Last 15 ka record of water column changes associated with Indian summer monsoon variability from the northeastern Bay of Bengal

IF 1.9 3区地球科学 Q3 GEOGRAPHY, PHYSICAL

Quaternary International Pub Date : 2025-02-28 DOI:10.1016/j.quaint.2025.109713

N.M. Gayathri , E. Sreevidya , A.V. Sijinkumar , B. Nagender Nath , K. Sandeep , P.J. Kurian , K. Pankaj

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引用次数: 0

Abstract

We studied planktonic foraminifera assemblages of ¹⁴C AMS dated sediment cores retrieved from the eastern Bay of Bengal (MGS 29 GC 02) and the northern Andaman Sea (SSD 18) to reconstruct water column changes associated with Indian Summer Monsoon (ISM) precipitation during the deglacial and Holocene periods. The temporal record of salinity and productivity tracking species combined with data from other ISM records, suggests several abrupt events in the monsoonal precipitation in the last 15 cal ka BP. The salinity tracking species show higher abundance during the early Holocene, 6.5 and 2 cal ka BP, pointing towards enhanced river runoff and direct precipitation associated with strong ISM during these periods. Whereas productivity species were abundant during Younger Dryas (YD; 13.6–12.6 cal ka BP), 7.7–5.3 cal ka BP, and its abundance decreased during the early Holocene and late Holocene periods, indicating weak water column stratification associated with reduced ISM. Our data indicate a considerable amount of freshwater runoff during Bølling/Allerød (B/A), early and late Holocene and comparatively less river influx during late glacial periods and YD. This suggests that monsoon intensification occurred during the early Holocene, and a weakening trend was seen during deglacial periods. The increased productivity events may reflect periods of weak stratification, which is possibly driven by weak ISM. The present study indicates the ISM has a direct influence on the Eastern BoB water column structure, with periods of weak (strong) stratification leading to enhanced (weak) productivity. Spectral analysis of the planktonic foraminiferal abundance records reveals statistically significant periodicities at 3105, 1980, 775, 680, 657, 483, and 403 years. Most of these millennial-to-centennial cycles exist in various monsoon and solar proxy records. The characteristic sub-orbital periodicities correspond mainly to solar irradiance variability. Wavelet analysis on planktonic foraminiferal data confirms that these periodicities persist over time without significant variation, indicating a degree of stationarity in the data.

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从孟加拉湾东北部开始的与印度夏季风变化相关的近15 ka水柱变化记录

研究了孟加拉湾东部（MGS 29 GC 02）和安达曼海北部（SSD 18） 14C AMS定年沉积物岩心的浮游有孔虫组合，重建了去冰期和全新世期间与印度夏季风（ISM）降水相关的水柱变化。盐度和生产力追踪物种的时间记录与其他ISM记录的数据相结合，表明在过去15 cal ka BP的季风降水中发生了几次突变事件。盐度追踪物种在全新世早期（6.5和2 cal ka BP）表现出较高的丰度，表明这一时期河流径流和直接降水的增加与强ISM有关。而新仙女木期(YD；13.6 ~ 12.6 cal ka BP)、7.7 ~ 5.3 cal ka BP，丰度在全新世早期和晚全新世期间呈下降趋势，表明水体分层弱，ISM减少。全新世早期和晚期Bølling/ allero ød （B/ a）期淡水径流量较大，晚冰期和YD期河流径流量相对较少，表明全新世早期季风强度增强，去冰期季风强度减弱。生产力增加事件可能反映了弱分层时期，这可能是由弱ISM驱动的。本研究表明，ISM直接影响东BoB水柱结构，弱（强）分层期导致生产力增强（弱）。对浮游有孔虫丰度记录的光谱分析显示，3105年、1980年、775年、680年、657年、483年和403年具有统计学意义的周期性。这些千年至百年周期中的大多数存在于各种季风和太阳代理记录中。特征的亚轨道周期主要与太阳辐照度的变化相对应。对浮游有孔虫数据的小波分析证实，这些周期性随时间持续存在而没有显著变化，表明数据具有一定程度的平稳性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Quaternary International 地学-地球科学综合

CiteScore

5.60

自引率

4.50%

发文量

336

审稿时长

3 months

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.