THE EARTH’S HYDROSPHERE
• The Earth’s liquid water constitutes the hydrosphere.
• The vast majority of Earth’s water is in the oceans (salt water),
with smaller, but geologically important, quantities of fresh water
in lakes, rivers, and ground water.
• The components of the hydrosphere, as well as the cryosphere
(frozen water), the atmosphere, and the biosphere, participate
in the global hydrologic cycle.
• Earth’s water supply has had, since Earth was created, major
influences on Earth’s climate, its landscape and mineralogy, the
composition of its atmosphere, and on the origin and evolution
of life.
o The total mass of Earth’s water is about 300 times the mass of the
atmosphere.
o Without water, which facilitates the formation of carbonate rock, the
atmospheric content of CO2 would be far higher than it is.
THE EARTH’S HYDROSPHERE:
Distribution of Water on Earth
Volume
Percent of Total
1,350 x 1015 m3
97.3
CRYOSPHERE
(Glaciers & Polar Ice)
29 x 1015 m3
2.1
UNDERGROUND
(Aquifers)
LAKES & RIVERS
8.4 x 1015 m3
0.6
0.2 x 1015 m3
0.01
OCEANS
ATMOSPHERE
BIOSPHERE
0.013 x 1015 m3
0.0006 x 1015 m3
0.001
4 x 10-5
Distribution of Water on Earth
The Hydrologic Cycle
Typical Elevation Profile of Oceanic Margins
Echo Sounders for Measuring Ocean Depths and Floor Profiles
Major Topographic Divisions and Profile of the
North Atlantic Ocean Basin
The World’s Ocean Floors
THE EARTH’S HYDROSPHERE
• The hydrosphere, along with the atmosphere and cryosphere,
are primarily responsible for weathering and erosion of land
surfaces.
• Rain water, in combination with atmospheric CO2, is primarily
responsible for chemical weathering by carbonic acid, H2CO3.
• The amount of CO2 dissolved in the oceans is much larger than
that currently in the atmosphere. Since the solubility of CO2 in
water decreases with temperature, global warming could
produce a positive feedback effect by releasing oceanic CO2.
• Man-made and volcanic pollution can increase weathering by
providing much stronger acids (“acid rain”; e.g. H2SO4), and by
increasing atmospheric CO2.
• Rain, plus the river and stream components of the hydrosphere,
also provide mechanical erosion of rocks and convert them to
soils and sediments.
Wave and Underwater Motions
Production of Tsunami Waves by Earthquakes
December 26, 2004 Earthquake-Generated Tsunami
(Red = Wave Heights Measured by Jason 1 Satellite)
“Black Smoker” Under-Sea Volcanic Activity
• Under-sea volcanic activity gives
rise to high-temperature plumes of
water, containing particles of
igneous rock that give rise to the
appearance of black smoke.
• The boiling point of water under
the high pressures on the ocean
floor can be considerably higher
than at the surface; hence the
temperatures of the volcanic
plumes can be much higher as
well.
• It has been discovered that some
species of animal life thrive on the
environment of these “black
smokers”, including their very high
temperatures.
Global Ocean Current Systems
THE EARTH’S TIDES
• Tides in Earth’s oceans are due to the differential of
gravitational attraction on different parts of Earth (relative to its
center); primarily by the Moon, and secondarily by the Sun.
• The part of the oceans on the side of the Earth facing the Moon
(or Sun) feels stronger gravity, and the part of the oceans on the
side of the Earth facing away from the Moon (or Sun) feels
weaker gravity, than does the center of the solid Earth.
• The maximum effective forces on Earth’s ocean waters are
those in the horizontal direction (which causes horizontal
motion), and occur at angles of 45 and 135 to the Moon or
Sun direction.
• This causes rises in sea level on opposite sides of the Earth (in
line with the Moon or Sun direction).
THE EARTH’S TIDES
• When the Sun and Moon are in line with the Earth, tides are
stronger than average (spring tides), and when the Sun and
Moon are at right angles to each other, tides are weaker than
average (neap tides).
• There are also variations in tide strength due to differences in
the Earth-Moon and Earth-Sun distances, and the orientations
of the orbit planes of the Earth and Moon with each other, and
with the Earth’s equatorial plane.
• Tide heights are also affected by the local sea level and coastal
topography.
View of the directions and magnitudes of gravitational forces exerted by the
Moon on the solid Earth and oceans (G), resultant effect on the solid Earth (C),
and net effects on ocean waters (residual difference vectors).
Net effective translational force on Earth’s surface water. Note it is zero at 90 to
the Earth-Moon direction, as well as at the zenith (Z) and nadir (N) directions.
LIFE IN THE OCEANS
• Throughout Earth’s history, the oceans have had major
influences on the evolution and propagation of life, and vice
versa.
