For sea level studies, coastal adaptation, and planning for future sea level scenarios, regional responses require regionally-tailored sea level information. Global sea level products from satellite altimeter missions are now available through the European Space Agency’s (ESA) Climate Change Initiative Sea Level Project (SL_cci). However, these global datasets are not entirely appropriate for supporting regional actions. Particularly for the Baltic Sea region, complications such as coastal complexity and sea-ice restrain our ability to exploit radar altimetry data.

This presentation highlights the benefits and opportunities offered by such regionalised advances, through an examination by the ESA-funded Baltic SEAL project (http://balticseal.eu/). We present the challenges faced, and solutions implemented, to develop new dedicated along-track and gridded sea level datasets for Baltic Sea stakeholders, spanning the years 1995-2019. Advances in waveform classification and altimetry echo-fitting, expansion of echo-fitting to a wide range of altimetry missions (including Delay-Doppler altimeters), and Baltic-focused multi-mission cross calibration, enable all altimetry missions’ data to be integrated into a final gridded product.

This gridded product, and a range of altimetry datasets, offer new insights into the Baltic Sea’s mean sea level and its variability during 1995-2019. Here, we focus on the analysis of sea level trends in the region using both tide gauge and altimetry data. The Baltic SEAL absolute sea level trend at the coast better aligns with information from the in-situ stations, when compared to current global products. The rise in sea level is statistically significant in the region of study and higher in winter than in summer. A gradient of over 3 mm/yr in sea level rise is observed, with sea levels in the north and east of the basin rising more than in the south-west. Part of this gradient (about 1 mm/yr) is directly explained by a regression analysis of the wind contribution on the sea level time series. A sub-basin analysis comparing the northernmost part (Bay of Bothnia) with the south-west reveals that the differences in winter sea level anomalies are related to different phases of the North-Atlantic Oscillation (0.71 correlation coefficient). Sea level anomalies are higher in the Bay of Bothnia when winter wind forcing pushes waters through Ekman transport from the south-west towards east and north.

The study also demonstrates the maturity of enhanced satellite altimetry products to support local sea level studies in areas characterised by complex coastlines or sea-ice coverage. The processing chain used in this study can be exported to other regions, in particular to test the applicability in regions affected by larger ocean tides. We promote further exploitation and identification of further synergies with other efforts focused on relevant oceanic variables for societal applications.

How to cite: Oelsmann, J. and the Baltic+ SEAL: Absolute Baltic Sea Level Trends in the Satellite Altimetry Era: A  Revisit, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2649, https://doi.org/10.5194/egusphere-egu21-2649, 2021.

Robust estimations of uncertainty for climate projections on the regional scale are highly needed but are still challenging. Regional climate projections rely on downscaling global climate scenarios. Typically, a number of different global climate models are downscaled to assess the inherent model uncertainty. The more models, the more robust the estimate of model uncertainty. However, this strategy is time consuming and so ensembles of regional projections are usually smaller than ensembles of global projections which can lead to an underestimation of regional uncertainty. With an increasing number of available global projections regional downscaling becomes increasingly expensive. We use a regional ensemble of coupled atmosphere-ice-ocean scenarios and a ensemble of ocean-ecosystem scenarios for the Baltic Sea to explore the effect of model selection on the representation of model uncertainty. Using a number of climate indices to characterize the regional system we apply a model selection that is representative of the original ensemble in terms of ensemble spread. We use existing algorithms to generate orthogonal patterns of climate change for the Baltic Sea. A small number of patterns is used to represent the climate change and its uncertainty in physical and biogeochemical parameters of the Baltic Sea. We show that climate change signals in atmosphere, ocean and ecosystem are coherent and that atmospheric or oceanic indices can be used to select global climate models for an ensemble of representative regional ecosystem scenarios for the Baltic Sea. Since the atmospheric climate in the regional climate model is close to its representation in the global climate model that latter can be used to perform an initial model selection.

How to cite: Dieterich, C., Gröger, M., Höglund, A., Wilcke, R. A. I., and Meier, H. E. M.: Representative climate projections for the North Sea and Baltic Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8631, https://doi.org/10.5194/egusphere-egu21-8631, 2021.

Detailed atmospheric, ocean physical and biogeochemical characteristics for the period 2015-2100 within the South Asia CORDEX domain have been obtained from simulations of the Regional Earth System Model ROM.

Comparative analysis of average climatic characteristics for the past (1975-2004) and future (2070-2099) climates has been carried out. It shows significant future SST increase, reaching 3ºC on average, over the considered area. The salinity of the ocean's upper layer will decrease by 1 ‰ on average, which indicates a change in the precipitation-evaporation balance in the future climate. The simulated annual MLD will decrease by 5 m in the future. However, this MLD change will be strongly irregular, both in time and space. Simulations also show a widespread decrease of the chlorophyll-a concentration in the surface layer (up to 2 mg Chl m-3) in the future, especially pronounced in the northern and western parts of the Arabian Sea. It is a significant change, given that absolute chlorophyll-a concentration in these areas is typically 3-4 mg Chl m-3 in spring and 5-8 mg Chl m-3 in summer, as obtained for the 1975-2004 model run. The model also shows that the chlorophyll-a concentration at the surface will decrease by 1–2 mg Chl m-3 along the western coast of the Bay of Bengal in the future. The relative decrease in the surface chlorophyll-a concentration will be about 40% in the future climate in the Arabian Sea and the Bay of Bengal.

