100 years of atmospheric and marine observations at the Finnish Utö Island in the Baltic Sea

Abstract

Abstract. The Utö Atmospheric and Marine Research Station introduced in this paper is located on Utö Island (59 • 46.84 N, 21 • 22.13 E) at the outer edge of the Archipelago Sea, by the Baltic Sea towards the Baltic Proper. Meteorological observations at the island started in 1881 and vertical profiling of seawater temperature and salinity in 1900. Since 1980, the number of observations at Utö has rapidly increased, with a large number of new meteorological, air quality, aerosol, optical and greenhouse gas parameters, and recently, a variety of marine observations. In this study, we analyze long-term changes of atmospheric temperature, cloudiness, sea salinity, temperature and ice cover. Our main dataset consists of 248 367 atmospheric temperature observations, 1632 quality-assured vertical seawater temperature and salinity profiles and 8565 ice maps, partly digitized for this project. We also use North Atlantic Oscillation (NAO), major Baltic inflow (MBI) and Baltic Sea river runoff data from the literature as reference variables to our data. Our analysis is based on a statistical method utilizing a dynamic linear model. The results show an increase in the atmospheric temperature at Utö, but the increase is significantly smaller than on land areas and has taken place only since the early 1980s, with a rate of 0.4 • C decade −1 during the last 35 years. We also see an increase in seawater temperatures, especially on the surface, with an increase of 0.3 • C decade −1 for the last 100 years. In deeper water layers, the increase is smaller and influenced by vertical mixing, which is modulated by inflow of saline water from the North Sea and freshwater inflow from rivers and by wind-driven processes influenced by the local bathymetry. The date when air temperature in the spring exceeds +5 • C became 5 days earlier from the period 1951-1980 to the period 1981-2010 and the date when sea surface water temperature exceeds +4 • C changed to 9 days earlier. Sea ice cover duration at Utö shows a decrease of approximately 50 % during the last 35 years. Based on the combined results, it is possible that the climate at Utö has changed into a new phase, in which the sea ice no longer reduces the local temperature increase caused by the global warming.

Measuring turbulent CO<sub>2</sub> fluxes with a closed-path gas analyzer in a marine environment

“…The Baltic Sea forms a large and diverse biogeochemical system, providing a great potential for studying interactions between the marine ecosystem and the aquatic carbonate system. However, only a few fixed measurement sites measuring sea-air CO 2 fluxes are located in the Baltic Sea (Rutgersson et al, 2008;Lammert and Ament, 2015). A micrometeorological tower placed on the shore of an island offers a costeffective alternative to ship measurements, as maintenance and installations are more feasible.…”

Toward a European Coastal Observing Network to Provide Better Answers to Science and to Societal Challenges; The JERICO Research Infrastructure

“…Initiated in 2010, the JERICO-FP7 project was the first Europe-wide effort toward the harmonization and coordination (Petihakis et al, 2015) of major coastal observing platforms including FerryBoxes, gliders, and fixed platforms (Ostrowski et al, 2016;Baschek et al, 2017;Laakso et al, 2018;Petihakis et al, 2018). (Table 1: exemple of regional infrastructure) Key physical and biogeochemical (e.g., oxygen and pCO 2 ) parameters were considered for harmonization, while emerging technologies such as Sediment Profiler Imagery and time-laps cameras were assessed.…”

Evaluating Strong Currents at a Fairway in the Finnish Archipelago Sea

“…Also, a longer period (1961-2016) of wind measurements from Utö was used with three-hour intervals to evaluate the occurrence and directionality of strong wind events. Further information on this 56-year dataset reader is referred to in Laakso et al [5].…”

“…This is the period from which there are synoptic observations available at three-hour intervals. We chose Utö data for this analysis as it has longer temporal coverage than Isokari and has been earlier used in oceanographic studies by e.g., [5,22]. While contemplating the following results, one should note that Utö is not the most representative station for winds from the northerly sector, and the directional distribution measured there differs from actual winds experienced in northern parts of the Archipelago Sea.…”

“…In order to receive real-time data from moored current measurements, such as Acoustic Doppler Current Profiler (ADCP), a cable is needed, and this is typically possible only close to the shoreline. One example of such a mooring in the Archipelago Sea area is the ADCP at the Utö Atmospheric and Marine research station [5]. Also, there are some real-time oceanographic buoys and stations elsewhere in the Baltic Sea that include current measurements, such as the Huvudskär Ost and FINO2 (www.fino2.de) stations.…”