THE DINAMIC OF THE HYDROSPHERE
EARTH SCIENCE
ÍNDEX
-
INTRODUCTION
·
The hydrosphere
·
The dynamics of the hydrosphere
·
Action of sea breezes.
-
OCEAN
MOVEMENTS
·
Ocean Currents
·
Density Currents
·
Ocean
waves
-
THE
GLOBAL OCEAN
·
The
Ocean Conveyor Belt
·
“El Niño “
·
“La Niña”
- ENSO REPERCUSIONS ON
GLOBAL CLIMATE
1. INTRODUCTION
The hydrosphere is the liquid water component of the Earth.
It includes the oceans, seas, lakes, ponds, rivers and streams. The hydrosphere
covers about 70% of the surface of the Earth and the 97´3% of it is composed by
oceans, which is always in motion.
The dynamics of the
hydrosphere, oceans regulate global
temperatures, shape weather and climate patterns, and cycle elements
through the biosphere. Life on Earth originated in the oceans and they are
home to many ecosystems that are important sources of biodiversity, such us from coral reefs to polar sea ice
communities.
As
we mentioned, the water oceans play a complex role in regulating climate. The oceans absorb the amounts of solar energy; ocean
currents transport this heat from the equator toward the Poles.
Shore
areas
have lower thermal amplitude than the center of continents because of
the action of sea breezes (during the day a cool breeze blowing from the sea toward the land;
during the night it reversed).
In the center of the
continent the thermal amplitude is higher. In winter the cool soil, so the air
cools too. This causes the permanent continental anticyclone.
2. OCEAN MOVEMENTS
Ocean Currents
-Surface ocean currents
are large and horizontal movements of water driven by wind. Their importance is
due to the transportation of heat energy
from the equator to the poles; they
also carry warm water to colder climates and warm them. They travel in circular
patterns called gyres, because they are deflected by Coriolis forces when their east-west flow is obstructed by
continental landmasses.
- Deep Water Currents are
water movement that takes place at 400m below the sea level. They are
influenced by ocean density and temperature changes. Cooler water has a higher
salt density than warm water, the warmer water in that region rises and the
cool water flowing into the area sinks.
Density Currents
Water density increases
as temperature decreases and salinity increases. The cooling and freezing of
polar waters and evaporation of warmer waters increase water density and form density currents. These slow moving
currents are not affected by wind and move at deeper depths independently of
surface waters. Antarctic bottom water is an example of a density current
formed in polar waters. We mean: “A
density current is where a warm current floats on top of a cold current”
Ocean Waves
A wave is a ridge
movement of a large body of water. It consists of a crest (the the highest part) and a
trough (the lowest part). The wavelength
is the horizontal distance between consecutive crests, and the wave height is the vertical distance
between the crest and trough.
Ocean surface waves are
produced by wind blowing on the
water’s surface. When a deep-water wave goes by, it is the wave form and energy
from the wind that is moving. The reason is, the water moves in a circular
pattern, circling downward and then upward to return to its original position.
1. 3. THE GLOBAL OCEAN
It is the set of all the seas and
oceans in the Earth. This name is
appropriate because of the whole communication
between them. This
study is really important,
it is the answer
to many questions on global
climate because it stores a large
amount of CO2, and it
is a very effective means of
transport of heat or cloudiness.
We will study several phenomenons
that make this fact clear: “The ocean conveyor
belt”, “El Niño “and “La Niña”
- - “The ocean conveyor belt” is a kind of
river with different water that runs
most of the world's oceans. In the first half of it
course, it does like deep current,
it is determined by the density, and on the second hand, like surface current, subject to the action of the predominate winds.
In the following picture we can observe that the beginning of this movement
is near the boundary of the ice, exactly in Groenlandia,
where water tends to sink due to its less salty, lower
temperature and higher density.
This stream runs along the bottom of the Atlantic Ocean from north to south until it comes in contact with the icy waters of the Southern Ocean
and rises, returning some of it to their place of origin. The rest is dipped again
due to intense surface cooling and it runs along the bottom of the Indian Ocean, where some amount of water rises, and other part goes to the Pacific Ocean, where it definitely rises and warms.
Then it makes the journey in reverse
like a surface current, dragging the warm waters and clouds which are formed in
warm oceans, causing rain in its path and raising the temperature of the Atlantic Coast through which flows north European.
The ocean conveyor belt makes
up for salinity and the imbalance temperature between the Atlantic and the
Pacific Oceans, it has lower salinity and it is mostly isolate from the Polar Regions.
This current is also responsible for the regulation of the amount of
atmospheric CO2. “Due to it, the cold
water sink, dragging a load of this gas, releasing a thousand years later in
upwelling areas”.
-
“El niño”:
El Niño is also
called Southern Oscillation, because of
a fluctuation coupled between the
atmosphere and the Austral Pacific. We will study three possible events:
·
“Neutral Enso”:
is the normal situation of the Peruvian coast in which there occur neither
"El Niño" or "La Niña",
according to which the trade winds that blow from east to west, pushing to the
west, the South Pacific surface water, creating a vacuum in the east, along the
coasts of Peru and Ecuador.
For this reason, the sea
level in Indonesia is about half a meter higher than along the coast of Peru.
This decrease in the sea level produces a suction effect that results in a
water gauging deep and rich in nutrients from the fund, which fertilize
phytoplankton and makes fishing increases. The trade winds are based on an
anticyclone located on Easter Island
(formed because the atmosphere is cooled by contact with the cold water
upwelling zone) and ends in a storm located in the Western Equatorial Pacific, near the Asia continent, where the low
pressure weather produces rainfall and typhoons.