The model solution according to the SSP5-8.5 scenario shows a decrease in the amount of precipitation in the future climate (up to 3-4 mm/day) over the northeastern part of India and over Nepal in summer. But over the central part of India, in the Andaman Sea, over Thailand and Myanmar, there will be an increase in the amount of precipitation. The total continental runoff into the Bay of Bengal will increase, but the runoff in the Ganges delta will be greatly weakened. Thus, despite the decrease in the runoff of the Ganges and Brahmaputra rivers, the total continental runoff into the Bay of Bengal turns out to be higher in the future climate (2070-2099) relative to retrospective calculations (1975-2004) due to the runoff of smaller rivers.

Acknowledgements: This work is funded by Russian Science Foundation (RSF, Project 19-47-02015) and Department of Science and Technology (DST, Govt. of India, grant DST/INT/RUS/RSF/P-33/G). The research was performed in the framework of the state assignment of the Ministry of Science and Higher Education of Russia (theme No. 0128-2021-0014). This work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID ba1144.

How to cite: Dvornikov, A. Yu., Sein, D. V., Martyanov, S. D., Ryabchenko, V. A., and Kumar, P.: Projected climate change in the South Asia and northern Indian Ocean by the end of the 21st century as obtained from a Regional Earth System Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11989, https://doi.org/10.5194/egusphere-egu21-11989, 2021.

The future changes in the physical conditions in the Gulf of Bothnia can have considerable impact on various human activities in the area. In this presentation we concentrate on marine heatwaves and ice conditions. The general changing trends of ice conditions, temperature and salinity give an idea of the changes to come. It is, however, also important to know the possible changes in extremes, and their frequencies in the future. To name a few examples, aquaculture activities can be affected by sudden exceptional warm or cold periods of water, and wind-energy construction benefits from knowing what kind of ice conditions can be expected.

In the SmartSea project we have made simulations of future scenarios for predicting the possible changes in the conditions in the Gulf of Bothnia. We have simulated a historical control period of 1976-2006 with three different downscaled global circulation models, and use these as comparisons for runs made with same model forcings for the years 2006-2060 with RCP 4.5 and RCP 8.5 scenarios. These scenarios are used to detect the type and frequency of extreme events, such as marine heatwaves or extreme ice conditions in the control period, and the change of these in the future for both RCP’s.

How to cite: Siiriä, S.-M., Fredriksson, S., Roiha, P., Alenius, P., and Oikkonen, A.: Extreme events on Gulf of Bothnia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11908, https://doi.org/10.5194/egusphere-egu21-11908, 2021.

Wave climate change in the Gulf of Bothnia in 2030–2059 was investigated using regional wave climate projections. For the simulations we used wave model WAM. As the atmospheric forcing for the wave model we had three global climate scenarios (HADGEM2-ES, MPI-ESM, EC-EARTH) downscaled with RCA4-NEMO regional model. The ice concentration for the wave model was obtained from NEMO ocean model simulations using the same atmospheric forcing. We used both RCP4.5 and RCP8.5 greenhouse gas scenarios. The spatial resolution of the simulation data was 1.8 km, enabling detailed analyses of the wave properties near the coast. From the simulation data we calculated statistics and return levels of significant wave heights using extreme value analysis, and assessed the projected changes in the wave climate in the Gulf of Bothnia. The projected increase in the significant wave heights is mainly due to the decreasing ice cover, especially in the Bothnian Bay. Projected changes in the most prevalent wind direction impacts the spatial pattern of the wave heights in the Bothnian Sea.

How to cite: Björkqvist, J.-V., Särkkä, J., Kanarik, H., and Tuomi, L.: Wave climate change in the Gulf of Bothnia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9808, https://doi.org/10.5194/egusphere-egu21-9808, 2021.

The Gulf of Bothnia is the only sub-basin of the Baltic Sea with no serious eutrophication. However, long-term observations have shown degradation of the water quality over the past years, indicating warning signals for the future. Here, we use a high resolution ocean circulation model including biogeochemistry to study 21st century nutrient and oxygen changes in the Gulf of Bothnia. We analyze ensembles for 5 different scenarios; a historical (1975-2005) and 4 future projections (2006-2100). For the projections, two atmospheric pCO₂ trajectories are used, RCP4.5 and RCP8.5, and two settings for nutrient loads are applied to each RCP scenario: one following the Baltic Sea Action Plan (BSAP) and the other assuming business as usual. We also test a historical scenario but with no local nutrient loads to better understand the biogeochemical influence of the lateral open boundary. The comparison of observations with the historical scenario shows that oxygen trends are well captured by the model despite a small bias in nutrient concentrations. Our results suggest that the Bothnian Bay is more sensitive to river loads than the Bothnian Sea, which is primarily affected by the inflows from the Baltic proper. All future projections show a decrease in phosphate concentrations and an increase in nitrate concentrations due to lower/higher input of phosphate/nitrate from the Baltic proper. Oxygen concentrations in bottom waters of the Gulf of Bothnia are not susceptible to become hypoxic in the future. However, when business as usual is applied for nutrient loads, oxygen concentrations decrease significantly over the entire future period and short episodes of low oxygen conditions in bottom waters (with less than 5 ml O₂/l) become more frequent and more pronounced in the Bothnian Sea, especially towards the end of the century.

