El Niño

Term Paper for Earth Science

Submitted by: Chrisma Marie Faris BSED 1

Submitted to: Ms. Rili May Oebanda

Introduction

El Niño was identified and named long before science caught up with the
phenomenon. For centuries, Peruvian fishermen reaped a bounty off the Pacific coast of
South America, where north- and west-flowing currents pulled cool, nutrient-rich water
from the deep. But every so often, the currents would stop or turn around; warm water
from the tropics would drive the fish away and leave the nets empty. These periodic
warm spells were most noticeable around December or January—around the time of
Christmas, the birth of "the boy child."

Some of the first scientific descriptions of El Niño came during exchanges

between the Lima Geographical Society and the International Geographic Congress in
the 1890s. But the roots of El Niño stretch far back into history, long before the birth of
Jesus of Nazareth or the arrival of Peruvian fisherman. The chemical signatures of
warmer seas and increased rainfall have been detected in coral samples and in other
paleoclimate indicators since the last Ice Age. This pattern of water and wind changes
has been going on for tens of thousands of years.

Earth scientists, historians, and archaeologists have theorized that El Niño had a
role in the demise or disruption of several ancient civilizations, including the Moche, the
Inca, and other cultures in the Americas. But the recorded history of El Niño really starts
in the 1500s, when European cultures reached the New World and met indigenous
American cultures.
BODY OF THE TOPIC

Pacific Wind and Current Changes Bring Warm, Wild Weather

Episodic shifts in winds and water currents across the equatorial Pacific can
cause floods in the South American desert while stalling and drying up the monsoon in
Indonesia and India. Atmospheric circulation patterns that promote hurricanes and
typhoons in the Pacific can also knock them down over the Atlantic. Fish populations in
one part of the ocean might crash, while others thrive and spread well beyond their
usual territory.

The GOES-West satellite observed four tropical cyclones roiling the Pacific on
September 1, 2015, during an El Niño event. (Image courtesy of the NASA/NOAA
GOES Project.)

During an El Niño event, the surface waters in the central and eastern Pacific
Ocean become significantly warmer than usual. That change is intimately tied to the
atmosphere and to the winds blowing over the vast Pacific. Easterly trade winds (which
blow from the Americas toward Asia) falter and can even turn around into westerlies.
This allows great masses of warm water to slosh from the western Pacific toward the
Americas. It also reduces the upwelling of cooler, nutrient-rich waters from the deep—
shutting down or reversing ocean currents along the equator and along the west coast
of South and Central America.

The circulation of the air above the tropical Pacific Ocean responds to this
tremendous redistribution of ocean heat. The typically strong high-pressure systems of
the eastern Pacific weaken, thus changing the balance of atmospheric pressure across
the eastern, central, and western Pacific. While easterly winds tend to be dry and
steady, Pacific westerlies tend to come in bursts of warmer, moister air.
 Atmospheric circulation over the equator—the Walker circulation—changes
substantially with the arrival of El Niño. (Illustration by NOAA/Climate.gov)

Because of the vastness of the Pacific basin—covering one-third of the planet—

these wind and humidity changes get transmitted around the world, disrupting
circulation patterns such as jet streams (strong upper-level winds). We know these
large-scale shifts in Pacific winds and waters initiate El Niño. What we don't know is
what triggers the shift. This remains a scientific mystery.
 El Niño usually alters the Pacific jet stream, stretching it eastward, making it
more persistent, and bringing wetter conditions to the western U.S. and Mexico. (NASA
Earth Observatory illustration by Joshua Stevens.)

What is not a mystery is that El Niño is one of the most important weather-
producing phenomena on Earth, a "master weather-maker," as author Madeleine Nash
once called it. The changing ocean conditions disrupt weather patterns and marine
fisheries along the west coasts of the Americas. Dry regions of Peru, Chile, Mexico, and
the southwestern United States are often deluged with rain and snow, and barren
deserts have been known to explode in flowers. Meanwhile, wetter regions of the
Brazilian Amazon and the northeastern United States often plunge into months-long
droughts.

Typically dry regions can experience nearly two times as much rain during a
strong El Niño. (NASA Earth Observatory chart by Joshua Stevens, using data from the
California-Nevada Climate Applications Program.)

