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Coastal hazards such as erosion, flooding and pollution are major problems globally, exacerbated by increasing frequency and severity of hydro-meteorological extremes amidst inadequate technology and adaptive capacity. The Ghanaian coast is an example of a region impacted by such problems. Factors hampering the management and improvement of these issues include the lack of data, insufficient communication structures between stakeholders and missing pathways to informed decisions with sustained impact.In this context, the MANCOGA project stands out by employing a co-design approach to develop a robust and participatory Nature-based Solution (NbS) to coastal hazards. The co-design pilot phase has drawn the focus onto steps for restoring wetlands, mangroves in particular, to provide sustainable livelihoods by protecting and reinvigorating coastal systems and environmental health.In the implementation phase, MANCOGA will evaluate mangrove ecosystem services for their potential as NbS to a number of pressing local issues. A Digital Twin will use What-If scenarios to predict the role of mangroves as NbS for flood mitigation and erosion prevention. Being a dominant Blue Carbon ecosystem, mangroves will also contribute to climate change adaptation strategies as well as provide socio-economic value (e.g., through carbon credits). The wider effects on water quality, through the reduction of eutrophication, is critical for local economics, including fisheries. We employ aerial photography and remote sensing to identify possible nature-based solution areas.The comprehensive community involvement of stakeholders from all societal and administrative levels facilitates frameworks to understand and evaluate effectiveness of NbS applications. The relationships and collaborative approach developed during the co-design phase will guarantee continued involvement of stakeholders. MANCOGA will provide a digital toolbox of intuitive, interactive tools to analyze and disseminate archived and new observational data, which will enable ecosystem service quantification before and after the application of NbS, and lead to knowledge-based decision-making.We envision MANCOGA as the start of sustained collaboration, knowledge transfer and capacity building. Therefore, we warmly invite researchers and stakeholders, from Africa and elsewhere, to connect to MANCOGA and share experiences and efforts.

In 2018, Europe experienced an unprecedented heatwave and drought, especially in central and northern Europe, which caused decreased terrestrial production and ecosystem health. The effects on the marine environment are yet unclear. Here we investigate the biogeochemical response to the event in the German Bight of the North Sea. Using time series data from FerryBoxes, research cruises, monitoring programs and remote sensing we compare conditions in 2018 to climatological values. We hypothesize that (1) the heatwave caused unusual warming of surface waters, (2) the drought reduced river discharge and nutrient loads to the coast, and (3) the combined effects altered coastal biogeochemistry and productivity. During 2018, both water discharge and nutrient loads from rivers discharging into the German Bight were extremely low from March onward. Throughout the study domain, water temperature was unusually low in March 2018, but extremely high in May 2018, representing the fastest spring warming on record. This extreme warming period saw concurrent unusually high peaks in chlorophyll a, dissolved oxygen and pH values, consistent with the development of a strong spring bloom. It appears that productivity was unusually strong in near-shore regions, while offshore it was unusually low in 2018. The drought related low discharge limited nutrient supply from the rivers, but likely enhanced near-shore water residence time, where a burst of effective nutrient utilization during the spring depleted nutrients available for transport off shore. There, the heatwave related rapid surface water warming resulted in the establishment of a stable thermal water column stratification, hindering vertical nutrient supply to the surface layer during the summer.

Fluvial extreme events, such as floods and droughts, have an impact beyond the river bed. The change in river discharge and concentration of nutrients and pollutants in freshwater also affects coastal waters, esp. their biogeochemistry. Examining these impacts has been traditionally difficult, as one needs to first detect the river plume in the seawater and then infer its spatio-temporal extent. The River Plume Workflow was developed to support researchers with these tasks and enable them to identify regions of interest, as well as provide tools to conduct a preliminary analysis of the riverine extreme events’ impacts on the coastal waters.The Riverplume Workflow is an open source software tool to detect and examine freshwater signals as anomalies in marine observational data. Data from a FerryBox, an autonomous measuring device installed on a commercial ferry, provide regular coverage of the German Bight, the region for which we developed this toolbox. Combined with drift model computations, it is possible to detect anomalies in the observational data and to comprehend their propagation and origin.The Riverplume Workflow uses the Data Analytics Software Framework (DASF) that was developed as part of the Digital Earth project. Through its modular structure, DASF supports collaborative and distributed data analysis. The Riverplume Workflow’s main feature is an interactive map with various data visualization options that allows users to examine the data closely and either manually select a presumed anomaly for analysis or use an automatic anomaly detection algorithm based on Gaussian regression. The Workflow offers a statistical analysis feature to compare the composition of the selected data to the surrounding measurements. Simulated trajectories of particles starting on the FerryBox transect at the time of the original observation and modelled backwards and forwards in time help verify the origin of the river plume and allow users to follow the anomaly across their area of interest. In addition, the workflow offers the functionality to assemble satellite-based chlorophyll observations along model trajectories as a time series. They allow scientists to understand processes inside the river plume and to determine the timescales on which these developments happen.The FerryBox data used in the Riverplume Workflow are pre-processed automatically and updated daily. Synoptic drift model data is provided for all Elbe extreme events since 2013. We plan to automatize the provision of model data as well.We currently use the Riverplume Workflow to monitor the impacts of Elbe extreme events in the German Bight, though we plan to adapt it to other regions or types of anomalies. The Workflows’ code and all components are available under open source licenses and registered under the DOI https://doi.org/10.5880/GFZ.1.4.2022.006.

