supported by several more regional or topical projects. Ideally these actions involve the global science community in a interdisciplinary manner and engage in co-design and co-production of knowledge generation that enables science based actions.A key aspect of the UN Ocean Decade is to deliver against the UN's stated ambition 'to leave no one behind'. This is a call to action for training, capacity exchange and ocean education and literacy.&nbsp, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Recent advances in High Performance Computing and Earth System Model resolution have enabled the Earth Science community to envision Digital Twins as an innovative approach to global environmental problems. This is also true of the Ocean Science community. A Digital Twin of the Ocean (DTO) merges marine system models with observational data and machine learning analytics to produce a digital replica of the real ocean. In addition to natural phenomena, DTOs can include socio-economic factors (e.g. ocean-use, pollution). Thus, DTOs can be used to monitor the current ocean state, but also to simulate future ‘what-if’ scenarios for varying human interventions. Another benefit of DTOs is that they can be used by a variety of stakeholders: by scientists to understand the ocean, by policymakers to make well-informed decisions, and by citizens to improve ocean literacy. As such, DTOs are a powerful tool in future-proofing sustainable development. Moreover, they provide strong motivation to improve the marine data landscape and build an interoperable system with agreed upon formats and standards. DTOs are tailored to a specific ocean area or purpose, such that a DTO framework is needed to implement data connectivity and interoperability, ease of access, standards and to highlight gaps. The UN Ocean Decade Program DITTO aims to provide such a framework. Specifically, DITTO advances worldwide collaboration between scientists, data and IT experts to develop a common understanding of DTOs, to establish best practices in their development, and to advance a digital framework for DTOs to empower ocean professionals from all sectors around the world to effectively create their own digital twins. DTOs offer the technology for building a social-ecologically integrated ocean ecosystem with observation- and modelling networks that support sustainable ocean governance.

Schmidt Ocean Institute, in partnership with The Ditchley Foundation, hosted Credit where credit is due: Authorship of open ocean data at Ditchley Park, in Chipping Norton, UK, on October 6-7, 2022, to identify actionable and implementable solutions to recognize and reward the dissemination of acquired data and knowledge. This report outlines the findings from that workshop.&nbsp

The ocean has recently taken centre stage in the global geopolitical landscape. Despite rising challenges to the effectiveness of multilateralism, attention to ocean issues appears as an opportunity to co-create pathways to ocean sustainability at multiple levels. The ocean science community, however, is not sufficiently well organised to advance these pathways and provide policy input. The Intergovernmental Panel on Climate Change and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services demonstrate how knowledge consensus and integration have been instrumental in charting global pathways and eliciting commitments to address, respectively, climate change and biodiversity loss. An equally impactful global platform with a thematic focus on ocean sustainability is needed. Here we introduce the International Panel for Ocean Sustainability (IPOS) as a coordinating mechanism to integrate knowledge systems to forge a bridge across ocean science-policy divides collectively. The IPOS will enrich the global policy debate in the Ocean Decade and support a shift toward ocean sustainability.

The ocean is an important part of the global system. Tracking the connectivity between bodies of water is crucial for understanding local, regional and global changes in the ocean dynamics that mediate the spreading of nutrients and influence the marine ecosystem and ocean productivity. We developed a Data Fusion approach that enhances and automates the existing methods for the analysis of this connectivity. This approach combines and condenses two different data sources in two stages, Data Enhancement followed by Data Reduction. The Data Enhancement stage fuses equidistantly gridded data containing physical measurements and trajectories representing movement data. The Data Reduction stage aggregates the fused data into a Markov Model representation of the transition probabilities between ocean regions. We applied this framework to an exemplary analysis for the connectivity between two oceanic areas using real ocean data stemming from marine research. We show that this method directly tackles the limitations of existing marine data analysis methods and furthermore introduces new means to answer questions that had no quantitative answers up to now.

Understanding and sustainably managing complex environments such as marine ecosystems benefits from an integrated approach to ensure that information about all relevant components and their interactions at multiple and nested spatiotemporal scales are considered. This information is based on a wide range of ocean observations using different systems and approaches. An integrated approach thus requires effective collaboration between areas of expertise in order to improve coordination at each step of the ocean observing value chain, from the design and deployment of multi-platform observations to their analysis and the delivery of products, sometimes through data assimilation in numerical models. Despite significant advances over the last two decades in more cooperation across the ocean observing activities, this integrated approach has not yet been fully realized. The ocean observing system still suffers from organizational silos due to independent and often disconnected initiatives, the strong and sometimes destructive competition across disciplines and among scientists, and the absence of a well-established overall governance framework. Here, we address the need for enhanced organizational integration among all the actors of ocean observing, focusing on the occidental systems. We advocate for a major evolution in the way we collaborate, calling for transformative scientific, cultural, behavioral, and management changes. This is timely because we now have the scientific and technical capabilities as well as urgent societal and political drivers. The ambition of the United Nations Decade of Ocean Science for Sustainable Development (2021–2030) and the various efforts to grow a sustainable ocean economy and effective ocean protection efforts all require a more integrated approach to ocean observing. After analyzing the barriers that currently prevent this full integration within the occidental systems, we suggest nine approaches for breaking down the silos and promoting better coordination and sharing. These recommendations are related to the organizational framework, the ocean science culture, the system of recognition and rewards, the data management system, the ocean governance structure, and the ocean observing drivers and funding. These reflections are intended to provide food for thought for further dialogue between all parties involved and trigger concrete actions to foster a real transformational change in ocean observing., This work was supported by the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No. 862626, project EuroSea (Improving and Integrating European Ocean Observing and Forecasting Systems for Sustainable Use of the Oceans).

