SEA ICE AND RELATED DATA SETS FROM THE BALTIC SEA AICSEX — METADATA REPORT Pekka Alenius, Ari Seinä, Jouko Launiainen & Samuli Launiainen Merentutkimuslaitos SCATTER DIAGRAM WAVE STATISTICS FROM THE NORTHERN Havsforskningsinstitutet BALTIC SEA Finnish Institute of Marine Research Kimmo K. Kahma, Heidi Pettersson & Laura Tuomi ASSESSMENT — STATE OF THE GULF OF FINLAND IN 2002 Matti Perttilä (Editor) SHORT-TERM EFFECTS OF NUTRIENT REDUCTIONS IN THE NORTH SEA AND THE BALTIC SEA AS SEEN BY AN ENSEMBLE OF NUMERICAL MODELS Tapani Stipa, Morten Skogen, Ian Sehested Hansen, Anders Eriksen, Inga Hense, Anniina Kiiltomäki, Henrik Soiland & Antti Westerlund Report Series of the Finnish Institute of Marine Research. MERI — Report Series of the Finnish Institute of Marine Research No. 49, 2003 SEA ICE AND RELATED DATA SETS FROM THE BALTIC SEA AICSEX — METADATA REPORT Pekka Alenius, Ari Seinä, Jouko Launiainen & Samuli Launiainen SCATTER DIAGRAM WAVE STATISTICS FROM THE NORTHERN BALTIC SEA Kimmo K. Kahma, Heidi Pettersson & Laura Tuomi ASSESSMENT — STATE OF THE GULF OF FINLAND IN 2002 Matti Perttilä (Editor) SHORT-TERM EFFECTS OF NUTRIENT REDUCTIONS IN THE NORTH SEA AND THE BALTIC SEA AS SEEN BY AN ENSEMBLE OF NUMERICAL MODELS Tapani Stipa, Morten Skogen, Ian Sehested Hansen, Anders Eriksen, Inga Hense, Anniina Kiiltomäki, Henrik Soiland & Antti Westerlund MERI — Report Series of the Finnish Institute of Marine Research No. 49, 2003 Cover photo by Riku Lumiaro. Publisher: Julkaisija: Finnish Institute of Marine Research Merentutkimuslaitos P.O. Box 33 PL 33 FIN-00931 Helsinki, Finland 00931 Helsinki Tel: + 358 9 613941 Puh: 09-613941 Fax: + 358 9 61394 494 Telekopio: 09-61394 494 e-mail: [email protected] e-mail: [email protected] Copies of this Report Series may be obtained from the library of the Finnish Institute of Marine Research. Tämän raporttisarjan numeroita voi tilata Merentutkimuslaitoksen kirjastosta. ISSN 1238-5328 Dark Oy Vantaa 2003 CONTENTS SEA ICE AND RELATED DATA SETS FROM THE BALTIC SEA AICSEX — METADATA REPORT 3 Pekka Alenius, Ari Seinä, Jouko Launiainen & Samuli Launiainen SCATTER DIAGRAM WAVE STATISTICS FROM THE NORTHERN BALTIC SEA 15 Kimmo K. Kahma, Heidi Pettersson & Laura Tuomi ASSESSMENT — STATE OF THE GULF OF FINLAND IN 2002 33 Matti Perttilä (Editor) SHORT-TERM EFFECTS OF NUTRIENT REDUCTIONS IN THE NORTH SEA AND THE BALTIC SEA AS SEEN BY AN ENSEMBLE OF NUMERICAL MODELS 43 Tapani Stipa, Morten Skogen, Ian Sehested Hansen, Anders Eriksen, Inga Hense, Anniina Kiiltomäki, Henrik Soiland & Antti Westerlund SEA ICE AND RELATED DATA SETS FROM THE BALTIC SEA AICSEX - METADATA REPORT Pekka Alenius, Ari Seinä, Jouko Launiainen & Samuli Launiainen Finnish Institute of Marine Research, P.O. Box 33, FIN-00931 Helsinki, Finland ABSTRACT The goals of the Arctic Ice Cover Simulation Experiment (AICSEX) are to assess and study the variability and trends of selected climatic parameters during the 20th century, to model these processes, to assess by model simulations the impact of possible melting of the ice cover and to assess the economic impact of these changes to marine transportation. One part of these studies focuses on the variations and possible changes in the Baltic Sea, a small semi-enclosed sea that is heavily affected by the climate and weather conditions of the Northern Atlantic and Arctic Seas. Most relevant data sets from the northern Baltic Sea have been collected for analysis and these data sets will be introduced in this meta-data report. Key words: sea ice, Baltic Sea, data, inventory, long-term data 1. INTRODUCTION Many recent analyses have indicated changes in the ice cover of the Arctic Oceans and adjacent areas. If the ice cover of the Arctic Ocean would diminish in a considerable amount, it would possibly have drastic effects on the climate of the Northern Europe, too. The Baltic Sea is a small semi-enclosed sea area in the Northern Europe (Fig. 1). The environmental conditions of the Baltic Sea depend heavily on the climate and weather conditions of the North Atlantic and Arctic Oceans. One example is the water exchange between the world ocean and the Baltic Sea. Major saline water inflows to the Baltic Sea are infrequent events that depend on the favourable wind conditions in the autumn and in the winter. The water exchange determines the stratification of the Baltic Sea and thus the amount of heat stored in the sea in summer months, too. This reflects to the ice conditions in the next winter. The northern parts of the Baltic Sea, The Gulf of Bothnia (that consists of Bothnian Bay, The Quark and Bothnian Sea) and the Gulf of Finland, have ice cover at least on the coasts every winter. Ice is a very important regulating parameter for