The estimations of the diffusive methane flux from the water phase into the atmosphere in coastal waters is relevant for a better estimate of the atmospheric greenhouse-gas budget. Unfortunately, so far, the numerical determination of the fluxes has a high level of uncertainty in coastal waters.To improve the estimation of coastal methane fluxes, not only a high temporal and spatial sampling resolution of the dissolved methane in the water are required. Besides, also the atmospheric methane concentration and the wind speed and wind direction above the surface is important. In most cases, these atmospheric data are obtained from near-by atmospheric and meteorologic monitoring stations. In this study, we measured wind speed, direction and atmospheric methane local directly on board of three research vessel cruising in the southern North Sea within the MOSES project and compared the effects of local versus remote measurements of these data on the flux data. In addition, using the wind direction and speed, we try to assess the origin of the atmospheric methane measured in the study area. Using these “improved” data sets, we discuss if local measurements of auxiliary data provide better insights in the determining factors of the methane flux, and thus also improve the regional aquatic methane budget.

Nutrient and carbon dynamics within the river-estuary-coastal water systems are key processes to understand the matter fluxes from the terrestrial environment to the ocean. In a large-scale study we analysed those dynamics with the focus of the prevailing low water conditions by following a sampling approach based on the travel time of water.We started with a nearly Lagrangian sampling along the River Elbe (German part; 580 km within 8 days travel time). After a subsequent investigation of the estuary, the plume of the river was followed by raster sampling the German Bight (North Sea) using three ships simultaneously. In the river, intensive growth of phytoplankton was determined connected with high oxygen saturation and pH values as well as under-saturation of CO2, whereas concentrations of dissolved nutrients declined. In the estuary, the Elbe shifted from an autotrophic to a heterotrophic system: Phytoplankton died off upstream of the salinity gradient causing minima in oxygen saturation and pH, supersaturation of CO2, and a release of nutrients. In the coastal region, phytoplankton and nutrient concentrations were low, oxygen close to saturation, and pH in a typical marine range. We detected a positive relationship between pH values and oxygen saturation and a negative one between pCO2 and oxygen saturation. Corresponding to the significant particulate nutrient flux via phytoplankton, flux rates of dissolved nutrients from the river into the estuary were low and determined by depleted concentrations. In contrast, fluxes from the estuary to the coastal waters were higher and the pattern was determined by tidal currents.Overall, the presented observation approach is appropriate to better understand land-ocean fluxes, particularly if it is performed under different hydrological conditions including extremes and seems to be suitable to investigate the impact of such events in freshwater on coastal systems in future.The study was conducted within the frame of the Helmholtz MOSES initiative (Modular Observation Solutions for Earth Systems) targeting processes and impacts of hydrological extremes.

Climate projections show high temperature extremes, meteorological droughts and heavy precipitation events are set to increase across Europe (Barros et al., 2014), where the decadel average has already increaed, with temperature in 2002-2011 already 1.3°C±0.1°C above the 1850-1899 mean (Barros et al., 2014). The observed seasonal precipitation pattern presents drier summers and wetter winters across Europe, also mirrored in river flow changes. Across small river catchments in Europe from 1962 to 2004, winter period showed positive trends whereas summers were characterized by negative trends in river flow (Stahl et al., 2010). Such changes can alter the residence time of an estuary. Estuaries are biogeochemical hotspots, and critical zones for carbon cycling, and changes in the hydrological balance, still largely not well characterized, may influence processes within the water column. The present study will assess the potential impacts of droughts on the carbonate system in the Elbe estuary. One of the largest in central Europe, the Elbe River catchment spreads over approximately 150,000 km2 in four countries. Between 2014 and 2018, regions of Northern Germany have been under drought conditions during certain months (UFZ, 2018), reducing discharge in the Elbe River. From 2014, annual Elbe river discharge has been relatively low, where 2018 exhibited the lowest annual mean river discharge of 441 m3 s-1 since 1992. Model projections show the annual river discharge for the Elbe river is likely to remain low at 410 m2 s-1 in 2046-2055 compared to >550 m2 s-1 in 1960-1990 (Krysanova et al., 2005).Analysis of the long-term FGG Elbe (Flussgebietsgemeinschaft Elbe) records of dissolved inorganic carbon (DIC) in the mid to lower Elbe estuary show that over spring and summer months DIC values have increased with time (1997-2018). In this period, DIC increased from the freshwater to the mesohaline region, followed by a decrease to the polyhaline zone. This is opposing to previous DIC patterns in the early 1980s, where DIC decreased towards the mid-estuary after which increased to the outer estuary. An increase in DIC in the mid-estuarine region coincided with increased turbidity and extended residence time, and during the productive months with higher organic matter from upstream regions. This could suggest that more time for heterotrophic activity and availability of labile organic matter, acts to enrich DIC within the water column in the turbid regions, thus changing carbon cycling within the estuary. Further analysis will focus on the changes in river discharge and inorganic carbon during the past two decades, thus inclusive of low discharge and drought conditions.

Geoscientific data analysis has to face some challenges regarding seamless data analysis chains, reuse of methods and tools, interdisciplinary approaches and digitalization. Computer science and data science offer concepts to face these challenges. We took the concepts of scientific workflows and component-based software engineering and adapted it to the field of geoscience. In close collaboration of computer and geo-experts, we set up an expedient approach and technology to develop and implement scientific workflows on a conceptual and digital level. We applied the approach in the showcase “Cross-disciplinary Investigation of Flood Events” to introduce and prove the concepts in our geoscientific work environment, and assess how the approach tackles the posed challenges. This is exemplarily demonstrated with the Flood Event Explorer which has been developed in Digital Earth.

