Tracing impact of El Niño Southern Oscillation on coastal hydrology using coral 87Sr/86Sr record from Lakshadweep, South-Eastern Arabian Sea

Waliur Rahaman; Mohd Tarique; A A Fousiya; Priyesh Prabhat; Hema Achyuthan

doi:10.1016/j.scitotenv.2022.157035

Tracing impact of El Niño Southern Oscillation on coastal hydrology using coral ⁸⁷Sr/⁸⁶Sr record from Lakshadweep, South-Eastern Arabian Sea

Sci Total Environ. 2022 Oct 15:843:157035. doi: 10.1016/j.scitotenv.2022.157035. Epub 2022 Jun 30.

Authors

Waliur Rahaman¹, Mohd Tarique², A A Fousiya³, Priyesh Prabhat⁴, Hema Achyuthan⁵

Affiliations

¹ National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa, India. Electronic address: waliur@ncpor.res.in.
² National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa, India.
³ Department of Earth Sciences, Indian Institute of Technology, Kanpur, India.
⁴ National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa, India; School of Earth, Ocean and Atmospheric Sciences, Goa University, Goa, India.
⁵ Institute of Ocean Management, Anna University, Chennai, India.

PMID: 35780895
DOI: 10.1016/j.scitotenv.2022.157035

Abstract

El Niño Southern Oscillation (ENSO) is one of the dominant climate modes influencing global precipitation and temperature. ENSO has a large impact on the monsoonal precipitations over the Indian subcontinent and thereby influences hydrological conditions. Due to dearth of long-term instrumental records of the hydrological parameters on sufficient spatial resolution, it is difficult to assess the impact of ENSO on regional hydrology. Though several geochemical proxies have been used to reconstruct past ENSO events through tracing the changes in past hydrological and climatic parameters, however, such reconstructions are often complicated by the influence of multiple processes and/or factors and their nonlinear relation with the proxy records. In this study, Sr isotope composition (⁸⁷Sr/⁸⁶Sr) was measured in Porites coral from the Lakshadweep, south-eastern Arabian Sea to reconstruct past ENSO events and to trace its regional hydrological impacts. The high precision measurements of ⁸⁷Sr/⁸⁶Sr in Lakshadweep coral show resolvable variations ranging from 0.709080 to 0.709210. The ⁸⁷Sr/⁸⁶Sr record shows an inverse relation with Niño 3.4 record; lower values matched with El Niño years and higher values with La Niña years. Our investigation reveals that ENSO driven precipitation changes impacted submarine groundwater discharge (SGD) to the Minicoy Atoll and resulted in ⁸⁷Sr/⁸⁶Sr variations of the Minicoy Atoll water. Therefore, deviation from the average seawater ⁸⁷Sr/⁸⁶Sr value can be quantified in terms of SGD contribution to the Minicoy Atoll. Our estimates based on binary mixing between seawater and SGD ⁸⁷Sr/⁸⁶Sr suggest a significant supply of SGD, maximum up to ~20 % of the total volume of the Minicoy Atoll during La Niña years due to higher rainfall compared to El Niño years. This finding highlights potential application of coral ⁸⁷Sr/⁸⁶Sr record as an alternate proxy to reconstruct past ENSO events and to trace its quantitative impact on regional hydrology, chemical and nutrient fluxes to coastal oceans via SGD.

Keywords: (87)Sr/(86)Sr; Arabian Sea; Corals; ENSO; Lakshadweep; SGD.

MeSH terms

Animals
Anthozoa* / chemistry
El Nino-Southern Oscillation*
Hydrology
Oceans and Seas
Strontium Isotopes* / analysis
Temperature

Substances

Strontium Isotopes