NSF Org:	AGS Div Atmospheric & Geospace Sciences
Recipient:	WILLIAM MARSH RICE UNIVERSITY
Initial Amendment Date:	January 28, 2022
Latest Amendment Date:	April 18, 2023
Award Number:	2147781
Award Instrument:	Standard Grant
Program Manager:	Eric DeWeaver edeweave@nsf.gov  (703)292-8527 AGS  Div Atmospheric & Geospace Sciences GEO  Directorate For Geosciences
Start Date:	June 1, 2022
End Date:	May 31, 2025 (Estimated)
Total Intended Award Amount:	$441,342.00
Total Awarded Amount to Date:	$472,024.00
Funds Obligated to Date:	FY 2022 = $441,342.00 FY 2023 = $30,682.00
History of Investigator:	Sylvia Dee (Principal Investigator) sylvia.dee@rice.edu James Doss-Gollin (Co-Principal Investigator)
Recipient Sponsored Research Office:	William Marsh Rice University 6100 MAIN ST Houston TX  US  77005-1827 (713)348-4820
Sponsor Congressional District:	09
Primary Place of Performance:	William Marsh Rice University 6100 MAIN ST Houston TX  US  77005-1827
Primary Place of Performance Congressional District:	09
Unique Entity Identifier (UEI):	K51LECU1G8N3
Parent UEI:
NSF Program(s):	Climate & Large-Scale Dynamics
Primary Program Source:	01002223DB NSF RESEARCH & RELATED ACTIVIT 01002324DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):	CL10
Program Element Code(s):	574000
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.050

ABSTRACT

The Mississippi River drains a continent, gathering water from as far as Pennsylvania and Montana and discharging it into the Gulf of Mexico. The channeling of so much water into a single river naturally raises the stakes for flooding, and the river has one of the most extensive flood mitigation systems in the world. But there are limits to the protection afforded by the current system and we do not know if it will prove adequate as climate warms. The effect of warming on flood risk is determined by a balance between competing effects: warming by itself would likely reduce discharge by increasing the amount of moisture that evaporates from the land rather than running off into streams. Warming also reduces snowpack, leading to a reduction in the springtime streamflow resulting from snow melt. On the other hand warmer air generally holds more moisture, which leads to increases in both mean and extreme precipitation, thus increasing flood risk.

This projects seeks to determine the net effect of these competing influences on Mississippi River discharge, which serves as a broad-brush proxy for flood risk. Much of the work involves assessments of Mississippi discharge in climate models, particularly the Community Earth System Model (CESM), which uses a River Transport Model (RTM) for the Mississippi. Preliminary results show river discharge increasing dramatically (by perhaps 130%) over the 21st century under a high greenhouse gas emissions scenario (RCP8.5) but remaining within historical norms under lower emissions (RCP4.5). This contrast suggests that the balance between streamflow increases from precipitation and decreases from evaporation and snow melt could be temperature dependent, with precipitation winning out at higher levels of warming.

The project also considers the factors driving Mississippi discharge over the last millennium using a combination of weather and streamflow observing networks, paleoclimate reconstructions, and ensembles of present-day and last millennium climate model simulations. Recent work by the Principal Investigators (PIs) suggests that the warm period of the Medieval Climate Anomaly featured lower discharge than the Little Ice Age, a result that is generally captured by CESM simulations of the last millennium. The result is also in keeping with the moderate warming scenario for the 21st century.

The work is of societal interest due to the focus on flood risk, and the PIs are working with stakeholders including the US Army Corps of Engineers and the Mississippi River Cities and Towns Initiative to understand the practical significance of their results and provide decision support. The project also involves education and outreach, supporting summer research experiences for high school students and working with the Girl Scouts of America to encourage girls and young women to consider careers in science. The project provides support and training to a postdoctoral researcher and two graduate students.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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