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Ocean warming - not el Niņo - drove severe Amazon drought in 2005 mongabay.com February 21, 2008
In 2005 the Amazon experienced the worst in memory. As rivers dried up, remote communities were isolated while commerce slowed to a standstill. Thousands of square kilometers of land burned for months on end, releasing more than 100 million metric tons of carbon into the atmosphere. At the time of the drought scientists observed an apparent correlation between sea surface temperatures in the Atlantic Ocean and precipitation in the Amazon. Now research by Dr. Jose Marengo and colleagues from Brazil's Instituto Nacional de Pesquisas Espaciais (INPE) and the Instituto de Aeronáutica e Espaço (IEA), confirms that "the 2005 drought was linked not to El Niņo as with most previous droughts in the Amazon, but to warming sea surface temperatures in the tropical North Atlantic Ocean."
"The Tropical North Atlantic Ocean was much warmer during all of 2005 and the meteorological analysis described in the paper showed that anomalous warm sea surface temperature over the Tropical North Atlantic created a relatively low pressure system over that oceanic region. That low pressure changed the wind system over the Tropics. The overall result was descending motion over SW Amazonia, which reduced cloudiness and rainfall." Lead author Marengo told mongabay.com that while previous droughts have been linked to El Niņo events, 2005 was an anomaly.
"The warming in the tropical North Atlantic was responsible for this drought, since the tropical Pacific was almost neutral (absence of El Niņo)." The conclusion is significant as climate models forecast continue warming in the North Atlantic Ocean due to rising emissions of greenhouse gases. Warm conditions in the North Atlantic Ocean have also been correlated with the formation of hurricanes in the Gulf of Mexico and along the Eastern seaboard of the United States. Hurricane Katrina struck New Orleans in August 2005 [note]. Several climate models for the Amazon project significant warming and drying by 2100 due to rising concentrations of carbon dioxide in the atmosphere. These changes, combined with forecast deforestation and continuing use of fire, could result in the conversion of much of the Amazon rainforest to savanna and scrub. Marengo, J.A. et al (2008). Hydro-climatic and ecological behaviour of the drought of Amazonia in 2005 [FREE OPEN ACCESS]. Phil. Trans. R. Soc. B, DOI: 10.1098/rstb.2007.0026 Dr. Marengo wanted to emphasize that drying in the Amazon and hurricanes are not linked to each other, but to sea surface temperatures:
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