High-resolution planktonic foraminiferal and geochemical proxy records reveal Holocene monsoon-driven changes and solar-cycle imprints in the northeastern Arabian Sea

Abstract

A multiproxy investigation was conducted on gravity core SK240/473 from the northeastern Arabian Sea to reconstruct monsoon-driven oceanographic variability over the last ∼16,000 years BP. Planktonic foraminiferal assemblages, planktonic/benthic (P/B) ratios, geochemical proxies (P%, and Ti/Al), and spectral–wavelet analyses were employed to evaluate changes in water-column structure, and monsoon forcing. The assemblage is dominated by Globigerinoides ruber and Globigerina bulloides, whose relative abundances reflect variations in upper-ocean stratification, nutrient availability, and monsoon-driven mixing. The northeastern Arabian Sea exhibits strong sensitivity to high-latitude climate oscillations, including ENSO variability, ITCZ migration, and NAO-related atmospheric circulation changes, which exert a major control on regional monsoon dynamics. The multiproxy record indicates weakened Indian Summer Monsoon (ISM) conditions during all Bond events (B0–B8) and during Meltwater Pulse-1a, consistent with reduced summer monsoon wind strength and diminished upwelling intensity. In contrast, Meltwater Pulse-1a and the interval ∼4000–3300 yrs BP are characterized by intensified Indian Winter Monsoon (IWM) influence, reflecting enhanced wintertime convective mixing and cooling. Located within a transitional zone influenced by both ISM and IWM systems, the core site records the shifting and combined impacts of these monsoon components through time. The lowest sedimentation rates during the mid-to late Holocene indicate relative sea-level rise and landward migration of sediment depocenters, resulting in reduced terrigenous input to the offshore site. Spectral analyses reveal prominent centennial to millennial scale periodicities in G. bulloides (%), ISM, and IWM assemblages. The G. bulloides record exhibits significant periodicities at ∼510, ∼351, ∼212, ∼152, and ∼148 years, while ISM assemblages show dominant cycles at ∼636, ∼351, ∼214, ∼152, and ∼148 years, and IWM assemblages are characterized by periodicities at ∼2264, ∼167, and ∼148 years. The recurrence of these periodicities underscores the role of solar-modulated climate forcing and large-scale atmospheric teleconnections in regulating monsoon variability and upper-ocean conditions in the northeastern Arabian Sea.