Nature's archive reveals Atlantic tempests through time
Paleo storm hunters need data to refine the record of history's
hurricanes

Date:
September 7, 2021
Source:
Rice University
Summary:
Scientists uncover how natural archives recorded Atlantic hurricane
frequency over the past 1,000 years. More data is needed to help
model how climate change will affect storms in the future.



FULL STORY ========================================================================== Atlantic hurricanes don't just come and go. They leave clues to their
passage through the landscape that last centuries or more. Rice University scientists are using these natural archives to find signs of storms
hundreds of years before satellites allowed us to watch them in real time.


========================================================================== Postdoctoral fellow Elizabeth Wallace, a paleotempestologist who joined
the lab of Rice climate scientist Sylvia Deethis year, is building upon techniques that reveal the frequency of hurricanes in the Atlantic basin
over millennia.

Paleoclimate hurricane data (or 'proxy' data) is found in archives like
tree rings that retain signs of short-term flooding, sediments in blue
holes (marine caverns) and coastal ponds that preserve evidence of sand
washed inland by storm surges. These natural archives give researchers
a rough idea of when and where hurricanes have come ashore.

In a new paper in Geophysical Research Letters, Wallace, Dee and
co-author Kerry Emanuel, a climate scientist at the Massachusetts
Institute of Technology, take hundreds of thousands of "synthetic"
storms spun up from global climate model simulations of the past 1,000
years and examine whether or not they are captured by the vast network
of Atlantic paleohurricane proxies.

Reconstructing the past will help scientists understand the ebb and
flow of Atlantic hurricanes over time. Previous studies by Wallace and
others have demonstrated that a single site capturing past storms cannot
be used to reconstruct hurricane climate changes; however, a network of
proxies might help refine models of how these storms are likely to be
affected by climate change going forward.

"These paleo hurricane proxies allow us to reconstruct storms into the
past, and we're using them to figure out how basin-wide storm activity
has changed," said Wallace, a Virginia native who earned her doctorate at
MIT and the Woods Hole Oceanographic Institution last year and connected
with Dee when the professor spoke there in 2017.



==========================================================================
"If I have a sediment core from Florida, it's only capturing storms
that hit Florida," she said. "I wanted to see if we can use the full
collection of records collected from the Bahamas, the East Coast and
the Gulf of Mexico over the past few decades to accurately reconstruct basin-wide storm activity over the last few centuries." The synthetic
storms they built helped illustrate what Wallace already knew: There's a
bias toward the Caribbean and Gulf of Mexico, and a need for more proxies
along the east coasts of North and Central America. The Rice team's quest
going forward will be to refine their climate simulations and add more
sites to the networks to better reconstruct past hurricane activity.

"In particular, there aren't really any sites from the Southeast U.S.,
places like the Carolinas," she said. "One of the goals of this work
is to highlight where scientists should go to core next." Wallace has first-hand experience drilling cores. "During a storm event, you get high
winds and waves that take the sand from the beach and essentially just
throw it back into a coastal pond," she said. "Only during storm events
do these sand layers get deposited in the pond, and in the sediment
cores you can see them interspersed with the fine mud that's typically
there. We can date these sand layers and know when a hurricane struck
the site." She noted there has not yet been an "intensive" effort to
compare sediment and tree ring records. "The tree record is still an
uncertain proxy," Wallace said.

"We're looking for tree ring records with rainfall signatures that
correspond to storms going over the past 200 or 300 years that match
the sediment records for that same interval." Dee said the work is fundamentally different from the paleoclimate models she most often
studies. "Here we're taking climate models and generating hundreds of pseudo-tropical storms," she said. "We're 'playing Gaia' by making a
plausible version of reality and combining it with our knowledge of
available proxy sites.

"This tells us how many records from how many places we realistically
need to capture a climate signal," Dee said. "It's really expensive to
go out and drill cores, and this helps give us a way to prioritize where
to drill.

"This research is crucial as we accelerate into a climate mean state
with ever- warmer Atlantic Ocean temperatures," she said. "Understanding
how these storms have evolved over time provides a baseline against
which to evaluate tropical cyclones with and without human impacts on
the climate system." A Pan Postdoctoral Research Fellowship and Rice
Academy Fellowship to Wallace and a Gulf Research Program grant to Dee supported the study. Dee is an assistant professor of Earth, environmental
and planetary sciences. Emanuel is the Cecil & Ida Green Professor of Atmospheric Science and co-director of the Lorenz Center at MIT.

========================================================================== Story Source: Materials provided by Rice_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. E. J. Wallace, S. G. Dee, K. A. Emanuel. Resolving long‐term
variations in North Atlantic tropical cyclone activity using
a pseudo proxy paleotempestology network approach. Geophysical
Research Letters, 2021; DOI: 10.1029/2021GL094891 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210907160545.htm

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