Observing and understanding the state of the Indian Ocean and its influence on climate and maritime resources is of critical importance to the populous nations that rim its border. Acute gaps have occurred in the Indian Ocean Observing System, which underpins monitoring and forecasting of regional climate, since the start of the COVID pandemic. The pandemic disrupted the deployment and maintenance cruises for the observational array and also resulted in supply chain issues for procurement and refurbishment of equipment. In particular, the observational platforms that provide key measurements of upper ocean heat variability have experienced serious multiyear declines. There is now record-low data reporting and the platforms that are successfully reporting are old and quickly surpassing their expected period of reliable operation. The overall impact on the observing system will take a few years to fully comprehend. In the meantime, there is a critical need to document the gaps that have appeared over the past few years and how this will impact our ability to improve understanding and model representations of the real world that support regional weather and climate forecasts. The article outlines the expected slow road to recovery for the Indian Ocean Observing System, documents case studies of successful international collaborative efforts that will revive the observing system and provides guidelines for resilience from unexpected external factors in the future.

Argo floats have been deployed in the global ocean for over 20 years. The Core mission of the Argo program (Core Argo) has contributed well over 2 million profiles of salinity and temperature of the upper 2000 m of the water column for a variety of operational and scientific applications. Core Argo floats have evolved such that the program currently consists of more than eight types of Core Argo float, some of which belong to second or third generation developments, three unique satellite communication systems (Argos, Iridium and Beidou) and two types of Conductivity, Temperature and Depth (CTD) sensor systems (Seabird and RBR). This, together with a well-established data management system, delayed mode data quality control, FAIR and open data access, make the program a very successful ocean observing network. Here we present Part 1 of the Best Practices for Core Argo floats in terms of how users can get started in the program, recommended metadata parameters and the data management system. The objective is to encourage new and developing scientists, research teams and institutions to contribute to the OneArgo Program, specifically to the Core Argo mission. Only by leveraging sustained contributions from current Core Argo float groups with new and emerging Argo teams and users who are eager to get involved and are actively encouraged to do so, can the OneArgo initiative be realized. This paper presents a list of best practices to get started in the program, set up the recommended metadata, implement the data management system with the aim to encourage new scientists, countries and research teams to contribute to the OneArgo Program.

Following on from Part 1: Best Practices for Core Argo floats - Getting started and data considerations, we present Part 2: Best Practices for Core Argo floats in terms of physical handling and deployments and recommended metadata parameters. The objective is to encourage new and developing scientists, research teams and institutions to contribute to the OneArgo Program through increased deployments regionally, specifically to the Core Argo mission. Only by leveraging sustained contributions of current Core Argo float groups with new and emerging Argo teams and users, can the OneArgo initiative be realized. This paper makes involvement with the Core Argo mission smoother by providing a framework endorsed by a wide community for these observations.

The years since 2000 have been a golden age in in situ ocean observing with the proliferation and organization of autonomous platforms such as surface drogued buoys and subsurface Argo profiling floats augmenting ship-based observations. Global time series of mean sea surface temperature and ocean heat content are routinely calculated based on data from these platforms, enhancing our understanding of the ocean’s role in Earth’s climate system. Individual measurements of meteorological, sea surface, and subsurface variables directly improve our understanding of the Earth system, weather forecasting, and climate projections. They also provide the data necessary for validating and calibrating satellite observations. Maintaining this ocean observing system has been a technological, logistical, and funding challenge. The global COVID-19 pandemic, which took hold in 2020, added strain to the maintenance of the observing system. A survey of the contributing components of the observing system illustrates the impacts of the pandemic from January 2020 through December 2021. The pandemic did not reduce the short-term geographic coverage (days to months) capabilities mainly due to the continuation of autonomous platform observations. In contrast, the pandemic caused critical loss to longer-term (years to decades) observations, greatly impairing the monitoring of such crucial variables as ocean carbon and the state of the deep ocean. So, while the observing system has held under the stress of the pandemic, work must be done to restore the interrupted replenishment of the autonomous components and plan for more resilient methods to support components of the system that rely on cruise-based measurements.

