Washington, Sept 20 (ANI): An international team of scientists investigated 50-million-year-old clamshells and wood from the Antarctic and came to the conclusion that the Earth warming will presumably not lead to a permanent El Nino state in the South Pacific Ocean.
The growth rings of these fossils indicate that there was also a climate rhythm over the South Pacific during the last prolonged interglacial phase of the Earth's history resembling the present-day interplay of El Nino and La Nina.
When the South Pacific Ocean warms up at an above-average rate every three to six years and "El Nino" influences weather patterns, the world in the coastal countries affected is turned completely around.
Fishermen come back with empty nets, crops are lost, food prices increase and nearly everyone hopes the warm phase of the climate phenomenon "El Nino Southern Oscillation (ENSO)" will abate as quickly as possible.
To see what things will be like in the future, and how the worldwide temperature rise will influence ENSO, scientists looked to the past particularly at the Eocene period 60 to 37 million years ago.
Thomas Brey, biologist at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, and colleagues from the USA and Germany have now succeeded for the first time in verifying a rhythm according to the pattern of the ENSO phenomenon in the growth patterns of fossil clams and wood from the early Eocene.
Brey and his colleagues investigated shells of the bivalve species Cucullaea Raea and Eurhomalea antarctica that are 50 million years old as well as a piece of wood from Seymour Island in the Antarctic.
"Like trees, clams form growth rings. We measured their width and examined them for growth rhythms," Brey said.
Whether clams grow depends on the availability of food and heat.
"That means the change from 'good' and 'poor' environmental conditions at that time is still reflected in the width of the growth rings we find today," Brey explained.
"And as we were able to show, this change took place in the same three to six year rhythm we are familiar with in connection with ENSO today.
"To verify ENSO, we need climate archives that cover the largest possible period year by year. Back then clams lived for up to 100 years. This is a good basis for our work.
"Our results are a strong indication that an ENSO phenomenon which fluctuated between warm and cold phases also existed in the warm Eocene," he added.
The results are set to appear in the journal Geophysical Research Letter and are already available on its website in a text entitled "El Nino in the Eocene greenhouse recorded by fossil bivalves and wood from Antarctica". (ANI)
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