El Niño events occur roughly every two to seven years, as the warm cycle
alternates irregularly with its sibling La Niña—a cooling pattern in the eastern Pacific—
and with neutral conditions. El Niño typically peaks between November and January,
though the buildup can be spotted months in advance and its effects can take months to
propagate around the world.

Though El Niño is not caused by climate change, it often produces some of the
hottest years on record because of the vast amount of heat that rises from Pacific
waters into the overlying atmosphere. Major El Niño events—such as 1972-73, 1982-
83, 1997-98, and 2015-16—have provoked some of the great floods, droughts, forest
fires, and coral bleaching events of the past half-century.
 El Niño years tend to be warmer than other years. (NASA Earth Observatory
chart by Joshua Stevens, using data from the Goddard Institute for Space Studies.)

NASA, the National Oceanic and Atmospheric Administration (NOAA), and other
scientific institutions track and study El Niño in many ways. From underwater floats that
measure conditions in the depths of the Pacific to satellites that observe sea surface
heights and the winds high above it, scientists now have many tools to dissect this
l'enfant terrible of weather. The data visualizations on the next page show most of the
key ways that we observe El Niño before, during, and after its visits.

Underwater Temperatures and Water Masses

The ocean is not uniform. Temperatures, salinity, and other characteristics vary in
three dimensions, from north to south, east to west, and from the surface to the depths.
With its own forms of underwater weather, the seas have fronts and circulation patterns
that move heat and nutrients around ocean basins. Changes near the surface often
start with changes in the depths.

The tropical Pacific receives more sunlight than any other region on Earth, and
much of this energy is stored in the ocean as heat. Under neutral, normal conditions,
the waters off southeast Asia and Australia are warmer and sea level stands higher than
in the eastern Pacific; this warm water is pushed west and held there by easterly trade
winds.

Temperature anomalies in the ocean depths reveal the fingerprints of El Niño and
the La Niña that follows. (NASA Earth Observatory visualization by Joshua Stevens,
using data from the Global Data and Assimilation Office.)

But as an El Niño pattern develops and trade winds weaken, gravity causes the
warm water to move east. This mass, referred to as the "western Pacific warm pool,"
extends down to about 200 meters in depth, a phenomenon that can be observed by
moored or floating instruments in the ocean: satellite-tracked drifting buoys, moorings,
gliders, and Argo floats that cycle from the ocean surface to great depths. These in situ
instruments (more than 3,000 of them) record temperatures and other traits in the top
300 meters of the global ocean.
 The visualization above shows a cross-section of the Pacific Ocean from January
2015 through December 2016. It shows temperature anomalies; that is, how much the
temperatures at the surface and in the depths ranged above or below the long-term
averages. Note the warm water in the depths starting to move from west to east after
March 2015 and peaking near the end of 2015. (The western Pacific grows cooler than
normal.) By March 2016, cooler water begins moving east, sparking a mild La Niña in
the eastern Pacific late in 2016, while the western Pacific begins to warm again.

Sea Surface Temperatures

For hundreds of years, the temperature near the water surface has been
measured by instruments on ships, moorings and, more recently, drifters. Since the late
1970s, satellites have provided a global view of ocean surface temperatures, filling in
the gaps between those singular points where floating measurements can be made.

El Niño is associated with above-average equatorial sea surface temperatures.

El Niño's signature warmth is apparent in the November 2015 map. (NASA Earth
Observatory maps by Joshua Stevens, using data from Coral Reef Watch.)

Sea surface temperatures are measured from space by radiometers, which

detect the electromagnetic energy (mostly light and heat) emitted by objects and
surfaces on Earth. In the case of the oceans, satellite radiometers—such as the
Advanced Very High Resolution Radiometer (AVHRR) on NOAA weather satellites and
the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and
Aqua satellites—detect the strength of infrared and microwave emissions from the top
few millimeters of the water.

The maps above show sea surface temperature anomalies in the Pacific from
winter and fall of 2015. The maps do not depict absolute temperatures; instead, they
show how much above (red) or below (blue) the surface water temperatures were
compared to a long-term (30-year) average. The maps were built with data from a multi-
satellite analysis assembled by researchers from NOAA, NASA, and the University of
South Florida.

