Saharan dust and the aerosols on the Canary Islands: past and present

Abstract

The Canary Islands are located on the western dominant transport path of atmospheric dust plumes generated in the Saharan desert. The Saharan region is widely regarded as the world's greatest source of natural mineral dust, much of which is delivered to the ocean and, from time to time, reaches Southern Europe and the Americas. The fact that the Canary Island archipelago is well placed to receive advected Saharan dust plumes was registered by the State Agency of Meteorology of Spain as long ago as the 1950s. Most studies focus on the observation and monitoring of the dust transport, by analyzing satellite images provided by various agencies (AERONET; MPLNET; EARLINET). Recent research on pa1iicu!ate matter has expanded in recent years to include particle size measurements, aggregation, mineralogy, geochemistry, and particle reactivity, as well as considering the impact on human health and global di.mate. This chapter will provide a review of previous research on Saharan dust and other aerosols unde1iaken on the Canary Islands, research groups and agencies involved and their key findings, as well as the main thrust of current research and prospects for future work. It will consider accumulation of Saharan dust both at present and in the pastas well as its textura! and mineralogical characteristics in deposits found on the islands. Paiticular attention will be afforded to the impact on the land surface and human population. It will be shown that for the period 2005-2007 the deposition rates on the island of Gran Canaria were of the order of 20 ± 11 g m·2 y"1 . A high percentage of aggregate in the deposited dust (> 60%) has been determined using Image Analysis of SEM-EDX. Results from these studies show that particle aggregates have lower bulk densities than individual particles, a characteristic with relevance to some existing dust plume transpmtation models. On the basis of geomorphologic mapping, GIS-calculations, luminescence dating and sedimentologic-pedologic analyses of sediments trapped in volcanically-dammed valleys on the Canmy Island of Lanzarote, estimates of soil moisture fluctuations in deposited Saharan dust and the hydrologic budget of the island are put forward for the Late Quaternary. These deposits provide information on anthropogenic influence on the dust source area of the nearby Saharan Desert during the Holocene and constitute a basis for quantitative estimates of dust input to this island during a Jarge part of the Quatemmy.