Beschreibung: The AL561 cruise was conducted in the framework of the project APOC (“Anthropogenic impacts on Particulate Organic Carbon cycling in the North Sea”). This collaborative project between GEOMAR, AWI, HEREON, UHH, and BUND is to understand how particulate organic carbon (POC) cycling contributes to carbon sequestration in the North Sea and how this ecosystem service is compromised and interlinked with global change and a range of human pressures include fisheries (pelagic fisheries, bottom trawling), resource extraction (sand mining), sediment management (dredging and disposal of dredged sediments) and eutrophication. The main aim of the sampling activity during AL561 cruise was to recover undisturbed sediment from high accumulation sites in the Skagerrak/Kattegat and to subsample sediment/porewater at high resolution in order to investigate sedimentation transport processes, origin of sediment/POC and mineralization processes over the last 100- 200 years. Moreover, the actual processes of sedimentation and POC degradation in the water column and benthic layer will be addressed by sampling with CTD and Lander devices. In total 9 hydroacoustic surveys (59 profiles), 4 Gravity Corer, 7 Multicorer, 3 Lander and 4 CTD stations were successfully conducted during the AL561 cruise.

Beschreibung: The ASTRA-OMZ SO243 cruise on board the R/V Sonne took place between the 5th and 22nd October 2015 from Guayaquil, Ecuador to Antofagasta, Chile. Scientists from Germany, the U.S.A, and Norway participated, spanning chemical, biological, and physical oceanography, as well as atmospheric science. The main goal of the cruise was to determine the impact of low oxygen conditions on trace element cycling and distributions, as well as to determine how air-sea exchange of trace elements is influenced by high productivity conditions. The subsequent impact of trace element ocean-atmosphere exchange on atmospheric chemistry and climate will be determined. A summary of the main preliminary results is below: - a strong source of nitrous oxide (N2O) and carbon dioxide (CO2) was detected from surface waters in the Peruvian upwelling, particularly in the near-coastal area between 9°S and 18°S - generally, surface N2O during the SO-243 cruise was lower than previously observed, probably due to the reduced extent of upwelling events because of El Niño conditions - less dimethyl sulphide (DMS) (〈 2nmol L-1) and isoprene (at 20-30 pmol L-1) than on board previous cruises in the coastal upwelling region (8°-12°S) were detected, likely due to suppressed upwelling off of Peru because of the El Niño conditions - a strong source for atmospheric carbonyl sulphide (OCS) was observed, as well as a strong correlation with oxygen. OCS decreased below the detection limit in oxygen depleted zones. - a strong contrast between normal and El Niño conditions were detected for the halocarbon compounds. Both surface and deeper water was characterized by much larger concentrations of bromocarbons than of iodocarbons during ASTRA-OMZ, which stands in contrast to the previous M91 cruise during neutral conditions. - it appears that the direct flux eddy covariance method was successful for sea-to-air flux measurements of N2O (for the first time) - a pronounced atmospheric inversion layer at approximately 1 km altitude was striking, which was accompanied by an accumulation of high relative humidity and moderate to fresh southerly winds below this inversion. Convective activity was limited and very few precipitation events were detected. Tropospheric ozone levels reveal distinct fluctuations within 9.5°S and 16.5°S latitude. - the oxygen distribution measured at about 9°S showed that the upwelling in October 2015 was very weak. Low oxygen water with less than 5 μmol kg-1 was located only below 250 m in October 2015 - higher oxygen distribution in 2015, as well as the changes in water temperature, salinity and density indicate the influence of El Niño. We have already published our first paper related to El Niño during SO243 (Stramma et al. 2016).