·
“El
niño”: it is due to excessive the surface heating (0.5 ° C)
of the Eastern Pacific waters off the coast of Peru. It happens every 3-5
years, peaking at Christmas (hence its name, the baby Jesus). However, they
have registered with periods of between 2-7 years. Usually it lasts 9-12 months
(sometimes up to 18 months). It is usually associated with
a reduction in North Atlantic tropical hurricanes, and
an increase in tropical North Pacific
The ENSO occurs when trade winds disappear and drag
the ocean surface water to the west. Then, the surface water heats and forms a
storm, remaining clouds over the central Pacific Ocean, or along the coast of
Peru, which, under normal conditions, is arid. It doesn´t occurs the outcrop
because the thermocline persists (surface separating up / down the waters of
different temperature and density, preventing their mixture) and fishing wealth
decays.
On the western
Pacific side is the anticyclone, which leads
to drought in Indonesia, Australia and
the Philippines.
Nowadays the cause is unknown, but
some scientists think that
might be the result of global warming decreases the thermal contrast between the Eastern and Western Pacific, decreasing
the intensity of the trade winds and therefore the ocean
currents.
·
“La Niña”: It
is the name of the exaggeration of the normal situation,
which happens on the occasions where
the trade winds blow more strongly
than usual. It is associated with declines in the average temperature
of ocean surface
east-central Pacific (about - 1.5 ° C). It happens every
3-5 years or so and usually lasts
1-3 years. It causes torrential
rains and typhoons increased
in Indonesia and
Australia and an increase in the number and intensity of Atlantic tropical cyclones.
“El
Niño” and “La Niña”
govern the geographical distribution
and intensity of tropical rainfall
and cause changes in weather patterns worldwide
In the image below you can see the frequency,
intensity and duration of this phenomenon. “El Niño” in 1997/1998
caused heavy rains and flooding in Peru, Mozambique and Kenya, several storms
in California and droughts in Brazil, South Africa, Indonesia and Philippines.
The most recent began in September of 2006 and lasted
until March of 2007. Since April of 2007 “La Niña” began and lasted until 2008
4. ENSO REPERCUSIONS ON GLOBAL CLIMATE
The Southern Oscillation is a major
component in the interannual variations of global climate. The Oregon State University global
climate model, with a dynamically interactive upper ocean, reproduces in
qualitatively correct fashion some of the major characteristics of the Southern
Oscillation. This model simulates the observed anti-correlation of annually
averaged sea-level pressure (SLP) between the eastern Pacific and the Indonesian region, the primary
atmospheric signal of the Southern Oscillation. In the composite of the
simulated warm events positive sea-surface temperature (SST) anomalies expand
eastward towards South America from
the tropical western Pacific during
the first half of the calendar year. The SST anomalies develop in conjunction
with eastward mixed layer current
anomalies in the tropical Pacific. In the late summer and early fall
anomalously warm water near South
America develops and moves westward to merge with the central
Pacific anomalies. This lagged development in the eastern Pacific is analogous to the evolution of the
1982/83 and 1986/87 El Niño. The temperature of the thermo cline layer also
increases, with the slope of the equatorial Pacific thermo cline decreasing in
response to the relaxation of the surface forcing. Enhanced precipitation
occurs in the mid-Pacific while in the Indian and Australian monsoon regions a
deficit occurs. The peak of the warm phase occurs in late northern fall/early
winter, somewhat earlier than during observed “El Niño”. The cold phase of the
Southern Oscillation, enhancement of the zonal circulation, evolves in a
fashion similar to the warm phase with the signs of the anomalies reversed,
similar to observations. Occurrence of Southern Oscillation in this coarse resolution
GCM indicates that high resolution ocean
waves do not play a crucial role in the generation of this phenomenon as
suggested by Pacific basin models. These results also show that
ocean-atmosphere global climate models are useful tools for investigation of time dependent changes on the
interannual timescale in addition to their hitherto accepted use for studying
equilibrium properties of climate.New studies are showing that “El Niño Southern Oscillation” (ENSO) has
major implications for the functioning of different ecosystems, ranging from
deserts to tropical rain forests. ENSO-induced pulses of enhanced plant
productivity can cascade upward through the food
web invoking unforeseen feedbacks, and can cause open dryland
ecosystems to shift to permanent woodlands. These insights suggest that the
predicted change in extreme climatic events resulting from global warming could profoundly alter
biodiversity and ecosystem functioning in many regions of the world. Our
increasing ability to predict “El Niño” effects can be used to enhance
management strategies for the restoration of degraded ecosystems.
“La Niña”,
sometimes informally called "anti-El Niño", is the opposite of El
Niño, where the latter corresponds instead to a higher sea surface temperature by a deviation
of at least 0.5 °C, and its effects are often the reverse of those of El
Niño. El Niño is known for its potentially catastrophic impact on the weather
along the Chilean, Peruvian, New Zealand, and Australian coasts, among others.
It has extensive effects on the weather in North
America, even affecting the Atlantic
Hurricane Season. “La Niña” is often, though not always, preceded by an “El
Niño”.
5. QUESTIONS
-
Sea
breezes: which is the difference between days and nights?
-
Explain
the differences between the two ocean currents.
-
Which
are the two parts of a wave?
-
Where
is the beginning of The Ocean Conveyor
Belt?
-
Explain
briefly the main differences between Neutral situation, “El Niño” and “La
Niña”.
-
Which
are the repercussions of these phenomenons?
2 6. PREZI PRESENTATION DAY 3rd OF DECEMBER
3 7. FORUM
DABATE ON CLEPSIDRA