The intraseasonal evolution of physical and biogeochemical properties during a coastal trapped wave event off central Peru is analysed using data from an extensive shipboard observational programme conducted between April and June 2017, and remote sensing data. The poleward velocities in the Peru–Chile Undercurrent were highly variable and strongly intensified to above 0.5 m s−1 between the middle and end of May. This intensification was likely caused by a first-baroclinic-mode downwelling coastal trapped wave, excited by a westerly wind anomaly at the Equator and originating at about 95∘ W. Local winds along the South American coast did not impact the wave. Although there is general agreement between the observed cross-shore-depth velocity structure of the coastal trapped wave and the velocity structure of first vertical mode solution of a linear wave model, there are differences in the details of the two flow distributions. The enhanced poleward flow increased water mass advection from the equatorial current system to the study site. The resulting shorter alongshore transit times between the Equator and the coast off central Peru led to a strong increase in nitrate concentrations, less anoxic water, likely less fixed nitrogen loss to N2 and a decrease of the nitrogen deficit compared to the situation before the poleward flow intensification. This study highlights the role of changes in the alongshore advection due to coastal trapped waves for the nutrient budget and the cumulative strength of N cycling in the Peruvian oxygen minimum zone. Enhanced availability of nitrate may impact a range of pelagic and benthic elemental cycles, as it represents a major electron acceptor for organic carbon degradation during denitrification and is involved in sulfide oxidation in sediments.

Oxygen minimum zones (OMZs) in the open ocean occur below the surface in regions of weak ventilation and high biological productivity with associated sinking organic matter. Very low levels of dissolved oxygen alter biogeochemical cycles and significantly affect marine life. One of the most intense though poorly understood OMZs in the world ocean is located in the Arabian Sea between 300 and 1000 m of depth. An improved understanding of the physical processes that have an impact on the OMZ in the Arabian Sea is expected to increase the reliability of assessments of its future development. This study uses reanalysis velocity fields from the ocean model HYCOM (Hybrid Coordinate Ocean Model), which are verified with observational data, to investigate advective pathways of Lagrangian particles into the Arabian Sea OMZ at intermediate depths between 200 and 800 m. In the eastern basin, the vertical expansion of the OMZ is strongest during the winter monsoon, revealing a core thickness 1000 m deep and oxygen values below 5 µmol kg−1. The minimum oxygen concentration might be favoured by a maximum water mass advection that follows the main advective pathway of Lagrangian particles along the perimeter of the basin into the eastern basin of the Arabian Sea during the winter monsoon. These water masses pass regions of high primary production and respiration, contributing to the transport of low-oxygenated water into the eastern part of the OMZ. The maximum oxygen concentration in the western basin of the Arabian Sea in May coincides with a maximum southward water mass advection in the western basin during the spring intermonsoon, supplying the western core of the OMZ with high-oxygenated water. The maximum oxygen concentration in the eastern basin of the Arabian Sea in May might be associated with the northward inflow of water across 10∘ N into the Arabian Sea, which is highest during the spring intermonsoon. The Red Sea outflow of advective particles into the western and eastern basin starts during the summer monsoon associated with the northeastward current during the summer monsoon. On the other hand, waters from the Persian Gulf are advected with little variation on seasonal timescales. As the weak seasonal cycle of oxygen concentration in the eastern and western basin can be explained by seasonally changing advection of water masses at intermediate depths into the Arabian Sea OMZ (ASOMZ), the simplified backward-trajectory approach seems to be a good method for prediction of the seasonality of advective pathways of Lagrangian particles into the ASOMZ.

State of the climate in 2019

There is debate about slowing of the Atlantic Meridional Overturning Circulation (AMOC), a key component of the global climate system. Some focus is on the sea surface temperature (SST) slightly cooling in parts of the subpolar North Atlantic despite widespread ocean warming. Atlantic SST is influenced by the AMOC, especially on decadal timescales and beyond. The local cooling could thus reflect AMOC slowing and diminishing heat transport, consistent with climate model responses to rising atmospheric greenhouse gas concentrations. Here we show from Atlantic SST the prevalence of natural AMOC variability since 1900. This is consistent with historical climate model simulations for 1900–2014 predicting on average AMOC slowing of about 1 Sv at 30° N after 1980, which is within the range of internal multidecadal variability derived from the models’ preindustrial control runs. These results highlight the importance of systematic and sustained in-situ monitoring systems that can detect and attribute with high confidence an anthropogenic AMOC signal.

