CSDMS 2016 annual meeting poster ScottHagen
A shift in the paradigm: Assessing & mitigating the impact of climate change to salt marshes
James Morris, University of South Carolina Columbia South Carolina, United States. morris@inlet.geol.sc.edu
Abstract:
Global satellite altimetry indicates that the rate of global mean sea level rise has increased from approximately 1.6 to 3.4 mm/year (Church & White, 2006). Over the 20th century the largely linear rate of eustatic sea level rise has been a function of an increase in the average annual global temperature that resulted in thermal expansion of seawater. Atmospheric carbon emission scenarios of the 21st century will increase global average temperatures and ultimately introduce additional contributions (e.g., land ice loss and changes in land water storage). The additions to thermal expansion will result in higher sea levels. And the increases in sea level will be attained by further accelerations in the rate of the rise (Passeri et al. 2015). Over the land mass the increased temperatures lead to changes in precipitation rates and patterns, etc. To properly assess the impacts of sea level change to bays and estuaries, we must accommodate global climate change in general. This presentation will explain our approach to assessing impacts of global climate change (as opposed to just an assessment of the impacts from sea level change) to a fluvial dominated estuary and bay, and demonstrate adaptation strategies that can enhance coastal resiliency.
Our study focuses on the Apalachicola River, estuary and bay, located in the eastern end of the Florida panhandle. The Apalachicola River is formed by the confluence of the Chattahoochee and Flint Rivers, and has the largest discharge in Florida. The river feeds into an array of salt marsh systems and ultimately empties into the Apalachicola Bay. Sediment is eroded and transported from overland areas, especially during extreme rainfall events, and carried through the Apalachicola River and surrounding tributaries. The salt marsh serves to filter out large quantities of sediment before the bay. The marsh surface is elevated by these infusions of sediment, which with rising sea levels prolongs its viability (Morris et al. 2002).
We have developed the hydro-MEM model to couple tidal hydrodynamics with the marsh equilibrium model (Alizad et al. 2016 & Hagen et al. 2013) to assess impacts from sea level change and introduce a means of mitigating the impacts. For this region we have assessed global climate changes to precipitation (Wang et al. 2013). Further, we have clearly demonstrated the nonlinear responses found by including population dynamics through land use and land cover changes when evaluating historical and future storm surge events (Bilskie et al. 2014 & Hovenga et al. 2016). Herein we formally incorporate global carbon emission scenarios such that our projections of eustatic sea level rise, precipitation and runoff, land use and land cover, etc. are all interconnected. The result is a coastal engineering tool that more completely evaluates the impact of global climate change to estuarine systems.
References:
Alizad, K., S.C. Hagen, J.T. Morris, P. Bacopoulos, M.V. Bilskie, & J.F. Weishampel, “A coupled, two-dimensional hydrodynamic-marsh model with biological feedback.” Ecological Modelling, Vol. 327, pp. 29-43, 2016.
Bilskie, M. V., S. C. Hagen, S. C. Medeiros, and D. L. Passeri (2014). “Dynamics of sea level rise and coastal flooding on a changing landscape”. Geophysical Research Letters, 41(3), 927-934.
Church, J. A., and White, N. J. (2006). “A 20th century acceleration in global sea-level rise”. Geophysical Research Letters. 33(1), L01602.
Hagen, S., Morris, J., Bacopoulos, P., and Weishampel, J. (2013). “Sea-Level Rise Impact on a Salt Marsh System of the Lower St. Johns River”. Journal of Waterway, Port, Coastal, Ocean Engineering. 139(2), 118–125.
Hovenga, P.A., D. Wang, S.C. Medeiros, S.C. Hagen, K.A. Alizad. "The response of runoff and sediment loading in the Apalachicola River, Florida to climate and land use land cover change." Earth’s Future, In press, March 29, 2016.
Morris, J. T., Sundareshwar, P. V., Nietch, C. T., Kjerfve, B. and Cahoon, D. R. (2002). “Responses of coastal wetlands to rising sea level”. Ecology. 83(10), 2869-2877.
Passeri, D.L., S.C. Hagen, S.C. Medeiros, M.V. Bilskie, K. Alizad, & D. Wang (April, 2015). “The dynamic effects of sea level rise on low-gradient coastal landscapes: a review”. Earth’s Future, Online.
Wang, D., S.C. Hagen, and K. Alizad (2013). “Climate Change Impact and Uncertainty Analysis of Extreme Rainfall Events in the Apalachicola River Basin, Florida”. Journal of Hydrology, Vol. 480, pp. 125-135.
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