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The measurement site is about 4 km from the eastern coast of Gotland located on Östergarnsholm which is a small, flat island which stretches about 2 km in a W-E and N-S direction respectively. The maximum depth of the sea within 1 km radius is about 30 m. The station location in WGS84 coordinates (Latitude, Longitude) are:

30 m tower: 57.43010 N, 18.98415 E
SAMI and Seabird sensor: 57.42333 N, 18.99450 E
Wave buoy (operated by FMI): 57.41667 N, 19.05333 E



On the island Östergarnsholm located about 2 nautical miles off the east coast of Gotland a 30 m micrometeorological tower was established in 1995 on the most southern tip of the island.  The measurement station consists of anemometers, temperature and humidity sensors as well as instrumentation for measuring gas exchange of carbon dioxide and other scalars between the sea and the atmosphere.

blue arrowMaps and images


Staff and Contact

  • Ocean station PI: Anna Rutgersson
  • research engineers: Erik Nilsson; Leonie Esters

contact: ostergarnsholm@icos-sweden.se


Anna Rutgersson
PI Anna Rutgersson
Erik Nilsson
Erik Nilsson
Leonie Esters



ICOS Östergarnsholm welcomes individual researchers and research groups to come to our measurement site and use existing infrastructure for their own measurements and collaborations.

blue arrowFacilities



Östergarnsholm is a small, flat island which stretches about 2 km in the W-E and N-S direction respectively. The southern part is very flat and rises only a few meters above sea surface.

The island is small and flat covered by small rocks and pebbles. The vegetation on the island consists of a few single trees (mainly in the N-E corner) as well as low herbs and grass together with small bushes.



With a mean annual air temperature of 7°C and a mean annual precipitation of 383 mm (data period 1961-1990, SMHI station Östergarnsholm) the climate is characterized after Köppen as a Cfb-climate, i.e. humid temperate with mild summers and mild winters.

The cold water in spring and summer gives dominantly stable atmospheric stratification during April to July. Despite low winter temperatures, the sea surrounding Östergarnsholm has ice free conditions throughout the year. Higher rates of cyclonic activity in winter result generally in higher wind speeds in winter than in summer.

The carbon cycle represented by the Östergarnsholm site shows a strong seasonal variation with marine carbon uptake from April to October, and emissions from November to March. Algae blooms with resulting biofouling on water-side sensor is fairly common in summer time.



Atmospheric measurements on the site includes 3D wind speed with sonic anemometers, eddy covariance measurements of CO2, H20 and heat fluxes. There is a gradient system for CO2 and H20 at the site and propeller anemometers and thermocouples in the 30 m tower. Relative humidity, atmospheric pressure, global radiation and precipitation is also measured on the site. During different time periods other parameters have also been observed such as methane, oxygen and clouds.

Water-side measurements are taken using several different sensors semi-continously during active deployment periods. These measurements include sea surface temperature and profile measurements of temperature and conductivity (measured as proxy for salinity) at depth ranging from about 0.5 to 20 m. Also measured are carbon dioxide (pCO2), oxygen, pH, Chlorphyll, Turbidity and fDOM as well as wave parameters in collaboration with Finnish Meteorological Institute (FMI). Discrete manual water side measurements and sampling include Phosphorous (TP, PO4), Nitrogen (TNm, NH4, NO3+NO2) and Silica (DSi).

 30 m tall tower is situated around 1 m above sea level on the southernmost tip of the small flat island Östergarnsholm. Two buoys are located 1 km (SAMI sensor) and 4 km (Wave rider buoy) southeast of the tower, respectively.

blue arrowMeasurements

Tower Oestergarnsholm
measurement towers on Östergarnsholm
map over installations on Östergarnsholm


areial image Oestergarnsholm
aerial view over Östergarnsholm


eddy covariance and profile tower