The Impact of Volcanic Eruptions on the Climate and Ecology of Ireland since A.D. 1800

Abstract

Global warming and the influence of anthropogenic changes to the environment are dominant themes in climate research today. However, the trends brought about by these processes have the potential to be abruptly altered by the impact of large-scale volcanic eruptions, particularly those at lower latitudes. The injection of volcanic matter into the atmosphere has the ability to influence temperature, precipitation and wind regimes. An additional outcome is the reduction of atmospheric transparency, which in turn has consequences for the biological environment and ecosystems through the limiting of photosynthesis. Although global and hemispheric impacts are known, the broad nature of this scale fails to indicate how local climate and ecosystems can be expected to react following volcanic eruptions. A number of studies have looked at individual aspects on more micro-scales -- Dawson et al. (1997) examined peaks in gale frequency in Edinburgh following three low-latitude volcanic eruptions; Jones et al. (2003) used temperature records from three stations to assess the long-term response to eruptions; Kyncl et al. (1990) examined Central European climatic and tree-ring response to a single eruption. Local assessments of volcano-climate interactions tend to focus on either one single climatic element, or one single eruption event.

The focus of this study is to determine to what extent five large-scale low-latitude volcanic eruptions and six lesser Iceland-based events have had on the climate and ecology of Ireland over the past ~200 years. The analysis used is two-fold, concentrating firstly on archival climate data, followed by the examination of dendroecological trends and a new dendroclimatic reconstruction. Armagh Observatory, Co. Armagh, provides detailed temperature, precipitation and wind direction data from 1796 onwards, while Taxus baccata (yew) tree-ring indices from Killarney National Park in Co. Kerry are used to reconstruct temperature and precipitation for that area since 1803. The newly constructed indices were also examined in conjunction with 13 other tree-ring series from throughout Ireland.

The temperature record from Armagh proved particularly responsive in the spring and autumn of the year following larger eruptions, displaying notable downturns. Precipitation tended to decrease in the summer following an eruption, while the wind regimes recorded increases in northeasterly, easterly and southwesterly directions in the months immediately after eruptions. This study is the first to systematically explore the impact of volcanic eruptions on tree-growth in Ireland. Dendrological data from Irish Quercus records showed that the changes in climatic patterns coupled with the reduced photosynthesis that follows eruptions have implications for growth in Ireland. In addition, temperature and precipitation reconstructions using T. baccata have proved that not only is the species a viable source of information in Ireland but that it can also be used to support the idea of post-volcanic eruption downturns in growing conditions. By combining each of these aspects (recorded and reconstructed climate, as well as dendroecological data), a more complete assessment of volcano-climate/ecology interactions was established.