Modular Observation Solutions of Earth Systems (MOSES) is a novel observation system that is specifically designed to unravel the impact of distinct, dynamic events on the long-term development of environmental systems. Hydrometeorological extremes such as the recent European droughts or the floods of 2013 caused severe and lasting environmental damage. Modeling studies suggest that abrupt permafrost thaw events accelerate Arctic greenhouse gas emissions. Short-lived ocean eddies seem to comprise a significant share of the marine carbon uptake or release. Although there is increasing evidence that such dynamic events bear the potential for major environmental impacts, our knowledge on the processes they trigger is still very limited. MOSES aims at capturing such events, from their formation to their end, with high spatial and temporal resolution. As such, the observation system extends and complements existing national and international observation networks, which are mostly designed for long-term monitoring. Several German Helmholtz Association centers have developed this research facility as a mobile and modular “system of systems” to record energy, water, greenhouse gas, and nutrient cycles on the land surface, in coastal regions, in the ocean, in polar regions, and in the atmosphere—but especially the interactions between the Earth compartments. During the implementation period (2017–21), the measuring systems were put into operation and test campaigns were performed to establish event-driven campaign routines. With MOSES’s regular operation starting in 2022, the observation system will then be ready for cross-compartment and cross-discipline research on the environmental impacts of dynamic events., Bulletin of the American Meteorological Society, 103 (2), ISSN:0003-0007, ISSN:1520-0477

Understanding river-sea-systems requires a thorough understanding of processes that span different Earth system compartments. To overcome issues related to the interaction of different scientific disciplines and compartments, such as different measurement and calibration standards, quality control approaches and data formats for specific environmental parameters, joint measurement campaigns have been initiated within the Helmholtz Association’s MOSES (Modular Observation Solutions for Earth Systems) project. Following multiple senor comparison and intercalibration campaigns in 2019, MOSES’ Hydrological Extremes event chain working group initiated joint field campaigns in summer 2020 covering the Elbe river from the Czech-German border to the tidal Elbe and further on into the estuary and the German Bight.The fundamental objective was to establish scientifically sound and resilient multi-ship applicable sampling procedures and to create reference data for the main environmental parameters for future investigation of extreme events such as flooding and drought and their overall impact on the catchment region and the adjacent estuarine area of a large European fresh water / marine system. The campaign involved four research vessels, four research centers and spanned nearly two months. Measurements included standard hydrological and oceanographic parameters, as well as quantities relevant to the nutrient and carbonate system. Furthermore, selected water quality indicators and atmospheric measurements were performed. In the fresh water section of the Elbe river measurements were taken while drifting with the water mass. In the tidal section of the river sampling was done against the ebb current while in the North Sea a grid covering a large part of the German exclusive economic zone (EEZ) was sampled.We detected a longitudinal increase of phytoplankton biomass along the 585 km freshwater part of the river towards the tidal system. In contrast, concentrations of dissolved nitrate and phosphate decreased to low values due the uptake by planktonic algae. The concentration of dissolved CO2 decreased caused by increasing photosynthesis while the concentration of methane increased along the river stretch, particularly in the most downstream part when sedimentation of phytoplankton increased the organic load of sediments. The tidal part of the transect showed a strong influence of Hamburg harbor on almost all quantities, while downstream towards the estuary, the effects of the tidal cycle dominated variabilities. In the marine area, elevated chlorophyll concentrations were mainly found near the west coast of Schleswig-Holstein, probably mostly influenced by the Eider river outflow or the adjacent tidal flats. While most of the measured parameters showed an expected behavior relative to their individual compartments, the transfer of quantities between the compartments revealed rather complex and sometimes difficult to understand behaviors and patterns, especially when considering a functional quantitative analysis. The first results of this trans-compartment campaign showed that a quantitative understanding of the fate and dynamics of water constituents across compartments from the spring to the sea needs enhanced scientific collaboration and awareness to finally come to a better integrated understanding of physical, biogeochemical and biological processes from the local to the global scale.

Surface waters are known to be significant sources of greenhouse gases (CH4 and CO2), but our understanding of large scale patterns is still incomplete. The greenhouse gases in rivers originate both from in-stream processes and interactions with the catchment. For coastal seas, rivers are suspected to be one of the main source of greenhouse gases, while the role of the interjacent tidal flats is still ambiguous. Especially the reaction of the entire system on terrestrial hydrological extremes such as low flow situations are still under consideration. The functional understanding of such events and their impacts on the water chemistry along its transition pathway in the terrestrial and limnic compartment as well as in the coastal marine environment is crucially needed for the evaluation of its relevance in the Earth system. As part of a MOSES campaign (Modular Observation Solutions for Earth Systems) spanning disciplines as well as earth system compartments we investigated the aquatic as well as the atmospheric compartemt in and above the Elbe River from inland waters through the tidal section of the river and the estuary to the North Sea with the goal to explore spatial heterogeneity of CO2 and CH4 concentrations in the water and in ambient air above the water during a low water period in summer 2020. Overall, dissolved CH4 concentrations ranged over three orders of magnitude. Along the freshwater part of the transect, dissolved CH4 increased and weirs and harbors appeared to be hot spots of elevated CH4 concentrations both for the dissolved and atmospheric phase. We observed a longitudinal gradient of CO2 in the river which was closely linked to primary production. In the estuary and the marine part, dissolved CH4 concentrations of the transect were determined by the variability of temperature and salinity. Correlations with other water parameters revealed the complex regulation of dissolved CH4 concentrations along the freshwater-seawater continuum. For atmospheric CH4 above the North Sea, wind direction and wind speed proved to be crucial. Besides the typical diurnal fluctuations of atmospheric CO2 and CH4, an observed link between dissolved and atmospheric concentrations has to be further clarified.