Lagrangian experiments for particle tracing in atmosphere or ocean models and their analysis are a cornerstone of earth-system studies. They cover diverse study objectives such as the identification of pathways or source regions. Data for Lagrangian studies are generated by releasing virtual particles in one or in multiple locations of interest and simulating their advective-diffusive behavior backwards or forwards in time. Identifying main pathways connecting two regions of interest is often done by counting the trajectories that reach both regions. Here, the exact source and target region must be defined manually by a researcher. Manually defining the importance and exact location of these regions introduces a highly subjective perspective into the analysis. Additionally, to investigate all major target regions, all of them must be defined manually and the data must be analyzed accordingly. This human element slows down and complicates large scale analyses with many different sections and possible source areas.We propose to significantly reduce the manual aspect by automatizing this process. To this end, we combine methods from different areas of machine learning and pattern mining into a sequence of steps. First, unsupervised methods, i.e., clustering, identify possible source areas on a randomized subset of the data. In a successive second step, supervised learning, i.e., classification, labels the positions along the trajectories according to their most probable source area using the previously automatically identified clusters as labels. The results of this approach can then be compared quantitatively to the results of analyses with manual definition of source areas and border-hitting-based labeling of the trajectories. Preliminary findings suggest that this approach could indeed help greatly to objectify and fasten the analysis process for Lagrangian Particle Release Experiments.

Over 30% of the world’s population lives within 100 km of the oceanic coast. More than three billion people rely on fishing and other ocean-related livelihoods. The ocean is a biodiversity hotspot and moderates the climate, having absorbed around 40% of the world’s total carbon emissions. Oceanscapes provide an essential cultural good, offer recreational opportunities, health benefits, artistic inspiration and an entire cosmology and way of life for indigenous communities. However, anthropogenic pressures have seriously impacted the ocean and threaten its ability to provide human societies with the required climatic and ecosystem conditions for life on earth. The German G7 presidency has proposed a G7 “Ocean Deal” for the sustainable use, protection and effective governance of the ocean and its resources. Several ongoing global ocean governance processes require strong multilateral leadership and close alignment between the G7, in particular in this period of serious international tensions following the Russian invasion of Ukraine. At the One Ocean Summit in February 2022, global leaders have put forth first commitments to make 2022 a decision year for the ocean. Building on the final declaration of the summit and the UK G7 Ocean Decade Navigation Plan, we highlight that a G7 “Ocean Deal” should include provisions for 1) ambitious ocean governance to safeguard ocean health and climate (in the G7’s own waters and through leadership in international settings), 2) improving ocean observation, data infrastructure and knowledge sharing, and 3) financing the transition towards more sustainable interactions with the ocean. Specifically, we recommend that G7 states: 1a. Eliminate national subsidies that contribute to overfishing and push to finalize the related WTO agreement; step up international cooperation, financial & technical assistance to prevent IUU fishing. 1b. Reduce marine debris through a comprehensive global agreement on plastic pollution. 1c. Pause deep sea mining until risks are better understood and a transparent, inclusive and accountable institutional structure is in place that guarantees the effective protection of the marine environment. 1d. Expand marine protected areas in line with the proposed goal of at least 30% by 2030, and accelerate work in the coming months to successfully finalize negotiations for a legally binding instrument to conserve and sustainably use marine biological diversity in areas beyond national jurisdiction (BBNJ). 1e. Fully recognize the importance of the ocean-climate nexus and strengthen the ocean dimension in key climate negotiations. 2a. Adopt a legal framework and binding commitments for a sustained and shared global coordination of ocean observations and infrastructure on marine data, compliant with FAIR and CARE principles. 2b. Ensure long-term, guaranteed funding, clear institutional affiliations, coordinated and integrated data products to enable continuous, comprehensive observations supporting policy monitoring & evaluation 3a. Redesign and scale up ocean finance by increasing funding of early-stage, nature-positive and science-based opportunities, and large-scale investment into zero-carbon, resilient and nature-based coastal blue infrastructure, and by integrating ocean criteria into sustainability finance frameworks (EU Taxonomy, Task Force on Climate-related Financial Disclosures (TCFD), Taskforce for Nature-related Financial Disclosures (TNFD)).

Highlights: • Field investigations of major pollutants along the coast of China were carried out. • The distributions of pollutants are correlated with specific industry sectors. • The distribution characteristics of pollutants varied in different climatic zones. • The ecological risks are affected by both climate and physicochemical properties. Abstract Coastal ecosystem health is of vital importance to human well-being. Field investigations of major pollutants along the whole coast of China were carried out to explore associations between coastal development activities and pollutant inputs. Measurements of target pollutants such as PFAAs and PAHs uncovered notable levels in small estuary rivers. The Yangtze River was identified to deliver the highest loads of these pollutants to the seas as a divide for the spatial distribution of pollutant compositions. Soil concentrations of the volatile and semi-volatile pollutants showed a cold-trapping effect in pace with increasing latitudinal gradient. The coastal ecosystem is facing high ecological risks from metal pollution, especially copper (Cu) and zinc (Zn), while priority pollutants of high risks vary for different kinds of protected species, and the ecological risks were influenced by both climate and physicochemical properties of environmental matrices, which should be emphasized to protect and restore coastal ecosystem functioning.

It is unequivocal that human influence has warmed the planet, which is seriously affecting the planetary health including human health. Adapting climate change should not only be a slogan, but requires a united, holistic action and a paradigm shift from crisis response to an ambitious and integrated approach immediately. Recognizing the urgent needs to tackle the risk connection between climate change and One Health, the four key messages and recommendations that with the intent to guide further research and to promote international cooperation to achieve a more climate-resilient world are provided. Graphical Abstract

This Commentary is a response on the Structured Conversation 'The future of transdisciplinarity: How do we relearn to be human in new ways?'.

