Earth's climate system is complex, and its major components - the ocean, atmosphere and vegetation - are closely interconnected. A change in one element can trigger widespread effects throughout the system. While these components exhibit some resilience and can absorb some fluctuations, climate and Earth system research suggests there are tipping points. If these tipping points are crossed, the climate system can quickly shift to another state.
Tipping points in the climate system are thought to be interactive, potentially triggering cascading effects. Two important global tipping points are the Amazon rainforest and the Atlantic Meridional Overturning Circulation (AMOC). Continued global warming may significantly weaken the Atlantic meridional overturning circulation, disrupting the ocean conveyor belt that carries warm water to northern latitudes. This will change the distribution of temperatures across the Atlantic Ocean, affecting the Amazon region. Changes in Atlantic temperatures will affect the atmospheric water cycle, causing changes in precipitation patterns, further destabilizing rainforest ecosystems.
There has not been extensive research on how the AMOC and the Amazon are interconnected as a system, and how ocean circulation affects the Amazon. A team of researchers led by Professors Dr. Thomas Akabane and Dr. Christiano Chiessi from the University of São Paulo have now analyzed changes in vegetation in the Amazon. Together with an international team, they analyzed pollen and carbon residues in marine sediment cores taken from the Amazon estuary, representing the past 25,000 years.
Through their analysis, the team gained a detailed understanding of the past of one of the most species-rich ecosystems on Earth. The data show how vegetation, as well as wet and dry periods, changed during the last Ice Age climate event, known as the Heinrich event, when the AMOC weakened sharply. In particular, the researchers found a dramatic decline in rainforest vegetation in the northern Amazon region.
"This study is the result of a long-term collaboration between Germany and Brazil. A joint expedition by the research vessel MERIAN in the Amazon River estuary region. Our data show that the Amazon ecosystem has been able to adapt to changes in precipitation patterns caused by weakening Atlantic circulation in the past. However, if the weakening of the Atlantic circulation coincides with increased deforestation in the future, it will threaten the stability of this important global system. Using climate and vegetation models Further research conducted suggests that under present-day conditions, a weakening of the AMOC will have effects on Amazon vegetation similar to those of past ice ages. Models show us that a complete collapse of the AMOC is not necessary to have an impact on the rainforest, and that northern areas of the Amazon would experience large impacts from only modest changes in the AMOC," explains Dr. Matthias Prange from MARUM.
These results illustrate how complex the global system is. "Driving processes at high latitudes, such as the melting of Greenland ice, can have dramatic effects in the tropics. Such long-distance effects often have severe consequences for regions that often only affect those who have only a small responsibility for causing climate change," adds Professor Gerrit Lohmann of the AWI.
Compiled from /ScitechDaily