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The INTAROS Roadmap describes the way forward to improve and sustain the observing capacity in the Arctic. The Roadmap addresses the full data delivery chain from observing sensors to data repositories with focus on in situ observations. The document describes key factors determining how well an observing system can function in the Arctic, involving technological advances, infrastructure and data networks. Furthermore, the document emphasize the importance of cross disciplinary collaboration and stakeholder engagement as part of the data delivery chain. The development of in situ observing systems in the Arctic, especially ocean-based observations in the ice-covered regions, depends heavily on mature technology, transport infrastructures and logistical services allowing personnel to access the areas. Deployment and operation of observing platforms require use of icebreakers, aircraft, manned ice stations and automated systems that can operate year-round Based on the experience and knowledge of the INTAROS consortium, the following recommendations are formulated: The importance of in situ observations must be promoted as the backbone for building knowledge about climate and environmental change in the Arctic, at the same level as satellite observations and modelling systems The funding mechanisms for in situ observing systems need to be strengthened and coordinated between programmes, projects and institutions involved in Arctic observation, including local communities The Joint Statement of Ministers (ASM 2021), signed by 25 countries and six Indigenous Peoples organizations, states that they agree to strengthen cooperation on implementing Arctic observing and data sharing, implying that they need to allocate resources for in situ measurements contributing to the observing systems. Technology development for more robust and reliable in situ observing systems is needed. Here, major industry actors can play a role by investing in platforms and sensors that can operate autonomously in the Arctic The data delivery chain from in situ observing systems must be operationalised for each of the discipline-oriented systems in order to facilitate data sharing. This requires collaboration between the research communities, data services and other actors involved in the delivery chain. Collaboration can be enhanced by setting up mediators who can communicate between the actors Observing systems must be adapted to evolving priorities, requirements, and technological developments. This requires regular dialogue with researchers, stakeholders in private and public sector, researchers, service providers, local communities and Indigenous rightholders in the Arctic. Competence building need to be strengthened in observing methods, technologies, and procedures across gender and generations. The INTAROS roadmap builds on the experience and knowledge from the INTAROS consortium comprising more than 300 scientists from 49 institutions in Europe, Asia, and North America. In addition the document builds on discussions with representatives of Indigenous and local communities, private and public stakeholders, scientists and service providers at more than 50 workshops organised by the INTAROS project.

This document provides a summary of sensors, platforms, and observing systems implemented during INTAROS field campaigns and presents technical recommendations based on experience gained from operating these components for collecting in situ observations during the project. This document is intended to: – Shortly summarize details of all individual sensors, platforms, and systems developed and deployed during INTAROS for collecting in situ measurements in the cryospheric, ocean, atmospheric and terrestrial domains, – Provide main recommendations for the technology used in INTAROS with the respect to become a component of a future sustained Arctic observing system, – Describe main limitations of technology used and recommendations to overcome these limitations to enable including this technology in a future observing system, – Overview other technical solutions which could better replace or complement technology used during INTAROS to provide similar set of observations for a future observing system, – Identify and describe cross-cutting technical recommendations based on recommendations for individual systems, – Summarize main challenges and achievements in implementing in situ observations in WP3, – Summarize main technical recommendations from WP3 for use in the INTAROS Roadmap for a future integrated Arctic observing system INTAROS has collaborated with many other field programs and projects which have contributed to the results in WP3. These programs and projects are listed in Annex A. A summary of platforms and sensors developed and implemented during INTAROS, including main challenges and final outcomes, is provided in Annex B.