How to cite: Ruvalcaba Baroni, I., Hieronymus, J., Fredriksson, S., and Arneborg, L.: 21st century nutrient and oxygen dynamics in the Gulf of Bothnia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7648, https://doi.org/10.5194/egusphere-egu21-7648, 2021.

River discharge and the associated nutrient loads are important factors that influence the functioning of the marine ecosystem. Lateral inflows from land carrying fresh, nutrient-rich water determine coastal physical conditions and nutrient concentration and, hence, dominantly influence primary production in the system. Since this forms the basis of the trophic food web, riverine nutrient concentrations impact the variability of the whole coastal ecosystem. This process becomes even more relevant in systems like the Baltic Sea, which is almost decoupled from the open ocean and land-borne nutrients play a major role for ecosystem productivity on seasonal up to decadal time scales.

In order to represent the effects of climate or land use change on nutrient availability, a coupled system approach is required to simulate the transport of nutrients across Earth system compartments. This comprises their transport within the atmosphere, the deposition and human application at the surface, the lateral transport over the land surface into the ocean and their dynamics and transformation in the marine ecosystem. In our study, we combine these processes in a modelling chain within the GCOAST (Geesthacht Coupled cOAstal model SysTem) framework for the northern European region. This modelling chain comprises:

• Simulation of emissions, atmospheric transport and deposition with the chemistry transport model CMAQ at 36 km grid resolution using atmospheric forcing from the coastDat3 data that have been generated with the regional climate model COSMO-CLM over Europe at 0.11° resolution using ERA-Interim re-analyses as boundary conditions
• Simulation of inert processes at the land surface with the global hydrology model HydroPy (former MPI-HM), i.e. considering total nitrogen without any chemical reactions
• Riverine transport with the Hydrological Discharge (HD) model at 0.0833° spatial resolution
• Simulation of the North Sea and Baltic Sea ecosystems with 3D coupled physical-biogeochemical NPZD-model ECOSMO II at about 10 km resolution

We will present first results and their validation from this exercise.

How to cite: Hagemann, S., Daewel, U., Matthias, V., and Stacke, T.: Modelling nitrogen transport across compartments over northern Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8166, https://doi.org/10.5194/egusphere-egu21-8166, 2021.

The St. Petersburg model of eutrophication (SPBEM) has been modified with an explicit description of the total amounts of organic nutrients, including both dissolved and particulate forms [1, 2]. This modification allows total nutrient amounts to be fully taken into account as reported in field measurements and presented in environmental documents, thereby eliminating one of the important sources of uncertainty in boundary conditions [3].

The SPBEM-2 model was validated and verified in the Gulf of Finland using data from more than 4,000 oceanographic stations for the period from 2009 to 2014. This results showed that the presented version of SPBEM-2 is able to plausibly reproduce all the main large-scale features and phenomena of the dynamics of nutrients in the Gulf of Finland, especially in its productive layer, which, for hypsographic reasons, contains and transforms the main reserves of nutrients.

Expansion of SPBEM-2 with dissolved organic nutrients makes it possible to fully take into account the loads on the land in both historical and scenario modelling, thereby reducing the uncertainty of impact.

Acknowledgements: The authors A.I. and V.R. conducted the present study within the framework of the state assignment (theme No. 0128-2021-0014).The authors O.V. and T.E. were supported by the Government Target Project N FSZU-2020-0009 of the Ministry of Education and Science of the Russian Federation. The author O.S. from the Baltic Nest Institute was supported by the Swedish Agency for Marine and Water Management through their grant 1:11—Measures for the marine and water environment.

References

1. Vladimirova O. M., Eremina T. R., Isaev A. V., Ryabchenko V. A., Savchuk O. P. Modelling dissolved organic nutrients in the Gulf of Finland. Fundamentalnaya i Prikladnaya Gidrofizika. 2018, 11, 4, 90—101. doi: 10.7868/S2073667318040111.

2. Isaev A, Vladimirova O, Eremina T, Ryabchenko V, Savchuk O. Accounting for Dissolved Organic Nutrients in an SPBEM-2 Model: Validation and Verification. Water. 2020; 12(5):1307.

3. Meier H.E.M., Edman M., Eilola K., et al. Assessment of Uncertainties in Scenario Simulations of Biogeochemical Cycles in the Baltic Sea. Front. Mar. Sci., 04 March 2019, Vol.6, Article 46. doi: 10.3389/fmars.2019.00046

How to cite: Isaev, A., Vladimirova, O., Eremina, T., Ryabchenko, V., and Savchuk, O.: Modelling dissolved organic nutrients in the Gulf of Finland: eliminating an uncertainty in boundary conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3868, https://doi.org/10.5194/egusphere-egu21-3868, 2021.

Sediment pore waters in the depositional areas of the Baltic Sea are enriched with the dissolved organic carbon (DOC), which results in a diffusive flux of DOC to the water column. It was found that up to 30% of OM deposited in the sediments returns to the water column and may alter processes occurring there e.g. increase the oxygen demand in the bottom waters. Still little is known about the bioavailability of sediment-derived DOC and its remineralization dynamics. Thus, the aim of this study was to assess the bioavailability, degradation rate constant and half-life time of sediment-derived DOC.

