2
1 Introduction
are actually quite widespread and are generally known as fronts…”. Increased
availability of satellite imagery nowadays challenge such a common-sense view
of the oceans as being a nearly homogeneous habitat, displaying at a glance that
the marine environment is characterized by very complex structures (Fig. 1.1). The
large-scale views of the ocean’s surface characteristics from earth-orbiting satellites, together with high resolution field measurements and numerical simulations,
have transformed our perceptions of the range of scales and the variety of patterns
of the marine ecosystems (Bakun 1996). Regions in the ocean are organized by
temperature and salinity. Those variables do not change gradually with horizontal distance; instead there are large regions where horizontal gradients are small,
bounded by narrow regions (referred to as fronts) where horizontal gradients are
high. Fronts localize at the meeting of two different water masses. At these boundaries, particular biological and ecological processes occur that are more determinant of the ecological properties of the region than the phenomena occurring
inside both water masses (Frontier 1986). Fronts are an integral part of the sea, of
its fluid processes and of its ecological functioning, and are characterized by high
biological activity (Cushman Murphy 1944; Sournia 1994; Acha et al. 2004).
But fronts are not merely a meeting of waters with dissimilar properties, more
importantly, they are a dynamic phenomenon. They are vertically inclined interfaces between different water masses, and frequently present a rather complex
three-dimensional structure (Uda 1938; Fedorov 1986). Fronts occur on a variety of
length scales, from a few meters up to many thousands of kilometers. They can be
short-lived (days), although many fronts are quasi-stationary and seasonally persistent; prominent fronts are present year-around. Cross-frontal differences in SST (sea
surface temperature) and sea surface salinity can be as large as 10–15 °C and 2–3
Fig. 1.1 Sea surface
temperature satellite image
of the Brazil-Malvinas
Confluence region. Note
the highly structured spatial
pattern. Image processed
at the Rosenstiel School of
Marine and Atmopsheric
Science, University of
Miami, USA
1 Introduction
are actually quite widespread and are generally known as fronts…”. Increased
availability of satellite imagery nowadays challenge such a common-sense view
of the oceans as being a nearly homogeneous habitat, displaying at a glance that
the marine environment is characterized by very complex structures (Fig. 1.1). The
large-scale views of the ocean’s surface characteristics from earth-orbiting satellites, together with high resolution field measurements and numerical simulations,
have transformed our perceptions of the range of scales and the variety of patterns
of the marine ecosystems (Bakun 1996). Regions in the ocean are organized by
temperature and salinity. Those variables do not change gradually with horizontal distance; instead there are large regions where horizontal gradients are small,
bounded by narrow regions (referred to as fronts) where horizontal gradients are
high. Fronts localize at the meeting of two different water masses. At these boundaries, particular biological and ecological processes occur that are more determinant of the ecological properties of the region than the phenomena occurring
inside both water masses (Frontier 1986). Fronts are an integral part of the sea, of
its fluid processes and of its ecological functioning, and are characterized by high
biological activity (Cushman Murphy 1944; Sournia 1994; Acha et al. 2004).
But fronts are not merely a meeting of waters with dissimilar properties, more
importantly, they are a dynamic phenomenon. They are vertically inclined interfaces between different water masses, and frequently present a rather complex
three-dimensional structure (Uda 1938; Fedorov 1986). Fronts occur on a variety of
length scales, from a few meters up to many thousands of kilometers. They can be
short-lived (days), although many fronts are quasi-stationary and seasonally persistent; prominent fronts are present year-around. Cross-frontal differences in SST (sea
surface temperature) and sea surface salinity can be as large as 10–15 °C and 2–3
Fig. 1.1 Sea surface
temperature satellite image
of the Brazil-Malvinas
Confluence region. Note
the highly structured spatial
pattern. Image processed
at the Rosenstiel School of
Marine and Atmopsheric
Science, University of
Miami, USA