Area groupings and findings
Area groupings
In order to describe the climatology of an area, stations that
display similar trends have been grouped together. Thus for
stations that include the base period, the groupings are: English
East Coast (stations 3 - 10), Thames region (stations 12 - 16),
Eastern Channel (stations 18 - 22), Western Channel (stations
23-24) and Eastern Irish Sea (stations 34 - 38). Figures 3 - 7 show
the annual temperature anomaly from the base period (1971 - 2000)
for 1970 - 2004. A trend line has been included from 1985 to 2004
to show the trend in temperature in the last 20 years.
Despite the number of stations included here, there is a
significant spatial gap in the South West coastal region. There is
no climatic grouping for the remainder of the Irish Sea because
there are an insufficient number of stations that run for the base
period of 1971 - 2000.
Comparisons have also been made between the temperatures
recorded from the ferry route (Position 2) and
the most appropriate inshore temperature network station (Figure
8).
Table 2
presents the annual temperature anomalies for selected stations for
1994 - 2004 from the base period (1971 - 2000), colour coded by the
range in temperature.
For all 9 sampling positions from the ferry route, Table 3 presents
annual salinity anomalies for 1994 - 2004 from the base period
(1971 - 2000), colour coded by the range in salinity.
Findings
This data set has quantified the inter-annual variability in the
near coastal temperatures in the seas around the UK. The evidence
is that the long-term change is distinguishable from the
inter-annual variability.
Figure 3: East Coast
area
All of the coastal sea areas show an overall increase in
temperature during the last 20 years (Figures 3 - 7). Combining a
group of twenty coastal stations which have similar statistical
characteristics, the average temperature rise in inshore waters is
0.3°C per decade since 1966 but with a greater rate of warming (0.5
to 0.75°C) in the last 20 years.
Figure 4: Thames
region
In Figures 3, 4 and 7, for the East coast, the Thames and the
Irish Sea, 1979, 1986 and 1996 show colder periods with 1986 and
1996 showing the most abrupt changes. The Eastern and Western
Channel areas (Figure 5 and 6) show the same trend apart from
experiencing a more abrupt colder period in 1991 than in 1996.
Although the very cold year of 1979 was most pronounced in the
Irish Sea, in other regions, the western channel, eastern channel
and Thames region, this cold period extended for three years from
1978 - 1980. The extremely cold period in 1986 was evident in all
of the sea regions.
Figure 5: Eastern
Channel area
Following this, was a dramatic shift in all sea areas (1988
- 1990), with a sharp rise in temperature leading to two very warm
years of 1989 and 1990 with continued temperature rise since that
time, with all areas showing similar trends. Previous to this warm
period, a short warming period occurred, starting in 1973 and
reaching a maximum in 1976. It was most pronounced in the western
Channel but was also evident in the other regions.
Figure 6: Western
Channel area
The stations offshore in the Southern Bight show an overall
increase in temperature from 1971 to present (Figure c: P2, P4 and
P7). The high temperatures of 1990 are also evident in all the
coastal regions, while the 1982 peak was only evident in the
English Channel region. The high temperatures in 2002 and
2003 are not evident in any of the other regions.
Figure 7: Irish Sea
area
The seasonal cycle of salinity is evident from Figure b,
positions 2, 4 and 7. The lowest salinity is consistent across the
transect, occurring in May to June, but with greater variability in
the time of maximum salinity, usually in the winter months.
Variability in all the salinity records is high but especially
large in the summer months. It is postulated that this variability
is dominated by flow through from the English channel (Dickson
et al., 2003).
In most areas of the North Sea low salinities were observed in
1994, 1995, 2001 and 2002 and returning to near normal values in
2004, after a period of very high salinity that persisted in 1997
and 1998. This trend is clear in the salinity time-series
figures for Position
2, Position
4 and Position
7 (Figures a, b and c) and Positions 1 - 9 (Table 3).
Figure 8: Comparison between ferry route position 2
and coastal temperature station Bradwell