Trans-Atlantic Connections between North African Dust Flux and Tree Growth in the Florida Keys, United States

Abstract

AbstractAtmospheric mineral aerosols include multiple, interrelated processes and feedbacks within the context of land?atmosphere interactions and thus are poorly understood. As the largest dust source in the world, North Africa supplies mineral dust aerosols each year to the Caribbean region and southeastern United States that alter cloud processes, ocean productivity, soil development, and the radiation budget. This study uses a suite of Earth Observation and ground-based analyses to reveal a potential novel effect of atmospheric aerosols on Pinus elliottii var. densa cambial growth during the 2010 CE growing season from the Florida Keys. Over the Florida Keys region, the Earth Observation products captured increased aerosol optical thickness with a clear geographical connection to mineral dust aerosols transported from northern Africa. The MODIS Terra and Aqua products corroborated increased Ozone Monitoring Instrument (OMI) aerosol optical thickness values. Anomalously high Aerosol Robotic Network aerosol optical depth data corresponding with low Ångstrom coefficients confirm the presence of transported mineral dust aerosols during the period circa 4?20 July 2010. The fraction of photosynthetically absorbed radiation over the region during July 2010 experienced an anomalous decrease, concurrent with reduced incoming total and direct solar radiation resulting in a reduced growth response in P. elliottii. The authors pose one of the primary mechanisms responsible for triggering growth anomalies in P. elliottii is the reduction of total photosynthetically active radiation due to a dust-derived increase in aerosol optical depth. As a rare long-lived conifer (300+ years) in a subtropical location, P. elliottii could represent a novel proxy with which to reconstruct annual or seasonal mineral dust aerosol fluxes over the Caribbean region.