Simulated isotopic fingerprint of the Atlantic Multidecadal Oscillation over South America and its relation to the Little Ice Age

Author(s)

Maksic, Jelena ; Shimizu, Marilia Harumi ; Sampaio, Gilvan ; Chiessi, Cristiano M. ; Prange, Matthias ; Vuille, Mathias ; Utida, Giselle ; Cruz, Francisco W. ; Lemes, Murilo Ruv

• Document type: Journal article
• Source: PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY; v. 659, p. 11-pg., 2024-12-10.

Abstract

Linkages have been established between the Atlantic Multidecadal Oscillation (AMO) and surface air temperature variations, low-level jet streams, and precipitation trends in both northeastern Brazil and southeastern South America. Previous studies have discerned distinct wet-season (March-May) precipitation responses in northeastern Brazil, with cold (warm) AMO phases triggering increased (decreased) precipitation. Findings from various records indicate that the AMO's variability extends for thousands of years. A recent reconstruction suggests a significant AMO role in the shift from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA) and reveals the LIA as the longest period with a persistent cold anomaly in the North Atlantic over the past similar to 3 millennia. Stable oxygen isotope records from South America show typical AMO periodicities (similar to 65 years), however, despite increased paleo precipitation data, the AMO's role in South American precipitation during the LIA and MCA remains unclear. In this study, the influence of AMO phases on atmospheric dynamics, precipitation patterns, and stable oxygen isotope composition (delta 18O) of precipitation over South America is assessed using the water isotope-enabled version of the Community Earth System Model version 1.2 (iCESM1.2). This research sheds light on the connection between AMO-induced precipitation anomalies and isotopic signals observed in paleoclimate records and emphasizes the significance of isotope-enabled climate models in unraveling the mechanisms behind past variations. The analysis involves comparing delta 18O simulations with published reconstructions from South America. By utilizing climate models that incorporate isotopes, we can delve deeper into understanding the impact of the AMO on precipitation patterns and isotopic ratios. Contrary to expectations, the simulated delta O-18(p) signal differ from speleothem records over the western Amazon and Andes during the LIA. That is, the simulated significant total precipitation amounts change over the western Amazon and Andes are not reflected in delta O-18(p) depletion. (AU)

• FAPESP's process: 18/23522-6 - South American Monsoon System simulation of the last millennium: interannual to multidecadal variability and forcing mechanisms
• Grantee: Jelena Maksic
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 19/24349-9 - Assessing the effects of past and future climate change on Amazonian biodiversity (CLAMBIO)
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants
• FAPESP's process: 18/15123-4 - Past perspectives on tipping elements of the climate system: the Amazon Rainforest and the Atlantic Meridional Overturning Circulation (PPTEAM)
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: Research Grants - Research Program on Global Climate Change - Young Investigators - Phase 2