the winter navigation especially for Finland, Sweden and St Petersburg area of Russia. Practically all Finnish harbours are ice covered every winter. The average length of the ice season varies from 90 days in the southern coasts of Finland to over 190 days in the northern end of the Bothnian Bay. In the Eastern end of the Gulf of Finland, in St Petersburg area, the average length of the ice season is over 140 days. Because of its great importance for the foreign trade, much effort has been put to the observations of the ice conditions already over a century. In this meta-data report we introduce shortly several time series that we consider valuable and useful for the analysis of the ice conditions and their variability in the Baltic Sea. The obvious link between the Baltic Sea ice conditions and the conditions in Northern hemisphere is the NAO. 4 Pekka Alenius, Ari Seinä, Jouko Launiainen & Samuli Launiainen MERI No. 49, 2003 Fig. 1. The location of the Baltic Sea and names of some of its parts. 2. AVAILABLE CLIMATOLOGICAL AIR TEMPERATURE AND SEA ICE DATA USED AT FIMR IN AICSEX PROJECT An important background parameter in the analysis of sea ice conditions is the air temperature. Good correlation between the Baltic Sea ice conditions and regional or local air temperature has been shown in many earlier studies. Some relatively long time series of air temperature around the northern Baltic Sea are available. We have chosen a couple of these (see Table 1 and Fig. 2) as basic local to regional background information of the ice conditions for especially the northern parts of the Baltic Sea where the ice conditions are most severe in the area and sea ice exists every winter. Two of these time series are from larger cities (Stockholm and Helsinki) and are as such subject to urbanisation effects. The originators of the time series have done careful work to eliminate urbanisation effects from the data (Raino Heino, Finnish Meteorological Institute, personal communication). Table 1. Air temperature time series from the Baltic Sea area used in the AICSEX study. Site Time series type Time series duration Helsinki Monthly mean Jan-Dec 1829-2000 Mariehamn Monthly mean Jan-Dec (1881) 1885-2000 Haparanda Monthly mean Jan-Dec 1860-2000 Stockholm Monthly mean Jan-Dec 1756-2000 Sea ice and related date sets from the Baltic Sea — AICSEX — metadata report 5 15" 17° 19° 21° 22' 25° 27° 29° 67'- Haparanda -66° 66°- 64°- 63 Finland -62° 62'- -61' 61` Helsinki -60° Sweden 60°,- Stockholm 59°- 58°- 57°- 56°- 55°- 54°- 13° 15° 17° 19' 21° 23' 25° 27` 2p. Fig. 2. Location of the air temperature observation stations in the Baltic Sea area used in AICSEX study. 3. MAXIMUM ANNUAL ICE EXTENT OF THE BALTIC SEA Maximum annual ice extent of the Baltic Sea is a parameter that has often been used as a good indicator of the severity of the winter in the Baltic Sea. This parameter describes the area of the ice cover in square kilometres in one single situation during the winter when the ice cover had its largest extent. The duration of this "event" may vary depending on the winter, but it is not included as a parameter. The total area of the Baltic Sea is in this context counted to be 420 000 km2. Time series of the maximum annual ice extent has been constructed from winter 1719/1720 onwards. Risto Jurva from Finnish Institute of Marine Research (see Seinä & Palosuo 1996) constructed the early part of the time series using many different types of data sources to estimate the severity of the winter and thus the ice extent. Later on the Finnish Ice Service has determined the value of this parameter for every winter on the basis of regular observations of different types. Today this parameter is a well-observed one and is based on direct remote sensing observations. The time series is updated every spring (Seinä & al. 2001) and is today 282 years long. The maximum ice extent occurs in mid winter and thus the exact year of the occurrence of the situation is inarked as the year value in the time series (e.g. winter 1719/1720 is marked 1720). In spite of the internal heterogeneity of the time series, it has been used in many studies (Alenius & Makkonen 1981) and is considered to be a useful data set. Table 2. Maximum annual ice extent time series of the Baltic Sea. 3.1.1 Parameter Seasons No of years Maximum ice extent 1720-2001 282 The time series of the maximum annual ice extent of the Baltic Sea shows very large variations from year to year (Fig. 3). The values have so far been between 52 000 km2 and 420 000 km2. Median value is 180 000 km2, average value 215 000 km2 and standard deviation 114 000 krn2. From the variability it can be seen that the memory of the system is shorter than one year.