Page 189 - (DK) Ocean - The Definitive Visual Guide

Oceanography 187

from Space

The world’s oceans are too vast to be adequately
FEATURES STUDIED FROM SPACE
studied using ships alone. Even if all of the depth
soundings that were taken during the 20th century CLOUDS Cloud cover is
detected using visible-light
were to be plotted, the resultant map would provide
cameras, and cloud-top height
only sparse information on the sea floor and would data is derived from infrared
even be blank in large areas. The advent of satellite radiometers on satellites such
as Meteosat. These systems
remote sensing in the 1960s brought a revolution are used to track storms and
in oceanography. For the first time, it was possible forecast the weather.
to take a picture showing an entire ocean basin.
Hurricane tracking and warning was one of the
RAINFALL The Tropical Rainfall
first benefits to accrue from early weather satellites.
Measuring Mission uses a
Eventually, a large range of sensors were developed microwave radiometer to see
to probe the physical attributes of the ocean surface through clouds and detect the
presence of liquid water in the
and the atmosphere above. atmosphere. Rainfall measures
Ocean colour and temperature, sea-level height, WEATHER are used in computer models
of the climate and ocean.
and surface roughness are among the parameters that
can be monitored in some detail. Satellite-derived
CHLOROPHYLL Ocean
information is a vital component of practical colour cameras use
applications such as weather forecasting, commercial wavelengths of visible light
to measure the concentration
fishing, oil prospecting, and ship routing. In some
of chlorophyll, which is
cases, 30 years of continuous observations have been present in phytoplankton.
built up, helping scientists to track seasonal and PLANT LIFE This information is used for
water-quality assessment,
long-term changes in the ocean environment and finding fish, and in various
understand its effects on the global climate. aspects of marine biology.

MICROWAVE SCATTEROMETER
Surface wind speed and direction
Measuring Ocean Depth from Space are measured by satellites that
bounce radio beams off the
Satellites cannot directly measure the depth of the sea floor, but surface of the ocean. Wind-
it can be derived from the height of the sea surface. The sea is not induced ocean waves modify
flat. Water piles up above gravity anomalies caused by ocean-floor the return signal, and the data
features such as seamounts, producing variations in the surface can be used for meteorology
that are much larger than those produced by tides, winds, and WIND SPEED and climate research.
currents. By comparing the height of the sea surface against a
reference height, the depth of the sea floor can be estimated.
JASON-2 SATELLITE
Jason-2 carries a radar altimeter, SYNTHETIC APERTURE
RADAR Imaging radar
which is similar to the instruments
systems, such as the one
on aircraft that measure their height
carried by Radarsat,
above the surface of the Earth.
penetrate clouds and can
ICE COVER and icebergs all year round.
satellite operate through the dark of
the extended polar night to
orbit satellite monitor ice shelves, sea-ice,
SURFACE TEMPERATURE
Infrared radiometers can measure
the shorter the temperature of the sea surface
the signal signal is precisely. Shifts in ocean currents,
time the bounced from cold-water upwelling, and ocean
higher the satellite off
ocean surface fronts can be monitored for
ocean surface ocean and climate research.
and timed
the longer the water surface
signal time THERMAL GLIDER A new generation of instrument platforms
the lower the varies is being developed to sample the vast subsurface volume of the
according to
ocean surface world’s oceans. Autonomous Underwater Vehicles, or “sea OCEAN ENVIRONMENTS
sea-bed profile
gliders”, can undertake long cruises, surfacing every
day to return their data via satellite
TEMPERATURE
communication links.
dish to track
satellite height
reference
ocean floor and to receive
surface
data