oai:www.era.lib.ed.ac.uk:1842/7602008-12-22T14:04:07Zhdl_1842_351PUB

Sub-Orbital Scale variations in the Intensity of the Arabian Sea Monsoonhttp://hdl.handle.net/1842/7602005-04-13T12:05:57Z2005-04-13T12:05:57Z2005-07Ivanochko, Tara SGaneshram, RajaA high-resolution multi-proxy reconstruction of the Arabian Sea Summer Monsoon (ASSM) intensity over the past 90,000 years has been determined using two marine sediment cores: one from the Somali margin and one from the Indian margin. This reconstruction indicates that changes in monsoon- induced upwelling, primary productivity and denitrification have varied in synchrony with Dansgaard-Oeschger (D-O) cycles. Increased monsoon intensity correlates with warm climate events (interstadials) and decreased monsoon intensity, which coincides with stadials and Heinrich Events, is confirmed by elevated dust concentrations in the marine cores. A comparison of the Somali and Indian margin cores with previously reported studies from the Northern and Western Basin allows the identification of discrete sediment signals from the Indus River, the Arabian Peninsula and from local riverine runoff. Sedimentary deposition on the Indian margin during interglacials is dominated by local terrestrial runoff, whereas during glacial periods increased dust input from the Arabian Peninsula is evident. Both signals are related to changes in the intensity of the ASSM. Monsoon intensity has decreased during the Holocene as the Intertropical Convergence Zone (ITCZ) has moved to a more southerly position. The ASSM-ITCZ relationship (increased ASSM intensity and a northern ITCZ, decreased ASSM intensity and a southern ITCZ) has remained consistent over the last glacial cycle suggesting that global millennial scale climatic variability is in part driven by modulations in tropical hydrological cycle. This ASSM reconstruction provides evidence that rearrangements in the tropical convection system affected atmospheric dust concentrations as well as the concentration and location of atmospheric water vapour. In addition to modulating terrestrial and marine emissions of greenhouse gases, variation in the tropical hydrological cycle provides a mechanism of amplifying and perpetuating millennial-scale climatic changes.Arabian Sea Summer MonsoonSomali marginIndian marginDansgaard-Oeschger cyclesHeinrich Eventsclimatic changeenUniversity of Edinburgh; College of Science and Engineering; School of GeoScienceThesis or Dissertation; Doctoral; Doctor of Philosophy (PHD(R))114513 bytes99409 bytes734506 bytes219447 bytes376352 bytes1084068 bytes226596 bytes756989 bytes338141 bytes203820 bytes104137 bytes95364 bytes82438 bytes35368 bytes59324 bytes60420 bytes57571 bytes30888 bytesapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfapplication/pdfhttp://www.era.lib.ed.ac.uk/dspace-oai/requestoai:www.era.lib.ed.ac.uk:1842/7602005-04-19T12:30:03Zhttp://www.openarchives.org/OAI/2.0/oai_dc/