When deciding whether the Pacific is in an El Niño state, the climatologists at

NOAA examine sea surface temperatures in the east-central tropical Pacific—referred
to as the Niño 3.4 region (between 120° to 170° West). An El Niño is declared when the
average temperature stays more than 0.5 degrees Celsius above the long-term average
for five consecutive months. In 1997-98 and 2015-16, sea surface temperatures rose
more than 2.5 degrees Celsius (4.5 degrees Fahrenheit) above the average.

Sea Surface Height

Sea level is naturally higher in the western Pacific; in fact, it is normally about 40
to 50 centimeters (15-20 inches) higher near Indonesia than off of Ecuador. Some of
this difference is due to tropical trade winds, which predominantly blow from east to
west across the Pacific Ocean, piling up water near Asia and Oceania. Some of it is also
due to the heat stored in the water, so measuring the height of the sea surface is a good
proxy for measuring the heat content of the water.

Water expands as it warms, causing the surface of the ocean to rise. (NASA
Earth Observatory map by Joshua Stevens, using Jason-2 data provided by Akiko
Kayashi and Bill Patzert, NASA/JPL Ocean Surface Topography Team.)

The animation above compares sea surface heights in the Pacific Ocean as
measured by the altimeter on the OSTM/Jason-2 satellite and analyzed by scientists at
NASA’s Jet Propulsion Laboratory. It shows sea surface height anomalies, or how much
the water stood above or below its normal sea level. Shades of red indicate where the
ocean was higher because warmer water expands to fill more volume (thermal
expansion). Shades of blue show where sea level and temperatures were lower than
average (water contraction). Normal sea-level conditions appear in white.
 As you watch sea surface heights change through 2015, note the pulses of
warmer water moving east across the ocean. When the trade winds ease and bursts of
wind come out of the west, warm water from the western Pacific pulses east in vast,
deep waves (Kelvin waves) that even out sea level a bit. As the warm water piles up in
the east, it deepens the warm surface layer, lowering the thermocline and suppressing
the natural upwelling that usually keeps waters cooler along the Pacific coasts of the
Americas. (Look back at the underwater temperature animation to see this
phenomenon.)

Ocean Color

As temperatures change due to El Niño, other effects ripple through the ocean. In
the eastern Pacific, the surge of warm water deepens the thermocline, the thin layer that
separates surface waters from deep-ocean waters. This thicker layer of warm water at
the surface curtails the usual upwelling of cooler, nutrient-rich water—the water that
usually supports rich fisheries in the region. This loss of the nutrient supply is evident in
declining concentrations of sea surface chlorophyll, the green pigment present in most
phytoplankton. Changes in water properties such as oxygen and carbon content also
affect marine life.

Chlorophyll concentrations rise and fall with the presence of phytoplankton.

During the 2015 El Niño, warming water temperatures changed where phytoplankton
bloomed in the Pacific Ocean. (NASA Earth Observatory maps by Joshua Stevens and
Stephanie Schollaert Uz, using data from MODIS, NASA OceanColor Web, and
SeaDAS.)

The images above compare sea surface chlorophyll in the Pacific Ocean as
observed in October 2014 and 2015. Shades of green indicate more chlorophyll and
blooming phytoplankton. Shades of blue indicate less chlorophyll and less
phytoplankton. (For a larger view of these maps, click here.)
 Historic observations have shown that with less phytoplankton available, the fish
that feed upon plankton—and the bigger fish that feed on the little ones—have a greatly
reduced food supply. In most extreme El Niños, the decline in fish stocks has led to
famine and dramatic population declines for marine animals such as Galapagos
penguins, marine iguanas, sea lions, and seals.

Surface Winds

The behavior of the winds and waters are tightly intertwined in the Pacific basin
during an El Niño event. "It is like the proverbial chicken-and-egg problem," says
Michael McPhaden of NOAA’s Pacific Marine Environmental Laboratory. “During an El
Niño year, weakening winds along the equator lead to warming water surface
temperatures that lead to further weakening of the winds.”

