North Atlantic iceberg discharge and South American monsoon

A study explores how the influx of icebergs into the North Atlantic Ocean influences monsoon precipitation in South America. The last glacial period was characterized by transitions between extreme cold and mild climate states known as the Greenland Stadials (GS) and Greenland Interstadials, respectively. Of the 26 well-documented GS events, six were marked with periods of iceberg discharge in the North Atlantic--events designated Heinrich Stadials (HS). Nicolas Strikis and colleagues used isotopic records from caves in Central-Eastern and Northeastern Brazil to uncover changes in precipitation from the South American Monsoon during HS events. The records, derived from stalagmite samples, produced stable oxygen isotope records spanning the last approximately 84,000 years. Comparison of the records with sea surface temperature and atmospheric methane reconstructions from the North Atlantic as well as Greenland Ice core chronologies revealed that iceberg discharge in the western subtropical North Atlantic likely resulted in an increase in monsoon precipitation in eastern South America. Further, the strengthening of the South American monsoon coincided with an increase in atmospheric methane concentrations, suggesting that HS events, through the action of enhanced monsoon precipitation in the Southern Hemisphere, led to an increase in global atmospheric methane. The findings carry implications for the improved understanding of the tropical hydrologic cycle, according to the authors.

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Article #17-17784: "South American monsoon response to iceberg discharge in the North Atlantic," by Nicolás M. Stríkis et al.

MEDIA CONTACT: Nicolás M. Stríkis, Universidade Federal Fluminense, Rio de Janeiro, BRAZIL; tel: +552126292193; e-mail: strikis@gmail.com