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| Titel |
Taming the Mighty Mississippi: Integrating paleo-flood data and modeling to understand the patterns and causes of extreme floods on a major river system |
| VerfasserIn |
Samuel Munoz, Liviu Giosan, Jeffrey Donnelly, Sylvia Dee, Zhixiong Shen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122705
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| Publikation (Nr.) |
 EGU/EGU2016-1808.pdf |
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| Zusammenfassung |
| The Mississippi River is an economic artery of the United States that is heavily managed to
provide flood control and maintain a navigable shipping channel. The current system of
levees and spillway structures was conceived in the early 20th century, but the ability of this
system to withstand the altered hydroclimatic conditions projected for the next century is
poorly understood. Here, we present initial results from a project that integrates new
sedimentary records from floodplain lakes with analyses of sediment geochemistry and
climate model simulations to better understand the causes of extreme floods on the lower
Mississippi River.
In our sedimentary paleoflood records, flood event beds are characterized by an upward
fining sequence from deposition of the bedload and suspended load during overbank floods,
identified here using high-resolution laser particle-size analysis and elemental composition
(XRF), and dated using radioisotopes (137Cs, 210Pb, 14C) and optically-stimulated
luminescence (OSL) on quartz. Grain-size descriptors and elemental ratios of Zr/Fe and
Fe/Rb are highly correlated, and are used alongside historical discharge records to develop a
statistical model for reconstructing flood magnitude in prehistoric contexts. Geochemical
analyses of sediments from the floodplains of major tributaries of the Mississippi are used to
assess the systematics of 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, and 208Pb/204Pb across the
basin, enabling identification of the synoptic patterns of individual paleo-flood
events.
We investigate the dynamical drivers of past floods on the lower Mississippi using both
reanalysis data and the last millennium simulation from NCAR model CESM1 to find that
increased likelihoods of extreme floods on the lower Mississippi River are associated with
enhanced moisture flux over midcontinental North America that is controlled by the
interaction of seasonally variable soil moisture over major tributaries with inter-annual (e.g.,
ENSO) and decadal (e.g., NAO, PDO) ocean-atmosphere variations. We also find preliminary
evidence for increased frequencies of large floods following major human modifications to
the Mississippi River and its watershed after the mid-19th century. The insights gained
through integrated paleoflood data-model comparison will improve seasonal to
decadal forecasts of flood risk for the largest river system in the United States. |
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