The image below shows the dominant direction of the winds and changes in their
intensity near the ocean surface as observed by NASA’s RapidScat instrument. Arrows
show how the primary wind direction changed from January 2015 to January 2016. The
change in wind speed is represented by colors, with surface wind speeds increasing in
teal-green areas and decreasing in purple areas.

During an El Niño, wind patterns shift all over the Pacific Ocean. Most
significantly, they get weaker (purple) in the eastern tropical Pacific, allowing warm
surface water to move toward the Americas (NASA Earth Observatory map by Joshua
Stevens using RapidScat data from the Jet Propulsion Laboratory.)

The El Niño signal is evident in the eastward-blowing winds in the tropical

western and central Pacific. Winds near the equator (5° North to 5° South) blew more
forcefully from west to east in the western and central Pacific; meanwhile, the easterly
(east to west) trade winds weakened near the Americas. These wind shifts allowed
pulses of warm water to slosh from Asia toward the Americas over the course of 2015.
The signal also shows up in a convergence in the eastern Pacific; that is, the winds in
the tropics (23°N to 23°S) were generally moving toward the equator. This reflects
intense convection, where warm surface waters promote intense evaporation and rising
air. (See the Walker circulation illustration on page 1.) Consequently, new air masses
move toward the equator to replace the rising air.

Other changes occurred well away from the equator; scientists refer to these as
teleconnections. For instance, RapidScat detected a strong clockwise-rotating (anti-
cyclonic) wind anomaly in the northeastern Pacific that may have been the result of
stronger-than-normal atmospheric circulation (Hadley cell). That is, air that rose above
the super-heated waters of the central tropical Pacific sank back to the surface at higher
latitudes with more than usual intensity.

Cloudiness and Precipitation

By changing the distribution of heat and wind across the Pacific, El Niño alters
rainfall patterns for months to seasons. As the warm ocean surface warms the
atmosphere above it, moisture-rich air rises and develops into rain clouds. So while the
majority of precipitation tends to occur over the west Pacific warm pool in neutral years,
much more develops over the central and eastern Pacific during an El Niño event.

Just as El Niño influences ocean surface temperatures, it also alters the amount
and location of clouds over the Pacific. (NASA Earth Observatory maps by Joshua
Stevens, using data from the NASA Earth Observations.)

The globes show cloud fraction over the Pacific Ocean in January and November
2015 as measured by the MODIS instrument on NASA's Aqua satellite. The data show
how often and how much the sky was filled with clouds over a particular region.
Cloudiness is a result of moisture rising from the ocean surface into the atmosphere.
During an El Niño (November image), cloud cover increases in the eastern
Pacific due to the warm water releasing more moisture and heat into the atmosphere.
Those clouds can lead to more rain, but they also shade the water by day and trap heat
near the surface at night.
CONCLUSION

This leads to dead material and plants struggling to survive. The eastern Pacific
is more affected because when there is air movement, the air rising over S. America
instead of descending. This leads to large storms as well as flooding due to the sea
level change. The El Nino of 1997/8 is one of the worst ever seen with its effects seen
across the world. Within the Sechura Desert for example, a place that has some of the
lowest rainfalls in the world the rainfall from the storms formed a temporary lake which
lasted six months. More seriously, the storms caused mudslides within Peru and
motorways were ripped up. In conclusion, there are many problems that causes El Nino
and is a natural phenomenon that can’t be stopped. Although human create it, it has
been heightened due to the other factors mentioned.

The impact of El Niño affects Philippines’ biodiversity hotspots. The country’s

weather officials define El Niño as a meteorological event that develops in the Pacific
Ocean and associated with extreme rains, winds, droughts, etc. In the Philippines, El
Niño has been seen as drought events. El Niño is also the sudden rise of oceanic
temperature and evaporation of surface water; therefore having an effect on coral
growth and sea life. Algae living inside the tissues of coral help their feeding mechanism
and other processes for survival. The distress to the sudden change of temperature
causes the coral to bleach. Fish no longer live inside the coral because the coral is
uneatable. The drought creates dry conditions for fish ponds. The drought also creates
a negative impact on marine biodiversity by shorter fish production, inhibit fish growth
and increase fish mortality due to stress, poor water quality and disease.