Surface seawater carbon dioxide partial pressure (pCO2) in the south-central North Sea was measured between 2014 and 2018 using FerryBox-integrated membrane sensors on ships-of-opportunity. Average annual pCO2 variability was biologically controlled, with thermal effects modulating its amplitude. Deseasonalized winter trends of seawater pCO2 were positive (4.4 ± 2.0–8.4 ± 2.9 µatm yr−1), biogeochemically driven, stronger than the atmospheric pCO2 trend, and more pronounced than previous analyses. The trends calculated including all deseasonalized monthly averages were even higher (9.7 ± 2.8–12.2 ± 1.4 µatm yr−1). During our investigation, the southern study area became a stronger source and the northern part became a weaker sink for atmospheric carbon. Overall, average sea-air CO2 flux in our study area, from the Skagerrak to the Southern Bight (53°N), changed from −0.75 ± 0.61 mmol m−2 day−1 in 2014 to +0.20 ± 0.96 mmol m−2 day−1 in 2018.

Although methane is a widely studied greenhouse gas, uncertainties remain with respect to the factors controlling its distribution and diffusive flux into the atmosphere, especially in highly dynamic coastal waters. In the southern North Sea, the Elbe and Weser rivers are two major tributaries contributing to the overall methane budget of the southern German Bight. In June 2019, we continuously measured methane and basic hydrographic parameters at a high temporal and spatial resolution (one measurement per minute every 200–300 m) on a transect between Cuxhaven and Helgoland. These measurements revealed that the overall driver of the coastal methane distribution is the dilution of riverine methane-rich water with methane-poor marine water. For both the Elbe and Weser, we determined an input concentration of 40–50 nmol/L compared to only 5 nmol/L in the marine area. Accordingly, we observed a comparatively steady dilution pattern of methane concentration toward the marine realm. Moreover, small-scale anomalous patterns with unexpectedly higher dissolved methane concentrations were discovered at certain sites and times. These patterns were associated with the highly significant correlations of methane with oxygen or turbidity. However, these local anomalies were not consistent over time (days, months). The calculated diffusive methane flux from the water into the atmosphere revealed local values approximately 3.5 times higher than background values (median of 36 and 128 μmol m–2 d–1). We evaluate that this occurred because of a combination of increasing wind speed and increasing methane concentration at those times and locations. Hence, our results demonstrate that improved temporal and spatial resolution of methane measurements can provide a more accurate estimation and, consequently, a more functional understanding of the temporal and spatial dynamics of the coastal methane flux.

Quantifying variability in the ocean carbon sink remains problematic due to sparse observations and spatiotemporal variability in surface ocean pCO2. To address this challenge, we have updated and improved ECCO‐Darwin, a global ocean biogeochemistry model that assimilates both physical and biogeochemical observations. The model consists of an adjoint‐based ocean circulation estimate from the Estimating the Circulation and Climate of the Ocean (ECCO) consortium and an ecosystem model developed by the Massachusetts Institute of Technology Darwin Project. In addition to the data‐constrained ECCO physics, a Green's function approach is used to optimize the biogeochemistry by adjusting initial conditions and six biogeochemical parameters. Over seasonal to multidecadal timescales (1995–2017), ECCO‐Darwin exhibits broad‐scale consistency with observed surface ocean pCO2 and air‐sea CO2 flux reconstructions in most biomes, particularly in the subtropical and equatorial regions. The largest differences between CO2 uptake occur in subpolar seasonally stratified biomes, where ECCO‐Darwin results in stronger winter uptake. Compared to the Global Carbon Project OBMs, ECCO‐Darwin has a time‐mean global ocean CO2 sink (2.47 ± 0.50 Pg C year−1) and interannual variability that are more consistent with interpolation‐based products. Compared to interpolation‐based methods, ECCO‐Darwin is less sensitive to sparse and irregularly sampled observations. Thus, ECCO‐Darwin provides a basis for identifying and predicting the consequences of natural and anthropogenic perturbations to the ocean carbon cycle, as well as the climate‐related sensitivity of marine ecosystems. Our study further highlights the importance of physically consistent, property‐conserving reconstructions, as are provided by ECCO, for ocean biogeochemistry studies.

Rivers are suspected to be a main suppliers of greenhouse gases (methane and carbon dioxide) to coastal seas, while the role of the interjacent tidal flats is still ambiguous. In this study we investigated the role of the Elbe and Weser estuaries as source of methane to the North Sea. We used high spatially resolved methane measurements from an underway degassing system and subsequent analysis with cavity ring down spectroscopy. Thus, a high-resolution representation of the methane distribution in surface waters as well as of hydrographic parameters was obtained for several cruises with two ships in 2019. For most areas, riverine methane was simply diluted by seawater, overlain by a strong tidal signal. However, on several occasions unexpectedly high methane concentrations were observed. Further detailed analysis will elucidate the role of riverine versus tidal impact on coastal North Sea methane fluxes.

