Indian monsoon variability in the last 2000 years as inferred from benthic foraminifera

Abstract

The effect of ambient conditions on living (Rose-Bengal stained) benthic foraminifera has been studied from the shelf and slope of the central-western Bay of Bengal to assess the applicability of temporal changes in benthic foraminiferal morpho-groups (angular asymmetrical and rounded symmetrical) to reconstruct past monsoon changes. We report that the riverine influx and associated processes control the relative abundance of angular asymmetrical (AABF) and rounded symmetrical (RSBF) benthic foraminiferal morpho-groups in the central-western Bay of Bengal. Subsequently, temporal variations in relative abundance of AABF in a gravity core collected from outfall region of the Pennar River, are used to reconstruct decadal scale past monsoon variability during the last -1887 years. An increased monsoon discharge is observed during the Medieval Warm Period (MWP) and lower during the Little Ice Age (LIA). The periodic changes with a frequency of -123 and -238 years are also identified, indicating a close relationship between monsoon and solar activity.