A review of the existing reporting tools about Regional Ocean Observing Systems and perspective toward future European Ocean Observing System monitoring and reporting services.

The Odyssey Project coordinated by OceanOPS, joint center of the World Meteorological Organization and the Intergovernmental Oceanographic Commission of UNESCO, will support and involve civil society, including citizens, sailors, businesses, etc., in observing the ocean and the atmosphere above it to contribute to the Global Ocean Observing System (GOOS) implementation. As the global population is set to reach more than 9 billion people by 2050, impacts on the ocean associated with human activities will escalate. Understanding the variability and trends of the ocean and the related impacts on our society, through sustained oceanographic and marine meteorological observations and ocean science, is essential to predict the consequences of change, guide mitigation, and design adaptation for the benefit of the nature and humankind. The Odyssey project embodies the level of response we need to face climate issues and will help strengthen collaborations within and outside the global ocean observing community. These collaborations, based on the met-ocean observations' collection, data sharing and analyses, scientific and technological developments, will be essential to develop such a project.

Report on the progress of the EuroSea project on glider network metadata management in Europe and globally

The joint WMO-IOC in situ Ocean Observing System Monitoring and Coordination Centre (OceanOPS, formerly JCOMMOPS) was mandated by the observations coordination group of the Global Ocean Observing System (OCG/GOOS) to maintain and manage metadata of OCG networks.Globally OceanOPS needs to make progress on the monitoring of GOOS Eulerian elements.Thus, OceanOPS activity within EuroSea project is an opportunity to highlight challenges and enable progress.OceanOPS has developed a metadata management system for standardization and harmonization of various OCG networks 1 , including long term Eulerian time series stations.The Eulerian stations considered are fixed moorings for ocean observations as against the mobile drifting buoys, floats, gliders under overall GOOS OCG.Other fixed stations like tidal gauges, high frequency radars are beyond current topic.The OceanSITES netCDF data format specification was reviewed to include metadata as required by OceanOPS.The EMSO community has started to use this format.However, and if this new format is widely used (which is not the case at the moment), it has to be made available before data are made available (often two years after the observations) otherwise our monitoring status will always lag behind.And what about the SITES for which the data sharing is not happening for some reasons.We won't have any monitoring capacity on these as we would only see the platforms sharing data.The alignment of metadata between OceanOPS requirements and final files for data users is needed, but this will not help our monitoring.Metadata have to be channelled to OceanOPS before (or just after) the SITE is serviced.The current approach to complete the catalogue are based on rare, irregular, and individual submissions to OceanOPS.This is not efficient for any of the stakeholders but is better than nothing.The prioritization of metadata submission to OceanOPS, according to its developing standard, seems to be the main challenge we face to deliver a robust and accurate metadata catalogue for Eulerian networks in Europe and beyond.Considering the complexity and often unique specificities of each of these Eulerian systems, the work load required to complete this harmonization might as well be underestimated.Without an active and regular cooperation between Eulerian platform operators and OceanOPS, our monitoring capacity in Europe for this system will remain rather poor.

The ocean observing system needs to be ensured by high-level integration and coordination to guarantee its longterm sustainability, efficient accessibility and usability by a wide range of users. Enormous advancements and efforts toward these objectives have been already conducted in Europe, partly through the activities of the IOC-UNESCO's International Oceanographic Data and Information Exchange (IODE) and EuroGOOS DATAMEQ working group, although there is still room for additional progress and gaps to be addressed. During the past two decades, a series of standards for data and metadata formats as well as exchange protocols have been established within the marine community where projects, organizations and data integrators like JCOMM, RDA (Research Data Alliance), EuroGOOS, EMODnet, SeaDataNet and Copernicus played a significant role. Taking into consideration that harmonized data are a key element in maintaining a usable and interoperable ocean observing system, this paper aims to provide some recommendations for the harmonization of the marine in situ networks involved in EuroSEA, which would be a useful product for the European data integrators, particularly EMODnet, SeaDataNet and Copernicus Marine service. This document proposes recommendations to enhance the in situ networks based on the assessment of what has been previously done.