Bottom water and pore water, collected during r/v Oceania cruise in March 2018 in the Gdańsk Deep, have been mixed in a volume ratio of 4:1. To ensure oxic conditions in the experiment, the mixture was bubbled with the ambient air to reach 100% O₂ saturation. Incubation of such prepared samples was conducted in 23±0.1°C for 126 days. At the beginning (t=0) and after 1, 2, 6, 18, 35, 73 and 126 days of the incubation the individual samples were analyzed for total dissolved organic carbon DOC. In parallel, untreated bottom water was incubated as a control, while the obtained results have been used to decouple the remineralization dynamics in the mixture.

The DOC decay had an exponential character. The highest dynamics of DOC remineralization was at the beginning of the experiment and it gradually decreased over time. During the incubation period pore water DOC concentration decreased from 1408 to 850 µmol l-¹_, which corresponds to almost 40% loss. In the control samples (bottom water) DOC concentration decreased from 304 to 260 µmol l^-1 i.e. by ~14%.

In the experiment three different DOC fractions have been identified: labile DOC (DOC_L), semi-labile DOC (DOC_SL) and refractory DOC (DOC_R). To quantify the DOC remineralization rate constants (k) and half-life times (t_1/2) the first order kinetics was used. The total bioavailable fraction of pore water DOC (DOC_L+DOC_SL) amounted to 54%, while k and t_1/2 were 0.0958 d^-1 and 7.24 d for DOC_L and 0.0082 d^-1 and 84.53 d for DOC_SL, respectively.

This study shows that about half of sediment-derived DOC is bioavailable, which gives a new insight on the Baltic Sea carbon cycle and O­₂ consumption in deeper water layers.

How to cite: Lengier, M.: Bioavailability and remineralization of sediment-derived dissolved organic carbon from the Baltic Sea depositional area, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7533, https://doi.org/10.5194/egusphere-egu21-7533, 2021.

A regional coupled eco-hydrodynamic model of the Barents and Kara Seas based on the MITgcm has been developed. The biogeochemical module is based on a 7-component model of pelagic biogeochemistry including the ocean carbon cycle. This regional model allows revealing and explaining the main mechanisms of the interaction between marine dynamic and biogeochemical processes in the Barents and Kara Seas under a changing climate. We present the main results of simulations for the past (1975-2005) and future (2035-2065) climate.

A clear relationship between the marginal ice zone area and primary production has been obtained, proving the importance of this zone in the functioning of the marine ecosystem. The interannual variability of the integrated primary production and the total sea ice area demonstrates an antiphase behavior, which means that the reduced sea ice cover area in the previous winter is one of the main reasons for the increase in primary production in the current year.

The model simulations demonstrate that, of all the external factors, sea ice area plays a primary role in the formation of primary production: in the overwhelming majority of cases, the contribution of the ice area prevails, and the pattern "more ice - less primary production" and vice versa is fulfilled in the Barents and Kara Seas. The effect of a decrease of incoming short-wave radiation becomes significant only when a significant decrease of the ice area occurs.

Compared to the period 1975-2005, the simulated total primary production in the Barents and Kara Seas is much higher for the period 2035-2065, while the sea ice area significantly decreases.

A regression dependence has been obtained for the total annual primary production as a function of sea ice area and incoming short-wave radiation. Its validity is verified for both past (dependent) and future (independent) climatic periods. It justifies the use of such simple statistical model for quick estimates of the primary production in the Barents and Kara Seas.

Acknowledgements: The research was performed in the framework of the state assignment of the Ministry of Science and Higher Education of Russia (theme No. 0128-2021-0014). This work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID ba1206.

How to cite: Martyanov, S. D., Dvornikov, A. Y., Ryabchenko, V. A., and Sein, D. V.: Study of the sea ice impact on primary production in the Barents and Kara Seas in past and future climates, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3431, https://doi.org/10.5194/egusphere-egu21-3431, 2021.

Global warming is one of the most imminent challenges facing humanity in the 21^st century. It will not only have a profound effect on ecosystems but also on economies around the world. The shift in habitats of economically important marine species caused by rising seawater temperatures will bring challenges to the existing fishing industry, especially small fishing businesses. This research tries to build mathematical models to find out shifts in herring and mackerel resources in the Northeast Atlantic under global warming, and offer advice on how to deal with potential development challenges.

First, several models are designed to predict the change in seawater temperature over the next 50 years. We base our prediction model on the Coupled Model Intercomparison Project Phase 6 (CMIP6) and conduct a detailed analysis of different possible levels of seawater temperature increases caused by different carbon emissions levels. Then the lifecycles and migration behavior of herring and mackerel are researched and the influence of seawater temperature increases on their ecosystems is predicted and charted. The tendency of herring and mackerel populations going further offshore and northerly is obvious.

Second, after analyzing the migration of fish populations, we research the fishing industry in the region and deem it necessary for small fishing companies to make adjustments to their fishing methods. If global warming follows the relatively moderate economic development model, which is the most likely scenario, fish populations will too far away for small fishing companies to harvest near 2091. Our suggested strategy is that fishing vessels capable of operating without land-based support should be increased so that they can operate in waters further from the coast to maintain the harvest.

Finally, the models’ sensitivity is tested, and the results demonstrate the effectiveness and robustness of our modeling. This research provides insights into how small fishing companies should relocate themselves to optimize their business, in order to deal with long-term development challenges, and seize the opportunity in fishing under the effects of Global Warming.