This report gives an overview of the activities, results and impacts of INTAROS Work Package 6 (WP6). The aim of WP6 is to demonstrate how an integrated observation system can be of specific benefit for society at local, regional or pan-Arctic scale. Through WP6 we show the capability of an enhanced Arctic Observation System towards advancing the economic role of the Arctic by providing support for better-documented processes and better-informed decisions within key sectors such as shipping, petroleum, fishing, and tourism. Further, WP6 demonstrates how the Arctic Observation system may be applied to further develop the accuracy of climate models, improve the understanding of biogeochemical cycles and ecosystem functioning, enhance fisheries and environmental management, increase the level of preparedness towards natural hazards, and develop better management and decision making concepts for selected local communities. Through WP6 INTAROS demonstrates enhanced data search and retrieval, assimilation into models, validation of estimated and projected climate parameters, scientific analysis, decision-support and policy-making. Following a general introduction to INTAROS WP6, eight chapters summarize, for each topic covered, the main activities and results, data and models used, stakeholder/user benefits, and further development and exploitation of results. The topics span broadly and target very different end-user groups but they all share the same overall challenge: how to synthesize data across time and space from different sources, formats and scientific disciplines into aggregated synoptic data products that are relevant for end-users. The following topics are addressed: Improving skill of model predictions in the Arctic, Applying observations and models for environmental and fisheries management, Ice-ocean statistics, Remote sensing applications, Natural hazards in the Arctic, Greenhouse gas exchange in the Arctic, Case studies of community-based observing systems and Benefits of ocean observing for blue growth in the Arctic. The report then describes concrete showcases, software applications. Selected main results across WP6 are then presented, before the report ends with conclusions and perspectives.

Denne rapporten baserer seg på artikkelen “Acidification of the Nordic Seas” av Fransner mfl. (2022). I tillegg presenteres havforsuringstrender (=endring over tid) i Nordsjøen og Skagerrak og trender i antropogent karbon (Cant) i de nordiske hav, Nordsjøen og Skagerrak. Måledata fra de nordiske hav i perioden 1981 til 2019 viser at pH i snitt har avtatt med 0,0028 yr-1 som tilsvarer en pH-reduksjon på 0,11 over 39 år. Dette er dobbelt så mye som den modellerte pH-reduksjonen over perioden 1850-1980 i samme område (–0,05 over 130 år). Modellkjøringer viser at fram til slutten av dette århundret forventes det ytterlige endringer i pH i overflatevann på mellom –0.04 og –0.4 avhengig av hvilket utslippsscenario som brukes. Måledata fra ulike regioner i de nordiske hav viser at pH-trenden i overflatevann er av størrelse –0,002 til –0,003 yr-1. Trenden er primært drevet av økende løst uorganisk karbon (CT) som delvis skyldes opptak av atmosfærisk, og dermed også antropogent, CO2. I overflatevann i Norskebassenget og Islandshavet avtar pH raskere enn det som kan forklares av CO2-opptak fra atmosfæren alene, og resten av endringa skyldes at partialtrykket av CO2 (pCO2) i havoverflata over tid øker raskere enn atmosfærisk CO2. Dette kan skyldes både redusert primærproduksjon og økende havtemperatur. pH-endringene i overflatevann i de nordiske hav er statistisk signifikante bortsett fra i Barentshavsåpningen, der en relativt kraftig økning i total alkalinitet (AT) motvirker den negative pH-trenden. Havforsuringssignalet kan i noen regioner måles helt ned til 2000 m. Vann på 1000-2000 m dyp nærmer seg nå grensen for undermetning av aragonitt (kalsiumkarbonat). I Nordsjøen og Skagerrak finnes måledata fra periodene 2001-2015 og 2001-2019. Trendene i pH og metningsgrad av aragonitt (ΩAr) i Nordsjøen er svake og ikke signifikante, mens i Skagerrak på dyp større enn 200 m avtar pH signifikant, og dypere enn 500 m er pH-trenden –0.0044 yr-1. Trenden er primært drevet av endring i varmt og salt atlantisk vann som strømmer inn i området. Antropogent karbon (Cant) øker i de fleste deler av de nordiske hav, bortsett fra i Barentshavsåpningen. I Norskebassenget øker Cant signifikant på alle dyp, mens i Lofotenbassenget er Cant-økningen signifikant mellom 200 og 2000 m dyp. I Nordsjøen er ikke trendene i Cant signifikante, men i Skagerrak øker Cant signifikant på alle dyp. Det er generelt godt samsvar mellom trender i CT og Cant, og dette viser at økende mengde Cant i havet er den dominerende driveren for økende CT. Observerte forekomstene av korallrev i de nordiske hav lever stort sett på dyp som i dag er overmetta med aragonitt. Dette vil endres i framtida avhengig av hvilket utslippsscenario for CO2 som følges. Hvis CO2-utslippene fortsetter som i dag (RCP8.5) vil alt vann dypere enn ca. 20 m i de nordiske hav bli undermetta med aragonitt når vi nærmer oss slutten på dette århundret, og dette vil få dramatiske konsekvenser for korallrev i hele de nordiske hav.

