Tracing the strength of the southwest monsoon using boron isotopes in the eastern Arabian Sea

• Published in: Geophysical research letters Vol. 42; no. 5; pp. 1450 - 1458
• Main Authors: Naik, Sushant S., Divakar Naidu, P., Foster, Gavin L., Martínez-Botí, Miguel A.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 16.03.2015; John Wiley & Sons, Inc
• Subjects: Arabian Sea; Atmospheric chemistry; Biological effects; Boron; Boron isotopes; Carbon; Deglaciation; Foraminifera; Fossil Foraminifera; Globigerinoides ruber; Holocene; Ice ages; Isotopes; Last Glacial Maximum; Marine; Meltwater; Meteorology; Mineral nutrients; monsoon; Monsoons; Nutrient utilization; Nutrients; Ocean-atmosphere interaction; Reconstruction; Reduction; Salinity; Seawater; Sediment; Southwest; Southwest monsoon; Strength; Temperature (air-sea); Wind; ΔpCO2; ISW, Arabian Sea
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063089

Here we present the first boron isotope‐based pCO2sw (pCO2 of seawater) reconstruction from the eastern Arabian Sea using the planktic foraminifera species Globigerinoides ruber. Our results from sediment core AAS9/21 show that pCO2sw varied between ~160 and 300 µatm during the last 23 kyr. The ΔpCO2, the sea‐air pCO2 difference, is relatively small during the last glacial maximum and becomes more negative toward the Holocene, with the exception of a significant excess during the last deglaciation centered on the Bølling‐Ållerød. Throughout the record, ΔpCO2 is predominantly negative, probably as a result of enhanced biological productivity (and higher nutrient and carbon utilization) during the southwest monsoon. A reduction in ΔpCO2 during the last glacial maximum is therefore consistent with a reduction in the strength of this monsoon system. Key Points The eastern Arabian Sea was an atmospheric carbon dioxide sink later to ~14 kyr ΔpCO2 was briefly in excess during the deglaciation Downcore salinity is significantly correlated to ΔpCO2