An investigation of tropical Holocene speleothems and their relationship to modern local precipitation

Marianne Brett

Research output: ThesisDoctoral Thesis

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Holocene speleothems from NE India and the South Pacific were analysed
using a robust multi-proxy approach, with contextual environmental monitoring
and daily resolution local precipitation. This study compares intraseasonal
and interannual variations in precipitation amount and isotopic signature with
proxy capture in speleothems to improve methods in climate reconstruction
from speleothem proxies, and presents novel records from India and the South
Krem Umsynrang cave, in NE India, is located in the core region of the Indian
Summer Monsoon, a highly seasonal environment where the controls on interannual precipitation intensity are complex and remain to be fully understood.
In the first part of this thesis, I present a new speleothem record spanning
the late Holocene, characterise seasonal proxy capture and analyse local precipitation isotopes. The study highlights the importance of fabric studies to
construct reliable age models and interpret hydrological changes recorded in
the proxy record.
Cave sites in the South Pacific afford the opportunity to reconstruct precipitation
records of a tropical maritime environment strongly influenced by the
position of the ITCZ and the state of ENSO. I report the results of a detailed
analysis of daily precipitation isotopes from Suva, Fiji, and present a new
speleothem record from nearby island, Vatulele, as well as pilot studies from
the island of Atiu, Cook Islands. These combine to make a novel dataset: the
rst proxy record to show interdecadal- and centennial-scale variability of the
South Pacific Convergence Zone.
The results argue that an interpretation of "the amount effect", which underpins
many palaeoclimate reconstructions from speleothem proxies, is belied by
complex behaviour of oxygen isotopes, hence, a simple transfer function from
speleothem calcite to rainfall amount requires corroboration from local precipitation data. The research emphasises a multi-proxy approach, supported
by cave monitoring and study of local rainfall, is crucial for palaeoclimatic
reconstruction from speleothem records.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Mattey, Dave, Supervisor
  • Harris, Nigel , Supervisor, External person
Thesis sponsors
Award date1 Apr 2018
Publication statusUnpublished - 17 Apr 2018

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