How to cite: Zeng, Y.: Shifts in Herring and Mackerel Resources in the Northeast Atlantic under Global Warming, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-327, https://doi.org/10.5194/egusphere-egu21-327, 2020.

Restricted basins, such as the Baltic Sea, experience particularly large impact from ongoing global climate change, including severe oxygen depletion, intensified stratification and increased water temperatures. This results in significant and lasting ecosystem alterations. IODP Expedition 347 recovered sediment cores from the Baltic Sea which allow reconstructions of such changes in an as yet unprecedented quality and resolution. We analysed Holocene sediments from the Landsort Deep (IODP Site M0063) using a combined palynological and biogeochemical approach in order to reconstruct palaeoclimate and associated terrestrial and marine ecosystem changes as well as identify anthropogenic influence in the Baltic region. Pollen are used as proxy for terrestrial vegetation changes, including agricultural activity indicated by the presence of cereals. Comparison of pollen data with organic-walled dinoflagellate cysts and other palynomorphs such as the algal taxa Pediastrum, Botryococcus, and Radiosperma from identical samples provides a direct land-sea comparison. These analyses are complemented with the reconstruction of sea surface temperatures (TEX^L₈₆, LDI) and mean annual air temperatures (MBT^’_5Me) in the Baltic Sea region. For the late to middle Holocene (~8000 to ~4000 years BP), our data imply a strong brackish-marine influence which decreases around 4000 years BP. A gradually increasing proportion of long-chain n-alkanes around this time indicates a stronger terrestrial influence. Increasing percentages of spruce (Picea) point to the immigration of this taxon in the central Baltic region. Warmth-loving tree taxa such as hazel (Corylus) imply warm conditions between ~5000 and 4000 years BP but subsequently their pollen percentages are decreasing in general. Otherwise our data indicate only minor terrestrial ecosystem changes until ca. 1000 years BP. The past ca. 1000 years witnessed increased agricultural activity, indicated by higher abundances of rye (Secale) pollen, and probably anthropogenically induced deforestation. This increase is paired with high percentages of the enigmatic palynomorph Radiosperma corbiferum. During the past 500 years sea surface temperatures increased significantly, culminating in values comparable to the Holocene Climatic Optimum. Generally, the most rapid changes in the terrestrial ecosystems seem to have happened during the past millennium under anthropogenic influence.

How to cite: Kotthoff, U. and Bauersachs, T.: Reconstructing Holocene palaeoenvironmental conditions in the Baltic: Palynological and biogeochemical data from the Landsort Deep (IODP Expedition 347, Site M0063), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2974, https://doi.org/10.5194/egusphere-egu21-2974, 2021.

Magdalena's river basin represents a quarter of Colombia's surface, yet neighbouring ecosystems remain ignored while enduring unacceptable environmental conditions. At its outlet in the Caribbean Sea, several channels link it to Cienaga Grande de Santa Marta (CGSM), a deltaic coastal-lagoon ecosystem (4200 km²) from which around 15 to 20 % are water bodies. According to several studies, Magdalena River's overflows represent its primary freshwater source. However, the recorded discharge has gradually reduced, though the basin's rainfall shows a rising tendency. Additional discharge measurements close to the outlet evidenced that it was even lesser than records upstream counterintuitively. Consequently, the energy gradient from the river to the sea through the ecosystem is reversing more frequently. That has resulted in a continuous salinisation process of the lagoons, diminishment of the mangrove forest and lagoons extension, fauna migration and low water quality. This research aims to elaborate on the Magdalena River's outlet discharges vulnerabilities in Colombia, thus providing better insight into impact-based decision-making. 

Results suggest that the discharge regime responds to the El Niño Southern Oscillation (ENSO) phenomenon as it controls the country's dry/rain season. Further analysis indicates that a) low flows relate to El Niño periods and high flows to La Niña; b) the flow duration curve's slope is getting milder, meaning that high flows are decreasing whereas low flows are increasing; c) extreme discharges are getting smoother, and less disperse so that high and low flow peaks are within a smaller range; d) the dispersion diminishes radically during severe El Niño events, and e) although a priori the assumption is that the more severe El Niño events might bring lower discharge values, the minimum values recorded are more significant than in neutral ENSO conditions. 

Moreover, extreme discharge values during ENSO events, despite their severity, tended to have a horizontal asymptote that suggests human-driven control upstream, especially during El Niño periods. The Magdalena basin holds Colombia's hydropower network representing more than 70% of its electricity supply distributed in 33 operating plants. On the one hand, it is clear that during El Niño, the plants guarantee a minimum discharge downstream, as it is when the National Hydrometeorological Agency only considers drought protocols. However, during neutral ENSO conditions, the flows are not controlled and thus, impacts downstream arise. On the other hand, reservoirs have increased evaporation due to a large accumulated open water surface (611 km² in total). Results show that water loss represents 40% to 80% of the current average discharge at the outlet (7000 m³/s), adding to the ecosystem depletion. The results urge decision-makers to reconsider the drought protocols applying an impact-based approach.

How to cite: Gómez-Dueñas, S., Bateman, A., Santos, G., and Sosa, R.: Exploring natural and induced drivers in the Magdalena River discharge impacting the Ciénaga Grande de Santa Marta coastal-lagoon ecosystem, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15533, https://doi.org/10.5194/egusphere-egu21-15533, 2021.

