Climate patterns linked in Amazon, North and South America, study shows


Date:
October 9, 2020
Source:
University of Arkansas
Summary:
Researchers have developed a tree-ring chronology from the Amazon
River basin that established a link between climate patterns in
the Amazon and the Americas.



FULL STORY ========================================================================== University of Arkansas researchers have established a link between climate patterns in the Amazon and large parts of North and South America using
their newly developed tree-ring chronology from the Amazon River basin.


==========================================================================
The discovery helps researchers better understand large-scale climate
extremes and the impact of the El Nin~o phenomenon.

Tree growth is a well-established climate proxy. By comparing growth rings
in Cedrela odorata trees found in the Rio Paru watershed of the eastern
Amazon River with hundreds of similar chronologies in North and South
America, scientists have shown an inverse relationship in tree growth,
and therefore precipitation patterns, between the areas. Drought in the
Amazon is correlated with wetness in the southwestern United States,
Mexico and Patagonia, and vice versa.

The process is driven by the El Nin~o phenomenon, which influences
surface- level winds along the equator, researchers said. El Nin~o is
the name given to a large-scale irregularly occurring climate pattern associated with unusually warm water in the Pacific Ocean.

"The new Cedrela chronologies from the Amazon, when compared with the
hundreds of tree-ring chronologies in temperate North and South America, document this Pan American resonance of climate and ecosystem extremes in
the centuries before widespread deforestation or human-caused climate
change," said Dave Stahle, Distinguished Professor of geosciences
and first author of a study documenting the findings in the journal Environmental Research Letters.

The connection was not documented until researchers at the University
of Arkansas Tree Ring Laboratory, along with colleagues from Brazil
and Argentina, developed rainfall reconstructions from growth rings in
Cedrela trees. Most rainfall records in the Amazon only date back about
70 years, but Cedrelas live for 200 to 300 years, providing valuable
rainfall proxies that pre-date human- influenced climate change.

In the past 40 years, drought and flood extremes have increased in the
Amazon basin, the researchers noted, raising the question of whether human-induced climate change and deforestation are affecting Amazon
climate. While that remains an open question, the longer Cedrela-based precipitation record indicates that periods of rainfall extremes occurred
in the past and the current extremes might be partly due to natural
climate rhythms.

The study will help researchers better understand an area of unequaled biodiversity. The Amazon is home to an estimated 16,000 species of trees
and one-tenth of all known species found on the planet, Stahle noted. "The
long climate history written in the growth rings of old Cedrela trees in Amazonia will surely be important to the sustainability of the biome."
Video: https://www.youtube.com/watch?v=YEGJDvdwAu8&feature=emb_logo

========================================================================== Story Source: Materials provided by University_of_Arkansas. Original
written by Bob Whitby.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. D W Stahle, M C A Torbenson, I M Howard, D Granato-Souza, A C
Barbosa, S
Feng, J Scho"ngart, L Lopez, R Villalba, J Villanueva, K
Fernandes. Pan American interactions of Amazon precipitation,
streamflow, and tree growth extremes. Environmental Research
Letters, 2020; 15 (10): 104092 DOI: 10.1088/1748-9326/ababc6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201009121932.htm

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