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Wednesday, August 26, 2015 The Nugget Newspaper, Sisters, Oregon
WINTER: Forecast could
mean another year of
low snowpack
Continued from page 1
the same.
For the past several
months, ocean tempera-
tures in the tropical Pacific,
stretching from about the
International Date Line to
just off the coast of Peru,
have been steadily warm-
ing. At the same time the
normal easterly trade winds
have weakened and may
even reverse direction and
start blowing from the west.
These are indications that a
healthy El Niño may indeed
be on the way.
The El Niño Southern
Oscillation, or ENSO, is the
single most important cou-
pled ocean-atmosphere phe-
nomenon to cause global cli-
mate variability. It describes
the see-saw pattern of revers-
ing atmospheric pressure
between the eastern and
western tropical Pacific that
causes warm surface water to
slosh back and forth.
An El Niño is said to exist
when warm ocean water
migrates eastward, pooling
in the eastern Pacific Ocean.
It’s a La Niña if strong trade
winds move the warmer
water into the western
Pacific. Both conditions dis-
rupt normal weather patterns,
to a greater or lesser degree,
at many locations throughout
the world.
Various indicators are
used to determine the con-
dition and strength of the
ENSO, but perhaps the
most widely used is the
Multivariate ENSO Index
(MEI). The MEI combines
the effects of atmospheric
pressure, wind, air and water
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temperature and cloud cover.
When the numerical value
is between -0.5 and 0.5 the
ENSO is said to be neutral.
An El Niño is rated weak in
the range between 0.5 and
0.75, moderate between 0.75
and 1.0, and strong when the
number is greater than 1.0.
The same scale is used to
grade La Niñas, except the
numbers are negative.
It turns out that winters
here in the Pacific Northwest
and northern Rockies are
more strongly correlated to
the ENSO than almost any-
where else in the country.
During an El Niño winter,
warmer and drier conditions
prevail about 65-75 percent
of the time. During very
strong El Niños that likeli-
hood goes up to 80 percent,
according to information
from the Western Regional
Climate Center (WRCC) in
Reno, Nevada.
The two strongest El
Niños in the last 65 years
occurred during the winters
of 1982-83 and 1997-98.
In both cases the maximum
MEI value was 3.0.
These very powerful
events, though, can behave
differently from the typical
El Niño. For example, dur-
ing the record El Nino of
1982-83 the subtropical jet
shifted so far to the north that
it brought heavy precipita-
tion and warm temperatures
to Oregon and Washington.
According to Kelly Redmond
of WRCC, it was the only
major exception in the last
70 years to the typically dry
El Niño winters expected in
the Pacific Northwest.
The current MEI value for
the two-month period June-
July 2015 is already 1.972,
and many scientists say it
will likely increase in the
next few months.
So, it does look like the
upcoming winter will be
warm and dry. But what
about the two previous win-
ters? They were warm and
extremely dry too, but the
ENSO was neutral. Why?
After being gone for six
years, El Niño is returning,
only to find that another
weather-related entity cur-
rently occupies the ocean
waters.
A mysterious accumula-
tion of usually warm water
off the coast of the Pacific
Northwest began to emerge
late in 2013. Originally, “the
mass of water was 1,000
miles long, 1,000 miles
wide, and 300 feet deep, with
temperatures 2 to 7 degrees
F above normal,” says
Washington State climatolo-
gist Nick Bond. He dubbed it
“the blob.”
In 2014, more blobs
appeared.
“The whole pattern is,
we really have warmer-than-
normal temperatures in the
Pacific all the way from the
Gulf of Alaska down to the El
Niño area,” claims Redmond
of WRCC.
While blobs of warm
ocean water have occurred
in the Pacific before, experts
insist these are some of the
biggest in the last 50 years.
Many meteorologists and cli-
matologists strongly suspect
there is a link between the
blob and the dry winters of
2013-2014 and 2014-2015.
An intriguing question is
emerging: How will the blob
and El Niño get along this
winter? How will their inter-
action influence the coming
winter? “They could accen-
tuate each other or subtract
from each other. They could
multiply each other or they
might cancel each other. The
jury is out,” says Redmond.
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Archaeologists
return to Fort Rock
Archaeologists from the
University of Oregon (UO)
will be returning to the site
of the 1938 discovery of the
oldest known footwear in the
world.
Fort Rock Cave in north-
ern Lake County is famous
for dozens of approximately
10,000-year-old sagebrush-
bark woven sandals that were
found there by the “Father
of Oregon Archaeology”
Luther S. Cressman, who
was on the UO faculty from
1929 until his retirement in
1963.
Scheduled for August
31 through September 4,
archaeologists will fol-
low up on Cressman’s
investigations.
Cressman discovered the
sandals beneath a layer of
volcanic ash produced by
the 7,600-year-old eruption
of Mt. Mazama — the same
eruption that created Crater
Lake. The age of the san-
dals was confirmed in the
1950s through radiocarbon
dating. In 1966, Cressman
returned to the site with
graduate student Stephen
Bedwell who uncovered a
hearth in Pleistocene (Ice
Age) gravels. Charcoal
from the fire pit was radio-
carbon dated to roughly
15,800 years before present,
the oldest reputed hearth in
Oregon.
“As important as the site
is to the human story of
North America, the archaeo-
logical work there was done
more than half a century
ago. We still have impor-
tant questions about the site
that might be answered with
recovery methods and ana-
lytical techniques that were
not available to Cressman
and his students,” said Tom
Connolly, project leader and
director of archaeological
research for the UO Museum
of Natural and Cultural
History.
“Our excavation will not
be extensive, but will focus
on the chronology and dat-
ing of the site deposits, and
drawing critical samples for
later analysis.”
Limited public access
to the site will be provided
by the Oregon Parks and
R ecreat i o n Dep art m en t
(OPRD) in partnership with
UO. If interested in visit-
ing Fort Rock Cave during
the archaeological excava-
tion, contact OPRD staff at
541-923-7551 x21 to make
arrangements. Fort Rock
Cave became part of the
OPRD system in 2000 and
is accessible only by guided
tour.
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