This document is a result of INTAROS WP6 Task 6.5 on Arctic greenhouse gas exchange. The reported work rests upon results provided in WP3, more specifically tasks 3.1, 3.2 and 3.3. It synthesizes data stored in databases SOCAT and GLODAP and additional data from a Ferry box system crossing the Barents Sea opening and from Greenland fjords. To show the potential establishing long term monitoring of the carbon system variables as suggested in INTAROS, trends in ocean uptake and transport of carbon, ocean acidification and deoxygenation can be produced. Examples on synthesis of carbon system data are shown, with the aim of analyzing trends in ocean acidification in the Nordic Seas. The results reported by each of the marine science partners in Task 6.5 include: UiB. The main task has been to prepare for a comparison of pCO2 field extracted from 2018 data in the SOCAT database, and test a self-organising map technique, a type of artificial neural network that uses machine learning. This was implemented to estimate surface water pCO2values for the Barents Sea opening (10°E-30°E; 70°N-77.5°N). NIVA. A FerryBox system was equipped on M/S Norbjørn which made approximately 25-30 round-trip crossings per year through the Barents Sea Opening between Tromsø, Norway and Longyearbyen, Svalbard. The FerryBox system included several physical, chemical, and biological sensors. UA. In Greenland, measuring ocean CO2and carbonate chemistry is included in the Greenland Ecosystem Monitoring (GEM) Programme. Although these long-term programs provide essential time-series of change, the three sites do not cover the spatial variation across the vast Greenland coastal zone

The H2020 project Integrated Arctic Observation System (INTAROS) aspires to increase the temporal and geographic coverage of in situ observations and add new key geophysical and biogeochemical variables in selected regions of the Arctic. By using a combination of mature and new instruments and sensors in integration with existing observatories, INTAROS aims to fill selected gaps in the present-day system and build additional capacity of the Arctic monitoring networks for ocean and sea ice. Three reference sites have been selected as key locations for monitoring ongoing Arctic changes: Costal Greenland, paramount for freshwater output from the Greenland ice sheet; North of Svalbard (covering the region from shelf to deep basin) - the hot-spot for ocean-air-sea ice interactions, and heat and biological energy input to the European Arctic; and Fram Strait - the critical gateway for exchanges between the Arctic and the World oceans. The existing observatories in the reference sites have been extended with new moorings and novel autonomous instrumentation, in particular for biogeochemical measurements and sea ice observations. Bottom-mounted instruments have been also implemented for seismic observations. A distributed observatory for ocean and sea ice in the Arctic Ocean and sub-Arctic seas includes non-stationary components such as ice-tethered observing platforms, float, gliders, and ships of opportunities, collecting multidisciplinary observations, still missing from the Arctic regions. New sensors, integrated platforms and experimental set-ups are currently under implementation during a two-year long deployment phase (2018-2020) with an aim to evaluate their sustained use in a future iAOS. New observations will be used for integration of new data products, demonstration studies and stakeholder consultations, contributing also to ongoing and future long-term initiatives (e.g. SAON).

