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(a)
(b)
0
-100
-150
0.26
-300
-200
0
25
50
75
-10
10
Distance (km)
Distance (km)
Figure 10.9
Model results of a canyon steering a downslope cascade of dense shelf water.
(a) The excess density (kg m
3
) along a transect down the central axis of the canyon;
(b) A section across the canyon, 30 km from the coastal boundary, of the downslope flow of
the density current. Adapted from Chapman and Gawarkiewicz,
1995
, courtesy of the
American Geophysical Union.
(a)
(b)
0
0
500
500
9.725<T<9.8 °
o
T<9.5 °C
35.4<S<35.44
35.3<S<35.32
1000
1000
10.2
10.0
9.8
10.2
10.0
9.8
(c)
(d)
0
0
500
500
0.175<Chl<0.225 mg m
-3
Chl>0.3 mg m
-3
27.31<
σ
<27.315 kg m
-3
t
1000
1000
10.2
10.0
9.8
10.2
10.0
9.8
Figure 10.10
Cross-section along the UB line (Fig.
10.3a
) on the Malin shelf edge and slope
during a winter cascade. (a) Temperature (
C), (b) Salinity (PSS78), (c) Density (s
t
,kgm
3
),
and (d) Chlorophyll (mg m
3
). Shaded areas in (c) and (d) indicate the descending plume of
water with a slight density excess carrying chlorophyll from the shelf down to 500m on the
slope. Adapted from Hill et al. (1998), courtesy of Journal of Marine Research.
cooling in February 1996 (Hill et al.,
1998
). At this time, winter convection pene-
trated down to depths of
500 metres in the adjacent Atlantic while on the shelf,
convective mixing was limited to the water depth of
∼
200 metres.
Fig. 10.10a
shows
that the temperatures on the shelf away from the slope were consequently signifi-
cantly lower than in the upper layers of the deep ocean, while in
Fig. 10.10b
you can
see that the cooler shelf water also had slightly higher salinity. This combination of
higher salinity and colder temperature resulted in high-density shelf water, which was
unstable. The subsequent cascading of the water down the upper slope can be seen in
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