"We have to make sure that as we grow the blue economy, it accelerates in a regenerative way. Moving to a sustainable blue economy would benefit food security, human health, underdeveloped communities - and of course, the environment." Alexandra Cousteau, President and Co-Founder Oceans 2050

The distribution of passively drifting particles within highly turbulent flows is a classic problem in marine sciences. The use of trajectory clustering on huge amounts of simulated marine trajectory data to identify main pathways of drifting particles has not been widely investigated from a data science perspective yet. In this paper, we propose a fast and computationally light method to efficiently identify main pathways in large amounts of trajectory data. It aims at overcoming some of the issues of probabilistic maps and existing trajectory clustering approaches. Our approach is evaluated against simulated larvae dispersion data based on a real-world model that have been produced as part of work in the marine science domain.

Die Meeresströmungen im Atlantik spielen für unser Klima eine wichtige Rolle. Klimamodelle zeigen, dass bei weiter steigenden Treibhausgas-Emissionen die Stärke der Strömungen abnimmt und sich ihr Verlauf ändert. Dies hat weitreichende Folgen für die regionale Erwärmung, Niederschläge, Meeresspiegel, Landwirtschaft und Fischerei auch in Deutschland. Deshalb haben die führenden deutschen Meeresforschungsinstitute Langzeitbeobachtungen der Meeresströmungen an Schlüsselstellen im Atlantik installiert. Durch sie kennen wir nun die Strömungsstärken und ihre Schwankungen über Zeiträume von Stunden bis Jahrzehnte und können Klimatrends frühzeitig erkennen. Die Messungen haben auch gezeigt, dass selbst in den aktuellsten Klimamodellen noch immer große Unterschiede zwischen den simulierten und den beobachteten Strömungen bestehen und auch die vorhersagte Abschwächung der Strömungen bis ins Jahr 2100 in den Modellen unterschiedlich ausfällt. Um die Ergebnisse der Klimamodelle auch in Zukunft durch Beobachtungen bewerten zu können, müssen die Langzeitbeobachtungen der Atlantikzirkulation aufrechterhalten werden. Diese Broschüre knüpft an die bereits erschienenen Bände „Zukunft der Golfstromzirkulation“ (2016) und „Zukunft der Meeresspiegel“ (2019) an, in die ebenfalls Resultate aus den Langzeit-Beobachtungssystemen eingeflossen sind.

Changes in the Atlantic Meridional Overturning Circulation, which have the potential to drive societally-important climate impacts, have traditionally been linked to the strength of deep water formation in the subpolar North Atlantic. Yet there is neither clear observational evidence nor agreement among models about how changes in deep water formation influence overturning. Here, we use data from a trans-basin mooring array (OSNAP—Overturning in the Subpolar North Atlantic Program) to show that winter convection during 2014–2018 in the interior basin had minimal impact on density changes in the deep western boundary currents in the subpolar basins. Contrary to previous modeling studies, we find no discernable relationship between western boundary changes and subpolar overturning variability over the observational time scales. Our results require a reconsideration of the notion of deep western boundary changes representing overturning characteristics, with implications for constraining the source of overturning variability within and downstream of the subpolar region., Western boundary current variability in the subpolar North Atlantic is thought to reflect interior convection changes and determine Atlantic Meridional Overturning Circulation variability. Here, the authors show with an extended OSNAP time series that neither linkage is robust due to the complex dynamics in the region.

In the earth-physics community Lagrangian trajectories are used within multiple contexts – analyzing the spreading of pollutants in the air or studying the connectivity between two ocean regions of interest. Huge amounts of data are generated reporting the geo position and other variables e.g. temperature, depth or salinity for particles spreading in the ocean. As state-of-the-art, these experiments are analyzed and visualized by binning the particle positions to pre-defined rectangular boxes. For each box a particle density is computed which then yields a probability map to visualize major pathways. Identifying the main pathways directly still remains a challenge when huge amounts of particles and variables are involved.We propose a novel method that focuses on linking the net fluctuation of particles between adaptable hexagonal grid cells. For very small areas the rectangular boxing does not imply big differences in area or shape, though when gridding larger areas it introduces rather large distortions. Using hexagons instead provides multiple advantages, such as constant distances between the centers of neighboring boxes or more possibilities of movement due to 6 edges instead of 4 with a lower number of neighbors at the same time (6 instead of 9). The net fluctuation can be viewed as transition strength between the cells.Through this network perspective, the density of the transition strength can be visualized clearly. The main pathways are the transitions with the highest net fluctuation. Thus, simple statistical filtering can be used to reveal the main pathways. The combination of network analysis and adaptable hexagonal grid cells yields a surprisingly time and resource efficient way to identify main pathways.