The increasing storm frequency and strength due to climate change, coupled with human activities along the coast unbalance the coastal dynamics. A constant monitoring is necessary to better understand and mitigate the effect on Spanish coastal environments. Spain has around 8 000 Km of coastal areas along the Iberian Peninsula, the Balearic and Canary island. These coasts have a high coastal geomorphology variability, from rocky coasts with large estuaries on the Atlantic face in the northwest of the Iberian Penisula, to long sandy beaches with dunes systems and large wetlands in the southwest. On the Mediterranean coast, low rocky cliffs and sandy beaches with a wide variety of coastal infrastructures and deltas. Although in-situ measurements are highly efficient on capturing coastal parameters and features at a given time, the cost of continuous acquisition campaigns for the whole coast is dissuasive. Earth Observations provide wide spatial coverage over a large temporal scale allowing us to develop a methodology adapted to all coastal morphologies and dynamics to follow the impact of climate change and human activities on Spain’s top touristic attraction, it’s coasts.

Our developed methodology uses the instantaneous boundary between land and sea on satellite images extracted using an algorithm based on the Liu & Jezek methodology. The use of the Canny edge detection is improved by a local adaptive threshold applied on a band ratio image. NDVI, BNDVI, GNDVI or others are applied depending on coastal features and natures to extract with high precision the land/ sea interface. Is then applied to the obtained waterlines waves, slope and tide correction to obtain inter-comparable lines to build some time-series product at different time scale. The spatial scale of the changes due to coastal dynamics within the coastal environment is a challenge for change detection due to the shifts between earth observations. The application of a geo-location method helps with the spatial accuracy constraint and ensure an accurate change detection by monitoring real movements and therefore allow us to capture coastal change at different temporal and spatial scales.

How to cite: Beck, A.-L. and Martinez Sanchez, J.: Spanish coast resilience face to storm and beach renourishment monitored from space. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14506, https://doi.org/10.5194/egusphere-egu21-14506, 2021.

The sedimentological and geochemical evolution of the internal platform located in front of the Llumeres cove (Asturias, North of Spain) has been studied, based on the analysis of selected sediment samples from 5 long corers, approximately 2 m thick, recovered for an offshore structures installation project. In each sample, a granulometric characterization has been carried out by the calculation of granulometric parameters (centile, mean, shorting, etc.) and the mineralogical composition (silica/biogenic carbonates). Geochemical analysis has also been made in the samples.  The enrichment of selected heavy metals and metalloids (Zn, As, Cu, Pb and Hg) has been studied, applying the Geo-accumulation Index (Igeo) and the Enrichment Factor (EF). The results have also been subjected to multivariate and bivariate statistical analyzes that have allowed establishing the relationships between the elements and determining in a preliminary way their potential origin.

The sedimentological results point to the fact that the sediment was incorporated into the internal platform during the last stages of the sea level rise, which began some 20,000 years ago (Pleisto-Holocene transgression). At present, the zone enjoys stability, since no sedimentation is detected. These sediments are relict, without existing agreement with the siliciclastic sedimentation that is taking place at the moment in the coastal zone (Llumeres beach). Three main sandy lithologies have been analyzed: siliciclastic, mixed and carbonate sands which are distributed irregularly in the vertical. This is indicative of changes in the origin of the sediment (siliciclastic, due to the coastal drift current and bioclastic, typical from the platform), as well as the energy of the depositional agent with a clear decrease in size towards the top, detecting relatively large variations in size and the coarse sediments would correspond to moments of storm.

The geochemical results show that the area does not have a remarkable anthropic condition along the sedimentological profile. However, enrichment of some potential contaminants was detected in the more recent sediments (first centimeters of the boreholes), but the enrichment does not appear to pose an environmental risk and their origin seem to be related to nearby areas such as the Nalón River or the industrial area of Aviles that may export contaminants to the marine environment.

How to cite: Flor-Blanco, G., García-Ordiales, E., Ruiz-Quesada, R., Pando, L., and Flor, G.: Sedimentological and environmental approach of the Llumeres offshore sediments (N Asturias-N Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9518, https://doi.org/10.5194/egusphere-egu21-9518, 2021.

Coastal wetlands are dynamic environments prone to climatic and anthropogenic forcing and ideal settings to study past climatic and environmental changes.  In the eastern Mediterranean region and particularly in Greece, the climate presents high spatiotemporal diversity, while human activity is a significant factor in shaping the landscape. This study presents a sediment record from Klisova lagoon, situated in central Greece, at the eastern part of Messolonghi lagoon complex. The area is recorded from antiquity to have great anthropogenic activity. The paleoenvironmental synthesis was based on standard sedimentological analysis (grain size, TOC, magnetic susceptibility), joint micropaleontological and palynological analysis, X-ray Fluorescence scanning, and radiocarbon dating. The Bayesian age-depth model is based on radiocarbon dating and yields an age of 4700 cal BP for the base of the recovered sediment sequence. For the last 4700 years, the freshwater influx, the progradation of the Evinos river delta and related geomorphological changes control the environmental conditions (e.g. depth and salinity) in the lagoon system. Prior to 4000 cal BP, a relatively shallow water depth, significant terrestrial/freshwater input and increased weathering in the lagoon area are inferred. Elemental proxies and increased dinoflagellate and foraminifera abundances, which indicate marine conditions with prominent freshwater influxes, point to the gradual deepening of the lagoon recorded at the drilling site up to 2000 cal BP. The marine and freshwater conditions equilibrium sets at 1300 cal BP, and the lagoonal system seems to reach its present state. Maxima of anthropogenic pollen indicators during the Mycenaean (~3200 cal BP), Hellenistic (~ 2200 cal BP) and Late Byzantine (~ 800 cal BP) periods suggest intervals of increased anthropogenic activities in the study area.  

