Predicting Coastal Flooding Under Long-Term Climate Change with MPAS-Ocean

Abstract:

The long-term impacts of coastal flooding due to hurricane storm surge depend on a variety of climate change factors. In addition to changes in the intensity of storms and sea level rise, the evolution of the land-ocean interface is an important consideration in determining how surge-induced flooding affects coastal regions. Our goal is to better describe the influence of long-term changes in the land-ocean interface by linking coastal ocean physics with coastline and vegetation dynamics. This work has focused on the MPAS-Ocean model which is the ocean component of the Department of Energy’s Exascale Energy Earth System Model (E3SM). Using the variable-resolution capability of MPAS-Ocean, we have developed regionally refined meshes that connect the global ocean and the coastal land-ocean interface. These meshes have facilitated the development of a wetting and drying capability within MPAS-Ocean to simulate the inundation process during a surge event. Resolving the land-ocean interface also has created an opportunity to incorporate the long-term evolution of the coastline and aquatic vegetation properties from other process-based models. These models include the Advanced Terrestrial Simulator (ATS) which simulates coastline change and the Functionally Assembled Terrestrial Ecosystem Simulator (FATES) which represents vegetation demographics. Astronomical forcing for the tides has also been added to MPAS-Ocean to include the tidal contribution to the overall water level in coastal regions. The integration of these processes at the land-ocean interface enables MPAS-Ocean to assess the impacts of future coastal flooding events within E3SM. These new capabilities are demonstrated in the Delaware Bay region in a hindcast study of Hurricane Sandy.