The shelf edge system - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 349

FURTHER READING

Carbon and Nutrient Fluxes in Continental Margins: A Global Synthesis, K. K. Liu, et al.,
editors. Springer-Verlag, Berlin Heidelberg, 2010.
HERMES Hotspot Ecosystem Research on the Margins of European Seas ( www.eu-hermes.
net/intro.html )
Huthnance, J. M. Circulation, exchange and water masses at the ocean margin: the role of
physical processes at the shelf edge. Progress in Oceanography, 35(4), 353-431, 1996.
The Dynamics of Marine Ecosystems: Biological-Physical Interactions in the Oceans,by
Kenneth H. Mann and John R. N. Lazier, Blackwell Publishing, 2006. Chapter 5.

Problems

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10.1. A barotropic current flows poleward along the continental slope between the
200-metre and the 500-metre isobaths at latitude 58 N. If, on the 15 km section
normal to the slope between these isobaths, the average speed of the current is
0.23 m s 1 , estimate the difference in sea surface height across the current.
Assuming that the bottom depth increases uniformly between 200 metres and
500 metres, estimate the total transport of the current. Assess the feasibility of
monitoring the transport in such a slope current by satellite altimeter observa-
tions of sea surface height (r.m.s. uncertainty

∼ 1-2 cm).

10.2. The thickness of the bottom Ekman layer, D, below a steady geostrophic flow,
speed V s , can be estimated from the empirical relation:

D ¼ 0 : 4u ? = f

=

1 2

V s is the stress at the
bottom boundary. Use this relation to show that the observed value of D in a
slope current can be used to estimate the bottom stress, the transport T b normal
to the slope in the bottom boundary layer and the speed of the along-slope
current, V s .
Temperature measurements in a slope current at latitude 49 N indicate a
uniform mixed bottom boundary layer of thickness D

where u ? ¼ð b =Þ is the friction velocity and b ¼ k b

45 metres. Estimate

t b , T b and V s given that k b ¼ 0.0025.

10.3. An upwelling-favourable along-shelf wind of 12 m s 1 drives water from
below the thermocline onto a narrow temperate shelf of width 20 km. The
sub-thermocline water has a nitrate concentration of 10 mmol m 3 .

(i) Estimate the rate of primary production that could be supported by the
upwelling.
(ii) What speed would a slope current have to have in order to drive the same
biological production?

10.4. Two moorings are used to estimate an internal tidal wave energy decrease of
5Jm

3 between them, with the wave taking 14 hours to pass from one