• Early in Earth’s history, before the advent of photosynthesis on a
large scale, there was no atmospheric ozone layer to protect life
forms on the surface from damaging solar ultraviolet radiation.
• Therefore, the oceans (and other large bodies of water)
provided the only UV-protected (but visible light illuminated)
habitats for the original procaryotic life forms, as well as
essential nutrients.
• Life forms have also had significant influences on the oceans
and ocean beds, because of their capabilities to convert carbon
dioxide and soluble calcium compounds into limestone (calcium
carbonate, CaCO3).
THE EARTH’S CRYOSPHERE
• Earth’s supply of frozen water, the cryosphere, is second only to
the oceans in water content.
• The cryosphere consists mainly of the permanent ice caps of
Antarctica and Greenland, with much smaller amounts in Arctic
and mountain glaciers.
• Major changes in sea level can occur during times of global
climate change (ice ages and global warming), due to
associated changes in the water content of the cryosphere.
• During ice ages, glaciers can cover major parts of Earth’s land
area year-round for hundreds or thousands of years.
• The advance and retreat of glaciers can also produce major
erosion and re-configuration of the landscape.
• Ice ages and global warming can have major effects on the
biosphere as well.
Permafrost in Land Areas
• Land areas in polar regions,
such as Antarctica and
Greenland, and the north
slopes of Alaska and Siberia,
have zones below their
surfaces in which ground water
remains frozen year-round.
• Regions in which soil water is
permanently frozen constitute
what is known as permafrost.
Ice Cover of Greenland and Antarctica
Ice Age North Polar Coverage
ICE AGES AND GLOBAL WARMING
• The most recent “ice age” ended about 12,000 years ago, which
was prior to the advent of civilized human history.
• It is still unknown as to what causes the advent of ice ages, and
the extent that they occur in cycles independent of human
activities.
• At the current time, we are experiencing a slow global warming,
but it is not known to what extent this is part of a natural cycle as
distinct from human-induced (by increasing the amount of carbon
dioxide and other “greenhouse gases”, due to combustion of fossil
fuels and other human activities).
• There is concern that the increasing use of fossil fuels might
induce a “runaway greenhouse” effect, because heating of the
atmosphere could, by heating of the oceans and other water
bodies, result in increasing water vapor in the atmosphere (which
is also a “greenhouse gas”)!
• Global warming would also result in melting of the polar ice caps,
which would raise the water level of the oceans and cause
flooding of coastal areas of the continents.
Sea Level Changes due to Ice Ages and Ice Cap Melting
Space-Based Remote Sensing of the Hydrosphere
and Cryosphere
• As is also the case for studies of Earth’s land surfaces, observations
of the Earth’s water surfaces from space provide important information
that would be difficult or impractical to obtain using only in-situ
measurements (such as from surface and submarine vessels) or by
aircraft-based remote sensing.
• Using spacecraft in the appropriate orbits, nearly all regions of the
hydrosphere and cryosphere can be observed at regular intervals
(and, in some cases, continuously) with remote-sensing instruments
such as imagers and spectrographs, operating in all wavelengths that
can penetrate the atmosphere to/from the surface (and, in some
cases, below the liquid water or ice surface).
• The most recent of these is the Aqua spacecraft, which along with
Terra (primarily land measurements) and Aura (primarily atmospheric
measurements) constitute the major instruments of NASA’s Earth
Observing System (EOS).
NASA’s Aqua Earth Observing Satellite
• Aqua, the second of NASA’s Earth Observing System (EOS)
family of satellite missions to be launched, has a broad range of
scientific objectives and corresponding scientific instrumentation.
• The Aqua scientific objectives are focused on the study of a wide
range of interrelated Earth system processes (involving the
atmosphere, oceans, and land surface) and their involvement in
both near- and long-term changes in the Earth system.
• Global change research efforts include studies of, and
instrumentation to measure, atmospheric temperature and
humidity profiles, clouds, precipitation and radiative balance,
terrestrial snow and sea ice; sea surface temperature and ocean
productivity; soil moisture; and the improvement of numerical
weather prediction.
• Aqua is also contributing to the monitoring of marine and
terrestrial ecosystem dynamics.
NASA’s Aqua Earth Observing Satellite
• Aqua is in a near-polar, low Earth orbit.
• Aqua has six primary scientific instruments:
o
o
o
o
o
o
Atmospheric Infrared Sounder (AIRS)
Advanced Microwave Sounding Unit (AMSU-A)
Humidity Sounder for Brazil (HSB)
Advanced Microwave Scanning Radiometer for
EOS (AMSR-E)
Moderate Resolution Imaging Spectroradiometer
(MODIS)
o Clouds and the Earth’s Radiant Energy System
(CERES)
• The simultaneous observations of this suite of
instruments, each having its own unique
characteristics and capabilities, contributes greatly to
the total scientific capability of this space mission.