Climatic periodicities recorded in lake sediment magnetic susceptibility data:Further evidence for solar forcing on Indian summer monsoon  

作　　者：Anish Kumar Warrier Kizhur Sandeep Rajasekharaiah Shankar 

机构地区：[1]Department of Marine Geology,Mangalore University,Mangalagangotri 574199,Karnataka,India [2]Department of Civil Engineering,Manipal Institute of Technology,Manipal University,Manipal 576104,Karnataka,India [3]Department of Geology,School of Earth Science Systems,Central University of Kerala,Tejaswini Hills,Periye(P.O.),Kasaragod,Kerala 671 123,India

出　　处：《Geoscience Frontiers》2017年第6期1349-1355,共7页地学前缘（英文版）

基　　金：the Department of Space,Government of India,for supporting this work through a research project to RS("Paleoclimate of the past few centuries from Lake-and Tank-bed sediments of Southern India";ISRO-GBP/WG-1 letter No.9/5/2/2004-11)under the Geosphere-Biosphere Program;AKW and KSthank the Department of Space,the Council of Scientific and Industrial Research and the University Grants Commission,Government of India for junior and Senior Research Fellowships

摘　　要：The Indian summer monsoon exhibits considerable spatio-temporal variability.It is therefore important to understand its dynamics and the inherent periodicities.In this study,we have performed spectral and wavelet analyses of magnetic susceptibility data for sediments from Thimmannanayakanakere(TK)-a small lake in southern India.The main objective of this investigation is to identify and explain the possible origin of the prominent periodicities present in the magnetic susceptibility data.Significant periodicities in the TK χ_(lf)data are centered at 906,232,147,128,96,61,54 and 44 years,which might have a solar origin.The wavelet power spectrum of the raw and detrended χ_(lf)data confirms the findings of spectral analysis and also provides temporal variations of the significant cyclicities during the past3700 cal.years B.P.Positive correlation is documented between sunspot activity and TK xif data;crossspectral analysis of the reconstructed sunspot data and TK xif data suggest that there is a strong coherence between the two datasets as significant periodicities are documented in both.There is a good match between the TK xif and the reconstructed total solar irradiance data for the past 1200 years.However,an out-of-phase relationship is documented at certain time-intervals,which may be attributed to uncertainties in the age-depth model.The results obtained from this study show that solar variations are the main controlling factor of the southwest monsoon and,like other archives from different regions in India,the TK lake sediments have also recorded these solar signatures.The Indian summer monsoon exhibits considerable spatio-temporal variability.It is therefore important to understand its dynamics and the inherent periodicities.In this study,we have performed spectral and wavelet analyses of magnetic susceptibility data for sediments from Thimmannanayakanakere(TK)-a small lake in southern India.The main objective of this investigation is to identify and explain the possible origin of the prominent periodicities present in the magnetic susceptibility data.Significant periodicities in the TK χ_(lf)data are centered at 906,232,147,128,96,61,54 and 44 years,which might have a solar origin.The wavelet power spectrum of the raw and detrended χ_(lf)data confirms the findings of spectral analysis and also provides temporal variations of the significant cyclicities during the past3700 cal.years B.P.Positive correlation is documented between sunspot activity and TK xif data;crossspectral analysis of the reconstructed sunspot data and TK xif data suggest that there is a strong coherence between the two datasets as significant periodicities are documented in both.There is a good match between the TK xif and the reconstructed total solar irradiance data for the past 1200 years.However,an out-of-phase relationship is documented at certain time-intervals,which may be attributed to uncertainties in the age-depth model.The results obtained from this study show that solar variations are the main controlling factor of the southwest monsoon and,like other archives from different regions in India,the TK lake sediments have also recorded these solar signatures.

关 键 词：Spectral analysis PERIODICITY Paleorainfall Lake SEDIMENTS Magnetic susceptibility SOUTHERN India 

分 类 号：P532[天文地球—古生物学与地层学]