 The
eight-year drought that plagued the central U.S. in the 1930s,
immortalized in The Grapes of Wrath, wracked the Great Plains
with devastating dust storms and affected two thirds of this country as
well as parts of Mexico and Canada. Paramount to determining why the
conditions were so severe and long-lasting is discerning what caused the
drought to begin with. Findings published today in the journal
Science suggest that unusual sea surface temperatures could be to
blame.
"The 1930s drought was the major climatic event in the nation’s
history," explains lead study author Siegfried Schubert of the NASA
Goddard Space Flight Center. "Just beginning to understand what occurred
is really critical to understanding future droughts and the links to
global climate change issues we’re experiencing today."
| Previous research had demonstrated a link between
some droughts and peculiar patterns of sea surface temperatures in
different parts of the world. Schubert and his colleagues used a
computer climate model to analyze conditions during the past 100
years. They found that ocean temperatures, particularly in the
tropics, heavily influenced the dry conditions experienced in North
America. In the early 1930s, the waters of the tropical Pacific were
cooler than normal, and those of the tropical Atlantic were warmer
than normal. Those conditions, the scientists say, weakened the jet
stream, a strip of fast-moving air that typically flows westward
over the Gulf of Mexico before turning northward and depositing rain
onto the Great Plains. In its altered state, the jet stream traveled
farther south than usual, lessening precipitation over the central
U.S. and compounding the drought conditions.
|
Other droughts that struck the U.S. also correspond to cooler
tropical Pacific temperatures, the researchers report, but only the
so-called Dust Bowl drought combined these condition with a warmer
Atlantic Ocean. A better understanding of the conditions that caused
severe climatic events of the past should help scientists better
recognize and forecast potentially dangerous conditions in the
future. --Sarah Graham |
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