This report presents a synthesis of the substantial assessment of Arctic observations within INTAROS.Since the assessed systems mainly belong to the European partners in the project, the assessment is unavoidably biased towards the European sector of the Arctic. The detailed results of the assessment can be found in previous deliverables (D2.1, D2.2, D2.4, D2.5, D2.7, D2.8 and D2.12). Also some higher-level recommendations for future improvements of Arctic observing are taken into account. The assessment addresses a substantial subset of Arctic observing systems, data collections and satellite products across scientific disciplines, also including some data repositories and a brief scientific gap analysis. In the assessment we analyzed sustainability, including funding, technical maturity and data handling for the entire chain from observation to users, including metadata procedures and availability of data. The gap analysis includes both technical characteristics, such as spatial and temporal coverage and resolution or accuracy, and a smaller set of scientific gap analyses where models and observations were used synergistically. Each characteristic of the observing systems were ranked from maturity 1 (lowest score) to maturity 6 (highest score) based on the results of the survey. In the synthesis wefirst ranked the systems according to general sustainability and then other characteristics were used. The range in maturity of sustainability varied from 1 to 6, and so did the other characteristics. A noteworthy result was that systems with high sustainability scores tended to score high also on other characteristics, such as data handling and technical maturity. Moreover, many systems with high maturity in sustainability, as well as in data handling and data availability, are supported by national or international monitoring or infrastructure programs. It is also noteworthy that several of these are mostly present at mid-latitudes, but poorly represented in the Arctic. For observations over Arctic land, the quality of some existing systems would benefit from being enhanced by new instruments or improved methods. As example, adequate observing of snow properties is problematic due to the high spatial variability of snow cover. While this also applies to hydrological observations, the situation improves as a result of large overarching international programmes. Observations of aerosols and some trace gases are also lacking in some specific regions. For the Arctic Ocean there is a lack of in-situ observing systems across all disciplines, which is connected to limited infrastructure provided by ships,icebreakers, and various types of autonomous observing platforms operating on sea ice with capacity to transfer data in near real-time.Subsurface observing systems such as bottom-anchored moorings and sea floor installations are robust and can operate autonomously over several year, but the data can only be delivered in delayed mode.In the atmosphere, icebreaker-based summer science expeditions provide the only reliable information on atmospheric vertical structure. While scientific expeditions likely provide the highest quality observations available for the Arctic Ocean region, the scores for almost all other aspects, sustainability as well as for data handling, in general and especially for atmospheric observations are among the lowest for vessel-based observations. Satellite observations provide the only possibility to obtain data with sufficient spatial and temporal coverage as well as resolution. Satellite data products have generally high score on data handling aspects, but for some data products the score on quality and uncertainty estimation is low. While retrieved temperature, and to a lesser extent, humidity at levels in the atmosphere is generally adequate for monitoring, satellite profiling of the atmosphere suffers from significant and seasonally varying biases and errors. Passive satellite sensing of clouds is also problematic; while some bulk products, such as cloud fraction, are useful during the sunlit season, more precise information, such as liquid water path, has high uncertainty as indicated by comparing different retrievals from the same set of sensors. In the dark season, when visible radiation channels vanish, most satellite cloud products are very unreliable. Regarding sea ice observations, there is significant uncertainty in the estimation of thickness and snow layer. There is also uncertainty in ice concentration in the summer season with melt-ponds on top of the ice. Traditionally, observation network assessments build on the network concept with a “comprehensive” level including all observations, a “baseline” level of an agreed subset of sustained observations, and a “reference” level, with observations adhering to specific calibrations and traceability criteria. An atmospheric example is the “comprehensive” global GCOS radiosounding network, and the “baseline” GUAN (GCOS Upper Air Network) and “reference” GRUAN (GCOS Reference Upper Air Network) networks. With the lack of in-situ observations and the logistical difficulties to deploy new stations, this concept does not work well in the marine part of the Arctic. In summary, we recommend to •Advance Arctic observing systems under national, international or regional programs that provide more sustainable funding than short-term research projects •Coordinate better between operational monitoring systems and research-funded observations, since both systems often use the same data and will have mutual benefit of collaboration •Improve the utilization of existing infrastructures on land and sea for more cost-effective collection of in situ data across multiple disciplines •Deploy more autonomous observing platforms in the sea ice areas for year-round operation and implement data collection from all types of ships operating in the Arctic ocean •Enhance the observing system on existing stations, including supersites, by use of new sensors and methods to validate satellite observations and support modelling and forecasting systems •Improve the exploitation of satellite data and coordinate better in situ and satellite observations for use in data assimilation, modelling and reanalyses •Clarify roles and responsibilities between data producers and managers and establish adequate funding mechanisms to support a functional data management system for multidisciplinary Arctic data., The reviewer's comments are not included in the present version, but are taken into account in the follow-up publications and in the Roadmap document (D1.10) developed during the final phase of the project.