Modern digital scientific workflows - often implying Big Data challenges - require data infrastructures and innovative data science methods across disciplines and technologies. Diverse activities within and outside HGF deal with these challenges, on all levels. The series of Data Science Symposia fosters knowledge exchange and collaboration in the Earth and Environment research community. We invited contributions to the overarching topics of data management, data science and data infrastructures. The series of Data Science Symposia is a joint initiative by the three Helmholtz Centers HZG, AWI and GEOMAR Organization: Hela Mehrtens and Daniela Henkel (GEOMAR)

The oceans' role in climate and climate change is manifold. The Ocean circulation transports large amounts of heat and freshwater on hemispheric space scales which have significant impacts on regional climate in the ocean itself but also noticeable consequences via atmospheric teleconnections on land. Due to the high heat capacity of seawater and the relatively slow ocean circulation, the oceans provide a significant “memory” for the climate system. Bodies of water that descend from the sea surface may reside in the ocean interior for decades and centuries, while preserving their temperature and salinity signature, before they surface again to interact with the overlying atmosphere. The residence time of water in the atmosphere is about ten days and the persistence of dynamical states of the atmospheric circulation may last up to a few weeks. Thus, on long time scales ocean dynamics becomes important for climate, which implies that climate variations and climate change can only partially be understood without consideration of ocean dynamics and the intricate ocean-atmosphere interaction. Since 1960 the heat uptake of the oceans has been 20 times larger than that of the atmosphere. Thus the oceans have been able to reduce the otherwise much more pronounced temperature rise in the atmospheric climate. Also, over the last 200 years the oceans have absorbed about half of the CO2 release into the atmosphere by human activities (fossil fuel combustion, de-forestation, cement production), thereby reducing the direct effect of greenhouse gases on atmospheric temperatures.This chapter aims to describe and explain fundamental principles of the ocean dynamics and gathers information about past, present and future states the world’s ocean and its role in climate change.

Im Fokus der siebten Ausgabe des »World Ocean Review« stehen die Auswirkungen des Klimawandels auf die Physik des Meeres und auf seine Lebensgemeinschaften; die Folgen von Fischerei, Schifffahrt, Ressourcenabbau, Energiegewinnung und Meeresverschmutzung sowie die Fragen, wie sich Wirkstoffe aus dem Meer nutzen lassen und wie der Ozean künftig so verwaltet werden kann, dass sowohl sein Schutz als auch die Teilhabe möglichst aller Menschen an seinen Leistungen und Gütern gewährleistet sind.

Increased human activities—in particular energy generation and land use—have led to atmospheric pollution by the significant emission of greenhouse gases such as carbon dioxide (CO2) and methane. The associated climate change is also affecting the ocean while, at the same time, the ocean plays a fundamental role in mitigating climate change by serving as a major heat and carbon sink. We highlight some of the most salient aspects of climate change impacting the ocean as articulated in the Special Report on the Ocean and Cryosphere in a Changing Climate by the Intergovernmental Panel on Climate Change (IPCC) released in 2019. It shows that the ocean is warming, the global sea level is rising, ocean heatwaves are more frequent, the ocean is becoming more acidic, marine ecology is shifting, levels of dissolved oxygen are reducing and the melting of ocean-terminating glaciers and ice sheets around Greenland and Antarctica is rapidly increasing. From the perspective of meeting the United Nations Sustainable Development Goals, in particular SDG 14, there are strong synergies between promoting climate mitigation and adaptation strategies, which are enshrined in SDG 13 and outlined in more detail by the Paris Agreement. Scientific research and solution-oriented knowledge generation require the growth and transformation of the science system. Specifically, they will require more freely shared ocean data, new and more effective ways of analyzing observational data fused with ocean and climate models, and enhanced timely assessment, predictions and scenario development of future ocean conditions. At the same time, knowledge from natural and social sciences, as well as informal knowledge, must be considered. Ocean science must be in a position to support decision makers by providing knowledge and frameworks to weigh the ecological, environmental and human impacts with an expected increase in use of the ocean for different sustainable development pathways. In recognition of this challenge, the United Nations declared 2021–2030 as the Decade of Ocean Science for Sustainable Development in order to advance “the science that we need for the ocean we want”. The ocean decade seeks to catalyze a change towards more international, shared and solution-oriented ocean science.

Oxygen minimum zones (OMZs) in the open ocean occur below the surface in regions of weak ventilation and high biological productivity with associated sinking organic matter. Very low levels of dissolved oxygen alter biogeochemical cycles and significantly affect marine life. One of the most intense though poorly understood OMZs in the world ocean is located in the Arabian Sea between 300 and 1000 m of depth. An improved understanding of the physical processes that have an impact on the OMZ in the Arabian Sea is expected to increase the reliability of assessments of its future development. This study uses reanalysis velocity fields from the ocean model HYCOM (Hybrid Coordinate Ocean Model), which are verified with observational data, to investigate advective pathways of Lagrangian particles into the Arabian Sea OMZ at intermediate depths between 200 and 800 m. In the eastern basin, the vertical expansion of the OMZ is strongest during the winter monsoon, revealing a core thickness 1000 m deep and oxygen values below 5 µmol kg−1. The minimum oxygen concentration might be favoured by a maximum water mass advection that follows the main advective pathway of Lagrangian particles along the perimeter of the basin into the eastern basin of the Arabian Sea during the winter monsoon. These water masses pass regions of high primary production and respiration, contributing to the transport of low-oxygenated water into the eastern part of the OMZ. The maximum oxygen concentration in the western basin of the Arabian Sea in May coincides with a maximum southward water mass advection in the western basin during the spring intermonsoon, supplying the western core of the OMZ with high-oxygenated water. The maximum oxygen concentration in the eastern basin of the Arabian Sea in May might be associated with the northward inflow of water across 10∘ N into the Arabian Sea, which is highest during the spring intermonsoon. The Red Sea outflow of advective particles into the western and eastern basin starts during the summer monsoon associated with the northeastward current during the summer monsoon. On the other hand, waters from the Persian Gulf are advected with little variation on seasonal timescales. As the weak seasonal cycle of oxygen concentration in the eastern and western basin can be explained by seasonally changing advection of water masses at intermediate depths into the Arabian Sea OMZ (ASOMZ), the simplified backward-trajectory approach seems to be a good method for prediction of the seasonality of advective pathways of Lagrangian particles into the ASOMZ.

