Density and Absolute Salinity of the Baltic Sea 2006–2009

Abstract

Abstract. The brackish water of the Baltic Sea is a mixture of ocean water from the Atlantic/North Sea with fresh water from various rivers draining a large area of lowlands and mountain ranges. The evaporation-precipitation balance results in an additional but minor excess of fresh water. The rivers carry different loads of salts washed out of the ground, in particular calcium carbonate, which cause a composition anomaly of the salt dissolved in the Baltic Sea in comparison to Standard Seawater. Directly measured seawater density shows a related anomaly when compared to the density computed from the equation of state as a function of Practical Salinity, temperature and pressure. Samples collected from different regions of the Baltic Sea during 2006–2009 were analysed for their density anomaly. The results obtained for the river load deviate significantly from similar measurements carried out forty years ago; the reasons for this decadal variability are not yet fully understood. An empirical formula is derived which estimates Absolute from Practical Salinity of Baltic Sea water, to be used in conjunction with the new Thermodynamic Equation of Seawater 2010 (TEOS-10), endorsed by IOC/UNESCO in June 2009 as the substitute for the 1980 International Equation of State, EOS-80. Our routine measurements of the samples were accompanied by studies of additional selected properties which are reported here: conductivity, density, chloride, bromide and sulphate content, total CO2 and alkalinity.

A global algorithm for estimating Absolute Salinity

“…(5)- (8) to enable a simple computer algorithm to deliver estimates of the Absolute Salinity S A based only on Practical Salinity S P and knowledge of location. In the Baltic Sea the approach of Feistel et al (2010) based on the Practical Salinity of the seawater sample has been used (see Eq. (12)).…”

“…Millero and Kremling (1976) were the first to make density measurements using the vibrating tube densimeter technique on samples from the Baltic Sea. More recent measurements have shown that the Absolute Salinity Anomaly S A − S R = δS A in the Baltic Sea has been quite variable over the past few decades of observation (Feistel et al, 2010). The present computer algorithm uses the relationship found by Feistel et al (2010) that applies in the years 2006-2009, namely (11) where S SO = 35.16504 g kg −1 is the standard-ocean Reference Salinity that corresponds to the Practical Salinity of 35.…”

“…More recent measurements have shown that the Absolute Salinity Anomaly S A − S R = δS A in the Baltic Sea has been quite variable over the past few decades of observation (Feistel et al, 2010). The present computer algorithm uses the relationship found by Feistel et al (2010) that applies in the years 2006-2009, namely (11) where S SO = 35.16504 g kg −1 is the standard-ocean Reference Salinity that corresponds to the Practical Salinity of 35. The Absolute Salinity Anomaly in the Baltic Sea is not due to biogeochemical activity, but rather is due to the rivers bringing material of anomalous composition into the Baltic.…”

100 years of atmospheric and marine observations at the Finnish Utö Island in the Baltic Sea

“…Parts of the Baltic Sea are ice covered every winter, so that the extent of the annual maximum ice cover varies between 50 × 10 3 and 340 × 10 3 km 2 (Seinä and Palosuo, 1996;Vainio, 2001) of the total area of 420 × 10 3 km 2 . The salinity varies from more than 20 ‰ in Kattegat down to less than 2 ‰ at the ends of the large bays in the northern part of the Gulf of Bothnia and Gulf of Finland (Feistel et al, 2010). In deep areas of the Baltic Proper, there is a permanent halocline somewhere between 60 and 80 m depth.…”

Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007–2013

“…While the raw salinity is recorded in units according to the Practical Salinity Scale 1978, the results on salinity distribution and variability are given in the paper (Sects. 3 and 4) in g kg −1 according to Feistel et al (2010). Particular care is taken to calibrate the SCUFA fluorometer; however, since we do not use the fluorometer data in this study, the used routine is not described here.…”