The main goal of Task 3.2 is to deliver in situ ocean and sea ice observations collected during two INTAROS field seasons and to provide recommendations for future implementation of the moored observing system north of Svalbard that can be applied to define a roadmap for observing future changes in the Arctic. The aim is to make comprehensive observations of the ongoing climate and environmental change that can be also applied as a validation tool for conceptual and three-dimensional modelling. This report describes the first implementation and operational use of the observing systems. Data delivery and report on results of the observing systems North Svalbard. The first implementation was deployed successfully in August 2018 using the Coast Guard icebreaker KV Svalbard and retrieved with KV Svalbard in August/September and with the research icebreaker RV Kronprins Håkon in September and November 2019. All recovered instrument and sensor provided full data return therefore a full annual cycle of multidisciplinary data was obtained that can be employed to address the following goals: −Document the performance of instruments and systems selected/integrated for measurements of key ocean physical variables on INTAROS moorings, including temperature, salinity and ocean currents −Document the performance of instruments and sensors selected/integrated for measurements of key biogeochemical variables including dissolved oxygen, nutrients and carbonate system parameters on the multidisciplinary BGC11mooring −Document the performance of novel instruments selected for sea ice measurements on the moorings along the INTAROS (22°E) and A-TWAIN (31°E) lines north of Svalbard −Document the performance of novel combination of ADCP with echo sounder selected for ocean currents and zooplankton/small fish abundance measurements −Document the performance and the state of technical development for a moored multisensor Octopus system for biological measurements, including an Underwater Vision Profiler, nutrient sensor and chlorophyll-a and CDOM fluorometer −Document the performance and technical development for microplastic samplers −Document the performance of technologies and deployment methodology for the sensors mounted at the seafloor, including Ocean Bottom Pressure sensors and Ocean Bottom Seismometers

The European Research Infrastructure Consortium “Integrated Carbon Observation System” (ICOS) aims at delivering high quality greenhouse gas (GHG) observations and derived data products (e.g., regional GHG-flux maps) for constraining the GHG balance on a European level, on a sustained long-term basis. The marine domain (ICOS-Oceans) currently consists of 11 Ship of Opportunity lines (SOOP – Ship of Opportunity Program) and 10 Fixed Ocean Stations (FOSs) spread across European waters, including the North Atlantic and Arctic Oceans and the Barents, North, Baltic, and Mediterranean Seas. The stations operate in a harmonized and standardized way based on community-proven protocols and methods for ocean GHG observations, improving operational conformity as well as quality control and assurance of the data. This enables the network to focus on long term research into the marine carbon cycle and the anthropogenic carbon sink, while preparing the network to include other GHG fluxes. ICOS data are processed on a near real-time basis and will be published on the ICOS Carbon Portal (CP), allowing monthly estimates of CO2 air-sea exchange to be quantified for European waters. ICOS establishes transparent operational data management