Description: During polar spring, ozone depletion events (ODEs) are often observed in combination with bromine explosion events (BEEs) in Ny-Ålesund. In this study, two long-term ozone data sets (2010–2021) from ozonesonde launches and in situ ozone measurements have been evaluated between March and May of each year to study ODEs in Ny-Ålesund. Ozone concentrations below 15 ppb were marked as ODEs. We applied a composite analysis to evaluate tropospheric BrO retrieved from satellite data and the prevailing meteorological conditions during these events. During ODEs, both data sets show a blocking situation with a low-pressure anomaly over the Barents Sea and anomalously high pressure in the Icelandic Low area, leading to transport of cold polar air from the north to Ny-Ålesund with negative temperature and positive BrO anomalies found around Svalbard. In addition, a higher wind speed and a higher, less stable boundary layer are noticed, supporting the assumption that ODEs often occur in combination with polar cyclones. Applying a 20 ppb ozone threshold value to tag ODEs resulted in only a slight attenuation of the BrO and meteorological anomalies compared to the 15 ppb threshold. Monthly analysis showed that BrO and meteorological anomalies are weakening from March to May. Therefore, ODEs associated with low-pressure systems, high wind speeds, and blowing snow more likely occur in early spring, while ODEs associated with low wind speed and stable boundary layer meteorological conditions seem to occur more often in late spring. Annual evaluations showed similar weather patterns for several years, matching the overall result of the composite analysis. However, some years show different meteorological patterns deviating from the results of the mean analysis. Finally, an ODE case study from the beginning of April 2020 in Ny-Ålesund is presented, where ozone was depleted for 2 consecutive days in combination with increased BrO values. The meteorological conditions are representative of the results of the composite analysis. A low-pressure system arrived from the northeast to Svalbard, resulting in high wind speeds with blowing snow and transport of cold polar air from the north.

Description: The transit of RV SONNE from Las Palmas (departure: 11.12.2021) to Guayaquil, Ecuador (arrival: 11.01.2022) is directly related to the international collaborative project SO287-CONNECT of GEOMAR in cooperation with Hereon and the University of Bremen, supported by the German Federal Ministry of Education and Research (BMBF) between October 15 2021 and January 15 2024. The research expedition was conducted to decipher the coupling of biogeochemical and ecological processes and their influence on atmospheric chemistry along the transport pathway of water from the upwelling zones off Africa into the Sargasso Sea and further to the Caribbean and the equatorial Pacific. Nutrient-rich water rises from the deep and promotes the growth of plant and animal microorganisms, and fish at the ocean surface off West Africa. The North Equatorial Current water carries the water from the upwelling, which contains large amounts of organic material across the Atlantic to the Caribbean, supporting bacterial activity along the way. But how the nutritious remnants of algae and other substances are processed on their long journey, biochemically transformed, decomposed into nutrients and respired to carbon dioxide, has so far only been partially investigated. Air, seawater and particles were sampled in order to provide new details about the large cycles of carbon and nitrogen, but also of many other elements such as oxygen, iodine, bromine and sulfur. Inorganic and organic bromine and iodine compounds are generally emitted naturally from the ocean into the atmosphere, promote cloud formation and affect climate, and some even reach the stratosphere where they contribute to ozone depletion. We measured how much of these compounds are released from the ocean, and at what locations and how they are transformed in the ocean and in the atmosphere. Sargassum algae, which have become a nuisance on beaches in the western and eastern Atlantic, support life and contribute to carbon cycling in the middle of the Atlantic, the Sargasso Sea and in the Caribbean, while their contribution to halogen cycling and marine bromine and iodine emissions was previously unknown. We investigated the influence of various natural parameters such as temperature and solar radiation on the biogeochemical transformation processes in order to understand the influence of climate change on these processes in incubation experiments with seawater and algae. We investigated how anthropogenic signals such as shipping traffic influence the nitrogen and sulphur cycle in the ocean, as well as the impact of nitrogen oxides from ship exhaust and sulphurous, acidic and dirty water from purification systems on organisms and biochemical processes. Plastic debris was sampled from the surface waters to investigate its contribution to global biogeochemical transformation processes. The working hypotheses of the research program were:  Bioavailability of dissolved organic carbon in surface waters decreases along the productivity gradient and transport pathway from the Eastern to the Western Tropical North Atlantic.  Nutrient gradients from East to West constrain the microbial utilization of organic matter- contributing to an accumulation of C-rich organic matter due to a) limited mineralization and b) enhanced exudation- also leading to gel-like particles accumulation in the western tropical North Atlantic and Sargasso Sea.  Tropospheric and stratospheric ozone are strongly impacted by biogeochemical and ecological processes occurring around and in the NA gyre system related to marine iodine and bromine cycles.  The long-range transport of natural and anthropogenic organic matter in water and of gases and aerosols in the air impact carbon-export, biogeochemical cycles in the water column, and the release of gases and particles from the ocean significantly. 4 SONNE -Berichte, SO287, Las Palmas - Guayaquil, 11.12.2021 - 11.01.202 The data and samples obtained specifically target carbon, nutrient and halogen cycling, the composition of phytoplankton, bacteria, the transport and sequestration of macro algae and the air-sea exchange processes of climate relevant gases and aerosols. The influence of ecological and transport processes, as well as anthropogenic impacts on the North Atlantic gyre system, specifically in the Sargasso Sea and the influence of ship emissions throughout the Atlantic towards the west and into the Pacific will be investigated with the data.