The Changing Marine
Environment
• Charting the Deep
• Understanding of the sea requires a shift in
perspective toward a “geological perspective”
that allows for our five-billion-year history
and vast distances greater than several
thousand kilometers.
The Changing Marine Environment
The Changing Marine
Environment
• Charting the Deep
• The interrelated concepts of continental drift
and plate tectonics have radically changed
our view of the ocean’s structure.
The Changing Marine Environment
•Fig. 1.5 The major plates of the earth's crusts.
The World Ocean
Visualizing the World Ocean
– Earth’s
oceans
exist as a
large interconnected
system of
mixing
seawater.
Fig. 1.10 An equatorial view of the world ocean.
The World Ocean
•Seeing in the Dark
– Water is nearly opaque to light, yet very
transparent to sound.
The World Ocean
•Fig. 1.11 Some large-scale features of the North Atlantic seafloor.
Properties of Seawater
• Pure Water
Properties of Seawater
•Pure Water
– The unique characteristics of pure water are
established by an electrical charge separation within
water molecules that forms hydrogen bonds between
adjacent water molecules.
Fig. 1.13 The arrangement of H and O
atoms in a molecule of water.
Fig. 1.14 Hydrogen bonding between
adjacent molecules of liquid water.
Blue dashed lines represent hydrogen
bonds.
Properties of Seawater
•Seawater
•Salt water contains a great variety of dissolved
salts, gases, and other inorganic and organic
substances.
•These dissolved molecules and compounds
affect many characteristics of seawater,
including its density, osmotic properties,
buffering capacity, and other biologically
significant features.
Properties
of
Seawater
•Fig. 1.20 A
comparison of the
osmotic conditions
of a sea cucumber
and a salmon in
seawater and fresh
water.
Properties
of
Seawater
•Fig. 1.21 Fate of
sunlight as it enters sea
water. The violet and red
ends of the visible
spectrum are absorbed
first.
Properties of Seawater
•Fig. 1.27 Earth's sea surface temperatures obtained from two weeks of
satellite infrared observations July 1984.
Properties of Seawater
•Fig. 1.30 Variations in water temperature (orange curve) and salinity (blue
curve) at a GEOSECS station in the western South Atlantic Ocean.
The Ocean in Motion
• The sea is constantly moving, both
horizontally and vertically. Winds,
waves, tides, currents, sinking water
masses, and upwelling all contribute to
the remarkable homogeneity of the
world ocean.
The Ocean in Motion
• Wind Waves
• The character of wind-driven ocean waves depends on
the wind’s speed, duration, and fetch.
Fig. 1.35 Wave form and pattern of water motion in a deepwater wave as
it moves to the right in to shore.
The Ocean in Motion
• Surface Currents
– Ocean surface currents are driven by stable
patterns of surface winds .
The Ocean in Motion
•Fig. 1.38 The major surface currents of the world ocean.
•Adapted from Pickard and Emory, 1982.
The Ocean in Motion
•Ocean Tides
– Ocean tides are driven by the gravitational
interactions of the Sun, Earth, and Earth’s
moon.
The Ocean in Motion
•Fig. 1.40 A point on the earth's surface
(indicated by the marker) experiences
high tides when under tidal bulges and
low tides when at right angles to tidal
bulges.
Fig. 1.41 Weekly tidal variations caused by
changes in the relative positions of the earth,
moon, and sun.
The Ocean in Motion
•Vertical Water Movements
– Vertical circulation of ocean water results
from density-driven sinking processes.
The Ocean in Motion
•Fig. 1.44 The general pattern of deep-ocean circulation in the major
ocean basins.
Adapted from Broecker et al, 1985.
Classification of the Marine
Environment
• Energy from the sun warms the sea’s
surface and creates winds that result in
a two-layered world ocean, with a
shallow, well-mixed, warm, sunlit layer
overlaying a much deeper, cold, dark,
high-pressure layer of slowly moving
water below.
Classification of the Marine
Environment
•The three-dimensional marine environment
can be separated into two broad divisions,
– the benthic realm of the sea floor
– and the pelagic water column.
•These in turn may be subdivided into
smaller categories based on water depth,
light availability, and ambient temperature.
Classification of the Marine
Environment
• The marine environment is a large and
complex system, so we create
classification systems to better
understand the relationships between
the physical characteristics of the
ocean.
Classification of the Marine
Environment
•Fig. 1.46 A system for classifying the marine environment.
•Adapted from Hedgpeth 1957.