Utö is one of the main observing sites of FMI. The Island can be reached 4 times a week by free public transport and has a hotel with conference facilities. Marine observations are mainly scientistsoperated, with strong support from FMI observing services unit. Infrastructure includes the following observations: • Surface waves and temperature; currents (-23 m … -0.5 m); temperature, salinity, turbidity, chlorophyll, O2 (-5 m); Ice cover; pCO2; sea-atmosphere CO2-flux; • Temperature, salinity, O2, nutrient profiles (-80 m…0 m) during open sea period only; • A continuous water flow from the sea (possible to install new instruments utilizing ~ 5 lpm sea water/instrument) • Atmospheric CO2- and CH4-concentrations; Meteorology: wind speed and direction, temperature, PAR, diffuse and global radiation, weather camera; atmospheric trace gases; physical, chemical and optical properties of aerosol particles.

The Utö Atmospheric and Marine Research Station of Finnish Meteorological Institute is located on Utö Island (59º 46’50N, 21º 22’23E) at the outer edge of the Archipelago Sea, Baltic Sea. Utö site specific open data is available at http://swell.fmi.fi/Uto/latest.html. Operational meteorological and marine observations, and model data produced at FMI is available through open data portal (https://en.ilmatieteenlaitos.fi/open-data).