Description: Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3 project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.

Description: The Atmosphere Flagship programme addresses various topics, including analyses of long term meteorological observations, the interaction between the surface and the atmospheric boundary layer, the composition of the atmosphere with respect to climate active trace substances like aerosols or green house gases, as well as pollutants, the role of clouds in the Arctic atmosphere, interactions of the atmosphere with the snow covered ground, land-fast and drifting sea ice, surface UV spectral fluxes and its dependency on specific conditions in the stratosphere (ozone) as well as troposphere (clouds). Recently, the role of biogenic aerosols and the observation of black carbon in snow and atmosphere received particular attention. Within the Ny-Aalesund Atmosphere Flagship, we particularly highlight the connections to observations at Barentsburg, Pyramiden, and Hornsund, as well as the pan Svalbard meteorological network.

Description: This book contributes to the current discussion on global environmental changes by discussing modifications in marine ecosystems related to global climate changes. In marine ecosystems, rising atmospheric CO2 and climate changes are associated with shifts in temperature, circulation, stratification, nutrient input, oxygen concentration and ocean acidification, which have significant biological effects on a regional and global scale. Knowing how these changes affect the distribution and abundance of plankton in the ocean currents is crucial to our understanding of how climate change impacts the marine environment. Ocean temperatures, weather and climatic changes greatly influence the amount and location of nutrients in the water column. If temperatures and currents change, the plankton production cycle may not coincide with the reproduction cycle of fish. The above changes are closely related to the changes in radiative forcing, which initiate feedback mechanisms like changes in surface temperature, circulation, and atmospheric chemistry.

Description: Svalbard Integrated Arctic Earth Observing System (SIOS) is an international consortium for developing and maintaining a regional observing system in Svalbard and the associated waters. SIOS brings together the existing infrastructure and data from its members into a multidisciplinary network dedicated to answering Earth System Science (ESS) questions related to global change. The Observing System is built around “SIOS Core Data” – long-term data series collected by SIOS partners. SIOS Core Data (SCD) are data that fulfil the following defined criteria: to be relevant for answering key Earth System Science questions (scientific requirements), to be available according to the FAIR principles (data availability), to be secured by members for more than 5 years (member commitment). The first set of SIOS core data variables has been identified by The Science Optimisation Advisory Group (SOAG) in cooperation with the Research Infrastructure Coordination Committee (RICC) and scientific experts. Many (but not all) SIOS core data variables are selected or derived from the Essential Climate Variables (ECVs) defined by The Global Climate Observing System (GCOS), and are described by WMO standards and the Global Change Master Directory (GCMD) Keywords. SIOS core data variables are critical for characterising the climate system and its changes in the Arctic, and answering the ESS science questions outlined in the SIOS Infrastructure Optimization Report. SIOS activities related to SCD are in line with SAON's Roadmap for Arctic Observing and Data Systems process as well as the new EC ArcticPASSION project and the idea of a set of Arctic Shared Variables.

Description: The Arctic region is considered to be most sensitive to climate change, with warming in the Arctic occurring considerably faster than the global average due to several positive feedback mechanisms contributing to the “Arctic amplification”. Also the maritime and mountainous climate of Svalbard has undergone changes during the last decades. Here, the focus is set on the current atmospheric boundary conditions for the marine ecosystem in the Kongsfjorden area, discussed in the frame of long-term climatic observations in the larger regional and hemispheric context. During the last century, a general warming is found with temperature increases and precipitation changes varying in strength. During the last decades, a strong seasonality of the warming is observed in the Kongsfjorden area, with the strongest temperature increase occurring during the winter season. The winter warming is related to observed changes in the net longwave radiation. Moreover, changes in the net shortwave are observed during the summer period, attributed to the decrease in reflected radiation caused by the retreating snow cover. Another related aspect of radiation is the intensity of solar ultra-violet radiation that is closely coupled to the abundance of ozone in the column of air overhead. The long term evolution of ozone losses in the Arctic and their connection to climate change are discussed.