Speleothem record of geomagnetic South Atlantic Anomaly recurrence

Author(s):Show less -

Trindade, Ricardo I. F. ^[1] ; Jaqueto, Plinio ^[1] ; Terra-Nova, Filipe ^{[1, 2]} ; Brandt, Daniele ^[1] ; Hartmann, Gelvam A. ^[3] ; Feinberg, Joshua M. ^[4] ; Strauss, Becky E. ^[5] ; Novello, Valdir F. ^[6] ; Cruz, Francisco W. ^[6] ; Karmann, Ivo ^[6] ; Cheng, Hai ^{[7, 8]} ; Edwards, R. Lawrence ^[8]

Affiliation

^[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil

^[2] Univ Nantes, Lab Planetol & Geodynam, F-44000 Nantes - France

^[3] Univ Estadual Campinas, Inst Geociencias, BR-13083870 Campinas, SP - Brazil

^[4] Univ Minnesota, Inst Rock Magnetism, Minneapolis, MN 55455 - USA

^[5] NIST, Mat Measurement Lab, Mat Sci & Engn Div, Gaithersburg, MD 20899 - USA

^[6] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[7] Xi An Jiao Tong Univ, Inst Global Environm Change, Xian 710049, Shaanxi - Peoples R China

^[8] Univ Minnesota, Dept Earth Sci, Minneapolis, MN 55455 - USA

• Document type: Journal article
• Source: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA; v. 115, n. 52, p. 13198-13203, DEC 26 2018.
• Web of Science Citations: 5

Abstract

The diminishing strength of the Earth's magnetic dipole over recent millennia is accompanied by the increasing prominence of the geomagnetic South Atlantic Anomaly (SAA), which spreads over the South Atlantic Ocean and South America. The longevity of this feature at millennial timescales is elusive because of the scarcity of continuous geomagnetic data for the region. Here, we report a unique geomagnetic record for the last similar to 1500 y that combines the data of two well-dated stalagmites from Pau d'Alho cave, located close to the present-day minimum of the anomaly in central South America. Magnetic directions and relative paleointensity data for both stalagmites are generally consistent and agree with historical data from the last 500 y. Before 1500 CE, the data adhere to the geomagnetic model ARCH3K. 1, which is derived solely from archeomagnetic data. Our observations indicate rapid directional variations (> 0.1 degrees/y) from approximately 860 to 960 CE and approximately 1450 to 1750 CE. A similar pattern of rapid directional variation observed from South Africa precedes the South American record by 224 +/- 50 y. These results confirm that fast geomagnetic field variations linked to the SAA are a recurrent feature in the region. We develop synthetic models of reversed magnetic flux patches at the core-mantle boundary and calculate their expression at the Earth's surface. The models that qualitatively resemble the observational data involve westward (and southward) migration of midlatitude patches, combined with their expansion and intensification. (AU)

• FAPESP's process: 17/50085-3 - PIRE: climate research education in the Americas using tree-ring speleothem examples (PIRE-CREATE)
• Grantee: Francisco William da Cruz Junior
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 18/07410-3 - Persistence of the South Atlantic Anomaly in geomagnetic observations, field models and numerical dynamos
• Grantee: Filipe Terra Nova dos Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 16/15807-5 - Paleoclimate and paleoenvironmental reconstructions over the last glacial period in the mid-west Brazil
• Grantee: Valdir Felipe Novello
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 16/24870-2 - Environmental significance of speleothem magnetism
• Grantee: Plinio Francisco Jaqueto
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/00299-4 - Geochemistry of vadose percolation in karst systems: implications for paleoclimatic interpretations os speleothem records
• Grantee: Ivo Karmann
• Support Opportunities: Regular Research Grants