Marine animals equipped with biological and physical electronic sensors have produced long-term data streams on key marine environmental variables, hydrography, animal behavior and ecology. These data are an essential component of the Global Ocean Observing System (GOOS). The Animal Borne Ocean Sensors (AniBOS) network aims to coordinate the long-term collection and delivery of marine data streams, providing a complementary capability to other GOOS networks that monitor Essential Ocean Variables (EOVs), essential climate variables (ECVs) and essential biodiversity variables (EBVs). AniBOS augments observations of temperature and salinity within the upper ocean, in areas that are under-sampled, providing information that is urgently needed for an improved understanding of climate and ocean variability and for forecasting. Additionally, measurements of chlorophyll fluorescence and dissolved oxygen concentrations are emerging. The observations AniBOS provides are used widely across the research, modeling and operational oceanographic communities. High latitude, shallow coastal shelves and tropical seas have historically been sampled poorly with traditional observing platforms for many reasons including sea ice presence, limited satellite coverage and logistical costs. Animal-borne sensors are helping to fill that gap by collecting and transmitting in near real time an average of 500 temperature-salinity-depth profiles per animal annually and, when instruments are recovered (∼30% of instruments deployed annually, n = 103 ± 34), up to 1,000 profiles per month in these regions. Increased observations from under-sampled regions greatly improve the accuracy and confidence in estimates of ocean state and improve studies of climate variability by delivering data that refine climate prediction estimates at regional and global scales. The GOOS Observations Coordination Group (OCG) reviews, advises on and coordinates activities across the global ocean observing networks to strengthen the effective implementation of the system. AniBOS was formally recognized in 2020 as a GOOS network. This improves our ability to observe the ocean’s structure and animals that live in them more comprehensively, concomitantly improving our understanding of global ocean and climate processes for societal benefit consistent with the UN Sustainability Goals 13 and 14: Climate and Life below Water. Working within the GOOS OCG framework ensures that AniBOS is an essential component of an integrated Global Ocean Observing System.

Citation: Testor P, Young Bd, Rudnick DL, Glenn S, Hayes D, Lee CM, Pattiaratchi C, Hill K, Heslop E, Turpin V, Alenius P, Barrera C, Barth JA, Beaird N, Bécu G, Bosse A, Bourrin F, Brearley JA, Chao Y, Chen S, Chiggiato J, Coppola L, Crout R, Cummings J, Curry B, Curry R, Davis R, Desai K, DiMarco S, Edwards C, Fielding S, Fer I, Frajka-Williams E, Gildor H, Goni G, Gutierrez D, Haugan P, Hebert D, Heiderich J, Henson S, Heywood K, Hogan P, Houpert L, Huh S, Inall ME, Ishii M, Ito S-i, Itoh S, Jan S, Kaiser J, Karstensen J, Kirkpatrick B, Klymak J, Kohut J, Krahmann G, Krug M, McClatchie S, Marin F, Mauri E, Mehra A, Meredith MP, Meunier T, Miles T, Morell JM, Mortier L, Nicholson S, O’Callaghan J, O’Conchubhair D, Oke P, Pallàs-Sanz E, Palmer M, Park J, Perivoliotis L, Poulain P-M, Perry R, Queste B, Rainville L, Rehm E, Roughan M, Rome N, Ross T, Ruiz S, Saba G, Schaeffer A, Schönau M, Schroeder K, Shimizu Y, Sloyan BM, Smeed D, Snowden D, Song Y, Swart S, Tenreiro M, Thompson A, Tintore J, Todd RE, Toro C, Venables H, Wagawa T, Waterman S, Watlington RA and Wilson D (2021) Corrigendum: OceanGliders: A Component of the Integrated GOOS. Front. Mar. Sci. 8:696100. doi: 10.3389/fmars.2021.696100 Corrigendum: OceanGliders: A Component of the Integrated GOOS

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.

Results of a cost and feasibility study of the present and planned integrated Atlantic Ocean Observing System, including assessing the readiness and feasibility of implementation of different observing technologies