COI Funded Project: Development of Tropical Cyclone Records from Coral Atoll and Fringing Lagoons: An Opportunity to Study Past Cyclone Activity in the Pacific
Project Funded 2007:
Developing records of past tropical cyclone activity are required if we
are to determine the climate conditions responsible for altering their
frequency, intensity, and tracks. Given the extremely short
instrumental record, little is known about past tropical cyclone
activity, and the impact of these extreme events on coastal landforms
and ecosystems in the Pacific. Much attention has been given to the
susceptibility of small islands to current and projected sea-level
rise, however changing climate patterns that may result in more
frequent intense tropical cyclones in some regions likely pose a far
greater threat. Sedimentary evidence of intense cyclone landfalls can
be used to extend the record of these extreme events back many
millennia, allowing for the examination of how changing climatic
conditions impacted the spatial and temporal patterns of intense
tropical cyclone landfalls. To date most of this effort has focused on
the western North Atlantic. As the types of sites most often used for
these kinds of reconstructions (backbarrier wetlands and ponds) are
extremely rare in the tropical Pacific, little work has taken place in
this basin. The only deposition environment that is widely distributed
across the tropical Pacific that may provide long-term records of past
tropical cyclone activity are fringing coral lagoons and coral atoll
lagoons. In this project I examine the potential of these deep lagoons
in the tropical Pacific for providing detailed records of past intense
tropical cyclone activity. This study focuses on two sites in French
Polynesia. The first is a fringing lagoon on the northwest side of the
island of Tahaa. The second is an atoll lagoon on the island of
Maupihaa. These sites are ideal in that they are typical of many of the
atolls and islands with fringing reefs that are scattered across the
tropical Pacific. The last intense cyclone to strike the islands of
Tahaa and Maupihea occurred in 1906 and provides a good test case to
determine if these lagoons provide a record of past intense cyclone
landfalls. Using a geophysical survey and coring I will determine if
there is sedimentological evidence of the 1906 cyclone in the Tahaa and
Maupihaa lagoons, establish if there is evidence of other event
deposits preserved within the recent lagoonal sediments, and provide an
estimate for the overall length of a cyclone record preserved in the
lagoons. If successful this work will open up the possibility of
reconstructing records of intense tropical cyclone activity from across
much of the tropical Pacific for the last several millennia.