Die Wissenschaftsplattform Nachhaltigkeit 2030 ist ein zentraler Ort der Wissenschaft, an dem sie drängende Fragen der Nachhaltigkeits-politik reflektiert und diskutiert – im Austausch mit Politik, Wirtschaft und Gesellschaft. Wissen für Nachhaltigkeit wird dort zusammengetragen und weitergetragen, insbesondere im Hinblick auf die Umsetzung der Deutschen Nachhaltigkeits-strategie. Die Plattform arbeitet unabhängig und ist systematisch eingebunden in den offiziellen politischen Steuerungs-, Dialog- und Umsetzungsprozess der Agenda 2030. Träger der Plattform sind SDSN Germany, DKN Future Earth und das IASS Potsdam.

3rd Report prepared by The World in 2050 initiative

The ocean is our planet’s largest life-support system. It stabilizes climate; stores carbon; produces oxygen; nurtures biodiversity; directly supports human well-being through food, mineral, and energy resources; and provides cultural and recreational services. The value of the ocean economy speaks to its importance: The Organization for Economic Cooperation and Development (OECD) estimates that by 2030, $3 trillion USD will be generated annually from ocean sectors such as transportation, fishing, tourism, and energy (1). Unsustainable resource extraction, pollution, climate change, and habitat destruction are on the rise and affecting many parts of the world’s oceans (2). The ocean is rapidly changing, and yet the ways in which these changes will play out are not yet clear. Although improved ocean management and conservation have helped to reduce threats and restore some key ecosystems, the basic benefits that people receive from a healthy ocean are in overall decline. Image credit: © World Wildlife Fund (WWF-US)/James Morgan. Although improved management and conservation have helped to reduce threats and restore some key ecosystems, the basic benefits that people receive from a healthy ocean are in overall decline (3). If left unchecked, a growing and resource-hungry human population will add additional pressures on the ocean. Scientific research, experimentation, data collection, monitoring, and modeling provide the knowledge, frameworks, and evidence needed to model and explore the environmental consequences of policy and development proposals and thus to chart a sustainable future ocean. The current scale, pace, and practice of ocean scientific discovery and observation are not keeping up with the changes in ocean and human conditions. We need fundamental changes in the way that researchers work with decision makers to co-create knowledge that will address pressing development problems. Researchers need to share their data more freely and sooner so that their work can inform decisions in near real … [↵][1]1To whom correspondence may be addressed. Email: linwood.pendleton{at}wwf.org. [1]: #xref-corresp-1-1

Water mass formation in the Subpolar North Atlantic and successive southward export, connects high latitudes with lower latitudes, as a part of the lower Atlantic meridional overturning (AMOC) limb. The role of regional importance, in particular the respective roles of the Labrador and Irminger Sea, in this process are in debate. This study analyses pathways connecting the Labrador and Irminger Sea in detail, using simulated Lagrangian particle trajectories. To give further insight on interconnectivity and flow patterns we used two setups with different velocity fields, a high-resolution ocean model (VIKING20X) and a gridded Argo float displacement climatology. Both setups indicate two distinct pathways with interconnectivity on the order of 20% of the total amount of seeded particles between the Labrador Sea and Irminger Sea. One pathway is following the recirculation in the Labrador Sea along the Greenland shelf break; the other is along the Newfoundland shelf break turning to the north/northwest at the Orphan-Knoll region towards the central Irminger Sea. For the Argo based advective-diffusive particle trajectory integration a 2.5–3.5 year travel time scale was derived between the Labrador and the Irminger Sea, while the experiments with the temporarily varying high-resolution model output revealed significantly shorter spreading times of about 1.5–2 years. While both pathways are represented in either setup, the pathway following the Newfoundland shelf break is populated stronger in the model-based experiments. In general we found that connectivity between the two regions is weaker in the experiments based on the climatological mean velocity output of the model than in those based on the Argo derived fields, first results indicate that this is due to stronger boundary currents and a weaker recirculation in the Labrador Sea.