routines following the FAIR (Findable, Accessible, Interoperable, and Reusable) guiding principles allowing amongst others reproducibility, interoperability, and traceability. The ICOS-Oceans network is actively integrating with the atmospheric (e.g., improved atmospheric measurements onboard SOOP lines) and ecosystem (e.g., oceanic direct gas flux measurements) domains of ICOS, and utilizes techniques developed by the ICOS Central Facilities and the CP. There is a strong interaction with the international ocean carbon cycle community to enhance interoperability and harmonize data flow. The future vision of ICOS-Oceans includes ship-based ocean survey sections to obtain a three-dimensional understanding of marine carbon cycle processes and optimize the existing network design. publishedVersion

Winter data of surface ocean temperature (SST), salinity (SSS) and CO 2 fugacity (fCO 2 ) collected on the VOS M/V Nuka Arctica in the subpolar North Atlantic between 2004 and 2017 are used to establish trends, drivers, and interannual variability. Over the period, waters cooled and freshened, and the fCO 2 increased at a rate similar to the atmospheric CO 2 growth rate. When accounting for the freshening, the inferred increase in dissolved inorganic carbon (DIC) was found to be approximately twice that expected from atmospheric CO 2 alone. This is attributed to the cooling. In the Irminger Sea, fCO 2 exhibited additional interannual variations driven by atmospheric forcing through winter mixing. As winter fCO 2 in the region is close to the atmospheric, the subpolar North Atlantic has varied between being slightly supersaturated and slightly undersaturated over the investigated period. ©2019. American Geophysical Union. All Rights Reserved.

The H2020 project Integrated Arctic Observation System (INTAROS) aspires to increase the temporal and geographic coverage of in situ observations and add new key geophysical and biogeochemical variables in selected regions of the Arctic. By using a combination of mature and new instruments and sensors in integration with existing observatories, INTAROS aims to fill selected gaps in the present-day system and build additional capacity of pan-Arctic monitoring networks. Three reference sites have been selected as key locations for monitoring ongoing Arctic changes: Costal Greenland, paramount for freshwater output from the Greenland ice sheet; North of Svalbard (shelf to deep basin) - the hot-spot for ocean-air-sea ice interactions, and heat and biological energy input to the European Arctic; and Fram Strait - the critical gateway for exchanges between the Arctic and theWorld oceans. Two distributed observatories: for ocean and sea ice and for terrestrial and atmospheric measurements will be extended with multidisciplinary observations, still missing from the central Arctic and remote coastal areas. New sensors, integrated platforms and experimental set-ups will be implemented during a two-year long deployment phase (2018-20020) with an aim for sustained use in a future iAOS. New observations will be used for integration of new data products, demonstration studies and stakeholder consultations and contribute to ongoing and future long-term initiatives (e.g. OSPAR, SAON, YOPP). Here we will address the technical development, integration and system design carried out for the selected reference sites and distributed observatories during the first phase of the project, and review new in situ observational efforts, implemented during the first INTAROS field season in 2018.

