Historical evolution and present state of the coastal dune systems in the Atlantic coast of Cádiz (SW Spain): Palaeoclimatic and environmental implications

Abstract

This paper examines the origin, evolution and present state of the coastal dunes along the South Atlantic Spanish coast from the Guadalquivir River mouth to the Strait of Gibraltar. Wind regime in the zone is strongly affected by the North Atlantic Oscillation (NAO). Low or negative NAO index values give rise to the prevalence of westerly humid winds, while during periods with a positive NAO index easterly, dry winds prevail. Several Holocene and historical aeolian phases have been identified in the zone, represented by different aeolian deposits, many of them containing archaeological remains. The oldest one dates to shortly after the mid-Holocene eustatic maximum. During historical times dune-building episodes were associated with a higher frequency and persistence of easterly winds. During the 20th century, and especially in the last few decades, the prevalence of positive values of the NAO index has favored the growth and advance of mobile dunes in the vicinity of the Strait of Gibraltar. In contrast, dune ridges associated with westerly winds are much less mobile or stable and form shore-parallel ridges covered by vegetation.