In the framework of the Peruvian Oxygen minimum zone System Tracer Release Experiment (POSTRE) about 70 kg of trifluoromethyl sulfur pentafluoride (SF5CF3) was injected into the bottom boundary layer of the upper Peruvian continental slope at 250m depth in October 2015. Three different injection sites, at 10°45’S, 12°20’S and 14°S were selected. At the tracer release sites and due to tide-topography interaction, mixing above the upper continental slope of Peru was intensified. Turbulent dissipation rates increase by about an order of magnitude in lower 50 to 100m above the bottom. During previous tracer release experiments, where tracer was injected into the stratified mixing layer above the bottom boundary layer, a change of the center of mass toward higher densities resulted. Newer theories suggest that this diapycnal downwelling is balanced by a diapycnal upwelling within the bottom boundary layer. Indeed, during the tracer survey it was found that the density of tracer’s center of mass had decreased by 0.13 kg m-3. This corresponds to an upward displacement of 70-100m. Using microsctructure shear data from 8 cruises, we obtain a diapycnal velocity of about 0.5 m day-1 within the bottom boundary layer. This suggests that on average, the tracer was trapped within the bottom boundary layer for a period between 1.5 and 3 month. Overall, our tracer study provides the first observational evidence of diapycnal upwelling occurring within the bottom boundary layer of a bottom enhanced mixing environment and supports recent ideas of a vigorous global overturning circulation.

Navigating the Future is a publication series produced by the European Marine Board providing future perspectives on marine science and technology in Europe. Navigating the Future V (NFV) highlights new knowledge obtained since Navigating the Future IV1 (2013). It is set within the framework of the 2015 Paris Agreement2 and builds on the scientific basis and recommendations of the IPCC reports3. NFV gives recommendations on the science required during the next decade to deliver the ocean we need to support a sustainable future. This will be important for the United Nations Decade of Ocean Science for Sustainable Development4 (2021 – 2030), the implementation of the UN Sustainable Development Goals5 and the European Commission’s next framework programme, Horizon Europe6 (2021 - 2027). There is a growing need to strengthen the links between marine science, society and policy since we cannot properly manage what we do not know. In recent years, the ocean and seas have received new prominence in international agendas. To secure a safe planet a priority is the management of the ocean as a “common good for humanity”, which requires smarter observations to assess of the state of the ocean and predictions about how it may change in the future. The ocean is a three-dimensional space that needs to be managed over time (thus four-dimensional), and there is a need for management and conservation practices that integrate the structure and function of marine ecosystems into these four dimensions (Chapter 2). This includes understanding the dynamic spatial and temporal interplay between ocean physics, chemistry and biology. Multiple stressors including climate change, pollution and over-fishing affect the ocean and we need to better understand and predict their interactions and identify tipping points to decide on management priorities (Chapter 3). This should integrate our understanding of land-ocean-atmosphere processes and approaches to reducing impacts. An improved science base is also needed to help predict and minimize the impact of extreme events such as storm surges, heat waves, dynamic sea-floor processes and tsunamis (Chapter 4). New technologies, data handling and modelling approaches will help us to observe, understand and manage our use of the fourdimensional ocean and the effect of multiple stressors (Chapter 5). Addressing these issues requires a strategic, collective and holistic approach and we need to build a community of sustainability scientists that are able to provide evidence-based support to policy makers within the context of major societal challenges (Chapter 6). We outline new frontiers, knowledge gaps and recommendations needed to manage the ocean as a common good and to develop solutions for a sustainable future (Chapter 7). The governance of sustainability should be at the core of the marine research agenda through co-production and collaboration with stakeholders to identify priorities. There is need for a fully integrated scientific assessment of resilience strategies, associated trade-offs and underlying ethical concepts for the ocean, which should be incorporated into decision support frameworks that involve stakeholders from the outset. To allow the collection, processing and access to all data, a key priority is the development of a business model that ensures the long-term economic sustainability of ocean observations.

Human activity has already affected all parts of the ocean, with pollution increasing and fish-stocks plummeting. The UN's recent announcement of a Decade of Ocean Science provides a glimmer of hope, but scientists will need to work closely with decision-makers and society at large to get the ocean back on track.

With Sustainable Development Goal (SDG) 14, the conservation and sustainable use of the ocean and its resources was put on a central place in the global sustainability agenda. But the complexity of ocean issues and the transboundary character of the human-ocean system challenge the implementation of the ocean goal. A fragmented ocean governance system is confronted with requirements such as cross-sectoral and cross-boundary cooperation. More coherent implementation strategies, transparent review systems and support for regional approaches together with investments in ocean research and ocean literacy are needed to achieve SDG 14 and the 2030 Agenda for Sustainable Development. Mit dem Ziel 14 der Ziele für nachhaltige Entwicklung (SDGs) wurden erstmals der Schutz und die nachhaltige Nutzung der Ozeane als zentrales Thema in der globalen Nachhaltigkeitsagenda verankert. Diese große Chance für den Meeresschutz trifft jedoch auf komplexe Herausforderungen in der Umsetzung.

