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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2017-105
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
25 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
One hundred years of atmospheric and marine observations at Utö Island, the Baltic Sea
Lauri Laakso1,2, Santtu Mikkonen3, Achim Drebs1, Anu Karjalainen1, Pentti Pirinen1, and Pekka Alenius1 1Finnish Meteorological Institute, Erik Palménin aukio 1, FI-00560 Helsinki, Finland
2North-West University, Unit for Environmental Sciences and Management, Potchefstroom, South Africa
3University of Eastern Finland, Kuopio, Finland
Abstract. Utö Atmospheric and Marine Research Station is located on Utö Island (59°46’50 N, 21°22’23 E) at the outer edge of the Archipelago Sea, Baltic Sea towards the Baltic Sea Proper. Meteorological observations at the island started in 1881 and vertical profiling of sea water temperature and salinity in 1900. In this study, we analyze long-term changes of atmospheric temperature, cloudiness and 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) and Major Baltic Inflow (MBI) data from the literature as reference variables to our data. Our analysis is based on statistical method utilizing 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 takes place only since early 1980's, with a rate of 0.4 °C/decade during the last 35 years. We also see an increase on sea water temperatures, especially on the surface, with an increase of 0.3 °C/decade 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 fresh water inflow. Date when air temperature in the spring exceeds +5 °C has become 5 days earlier from the period 1951–1980 to period 1981–2010 and date when sea surface water temperature exceed +4 °C has changed 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 may have changed into a new phase, in which ice do not reduce the local effects of global temperature increase.

Citation: Laakso, L., Mikkonen, S., Drebs, A., Karjalainen, A., Pirinen, P., and Alenius, P.: One hundred years of atmospheric and marine observations at Utö Island, the Baltic Sea, Ocean Sci. Discuss., https://doi.org/10.5194/os-2017-105, in review, 2018.
Lauri Laakso et al.
Lauri Laakso et al.
Lauri Laakso et al.

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Short summary
Meteorological observations at Utö Atmospheric and Marine Research Station, the Baltic Sea, started in 1881 and sea water temperature and salinity observations in 1900. Based on the dataset of more than 100 years of observations, we see a clear increase in atmospheric temperatures since 1980's, in-line with changes in ice cover and influence of Major Baltic Inflows in vertical stratification and sea-water temperatures close to bottom.
Meteorological observations at Utö Atmospheric and Marine Research Station, the Baltic Sea,...
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