Northern Baltic

The frequency of ice occurrence in the outer sea is 10-20% from about 57 N northward, 25% from about 58 N, and 50% on the northern and northeastern margins of the area. The frequency of ice occurrence in the other, southerly part of the Gotland Sea is extraordinarily low. Only a combination of several unfavorable factors (particularly low salinity, particularly low heat storage, long-term inflow of extremely cold air masses from the east as early as December and through March, high radiation of heat) can lead to ice formation in this area. During the past century, there have been only three winters with major ice formation in the entire sea area (1939/1940, 1940/1941, 1946/1947), and within the past 50 years only two winters (1955/1956 and 1986/1987) with some drift ice occurrence, which is a frequency clearly below 5%. 

The period of ice occurrence and extent of ice fields vary considerably in the different winter seasons, depending on meteorological conditions. Although short periods of ice formation with loose floe ice prevail in the outer sea areas, several-month periods with very close ice have occurred as well. Here, as everywhere, experience has shown that an early or late beginning of ice formation does not allow any conclusions as to the later development of the winter season. It is quite possible that a late beginning of ice formation is followed by an ice-rich winter or, vice versa, that an early onset of ice formation is followed by a mild winter. In the outer sea, ice has to be expected from mid-February. In extreme ice seasons, maximally 60-90 days of ice are observed. In outer sea areas, the last ice after a severe ice season does not melt until early May normally this date is 1 month earlier. 

In the southern and middle parts of Kalmar Sound including the coasts, ice forms in over 75 % of all winters. In the northern part of the Sound and at the coast of East Sweden up to the northern boundary of the western Gotland Sea, ice formation occurs in 60% of winters, and in all sheltered areas as well as in the fairways leading inland in 70-95% of winters. On the west coast of Gotland, ice forms in about 20% of all winter seasons. 

The average number of days with ice per winter is 20-30 in the southern and northern inshore waters of Kalmar Sound, and 40-50 days in the largest part of the Sound. At the northern coast of East Sweden, up to the northern boundary of the Gotland Sea, about 20 days of ice is to be expected, 40-50 days in all sheltered waters, and 50-75 days per winter in fairways extending far inland (e.g., Oxelosund, Stockholm). In extreme ice seasons, the maximum number of days of ice in all areas exceeds 60, in sheltered areas over 100, and from 120 to 130 days in the fairways to inland harbors. At the west coast of Gotland, maximally 70 days of ice has been recorded in winter. 

On the outer coasts of the B altic States, the frequency of ice seasons vary between 40% in the southern part and about 60% in the northern part. In the coastal waters of East Sweden, between Landsort and the latimde of Norrtalje, ice forms in over 70% of all winter seasons, with values in the inner archipelago region reaching about 80%, and in particularly exposed areas (e.g., fairway to Stockholm) up to 90%. 

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Broman D, Naf C, Rolfif C, Zebuhr Y, Fry B, Hobbie J. 1992. Using ratios of stable nitrogen isotopes to estimate bioaccumulation and flux of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in two food chains from the northern Baltic. Environ Toxicol Chem 11 331-345. 

Moilanen, R., H. Pyysalo, K. Wickstrom, and R. Linko. 1982. Time trends of chlordane, DDT, and PCB concentrations in pike (Esox lucius) and Baltic herring (Clupea harengus) in the Turku archipelago, northern Baltic Sea for the period 1971-1982. Bull. Environ. Contam. Toxicol. 29 334-340. 

Wickstrom, K., H. Pyysalo, and M. Perttila. 1981. Organochlorine compounds in the liver of cod (Gadus morhua) in the northern Baltic. Chemosphere 10 999-1004. 

Case Study of F. vesiculosus in the Eutrophic Northern Baltic Sea Genotypically Variable, Plastic Phlorotannins as Chemical Defenses... 

In this section, we illustrate some patterns of variation in temperate macroalgal chemical ecology by focusing on one model system, the bladderwrack F. vesiculosus and its phlorotannins in the Northern Baltic Sea. In this region, F. vesiculosus is the... 

