Fourth Study Conference on BALTEX Scala Cinema Gudhjem

Figure 1 shows the total number of observations per year in
BED. Notable is the extremely low number of observations
in the late 1980s. The spatial resolution of the number of
samples in BED and from the lightships is shown in
Figure 2. This shows that Gulf of Bothnia is least visited,
and that Baltic Proper is visited more often.
Figure 1. The total number of observations each year in
BED.
65 o N
60 o N
55 o N
8
71
2
82
34
19
296 684
200 1750 57
28
32
165 465
34
7
40
71
7
115 112 134 93
233 362 164 150 9
48 107 42 528 386 52
1 173 460 85 212 220 528 1390 652 331 462 229 22 1
16 258 183 170 254 151 310 58 10 276 589
42
46 204 79 64
96 118 74 33
187 248 85 181 2
39 182 27 290 533 37 43 134 40
10 o E 20 o E 30 o E
25
4
62
54 162 95 4
6 82 230 69 298 190 148 265 91 31 17
14
2
42
35
5
6
88
60
147 43 19
Figure 2. The number of observations, in hundreds,
available in BED and from 11 Swedish lightships. Data were
sampled during 1900-2000 and arranged in 1 o x1 o grid cells.
Figure from Green, (2004).
4. Climate variability and change
Climate studies require high quality data and homogeneous
time series. Figure 3 shows how the mean Baltic salinity has
varied during the 20 th century (Winsor et al., 2001, 2003).
Mean salinity was calculated by first using salinity profiles
from all the major sub-basins of the Baltic Sea for 1977 to
1987. This is a period with good coverage in all sub-basins.
The mean was compared with data from a station in the
central Baltic Sea (BY15). This station has observations for
more than 100 years. The comparison illustrated that the
station BY15 represents the Baltic Sea well, and based on
data from this station the mean salinity was estimated for the
entire 20 th century. This curve has been an important
contribution in climate and water balance studies, but we do
not yet know the quality of the time series.
- 144 -
/ oo)
Salinity ( o
8.2
8.0
7.8
7.6
7.4
7.2
Baltic Sea mean
Bornholm Basin (BY5)
7.0
7.0
1900 1920 1940 1960 1980 2000
Year
Figure 3. Mean salinity of the Baltic Sea (solid curve)
and surface salinity in the Bornholm Basin. Both series 5
year running mean. For details see Winsor et al. (2001,
2003).
5. Work strategy?
We propose that the BALTEX community assemble longterm
data sets of temperature, salinity and oxygen together
in a joint database. This database could be managed by the
Oceanographic Data Centre for BALTEX. The best and
longest lighthouse, lightship and offshore station data sets
should be put together, and methods developed to
construct homogeneous time series of known quality.
References
Björk, G. and Nordberg, K., 2003: Upwelling along the
Swedish west coast during the 20 th century.
Continental Shelf Research 23, 1143pp.
Ekman, F. L., 1893: Den svenska hydrografiska
expeditionen år 1877. Kongliga Svenska Vetenskapsakademiens
Handligar. Bandet 25. N:o 1.
Green, J. A. M., 2004: On the effects of sloping bottoms
on wind-forced near-coast density variability,
Submitted to Continental Shelf Research.
Sokolov, A. V., Andrejev, O. A., Wulff, F., Rodriguez-
Medina, M. (1997). The Data Assimilation System for
data analysis in the Baltic Sea; Contrib. Systems Ecol.,
Stockholm University, Stockholm, Sweden.
Winsor P, Rodhe J, and A Omstedt, 2001. Baltic Sea
ocean climate: an analysis of 100 yr of hydrographic
data with focus on the freshwater budget. Climate
Research, 18, 5–15, 2001.
Winsor P, Rodhe J, and A Omstedt, 2003. Erratum Baltic
Sea ocean climate: an analysis of 100 yr of
hydrographic data with focus on the freshwater
budget. Climate Research, 25,183.
8.2
8.0
7.8
7.6
7.4
7.2