A major goal of WP2: “Exploitation of existing observing systems” is to analyze strengths, weaknesses, gaps in spatial/temporal coverage, and missing monitoring parameters of the existing observation networks and databases in relation to the requirements from different user groups. This report is prepared to assess the existing ocean and sea ice observing systems in the Arctic, primary those where the INTAROS partners have responsibilities, but also where the partners contribute to larger, international observing systems. A core activity in the first 18 months of WP2 has been to conduct a survey where partners have responded to three sets of questionnaires: Questionnaire A: Existing Arctic In-situ Observing Systems, Questionnaire B: In-situ data collections, and Questionnaire C: Satellite Products. The survey has covered the scientific disciplines addressed in INTAROS, including atmosphere, ocean and terrestrial disciplines. The focus of the survey has been on in-situ observing systems, which is the priority of INTAROS, while satellite observing systems are treated more generally. This report therefore provides more details on selected in-situ systems and data collections than previous surveys and inventories. The reason or the detailed survey is that INTAROS will develop and demonstrate machine-to-machine operations between data repositories, following the FAIR data management principle (“Findable, Accessible, Interoperable and Re-usable”). An expected outcome of the survey is identification of selected observing systems and data collections that will be used further in the project, especially in WP5 (“Data integration and management”) and WP6 (“Application of iAOS towards stakeholders”). A major part of the report is a status description of in situ observing systems that are operated by the partners (Section 2). In INTAROS we identify a set of data collected from the same types of instruments and platforms over time to be an observing system (for example CTD surveys by ships, network of moorings, glider surveys). An observing system is often defined programmatically, where many institutions agree to establish and operate a network of instruments collecting a set of standard measurements and agree on sharing and exploitation of the data (for example International Arctic Buoy Programme). We have also analysed selected in-situ data collections, which can be part of one or more observing systems, or can be a stand-along data set. This analysis has been more detailed, addressing spatial/temporal coverage, uncertainty characterisation and metadata description. Requirements for observing systems is discussed in Section 3, where requirements to platforms, instruments and data management are central. For in-situ data, it is most important to focus on data at level 0 (raw data), level 1 and level 2 (physical, biological variables). These data are needed by different users along the downstream processing chain. Level 3 and level 4 data are gridded data, usually coming from satellite data and reanalysis fields, with input from in-situ data where these are available. Ocean modelling, reanalysis of forecasting are important users of data from level 2 and higher. Requirements to observational data are described in documents from programmes such as WMO, GCOS, Copernicus. Other users are marine ecosystem management, marine hazards and environmental monitoring. The assessment of the observing systems is described in Section 4. The assessment criteria include the spatial and temporal coverage of the data collection, scientific-technical support, sustainability of funding, data management, data usage, user feedback and others. The criteria are assessed on a scale from 1 (low maturity) to 6 (high maturity). The technical readiness level for all the instruments is generally high, showing that the observing systems are generally robust. For biogeochemical, observations there are fewer automated systems compared to physical observation systems. This is reflected in much less collection of biogeochemical data compared to physical data. For the ice-covered Arctic, there is a huge gap in collection in-situ measurements Uncertainty characterisation and metadata have mid to low maturity, while data management varies a lot. It is noteworthy that data management becomes a discipline in itself because the amount of data grows very rapidly. Therefore, data producers and data managers require experts and training to be able to do a good job. Recommendations to develop and maintain in-situ observing systems are described in Section 5. There are significant efforts to build observing systems by many countries, organisations and projects in the Pan-Arctic region. The amount of data collected in the Arctic is growing and there are numerous initiatives to establish observing systems for collection of data in different disciplines. Many recommendations deal with technology development, collaboration and organisation. However, the funding of the observing systems is to a large extent dependent on time-limited research and observation projects. These systems are therefore not sustainable and there is a high risk that many will not be maintained in the future. Some satellite Earth Observation programmes, such as Copernicus, have long-term perspectives and funding plans for 5 – 10 years, but most of the observations from in-situ systems on ground and in water have no long-term funding. It is therefore essential to develop and maintain long-term in-situ observing systems to monitor trends, and to detect natural variations and human impacts on climate, environment, livelihoods and societies. This requires mechanisms for long-term funding to be established. This report only provides preliminary results of the assessment, because organisations outside of the consortium are not yet included in the survey. It is therefore planned to update the assessment later in the project.