Lignell, R., and K. Lindqvist. 1992. Effect of nutrient enrichment and temperature on intracellular partitioning of 14C02 in a summer phytoplankton community in the northern Baltic. Marine Ecology Progress Series 86 273-281. 

Broman D, Naef C, Zebuehr Y, et al. 1989. The composition, distribution, and flux of PCDDs and PCDFs in settling particulate matter (SPM) A sediment trap study in the northern Baltic. Chemosphere 19 445-450. 

Laamanen, MJ. (1997) Environmental forms affecting the occurrence of different morphological forms of cyanprokaryotes in northern Baltic Sea. J. Plankton Res. 19, 1385-1403. 

Rolff, C. (2000) Seasonal variation in 513C and size-fractionated plankton at a coastal station in the northern Baltic proper. Mar. Ecol. Prog. Ser. 203, 47-65. 

Sandberg, J., Andersson, A., Johansson, S., and Wikner, J. (2004) Pelagic food web structure and carbon budget in the northern Baltic Sea potential importance of terrigenous carbon. Mar. Ecol. Prog. Ser. 268, 13-29. 

Hietanen, S., Tuominen, L., and Kuparinen, J. (1999). Benthic bacterial production in the northern Baltic Sea measured using a modihed [C-14]leucine incorporation method. Aquat. Microb. Ecol. 20,... 

Kempton P. D., Downes H., Sharkov E. V., Vetrin V. R., Ionov D. A., Carswell D. A., and Beard A. (1995) Petrology and geochemistry of xenoliths from the northern Baltic shield evidence for partial melting and metasomatism in the lower crust beneath an Archaean terrane. Lithos 36 (3—4), 157-184. 

In Table 7.10 the absolute and relative frequency distributions of the wave height for the area of the Northern Baltic Sea have been compiled by DWD, (2006). In the rows Longitude/ Latitude of part (c) of the table positional information is provided. This information was calculated from the observations and marks the center of the area. 

Table 7.11 contains a comparison of significant wave heights for the northern Baltic Sea. The data of Weisse (2007) and Augustin (2005) are based on model hindcast simulations for different time periods. 

TABLE 7.11 Comparison of Monthly Averages of the Significant Wave Height (in meters) for the Northern Baltic Sea... 

The ice season of 1965/1966 was the opposite. January and February were very cold, especially in the north. Severe ice conditions prevailed in the Gulf of Bothnia and in the northern Baltic, while conditions were somewhat milder in the southern Baltic. This ice winter was very long, especially in the northern Baltic and Sea of Bothnia. The last ice disappeared from these areas as late as the beginning of May, while in the northern Bay of Bothniaremnants of ice lasted until early June. The southern Baltic was ice-free early, at the beginning of March. 

The thermal development in the Baltic Sea is characterized by a strong annual cycle with minimum temperatures in February/March and a maximum in August. The mean seasonal cycle is regionally different with extended winter and shortened summer seasons in the northern Baltic Sea. Interannual variations are indicated by strong regional differences particularly in May/June and September/October, in the warming and cooUng phases. 

A trend analysis forthe investigated period reflects that the seven warmest years were observed since 1999. The positive trend in the yearly mean SSTs with an increase of 0.97K in 16 years (0.65K/decade) confirms the global observation also for the Baltic Sea. Summer and autumn temperatures mostly contribute to this positive trend. The monthly resolved trend varies between the slightly negative trends in March and the highest positive trends in July in the northern Baltic Sea. The yearly trend of the entire Baltic Sea is stronger than that of the northern hemisphere. 

In Siegel et al. (2006), the regional differences were additionally discussed separately for the winter and summer months. In the northern Baltic Sea, particularly in Bothnian Bay, the SST every year in February is below 0°C and the water is often covered by ice. From the western part (Pl) to the northern Gotland Sea (P16), the mean SST is around 2°C. The warmest February was in 1990 with SST between 3 C and 4 C in the main parts. The coldest was in 1996 in the southwestern Baltic and in 2003 in the northern Baltic. The... 

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