Nino-Like Climate Patterns Existed During Last Ice Age, Study Finds
11, 2000 -- El
Nino-like climate patterns occurred in the New England region during
the last ice age, 17,500 to 13,500 years ago, according to a new
study. This is the first time scientists have been able to document
evidence of El Nino activity during that time period. It previously
was unclear whether El Nino was active during the last ice age.
findings will be reported in the May 12 issue of the journal Science.
evidence suggests that the El Nino phenomenon is more robust than
we previously imagined," says Michael Mann, assistant professor
in the Department of Environmental Sciences at the University of
Virginia, and one of the study's authors. "We have found evidence
of a strong three-to-seven-year cycle of El Nino activity during
the later part of the last ice age, which is much like the present
three-to-seven-year cycle of El Nino events."
and his colleagues analyzed sediment cores from the bottom of a
sequence of glacial lakes in New England. The lakes formed in an
area where an ice sheet covering a large part of the North American
continent left yearly sediment deposits when it retreated northward
through the Connecticut Valley as the climate began warming. The
layers of sediment offered Mann and his team a detailed record of
climate variability. During the periodic El Nino events the glacier
melted more quickly, leaving thicker annual layers of sediment.
Nino, a warming of sea surface temperatures in the equatorial Pacific,
is important to scientists because of its large effects on global
weather patterns and its possible long-term role in global climate
change. Climatologists are trying to understand how persistent the
phenomenon is -- how long it has existed, and for how long it may
continue. Recent studies suggest that El Nino activity has moderated
in recent decades.
findings provide a new perspective on the changes observed in El
Nino activity in recent decades, and their possible relationship
with global climate change," Mann says. "We are trying to understand
what drives El Nino. We have found that this is not only a warm-climate
phenomenon -- it can happen under many types of climate conditions,
even when large parts of the earth are covered with ice.
looking back to a time before human impact on the environment, we
can compare previous climate conditions to what we are seeing today,"
Mann adds. "This may help us to understand subtle ways in which
global warming could be influencing the behavior of the climate."
other authors of the paper are geoscientist Julie Brigham-Grette
of the University of Massachusetts and graduate student Tammy Rittenour
at the University of Nebraska.
Fariss Samarrai, (804) 924-3778