The ambition of INRAROS Initial Requirement Mapping was to define the high-level requirements of an integrated Arctic Observing System (iAOS) based on identification of the major societal drivers of a sustained observing system in the Arctic region, driven by issues affecting the entire area and expressed through international agreements (i.e. climate, environment, biodiversity, sustaining ecosystem services, improving the livelihoods of indigenous and local communities, support to maritime safety, etc.). The work was based on knowledge collected from literature studies, projects, programmes and workshops, and cover an evaluation of feasibility, readiness, and impact to provide guidance on future network design. It was decided to focus on the individual thematic areas - meteorology, terrestrial, cryosphere, sea ice and ocean – separately with the purpose of capturing the special requirements, phenomena and essential variables to observe within each of them. It very well known that these thematic areas are closely interconnected and have different levels of maturity in scientific understanding of the phenomena, definitions of essential variables and observing capacity. It is therefore a big challenge to INTAROS to use the collected information to design an integrated multipurpose and multiplatform observations system to optimises efforts and costs. Observations serve several purposes: • Process studies to gain fundamental understanding of phenomena, processes and interrelationships, which is fundamental for development of reliable forecasting models • Establish long timeseries of Essential variables at key locations to monitor variability and changes in the system • To assimilate into as well as to validate models The detailed analysis of phenomena and observation requirements for the entire region given in this report reveals the following conclusions: • The Arctic is a region very sensitive to environmental changes. There is a very close interrelation and delicate balance between the five thematic areas (atmosphere, terrestrial, cryosphere, sea ice and ocean) especially in relation to solar energy retainment and radiation budget and hydrological cycle. This has a great impact on physical, chemical and biological processes in the area. • Due to the hostile environment, there is a great lack of basic observations in the Arctic that can support scientific understanding of key processes. Most of the existing data are collected via time limited research project. This lack of process knowledge is reflected in big errors in forecasting models – operational as well as climate. • It is therefore crucial to establish a sustained Integrated Arctic Observing System that in the short timeframe can increase fundamental scientific understanding of the complex and sensitive Arctic environment and in a longer timeframe can secure a robust basis for decision making to the benefit of the people living in the Arctic, the environment, the broader international society, and commercial activities. • It is foreseen that a future Arctic observation system will rely heavily on satellite observations supplemented more traditional in-situ platforms. Especially the ocean will use several other platforms such as ships, profiling floats, gliders, moorings, AUV’s etc. to monitor the interior of the Arctic Ocean. • In all countries around the Arctic, there are community based observing systems that represent a strong potential for further development. Existing activities shall form the natural basis for a future more intensive and integrated sustainable Arctic Observing System.

The detailed analysis of phenomena and observation requirements for the Arctic region given in this report reveals the following conclusions: • The Arctic is a region very sensitive to environmental changes. There is a very close interrelation and delicate balance between the five thematic areas investigated(atmosphere, terrestrial, cryosphere, sea ice and ocean),especially in relation to solar energy and radiation budget and hydrological cycle. This has a great impact on physical, chemical and biological processes in the area. • Due to the hostile environment, there is a great lack of basic observations in the Arctic,that can support scientific understanding of key processes. Most of the existing data are collected via time limited research projects. This lack of process knowledge is reflected in big errors in forecasting models –operational as well as climate. • It is therefore crucial to establish a sustained Integrated Arctic Observing System,that in the short time frame can increase fundamental scientific understanding of the complex and sensitive Arctic environment and in a longer time frame can secure a robust basis for decision making to the benefit of the people living in the Arctic, the environment, the broader international society, and commercial activities. • It is foreseen that a future Arctic observation system will rely heavily on satellite observations supplemented by more traditional in-situ platforms. Especially the ocean will use several other platforms such as ships, profiling floats, gliders, moorings, AUVs etc. to monitor the interior of the Arctic Ocean. • In all countries around the Arctic, there are community based observing systems that represent a strong potential for further development. Existing activities shall form part of the natural basis for a future more intensive and integrated sustainable Arctic Observing System. • A stakeholder workshop was held in Brussel on 5 May, organised by EuroGOOS, where status and challenges regarding development of Arctic Observing Systems were discussed. In addition to technical and logistical challenges, there are also organisational barriers to building and operating a multidisciplinary observing system. These issues will be addressed in follow-up workshops.

The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID.