Processes Controlling the Surface Energy Balance Along a Latitudinal Gradient in the Eastern Coast of the United States

Coastal ecosystems have become highly susceptible to regional water management practices, land use changes, and sea level rise. Components of the surface energy balance, such as the latent heat flux density, can be employed to evaluate the state and function of coastal ecosystems. Due to their unique juxtaposition between the land and the ocean, coastal ecosystems provide opportunities to test and determine how the surface energy balance attains closure in such ever-changing and complex environments. This presentation will synthesize several years of surface energy balance data for coastal sites along a latitudinal gradient extending from the mangrove forests in the Florida Everglades, the salt marshes of South Carolina and Virginia, to the tidal marshes in Delaware Bay. Diurnal and seasonal controls on energy fluxes are investigated to determine how available energy is partitioned between sensible and latent heat fluxes across the latitudinal gradients. During certain times of the growing season, coastal ecosystems behave akin to semiarid environments as most of the available energy partitions into sensible heat, giving Bowen ratio values that exceed 1. Such results provide evidence that, despite the abundant availability of water and sufficient evaporative demand to sustain evapotranspiration, vegetation regulates water vapor transport from the soil to the plat shoot and the atmosphere. In the lower latitudes, the sensible heat and latent heat fluxes exhibit marked seasonal patterns in response to well-defined dry and wet seasons. Results from multiple sites indicate that the surface energy balance seldom attains closure. In most cases, the surface energy closure is around 80 %. Likely regional and global controls on the lack of energy closure will be presented and discussed during the conference.