Arun Kaushik , Anil K. Gupta , Steven C. Clemens , Pankaj Kumar , Prasanta Sanyal , Manoj Kumar Jaiswal , Abhayanand S. Maurya , Sreya Sengupta
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引用次数: 0
Abstract
The Siwalik hills, part of the Himalayan foreland basin, receive precipitation mainly during the Indian summer monsoon (ISM) season and are an important factor for monsoon variability in northern India. To understand monsoon strength during the past six centuries, we analyzed proxy record from the Sherla lake which is a closed lake located in the northern state of Haryana, India. Chronology of the sediment is based on five radiocarbon AMS 14C dates, encompassing the last ∼600 years. Among proxies, we have analyzed stable isotope ratios (δ18Ocarb, δ13Ccarb, δ15N and δ13COM) in bulk sediment samples (carbonate and organic) along with grain size distribution (GSD) and geochemical parameters (CaO%, Rb/Sr and Si/Ca ratios). The Sherla lake data reveal significant changes since the Little Ice Age (LIA) (∼1360-1750 CE) to the Current Warm Period (∼1850 CE to the Present). From ∼1360 to ∼1500 CE (early phase of the LIA), the proxy data indicate more evaporative and less humid conditions along with low energy conditions corroborated by limited catchment weathering in the study area which suggests a weak ISM with mixed C3- and C4-type vegetation. From ∼1600 to ∼1780 CE (later phase of the LIA), multi-proxy parameters suggest that precipitation was more stable with high energy conditions along with enhanced catchment weathering and increasing trend of C3-type vegetation, reflecting moist and wet conditions during this time slice. Spectral analysis of different proxies suggests prominent influence of El Niño-Southern Oscillation (ENSO) and solar forcing on Indian monsoon. Increased precipitation over the Himalayan foothills may have resulted from more break events in the core monsoon zone in India during periods of increased ENSO activity. During the later phase of the LIA, the study area received significant moisture during winter months as the winter precipitation over the Himalayan foothill region is largely controlled by the changes in the intensity of North Atlantic Oscillation (NAO) index.
期刊介绍:
Quaternary International is the official journal of the International Union for Quaternary Research. The objectives are to publish a high quality scientific journal under the auspices of the premier Quaternary association that reflects the interdisciplinary nature of INQUA and records recent advances in Quaternary science that appeal to a wide audience.
This series will encompass all the full spectrum of the physical and natural sciences that are commonly employed in solving Quaternary problems. The policy is to publish peer refereed collected research papers from symposia, workshops and meetings sponsored by INQUA. In addition, other organizations may request publication of their collected works pertaining to the Quaternary.