A
LOOK AT EL NINO...
El
Nino is Spanish for "The Child," or in liturgical terms "The
Christ Child," an appropriate name for a major event that
generally occurs around Christmas. El Ninos, which
have been documented back to 1726 and doubtless occurred
before then, generally last a about twelved to eighteen months,
and develop once or twice a decade. In recent years,
however, the incidence, duration, and perhaps the intensity
of El Ninos have increased. some scientists believe
this is due to worldwide global warming resulting from the
increasing amounts of greenhouse gases accumulating in our
atmosphere.
In simple terms
then, an El Nino is an unusual warm current, initially off
the coast of Peru and Chile, that has the ability to cause
major weather and climate changes over many parts of the
world. How can an El Nino have such far-reaching climatic
effects? The answer seems to be that the warmer surface
waters in the equatorial Pacific change the overall pattern
of the atmospheric jet stream in the Northern Hemisphere. This
change causes storms in some regions and mild weather or
droughts in other regions.
The 1997 to 1998
El Nino was the strongest of the twentieth century. During
its tenure, several states had their warmest and/or wettest
conditions ever recorded. Many severe coastal storms
and considerable flooding occurred along much of the West
Coast of the United States. El Nino conditions in the
Pacific usually cause a smaller number of hurricanes in the
Atlantic, which is what seemed to happen in 1997.
There are several
ways that an El Nino can affect fish. One is that the
rising surface-water temperature will cause fish to migrate
away from their natural range to seek out cooler water or
food. They may eventually reach dangerously cool waters
that were unchanged by the El Nino, at which temperatures
they may die. Fish that do not migrate and remain in
an El Nino area may suffer or die from the increasing water
temperature or the lack of food.
Another El Nino
outcome may result from an increase in rainfall, which will
affect coastal habitats and the fish that live in these waters.
The rains will increase river discharge and therefore turbidity
in the water, and will reduce salinity. The runoff from land
may also carry increased amounts of pollutants into the streams
and estuaries where fish live, Any of these changes will
badly alter resident fish populations by inhibiting spawning
success, or by simply killing fish.
Another impact
can result from the changing wind patterns that in turn can
restrict or reduce coastal upwelling ( a current that brings
subsurface waters rich in nutrients to the surface). Less
upwelling will mean that there are fewer nutrients in the
water, and plants need nutrients to produce organic matter,
the basic food of the ocean. A reduction in this food
supply will cause problems throughout the food chain, and
will make life difficult for marine fish.
Fishery scientists
in the National Marine Fisheries Service (NMFS), a division
of the National Oceanic and Atmospheric Administration (NOAA),
correctly anticipated that the warming of the water off California
due to the 1997 to 1998 El Nino would expand the range of
tropical marine fish species to the north and bring excellent
fishing to California. For example, migrating yellowtail,
albacore, and bluefin tuna made an appearance in southern
California waters earlier in the season than usual. The
warm waters also created favorable conditions for small schooling
fish such as mackerel and sardines, and for larger species
such as mahi-mahi (dolphin) and billfish. Some species
of fish, especially bottom-living fish such as rockfish,
were adversely affected by the warmer water, since they do
not migrate and cannot avoid the changing water temperatures. Large
numbers of migrating sockeye salmon died because of warmer-than-usual
waters along their migration path.
It is clear that
a strong El Nino, such as the one from 1997 to 1998, will
dramtically affect global weather patterns and inflict considerable
damage, as well as have a major impact on the distribution,
movement, and survival of many species of marine life. Unfortunately,
the biological impacts of an El Nino are not always obvious
or can take years to be discovered. Scientists have
started to examine old fishing records and have noted that
some anomalies, such as low or outstanding harvests of a
particular species, seem to correlate with times of past
El Ninos.
It seems probable
to me that El Ninos and fish-population numbers and fish
harvest ultimately will be found to be more closely related
than previously anticipated.
As if El Ninos
didn't cause enough problems, there is a similar but opposite
phenomenon called La Nina. La Nina is the Spanish name
for a female child, and refers to an event that can cause
more trouble for the United States than its better known "brother." La
Nina will occur after an El Nino, when the more typical wind
pattern returns to the eastern Pacific, causing colder and
deeper water to replace the warmer waters that resulted from
the El Nino. The most recent La Nina, starting in 1998,
caused lower surface-water temperatures than usual. One
of the effects of La Nina is that the jet stream over the
United States is pushed northward toward Canada and Alaska,
and then returns carrying cold air south into the United
States. This could mean colder and wetter winters for
the central and western states, and mild and dry conditions
for the southern states. Of most concern is the possible
increased incidence of hurricanes along the Atlantic seaboard
during summer and autumn, and more tornadoes and very dry
conditions in the southeastern parts of the United States
in spring.
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