12
2 Frontal types
contribute to pumping nutrients to the upper layer, subsequently increasing the
ocean primary productivity (Lévy et al. 2001, 2012; Klein and Lapeyre 2009;
D’Asaro et al. 2011). Fronts are therefore “hot spots” of intense biological and
physical activity (Olson and Backus 1985; Olson et al. 1994; McGillicuddy et al.
1988; Bakun 2006a).
2.8 Fronts Associated to Geomorphic Features
Some fronts are topographically controlled. When tidal or other currents interact
with irregularities in the sea bed, or coastline, it is usual to find consistent patterns
of eddies and associated fronts. These obstacles to the flow create accelerations
in the direction perpendicular to the upstream flow direction as well as frictional
boundary layers close to the obstacle. These forces, together with vertical stratification and the Earth’s rotation determine the path of flow particles around the
obstacle. Thus, the presence of a headland, an island, a bank, a reef or an undersea
mountain cause a disturbance in the flow generating complex three-dimensional
secondary flows of various scales (Arístegui et al. 1994; Dong et al. 2007) that
result in a physical front (Fig. 2.3d) (Wolanski and Hamner 1988). Direct observations and numerical simulations indicate that these structures display enhanced
phytoplankton growth (Dong et al. 2009).
2 Frontal types
contribute to pumping nutrients to the upper layer, subsequently increasing the
ocean primary productivity (Lévy et al. 2001, 2012; Klein and Lapeyre 2009;
D’Asaro et al. 2011). Fronts are therefore “hot spots” of intense biological and
physical activity (Olson and Backus 1985; Olson et al. 1994; McGillicuddy et al.
1988; Bakun 2006a).
2.8 Fronts Associated to Geomorphic Features
Some fronts are topographically controlled. When tidal or other currents interact
with irregularities in the sea bed, or coastline, it is usual to find consistent patterns
of eddies and associated fronts. These obstacles to the flow create accelerations
in the direction perpendicular to the upstream flow direction as well as frictional
boundary layers close to the obstacle. These forces, together with vertical stratification and the Earth’s rotation determine the path of flow particles around the
obstacle. Thus, the presence of a headland, an island, a bank, a reef or an undersea
mountain cause a disturbance in the flow generating complex three-dimensional
secondary flows of various scales (Arístegui et al. 1994; Dong et al. 2007) that
result in a physical front (Fig. 2.3d) (Wolanski and Hamner 1988). Direct observations and numerical simulations indicate that these structures display enhanced
phytoplankton growth (Dong et al. 2009).