Seasonal and annual nitrate and phosphate loads were determined from FerryBox measurements to investigate the high seasonal and inter-annual variability of carbon and nutrient exchange between the Elbe estuary and North Sea. At the inner continental shelf, high biological activity is driven by riverine nutrient inputs, which can contribute to the net carbon dioxide (CO2) uptake. It is possible that in tidal systems this newly formed phytoplankton is transported back into the estuary over the flood tide, and this organic matter can be remineralized in the intertidal region. At present, the influence of this tidally driven mechanism on the nutrient exports and primary production in the coastal zone is not fully characterized, hence carbon sources and sinks at the estuary-coastal boundary may not be well accounted for.The coupling between nutrient inputs from the Elbe estuary to adjacent coastal waters and the subsequent biological activity are now being investigated with a high-frequency dataset provided by a FerryBox situated at the mouth of the estuary. The FerryBox continuously measures physical and biogeochemical parameters every 10 to 60 minutes. Prelimary seasonal and nutrient (nitrate and phosphate) loads from the Elbe estuary to the coastal waters were calculated with FerryBox data between 2014 and 2017. The nutrient loads exhibited high seasonal and inter-annual variability. For example, in summer 2014 nitrate loads reached 100 x 107 mol yr-1 whereas, in summer 2017 nitrate loads were 50 x 107 mol yr-1, which cannot be explained by river discharge alone. Such changes in nutrient loads are likely to influence primary production rates in the adjacent coastal waters and impact CO2 uptake and therefore carbon cycling.Time-series analysis is employed to determine patterns in oxygen changes in relation to photosynthesis and respiration, along with nutrient fluctuations, between 2014 and 2017. Salinity is used to differentiate between the coastal and estuarine end members, with low and high salinity representing flood tide (estuarine waters) and ebb tide (coastal waters), respectively. Changes in dissolved oxygen concentrations are used to estimate primary production (P) and community respiration (R) rates in the water column. The P/R ratio provides the ability to classify the community into autotrophic and heterotrophic systems. Results of this analysis will show the role of varying nutrient loads in supporting primary production in the coastal waters, along with estimating net ecosystem metabolism, and therefore give us a better understanding of nutrient and carbon cycling.

A sensor network surrounds the island of Helgoland, supplying marine data centers with autonomous measurements of variables such as temperature, salinity, chlorophyll and oxygen saturation. The output is a data collection containing information about the complicated conditions around Helgoland, lying at the edge between coastal area and open sea. Spatio-temporal phenomena, such as passing river plumes and pollutant influx through flood events can be found in this data set. Through the data provided by the existing measurement network, these events can be detected and investigated. Because of its important role in understanding the transition between coastal and sea conditions, plans are made to augment the sensor network around Helgoland with another underwater sensor station, an Underwater Node (UWN). The new node is supposed to optimally complement the existing sensor network. Therefore, it makes sense to place it in an area that is not yet represented well by other sensors. The exact spatial and temporal extent of the area of representativity around a sensor is hard to determine, but is assumed to have similar statistical conditions as the sensor measures. This is difficult to specify in the complex system around Helgoland and might change with both, space and time.Using an unsupervised machine learning approach, I determine areas of representativity around Helgoland with the goal of finding an ideal placement for a new sensor node. The areas of representativity are identified by clustering a dataset containing time series of the existing sensor network and complementary model data for a period of several years. The computed areas of representativity are compared to the existing sensor placements to decide where to deploy the additional UWN to achieve a good coverage for further investigations on spatio-temporal phenomena.A challenge that occurs during the clustering analysis is to determine whether the spatial areas of representativity remain stable enough over time to base the decision of long-term sensor placement on its results. I compare results across different periods of time and investigate how fast areas of representativity change spatially with time and if there are areas that remain stable over the course of several years. This also allows insights on the occurrence and behavior of spatio-temporal events around Helgoland in the long-term. Whether spatial areas of representativity remain stable enough temporally to be taken into account for augmenting sensor networks, influences future network design decisions. This way, the extended sensor network can capture a greater variety of the spatio-temporal phenomena around Helgoland, as well as allow an overview on the long-term behavior of the marine system.

Measuring environmental variables over longer times in coastal marine environments is a challenge in regard to sensor maintenance and data processing of continuously produced comprehensive datasets. In the project “MOSES” (Modular Observation Solutions for Earth Systems), this procedure became even more complicated because seven large Helmholtz centers from the research field Earth and Environment (E&E) within the framework of the German Ministery of Educatiopn and Research (BMBF) work together to design and construct a large scale monitoring network across earth compartments to study the effects of short-term events on long term environmental trends. This requires the development of robust and standardized automated data acquisition and processing routines, to ensure reliable, accure and precise data.Here, the results of two intercomparison workshops on senor accuracy and precicion for selected environmental variables are presented. Environmental sensors which were to be used in MOSES campaigns on hydrological extremes (floods and draughts) in the Elbe catchment and the adjacent coastal areas in the North Sea in 2019 to 2020 were compared for selected parameters (temperature, salinity, chlorophyll-A, turbidity and methane) in the same experimentally controlled water body, assuming that all sensors provide comparable data. Results were analyzed with respect to individual sensor accuracy and precision related to an “assumed” real value as well as with respect to a cost versus accuracy/precision index for measuring specific environmental data. The results show, that accuracy and precision of sensors do not necessarily correlate with the price of the sensors and that low cost sensors may provide the same or even higher accuracy and precision values as even the highest price sensor types.

