Late Holocene Paleohurricane Reconstruction from the Central Texas
Shelf, Western Gulf of Mexico, USA
Abstract
Paleotempestology assists in extending the instrumental storm record
through sedimentary-based, high-resolution records of storms over
millennia. A fundamental understanding of the paleorecord provides
essential context for modern climate models and, therefore, a broader
understanding of our climate system. The Texas (TX) coastline receives
the second largest number of hurricane landfalls per year in the United
States; since 1900, 92 tropical storms and hurricanes have made landfall
on the TX coast. During storm impacts, coastal downwelling storm
channels deliver coarse sediment to the muddy shelf. This return flow or
“backwash” process results in thin but expansive storm deposits in the
region, making it ideal for paleotempestological reconstructions. In
this work, three sediment cores from the central TX shelf, approximately
six kilometers off the coast of Matagorda Island, were collected and
analyzed. Several historic and Holocene storm events have been
identified in cores by conducting detailed grain size analysis at
one-centimeter intervals. Bayesian-based age models couple short-lived
isotopic dating techniques (210-Pb and 137-Cs) with radiocarbon ages.
X-ray fluorescence (XRF) analysis is used to determine geochemical
signatures of the sediments and thus the material source for cross
validating the depositional mechanism. Specifically, XRF is utilized to
differentiate the effects of the 1929 Colorado River diversion relative
to marine deposition. Our new record of tropical cyclone (TC) occurrence
from the TX shelf is compared to paleoclimate models and proxy records
of El Niño Southern Oscillation (ENSO) and Gulf of Mexico (GOM) sea
surface temperature (SST). Preliminary results suggest that periods of
decreased ENSO and increased GOM SST correspond with enhanced TX TC
activity. Understanding these complex climatic interactions will help us
to understand the changes in TC activity expected in the future against
the background of accelerating climate change. Given that the frequency
of extreme ENSO events is projected to increase, changes in the
occurrence and severity of ENSO-TX TC events may prove detrimental to
many coastal populations.