How to cite: Emmanouilidis, A., Panagiotopoulos, K., Kouli, K., and Avramidis, P.: Middle-to late Holocene environmental changes based on a multi-proxy lagoonal record, Klisova lagoon, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14754, https://doi.org/10.5194/egusphere-egu21-14754, 2021.

Over a billion people currently live in coastal areas, and coastal urbanization is rapidly growing worldwide. Here, we explore the impact of an extreme and rapid coastal urbanization on near-surface climatic variables, based on MODIS data, Landsat and some in-situ observations. We study Dubai, one of the fastest growing cities in the world over the last two decades. Dubai's urbanization centers along its coastline – in land, massive skyscrapers and infrastructure have been built, while in sea, just nearby, unique artificial islands have been constructed.

Studying the coastline during the years of intense urbanization (2001-2014), we show that the coastline exhibits surface urban heat island characteristics, where the urban center experiences higher temperatures, by as much as 2.0°C and more, compared to the adjacent less urbanized zones. During development, the coastal surface urban heat island has nearly doubled its size, expanding towards the newly developed areas. This newly developed zone also exhibited the largest temperature trend along the coast, exceeding 0.1°C/year on average.

Overall, we found that over land, temperature increases go along with albedo decreases, while in sea, surface temperature decreases and albedo increases were observed particularly over the artificial islands. These trends in land and sea temperatures affect the land-sea temperature gradient which influences the breeze intensity. The above findings, along with the increasing relative humidity shown, directly affect the local population and ecosystem and add additional burden to this area, which is already considered as one of the warmest in the world and a climate change 'hot spot'.

References:

E. Elhacham and P. Alpert, "Impact of coastline-intensive anthropogenic activities on the atmosphere from moderate resolution imaging spectroradiometer (MODIS) data in Dubai (2001–2014)", Earth’s Future, 4, 2016. https://doi.org/10.1002/2015EF000325

E. Elhacham and P. Alpert, "Temperature patterns along an arid coastline experiencing extreme and rapid urbanization, case study: Dubai", submitted.

How to cite: Elhacham, E. and Alpert, P.: Effects of Dubai coastline extreme urbanization in land and sea on local near-surface climate variables patterns, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6348, https://doi.org/10.5194/egusphere-egu21-6348, 2021.

Sustainable development of the aquaculture industry depends on wise coastal zone management.  Aquaculture in Norway is typically found in small, rural municipalities that may lack expertise in marine ecology. In the project “Precise coastal zone planning with focus on aquaculture” we combine marine maps with in situ data and model results to produce a management tool for easier and more efficent aquaculture planning.

Our study area comprises five municipalities in Western Norway and includes both fjords and open coast. High resolution marine maps exist for the area. We also have access to environmental assessments from aquaculture sites, sediment samples for Total Organic Carbon (TOC), and current velocity time series from oceanographic moorings. We will compare the in situ data with output from two current models (Sinmod and NorKyst-800). The data will be used to produce thematic maps of key characteristics, mainly current and organic carbon content, to help administrators identify areas suitable for different types of aquaculture.

Here, we present results from in situ measurements that will provide the current velocity input to the thematic maps. Data from seven oceanographic moorings placed in the fjord system show the current variability on time scales from hours to years. In addition we have done four 1-month deployments of a current profiler on sites selected to improve the geographical data coverage. We show preliminary results and discuss the challenges in simplifying variable current fields in an area with complex geography into an overall map.

How to cite: Ullgren, J. and Stene, A.: Combining current velocity data from different sources as input to coastal zone management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15481, https://doi.org/10.5194/egusphere-egu21-15481, 2021.

Asia is the world’s most important region for aquaculture and generates almost 90 percent of the total production. The farming of fish and shrimp in land-based aquaculture systems expanded mainly along the shorelines of South Asia, Southeast Asia, and East Asia, and is a primary protein source for millions of people. The production of fish and shrimp in freshwater and brackish water ponds in coastal regions of Asia has increased rapidly since the 1990s due to the rising demand for protein-rich foods from a growing (world) population. The aquaculture sector generates income, employment and contributes to food security, has become a billion-dollar industry with high socio-economic value, but has also led to severe environmental degradation. In this regard, geospatial information on aquaculture can support the management of this growing food sector for the sustainable development of coastal ecosystems, resources and human health.

With free and open access to the rapidly growing volume of data from the European Sentinel satellites as well as using machine learning algorithms and cloud computing services, we extracted coastal aquaculture at a continental-scale. We present a multi-sensor approach which utilizes Earth Observation time series data for the mapping of pond aquaculture within the entire Asian coastal zone, defined as a buffer of 200km from the coastline. In this research, we developed an object-based framework to detect and extract aquaculture at single pond level based on temporal features derived from high spatial resolution SAR and optical satellite acquired from the Sentinel-1 and Sentinel-2 satellites. In a second step, we performed spatial and statistical data analyses of the Earth observation derived aquaculture dataset to investigate spatial distribution and to identify production hotspots in various administrative units at regional, national, and sub-national scale.