Within the context of predicted and observed increase in droughts and floods with climate change, large summer floods are likely to become more frequent. These extreme events can alter typical biogeochemical patterns in coastal systems. The extreme Elbe River flood in June, 2013 not only caused major damages in several European countries, but also generated large scale biogeochemical changes in the Elbe Estuary and the adjacent German Bight. Due to a number of well documented and unusual atmospheric conditions, the early summer of 2013 in Central and Eastern Europe was colder and wetter than usual, with saturated soils, and higher than average cumulative precipitation. Additional precipitation at the end of May, and beginning of June, 2013, caused widespread floods within the Danube and Elbe Rivers, as well as billions of euros in damages. The floods generated the largest summer discharge on record within the last 140 years. The high-frequency monitoring network in the German Bight available within the Coastal Observing System for Northern and Arctic Seas (COSYNA) captured the flood influence on the German Bight. Monitoring data from a FerryBox station in the Elbe Estuary (Cuxhaven) and from a FerryBox platform aboard the M/V Funny Girl Ferry (traveling between Büsum and Helgoland) documented the salinity changes on the German Bight, which persisted for about 2 months after the peak discharge. The flood generated a large influx of nutrients, dissolved and particulate organic carbon on the coast. These conditions subsequently led to the onset of a chlorophyll bloom within the German Bight, observed by dissolved oxygen supersaturation, and higher than usual pH in surface coastal waters. The prolonged stratification also led to widespread bottom water dissolved oxygen depletion, unusual for the south eastern German Bight in the summer.

Marine biogeochemical processes can strongly interact with processes occurring in adjacent ice and sediments. This is especially likely in areas with shallow water and frequent ice cover, both of which are common in the Arctic. Modeling tools are therefore required to simulate coupled biogeochemical systems in ice, water, and sediment domains. We developed a 1D sympagic&ndash, pelagic&ndash, benthic transport model (SPBM) which uses input from physical model simulations to describe hydrodynamics and ice growth and modules from the Framework for Aquatic Biogeochemical Models (FABM) to construct a user-defined biogeochemical model. SPBM coupled with a biogeochemical model simulates the processes of vertical diffusion, sinking/burial, and biogeochemical transformations within and between the three domains. The potential utility of SPBM is demonstrated herein with two test runs using modules from the European regional seas ecosystem model (ERSEM) and the bottom-redox model biogeochemistry (BROM-biogeochemistry). The first run simulates multiple phytoplankton functional groups inhabiting the ice and water domains, while the second simulates detailed redox biogeochemistry in the ice, water, and sediments. SPBM is a flexible tool for integrated simulation of ice, water, and sediment biogeochemistry, and as such may help in producing well-parameterized biogeochemical models for regions with strong sympagic&ndash, benthic interactions.

[1] Few Southern Hemisphere time series measurements of biogeochemical tracers are available, and this scarcity is a major impediment in understanding the biological and physical processes underlying the oceanic carbon and nutrient cycles in vast parts of the global oceans. We make use of bi-monthly measurements of carbonate parameters from 1998 to 2010 in upper Subantarctic Surface Water east of New Zealand's South Island at 45.85°S 171.50°E to investigate seasonal cycles and trends in these species and processes controlling their variability. This time series reveals positive trends in salinity normalized dissolved inorganic carbon (sDIC) and the partial pressure of carbon dioxide (pCO2) that are smaller than would be expected from the anthropogenic increase in atmospheric pCO2 alone, possibly due to a decrease of the average temperature over the observational period. The seasonal cycle of pCO2 is dominated by that of DIC, but is substantially modified by the influence of the annual cycle of sea surface temperature. Investigations with a δ13COC-constrained diagnostic box model suggest that net community production (NCP) is the dominant process controlling the observed seasonal variability in sDIC by removing 1.2 ± 0.7 mol C m−2 yr−1 from the mixed layer. This carbon drawdown, aided by an additional carbon removal due to horizontal transport, is balanced by vertical diffusion, entrainment, and air-sea gas exchange of CO2. Oceanic pCO2 is below atmospheric pCO2 for nearly the entire year, leading to an annual mean surface ocean pCO2 undersaturation of about 12 µatm and an annual oceanic uptake of CO2 from the atmosphere of 0.9 ± 0.1 mol C m−2 yr−1.

During the inaugural Physical Oceanography Dissertation Symposium in June 2002 we found that the graduate school experience varied markedly amongst the 20 international participants. The diversity of backgrounds led to lively discussion about the differences between physical oceanography programs. Here we review the length, content, and quality of education for graduate programs in Australia, France, Germany, the UK, and the USA. We also comment on the financial, social, and scientific status of graduate students in these countries. Graduate programs in physical oceanography face the challenge of introducing students to the wide range of tools and techniques which define the field, ranging from observational work and remote sensing, through dynamical theory and laboratory experiments, to numerical modelling. While individual character largely determines the success of the PhD experience, a graduate education in physical oceanography should include the following factors to best serve students in their future career: solid mentorship, regular department level progress checks, course work, summer schools, field work, practise in communication skills, scientific and social integration, international exchange, and stable and sufficient funding. We propose a model four year physical oceanography graduate degree structure, distilled from the best aspects of international physical oceanography programs.

