HoStIr: Holocene Storminess in Ireland

HoStIr is a palaeoclimate research project investigating how and why storminess has changed throughout the Holocene in Ireland. The project has three stages: 1) testing of proxies for storminess, 2) development of three Holocene storm reconstructions for Ireland, and 3) a data-model comparison of past storminess. Here, we present the preliminary results of the first stage of the project, where we are testing two potential indicators of past sea spray deposition in coastal peatlands. Past storminess has primarily been investigated using sand-based proxies deposited by wind or waves into coastal depositional environments. By testing proxies related to the deposition of sea spray during storms, it is anticipated that storminess reconstructions can be developed from a wider range of sites. The first potential proxy is preserved bromine within peat, which potentially reflects the deposition and retention of sea salt. The second is the biomass of microscopic testate amoebae preserved in peat, as a previous study from the sub-Antarctic suggests this can be influenced by changing salinity as a result of sea spray (Whittle et al. 2019). Thirty cores have been sampled along a transect from a coastal peatland on the west coast of Ireland, spanning a gradient of marine influence. We will present preliminary results of the bromine retention along this transect, measured using XRF analysis and with tephrochronology used for age control, as well as the results of the testate amoebae biomass. Bromine concentrations along two cores has also been assessed by ITRAX (X-Ray Fluorescence) core scanning and compared with humification analysis, to test the possibility that bromine concentrations are influenced by the degree of peat humification. Analyses of this and the remaining project stages is ongoing. It is anticipated that this first stage, if successful, will provide a methodological breakthrough by proving that peatland sea-spray proxies provide reliable evidence for past storminess and would enable storminess records to be developed more extensively than sand-based approaches alone.   Whittle, A. et al. (2019) ‘Salt-Enrichment Impact on Biomass Production in a Natural Population of Peatland Dwelling Arcellinida and Euglyphida (Testate Amoebae)’, Microbial Ecology, 78, pp. 534–538.