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0
mg Chl m
-3
(a)
10
20
20
15
10
30
5
40
o
o
o
o
o
o
9W
6W
3W
9W
6W
3W
(b)
Irish
Sea
UK
(c)
Ireland
o
52 N
52
o
N
B
Celtic
Sea
o
50
o
N
50 N
A
Isles of
Scilly
France
15
16
17
18
19
0.2
0.5
1
3
5
mg Chl m
-3
o
C
Figure 8.12
(a) See also
colour plates section.
A section of temperature (lines) and chlorophyll
concentration (shaded) through the tidal mixing front off Ushant, NW France (from Pingree
et al.,
1975
, courtesy of Nature). The water depth was 100 metres; only the upper 40 metres has
been plotted. (b) and (c) Satellite images of sea surface temperature and chlorophyll for the
Celtic Sea. Images are composites over July 12-18, 2005, provided by NEODAAS Plymouth
Marine Laboratory. Tidal mixing front A is the Ushant front across which the section in
(a) was collected. Front B is the Celtic Sea front. Note also the 'island mixing front' and patch
of mixed water surrounding the Isles of Scilly, along with an associated increase in sea surface
chlorophyll.
(a)
(b)
(c)
0
26.0
<0.25
30
>16
60
5 km
kg m
-3
mg m
-3
mmol m
-3
90
Figure 8.13
A section across the island mixing front around the Isles of Scilly in summer. (a)
Density, showing the sharp pycnocline away from the islands, expanding to form bottom and
surface fronts in the shallower water by the islands. (b) Chlorophyll concentration,
indicating increased surface chlorophyll approaching the islands. (c) Nitrate concentration,
with mixing close to the islands driving nitrate towards the surface. The tick marks along
the upper axes indicate the positions of the sampling sites. Adapted from Simpson et al.,
1982
,
with permission from Elsevier.
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