The Coastal Observing System for Northern and Arctic Seas (COSYNA) was established in order to better understand the complex interdisciplinary processes of northern seas and the Arctic coasts in a changing environment. Particular focus is given to the German Bight in the North Sea as a prime example of a heavily used coastal area, and Svalbard as an example of an Arctic coast that is under strong pressure due to global change.The COSYNA automated observing and modelling system is designed to monitor real-time conditions and provide short-term forecasts, data, and data products to help assess the impact of anthropogenically induced change. Observations are carried out by combining satellite and radar remote sensing with various in situ platforms. Novel sensors, instruments, and algorithms are developed to further improve the understanding of the interdisciplinary interactions between physics, biogeochemistry, and the ecology of coastal seas. New modelling and data assimilation techniques are used to integrate observations and models in a quasi-operational system providing descriptions and forecasts of key hydrographic variables. Data and data products are publicly available free of charge and in real time. They are used by multiple interest groups in science, agencies, politics, industry, and the public.

Oxygen (O(2)) is a critical constraint on marine ecosystems. As oceanic O(2) falls to hypoxic concentrations, habitability for aerobic organisms decreases rapidly. We show that the spatial extent of hypoxia is highly sensitive to small changes in the ocean's O(2) content, with maximum responses at suboxic concentrations where anaerobic metabolisms predominate. In model-based reconstructions of historical oxygen changes, the world's largest suboxic zone, in the Pacific Ocean, varies in size by a factor of 2. This is attributable to climate-driven changes in the depth of the tropical and subtropical thermocline that have multiplicative effects on respiration rates in low-O(2) water. The same mechanism yields even larger fluctuations in the rate of nitrogen removal by denitrification, creating a link between decadal climate oscillations and the nutrient limitation of marine photosynthesis.

It has been proposed that net primary production (NPP), net community production (NCP), particulate organic carbon export (Phi(POC)) and the relationships among them are governed by local environmental conditions that favor either a microbially dominated assemblage leading to a regeneration loop (low ratio of (Phi(POC) to NPP) or a system dominated by large plankton with export pathway characteristics (high ratio of (Dpoc to NPP). We analyze more than 10 years of data from two subtropical time-series stations (Hawaii Ocean Times-series (HOT) in the North Pacific, and Bermuda Atlantic Time-Series (BATS) in the North Atlantic) in order to investigate this regeneration loop versus export pathway hypothesis and in particular to test the idea that the switch between the two is controlled by enhanced input of nutrients. In the decadal long-term mean, the relationships between NPP, (Dpoc and NCP, which we take here as a proxy for export production, reveal export pathway characteristics at BATS, while HOT is dominated by the regeneration loop. This difference is consistent with the stronger seasonal forcing at BATS and the resulting higher new nutrient input. However, these characteristics are only valid for parts of the year. Especially at BATS, the export pathway exists only in spring and the system reverts to a regeneration loop in summer and fall. This is consistent with our hypothesis given the strong summer-time stratification and the resulting low levels of new nutrient input. On interannual time-scales, we find little evidence for statistically significant alterations of the long-term mean characteristics, a finding we ascribe to a combination of limited magnitude of forcing, length of the data records, and possibly an inherent lack of predictability. A comparison of our results for the ratio between NCP and NPP (e-ratio) and the ratio between Phi(POC) and NPP (pe-ratio) with those predicted by the models of Laws et al. [Temperature effects on export production in the open ocean. Global Biogeochemical Cycles 14(4), 1231-1246] and Dunne et al. [Empirical and mechanistic models for particle export ratio. Global Biogeochemical Cycles 19, GB40261 respectively, show reasonable agreement for the long-term mean, but these models fail to capture the observed interannual variability in these ratios. (c) 2006 Elsevier Ltd. All rights reserved.

Within the Subantarctic Mode Water (SAMW) density level, we study temporal changes in salinity, nutrients, oxygen and TTD (Transit Time Distribution) ages in the western (W) and eastern (E) subtropical gyre of the Indian Ocean (IO) from 1987 to 2002. Additionally, changes in Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC) are evaluated between 1995 and 2002. The mechanisms behind the detected changes are discussed along with the results from a hindcast model run (Community Climate System Model). The increasing salinity and decreasing oxygen trends from 1960 to 1987 reversed from 1987 to 2002 along the gyre. In the W-IO a decreasing trend in TTD ages points to a faster delivery of SAMW, thus less biogenic matter remineralization, explaining the oxygen increase and noisier nutrients decrease. In the E-IO SAMW, no change in TTD ages was detected, therefore the trends in oxygen and inorganic nutrients relate to changes in the Antarctic Surface Water transported into the E-IO SAMW formation area. In the W-IO between 1995 and 2002, the DIC increase is equal or even less than the anthropogenic input as the reduction in remineralization contributes to mask the increasing trend. In the E-IO between 1995 and 2002, DIC decreases slightly despite the increase in the anthropogenic input. Differences in the preformed E-IO SAMW conditions would explain this behavior. Trends in the W and E IO SAMW are decoupled and related to different forcing mechanisms in the two main sites of SAMW formation in the IO, at 40°S–70°E and 45°S–90°E, respectively., 3