Oxygen minimum zones (OMZs) in the open ocean occur below the surface in regions of weak ventilation and high biological productivity. Very low levels of dissolved oxygen affect marine life and alter biogeochemical cycles. One of the most intense but least understood OMZs in the world ocean is located in the Arabian Sea in a depth range between 300 to 1000 m. An improved understanding of the physical processes that have an impact on the OMZ in the Arabian Sea is necessary for a reliable assessment of its current state and future development. This study uses a combination of observational data as well as reanalysis velocity fields from the ocean model HYCOM (Hybrid Coordinate Ocean Model) to investigate the advective pathways of Lagrangian particles into the Arabian Sea OMZ at intermediate depths. In the eastern basin, the OMZ is strongest during winter monsoon with a core thickness of 1000 m depth and oxygen values of less than 5 μmol/kg. The minimum of oxygen concentration might be favored by a maximum advection of Lagrangian particles that follows the main advective pathway along the perimeter of the basin into the eastern basin of the Arabian Sea during winter monsoon. These Lagrangian particles pass regions of high primary production and respiration contributing to a transport of low oxygenated water into the eastern part of the OMZ. The maximum of oxygen concentration in the western basin of the Arabian Sea in May coincides with a maximum southward advection of particles along the western boundary during spring intermonsoon supplying the western core of the OMZ with higher oxygenated water. The maximum of oxygen concentration in the eastern basin of the Arabian Sea in May might be associated with the northward inflow of Lagrangian particles across 10° N into the Arabian Sea which is highest during spring intermonsoon. The Red Sea outflow of advective particles into the western and eastern basin starts during the summer monsoon associated with the northeastward current during the summer monsoon. Whereas particles from the Persian Gulf advect over the whole year. As the weak seasonal cycle of oxygen concentration in the eastern and western basin can be explained by seasonal changing advective pathways at intermediate depths into the ASOMZ, the simplified backward trajectory approach seems to be a good method for prediction of the seasonality of advective pathways of Lagrangian particles into the ASOMZ.

The intraseasonal evolution of physical and biogeochemical properties during a coastal trapped wave event off central Peru is analysed using data from an extensive shipboard observational programme conducted between April and June 2017, and remote sensing data. The poleward velocities in the Peru–Chile Undercurrent were highly variable and strongly intensified to above 0.5 m s−1 between the middle and end of May. This intensification was likely caused by a first-baroclinic-mode downwelling coastal trapped wave, excited by a westerly wind anomaly at the Equator and originating at about 95∘ W. Local winds along the South American coast did not impact the wave. Although there is general agreement between the observed cross-shore-depth velocity structure of the coastal trapped wave and the velocity structure of first vertical mode solution of a linear wave model, there are differences in the details of the two flow distributions. The enhanced poleward flow increased water mass advection from the equatorial current system to the study site. The resulting shorter alongshore transit times between the Equator and the coast off central Peru led to a strong increase in nitrate concentrations, less anoxic water, likely less fixed nitrogen loss to N2 and a decrease of the nitrogen deficit compared to the situation before the poleward flow intensification. This study highlights the role of changes in the alongshore advection due to coastal trapped waves for the nutrient budget and the cumulative strength of N cycling in the Peruvian oxygen minimum zone. Enhanced availability of nitrate may impact a range of pelagic and benthic elemental cycles, as it represents a major electron acceptor for organic carbon degradation during denitrification and is involved in sulfide oxidation in sediments.

The health of the ocean, central to human well-being, has now reached a critical point. Most fish stocks are overexploited, climate change and increased dissolved carbon dioxide are changing ocean chemistry and disrupting species throughout food webs, and the fundamental capacity of the ocean to regulate the climate has been altered. However, key technical, organizational, and conceptual scientific barriers have prevented the identification of policy levers for sustainability and transformative action. Here, we recommend key strategies to address these challenges, including (1) stronger integration of sciences and (2) ocean-observing systems, (3) improved science-policy interfaces, (4) new partnerships supported by (5) a new ocean-climate finance system, and (6) improved ocean literacy and education to modify social norms and behaviors. Adopting these strategies could help establish ocean science as a key foundation of broader sustainability transformations.

Die Wissenschaftsplattform Nachhaltigkeit 2030 ist ein zentraler Ort der Wissenschaft, an dem sie drängende Fragen der Nachhaltigkeits-politik reflektiert und diskutiert – im Austausch mit Politik, Wirtschaft und Gesellschaft. Wissen für Nachhaltigkeit wird dort zusammengetragen und weitergetragen, insbesondere im Hinblick auf die Umsetzung der Deutschen Nachhaltigkeits-strategie. Die Plattform arbeitet unabhängig und ist systematisch eingebunden in den offiziellen politischen Steuerungs-, Dialog- und Umsetzungsprozess der Agenda 2030. Träger der Plattform sind SDSN Germany, DKN Future Earth und das IASS Potsdam., IASS Brochure

Auf 32 Seiten geben die beiden Wissenschaftsverbände einen verständlichen Überblick zum Meeresspiegelanstieg. 14 Wissenschaftlerinnen und Wissenschaftler unterschiedlicher Forschungseinrichtungen ordnen gemeinsam die Informationen ein, die immer wieder in der Öffentlichkeit diskutiert werden, und erklären die wichtigsten Zusammenhänge und zugrundeliegenden Prozesse in klaren Worten. Damit bietet die Broschüre Orientierung in Bezug auf plausible Zukunftsszenarien, und hilft, die Risiken besser einzuschätzen. Zusätzlich erläutern die Forschenden die Situation an den deutschen Küsten, denn Klimawandel und Meeresspiegelanstieg betreffen auch die Nord- und Ostsee.

This policy brief provides recommendations for the science needed for the next decade and beyond to support the 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals (SDGs). The document outlines the societal outcomes of the UN Decade of Ocean Science for Sustainability (A Clean Ocean, A Sustainably Harvested Ocean, A Safe Ocean, A Healthy Ocean, A Predicted Ocean, A Transparent Ocean) and provides recommendations from the 'Navigating the Future V' Position Paper (2019) by the European Marine Board to address each societal outcome.