Storminess in North West Europe and volcanic activity during the Holocene

Abstract. Evidence from observational records and model simulations suggest that volcanic eruptions can strengthen mid-latitude atmospheric circulation and enhance westerly wind strength, with recent proxy data-model assimilations supporting this. However, assessments of Holocene variability in storminess rarely consider whether major volcanic eruptions could be a possible driver of reconstructed periods of enhanced storminess. This research presents a new reconstruction of past storminess from a coastal peatbog situated in western Ireland spanning the last ~7 ka. The record is based on the measurement of the sand content along the core, with XRF core scanning analysis also applied to test whether variations in quartz sand, shell sand and sea spray can be detected by variations in silica, calcium and bromine respectively. While Ca measurements were similar to the long-term changes in sand content along the core, peaks in sand content were not detected by Si or Ca, and Br concentrations appear to have been influenced by humification. We compared sand-based storminess records from northwest Europe. Six multi-decadal to centennial periods with enhanced storminess are common to records from Ireland and Wales during the last 2.5 ka BP, centred at c. 2.25, 2, 1.4, 1.1, 0.5 and 0.2 ka BP, with less agreement between records before this time. The storm periods at 2.8, 2.2–2, 1.1 and 0.5 ka BP are more widespread events and agree with records from Sweden and Scotland. Each of the episodes of increased storminess coincide roughly with major volcanic eruptions during the late Holocene, as well as with periods of enhanced North Atlantic ice-rafting. We hypothesise therefore that both the enhanced storminess and ice-rafting may have resulted from the climate and environmental impacts of these eruptions, aligning with the findings of recent observational and modelling studies on the climate response to eruptions. Challenges remain however in testing this hypothesis, given chronological uncertainties in peatland records and uncertain interpretations of the factors influencing sand deposition. Therefore, to provide an independent assessment of the influence of explosive eruptions on storminess for Ireland’s northeast Atlantic position, we draw upon the rich tradition of annalistic record keeping on the island, including many reports of major storms and windy seasons, to develop a windiness index running from the sixth to seventeenth centuries CE. A set of superposed epoch analyses shows that the ice-core-based dates of explosive volcanic eruptions are statistically significantly associated with the dates of documented storms and windy seasons in Ireland, suggesting avenues for future research.