[1] Long-term trends and average seasonal variability in the upper ocean carbon cycle are investigated at Station ALOHA, the site of the U.S. JGOFS Hawaii Ocean Time series program (HOT), on the basis of a 14-year time series (1988–2002) of dissolved inorganic carbon (DIC), alkalinity, and 13C/12C ratio of DIC data. Salinity-normalized DIC (sDIC) and computed oceanic pCO2 show distinct upward trends of 1.2 ± 0.1 μmol kg−1 yr−1 and 2.5 ± 0.1 μatm yr−1, respectively, while the 13C/12C isotopic ratio of DIC (expressed as δ13Coc) decreases at a mean rate of −0.027 ± 0.001‰ yr−1. More than half of the rates of change in sDIC and oceanic pCO2, and most of the change in 13C/12C, are attributed to the uptake of isotopically light anthropogenic CO2 from the atmosphere. The residual trends appear to be caused mainly by a regional change in the net freshwater budget, perhaps associated with a regime change of the North Pacific climate system near 1997. Computed oceanic pCO2 is below atmospheric pCO2 for nearly the entire year, leading to an annual mean surface ocean pCO2 undersaturation of about 18 μatm, and to an annual uptake of CO2 from the atmosphere, which we compute to be 1.0 ± 0.1 mol m−2 yr−1. We estimate that about 30% of this flux relates to the uptake of anthropogenic CO2, and the remainder to biologically mediated export of organic carbon. Using a modified version of the diagnostic model of Gruber et al. [1998], constrained by δ13Coc, we infer net community production of organic carbon (NCP) to be the dominant process generating the observed seasonal variability in sDIC. The annual integral of NCP, 2.3 ± 0.8 mol m−2 yr−1, is comparable to previous estimates of biological production in the subtropical North Pacific. Annually integrated fluxes of air-sea gas exchange and NCP at Station ALOHA are each about two thirds of those computed for the upper ocean near Bermuda using similar methods of estimation [Gruber et al., 1998, 2002]. However, the seasonal amplitudes of sDIC and δ13Coc near Hawaii are only half as large as near Bermuda, because air-sea gas exchange and NCP tend to oppose each other near Hawaii, but reinforce each other near Bermuda.

[1] Interhemispheric signal transmission in the Atlantic Ocean connects the deep water production regions of both hemispheres. The nature of these interactions and large-scale responses to perturbations on timescales of years to millennia have been investigated using a global three-dimensional ocean general circulation model coupled to a dynamic-thermodynamic sea ice model. The coupled model reproduces many aspects of today's oceanic circulation. A set of experiments shows the sensitivity to changes in different surface boundary conditions. Buoyancy changes in the Weddell and Labrador Seas exert a direct effect on the overturning cells of the respective hemisphere. They influence the density structure of the deep ocean and thereby lead to alterations in the strength of the ACC. Changing the wind stress south of 30°S influences the magnitude of the deep water production of both hemispheres. The interhemispheric effect in these experiments cannot be explained solely by advective mechanisms. Switching off the wind stress over the latitude band of the Drake Passage leads to a slow gradual decrease of the water mass transport in the ACC, resulting in an almost complete cessation. The model results prove the necessity to continue integrations over thousands of years until new equilibria are established.

Using an Observing System Simulation Experiment (OSSE), we investigate the impact of JAXA Greenhouse gases Observing SATellite ‘IBUKI’ (GOSAT) sampling on the estimation of terrestrial biospheric flux with the NASA Carbon Monitoring System Flux (CMS-Flux) estimation and attribution strategy. The simulated observations in the OSSE use the actual column carbon dioxide (X CO 2 ) b2.9 retrieval sensitivity and quality control for the year 2010 processed through the Atmospheric CO 2 Observations from Space algorithm. CMS-Flux is a variational inversion system that uses the GEOS-Chem forward and adjoint model forced by a suite of observationally constrained fluxes from ocean, land and anthropogenic models. We investigate the impact of GOSAT sampling on flux estimation in two aspects: 1) random error uncertainty reduction and 2) the global and regional bias in posterior flux resulted from the spatiotemporally biased GOSAT sampling. Based on Monte Carlo calculations, we find that global average flux uncertainty reduction ranges from 25% in September to 60% in July. When aggregated to the 11 land regions designated by the phase 3 of the Atmospheric Tracer Transport Model Intercomparison Project, the annual mean uncertainty reduction ranges from 10% over North American boreal to 38% over South American temperate, which is driven by observational coverage and the magnitude of prior flux uncertainty. The uncertainty reduction over the South American tropical region is 30%, even with sparse observation coverage. We show that this reduction results from the large prior flux uncertainty and the impact of non-local observations. Given the assumed prior error statistics, the degree of freedom for signal is ~1132 for 1-yr of the 74 055 GOSAT X CO 2 observations, which indicates that GOSAT provides ~1132 independent pieces of information about surface fluxes. We quantify the impact of GOSAT’s spatiotemporally sampling on the posterior flux, and find that a 0.7 gigatons of carbon bias in the global annual posterior flux resulted from the seasonally and diurnally biased sampling when using a diagonal prior flux error covariance. Keywords: NASA CMS-Flux, GOSAT, OCO-2, variational inversion, biased sampling, Monte Carlo (Published: 9 May 2014) Citation: Tellus B 2014, 66 , 22486, http://dx.doi.org/10.3402/tellusb.v66.22486

1. The study demonstrated that the internal plant water balance, expressed as leaf moisture content in percentage of oven dry weight, could be used to determine viability of loblolly pine (Pinus taeda L.) seedlings after wilting. 2. Under the conditions of the experiment a leaf moisture content of 110% was shown to indicate a critical plant water balance, below which the plants did not recover after rewatering. 3. It was significant changes in the roots which restricted water transport to the leaves below this plant water balance, because leaves with a leaf moisture content as low as 76% would regain turgidity when either detached leaves or plants with the roots excised were placed with the cut end in water.