How to cite: Ottinger, M., Bachofer, F., and Huth, J.: Mapping pond aquaculture for the entire coastal zone of Asia using high resolution Sentinel-1 and Sentinel-2 data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16024, https://doi.org/10.5194/egusphere-egu21-16024, 2021.

Atlantic salmon swim upstream from the North sea through Frierfjorden to spawn in the Skien watershed, the third largest in Norway. There are two hydroelectric power plants in the lower reaches of the Skienselva: Klosterfoss and Skotfoss. Salmon caught swimming up the fish ladder at the downstream power plant (Klosterfoss) were tagged, released, and at the downstream power plant tracked from the beginning of the upstream migration to the end of the spawning period in the entire anadromous watershed. Salmon spent unequal amounts of time at the four spawning areas in the main river and a tributary between Klosterfoss and Skotfoss. Salmon spent less time at the larger spawning site, Vadrette, compared to the smaller Fossum and Grøtsund spawning sites. 26% of tagged salmon which swam upstream to the Skotfoss hydroelectric power plant ascended the fish ladder. Further, 16% of all salmon ascended the fish ladder at Skotfoss and continued to upstream spawning sites, indicating that they were homing to sites in the upper watershed. This is much smaller than the what is expected based on the fry populations in the rivers of the Skien watershed, which are augmented by yearly stocking in some of the rivers. Salmon which ascended the Klosterfoss ladder relatively early, swam upstream to Skotfoss more quickly than salmon that arrived relatively late at the Klosterfoss ladder. Short and repeated movements upstream to Skotfoss, and downstream to areas in the Farelva, and back again to Skotfoss were observed in the majority of tagged salmon that approached Skotfoss. The “yo-yo” migration of salmon in the Farelva is for the most part unexplained, but the movement costs the salmon valuable energy before and during the spawning season and may have negative consequences. Overall, these results indicate that salmon find the entrance to the fish ladder and do not remain stuck at the tunnel outlet, but most do not successfully ascend it. This could be the result of poor ladder construction, too low flow from the ladder, low survival of fry from upstream of Skotfoss reducing the number of salmon that are homing to upstream spawning areas, or that not all salmon which approach Skotfoss are homing to areas above the ladder. The possibility exists that salmon which will eventually spawn in areas downstream of the ladder engage in searching behavior near the fish ladder. If efforts to restore the populations in the upper watershed are to continue, issues salmon have with ascending the Skotfoss fish ladder must be addressed first.

How to cite: Schwert, S.: Adult Atlantic salmon (Salmo salar) spawning migration and behaviour in the lower Skienselva, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10384, https://doi.org/10.5194/egusphere-egu21-10384, 2021.

The “German Strategy for Adaption to Climate Change” (DAS) is the political framework to climate change adaption in Germany. The newly established DAS basic service “Climate and Water” will provide monitoring and projection data to evaluate requirements for climate change adaption. Various products covering the German water bodies (coastal and inland) and its response to climate change will be generated and frequently updated by a cooperation of four German federal agencies. The products will be tailored to a variety of stakeholders needs.

Within this framework, the Federal Maritime and Hydrographic Agency (BSH) will provide products based on an ensemble of climate projections for the German coast which will be created in cooperation with different research institutes and authorities, e.g. the Danish Meteorological Institute (DMI).

Data from a DMI climate projection run based on the HIROMB-BOOS model (HBM) with a meteorological forcing from DMI-HIRHAM5 (one of the RCMs in EURO-CORDEX ensemble) and for the RCP 8.5 scenarios has been analysed in view of different oceanographic parameters such as sea level, sea surface temperature, salinity, currents and ice. This data set includes the historical periods 1981-2010 and the RCP 8.5 periods 2041-2070 and 2071-2100. Therefore, it provides an expedient basis to develop prototype products regarding climate change adaption at the German coasts for customers of the DAS basic service “Climate and Water”. The initial prototype products are presented and discussed in regards to the sufficiency to evaluate requirements for climate change adaption.

How to cite: Ehlers, B.-M., Janssen, F., and Su, J.: Prototype products for climate change adaption in German coastal regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11993, https://doi.org/10.5194/egusphere-egu21-11993, 2021.

In a series of ad-hoc surveys, students and young scholars from various institutions in the Baltic Sea region are asked about their perceptions about the reality and seriousness of climate change, and how these compare to other pressures on the Baltic Sea. The same questionnaire, albeit adopted to the different nationalities, have been run in Sweden, Denmark, Poland and Germany, among students with different backgrounds, such as oceanography, geography, environmental sciences and chemistry. The surveys were done in 2019, 2020 and 2021. While the individual surveys at the different institutes can not be considered representative, the ensemble of the so far 7 surveys provides a consistent summary of what is common understanding, and which issues may be considered less uniformly.

Climate, eutrophication and disposal of waste are listed most often as serious issues, while overfishing and tourism less often, and the construction of bridges and pipelines are least often chosen as serious issue. Climate issues are mostly not considered a scientific issue but a public/political issue, and climate science is mostly tasked with “motivate people to act on climate change” or “determine solutions to climate change” but less so with “define the climate problems and attribute cause of climate change”.

How to cite: von Storch, H.: Perceptions among students and young scholars of drivers endangering the Baltic Sea., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-814, https://doi.org/10.5194/egusphere-egu21-814, 2021.