title: Bromine soil/sediment enrichment in tidal salt marshes as a potential indicator of climate changes driven by solar activity: New insights from W coast Portuguese estuaries.
abstract: This paper aims at providing insight about bromine (Br) cycle in four Portuguese estuaries: Minho, Lima (in the NW coast) and Sado, Mira (in the SW coast). The focus is on their tidal marsh environments, quite distinct with regard to key biophysicochemical attributes. Regardless of the primary bromide (Br-) common natural source, i.e., seawater, the NW marshes present relatively higher surface soil/sediment Br concentrations than the ones from SW coast. This happens in close connection with organic matter (OM) content, and is controlled by their main climatic contexts. Yet, the anthropogenic impact on Br concentrations cannot be discarded. Regarding [Br] spatial patterns across the marshes, the results show a general increase from tidal flat toward high marsh. Maxima [Br] occur in the upper driftline zone, at transition from highest low marsh to high marsh, recognized as a privileged setting for OM accumulation. Based on the discovery of OM ubiquitous bromination in marine and transitional environments, it is assumed that this Br occurs mainly as organobromine. Analysis of two dated sediment cores indicates that, despite having the same age (AD ~1300), the Caminha salt marsh (Minho estuary) evidences higher Br enrichment than the Casa Branca salt marsh (Mira estuary). This is related to a greater Br storage ability, which is linked to OM build-up and rate dynamics under different climate scenarios. Both cores evidence a fairly similar temporal Br enrichment pattern, and may be interpreted in light of the sun-climate coupling. Thereby, most of the well-known Grand Solar Minima during the Little Ice Age appear to have left an imprint on these marshes, supported by higher [Br] in soils/sediments. Besides climate changes driven by solar activity and impacting marsh Br biogeodynamics, those Br enrichment peaks might also reflect inputs of enhanced volcanic activity covarying with Grand Solar Minima.
authors.affiliation: IDL - Instituto Dom Luiz, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal; Departamento de Geologia da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal. Electronic address: jcmoreno@fc.ul.pt.
authors.forename: J
authors.initials: J
authors.lastname: Moreno
authors.affiliation: IDL - Instituto Dom Luiz, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal; Departamento de Geologia da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Fatela
authors.affiliation: East Carolina University, Department of Geological Sciences, Greenville, NC 27858-4353, USA.
authors.forename: E
authors.initials: E
authors.lastname: Leorri
authors.affiliation: Independent Researcher, Caminho da Portela, 97, 4940-061 Bico PCR, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Moreno
authors.affiliation: IDL - Instituto Dom Luiz, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal; Departamento de Geologia da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.
authors.forename: M C
authors.initials: MC
authors.lastname: Freitas
authors.affiliation: Instituto de Ciências da Terra (ICT), Polo da Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal; Centro de Investigación para la Ingenieria en Mineria Sostenible (CIPIMS), Universidad de Huelva, Ctra. Palos Fra. s/n, 21819 Palos de la Frontera, Huelva, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Valente
authors.affiliation: Universidade de Lisboa, Instituto Superior Técnico, Centro de Ciências e Tecnologias Nucleares (C(2)TN), Estrada Nacional 10, km 139,7, 2695-066 Bobadela LRS, Portugal.
authors.forename: M F
authors.initials: MF
authors.lastname: Araújo
authors.affiliation: University of Murcia, Department of Physics-Physics of the Earth, Campus de Espinardo, 30100 Murcia, Spain.
authors.forename: J J
authors.initials: JJ
authors.lastname: Gómez-Navarro
authors.affiliation: Departamento de Ciências da Terra, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: L
authors.initials: L
authors.lastname: Guise
authors.affiliation: School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth, Devon PL4 8AA, UK.
authors.forename: W H
authors.initials: WH
authors.lastname: Blake
keywords: Br cycle; Climate modelling; Climate variability; Grand Solar Minima; OM storage; Salt marshes