27 D6. Geomorphology

Monday, 26 October 2020
5:30 PM - 8:00 PM
Meeting Rooms

REDUCED LOWER MISSISSIPPI RIVER DISCHARGE DURING THE MEDIEVAL ERA

Paper number: 27-5
Program: Technical Sessions
Time: 6:30 PM – 6:45 PM

Authors

Abstract

Changes in climate are expected to influence discharge of the lower Mississippi River, but projections disagree on whether discharge will increase or decrease over the coming century. Here we show that discharge on the lower Mississippi River decreased during the Medieval era (c. AD 1000–1200) — a period of regionally warm and dry conditions that serves as a partial analogue for projected warming — using a reconstruction median peak annual flow for the past 1,500 years based on geomorphic scaling laws. These changes in discharge inferred from channel morphology track discharge simulated in the Community Earth System Model Last Millennium Ensemble (CESM-LME), and simulations show that decreased Medieval-era discharge is driven primarily by regionally enhanced evaporative loss, though reduced precipitation and snowmelt are also simulated at this time. Our findings are consistent with 21st century projections of decreased discharge on the lower Mississippi River under moderate greenhouse forcing scenarios, but do not account for anthropogenic modifications to the basin and river channel which have served to increase flood hazard the past century. Instead, our findings point to the importance of the hydrologic properties of the basin and channel hydraulics in mediating flood hazard today and in the future, and demonstrates consistency between reconstructed and simulated discharge over the past millennium.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-352723

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