Identifying volcanic signals in Irish temperature observations since AD 1800

Large volcanic eruptions have been shown to affect temperature patterns to varying degrees on continental, hemispheric or global scales. However, few studies have systematically explored the influence of volcanic eruptions on temperatures at a local, Irish level. The focus of this paper is to determine the impacts of five high-magnitude low-latitude volcanic eruptions and one such Icelandic event on Irish climate over the past �200 years. Daily temperature data from the Armagh Observatory, Co. Armagh, Northern Ireland was used to assess the influence of volcanic eruptions on seasonal and yearly values through time. The paper explores volcanically-induced temperature trends by filtering out the influence of the North Atlantic Oscillation (NAO) and solar variability, and goes on to employ a variation of Superposed Epoch Analysis to identify which seasons and years are most significantly affected by large volcanic eruptions. Armagh temperatures proved particularly responsive in the spring, with a significant decrease in values in the four years following an eruption. Winter temperatures also exhibited a volcanic influence, with a small initial increase in the year of and year following an eruption, and a significant decrease in residual temperature in years two and three after the event

The long-term temperature record from Markree Observatory, County Sligo, from 1842 to 2011

This study analysed long-term temperature patterns in the north-west of Ireland using a previously unexplored data-set from Markree Observatory, County Sligo. The Markree series extends back to 1842, making it one of the longest instrumental temperature records in Ireland and is renowned for holding the lowest recorded temperature for the island of Ireland, 198C on 16 January 1881. Despite its length, this record has been largely absent from past analyses of Ireland’s long-term temperature trends, rendering spatial coverage for the extended Irish climate chronology incomplete. Daily data stored in a variety of the historical archives were gathered and digitised and monthly records created. Calibrations to account for instrumentation, time of reading and exposure were applied where possible in order to standardise the record. Trends were subsequently investigated for seasonal averages of daily minimum, maximum and mean temperatures, and a comparison with previously published long Irish temperature records was carried out to situate the Markree record among the existing long-term series. Although the Markree series follows similar patterns to the other long-term temperature records, it displays more decadal variability, particularly in its minimum values which show a higher rate of late twentieth century warming compared to the other records. Due to its geographic location and surrounding topography shielding the site from direct ocean influences and prevailing south-westerly winds, Markree displays characteristic features of a more inland station (low minimum temperatures and large diurnal ranges) even though it is located only 7 km from the Atlantic Ocean. Such findings highlight the necessity of including the Markree data-set in future Irish climate change research

Identifying volcanic signals in Irish temperature observations since AD 1800

Large volcanic eruptions have been shown to affect temperature patterns to varying degrees on continental, hemispheric or global scales. However, few studies have systematically explored the influence of volcanic eruptions on temperatures at a local, Irish level. The focus of this paper is to determine the impacts of five high-magnitude low-latitude volcanic eruptions and one such Icelandic event on Irish climate over the past 200 years. Daily temperature data from the Armagh Observatory, Co. Armagh, Northern Ireland was used to assess the influence of volcanic eruptions on seasonal and yearly values through time. The paper explores volcanically-induced temperature trends by filtering out the influence of the North Atlantic Oscillation (NAO) and solar variability, and goes on to employ a variation of Superposed Epoch Analysis to identify which seasons and years are most significantly affected by large volcanic eruptions. Armagh temperatures proved particularly responsive in the spring, with a significant decrease in values in the four years following an eruption. Winter temperatures also exhibited a volcanic influence, with a small initial increase in the year of and year following an eruption, and a significant decrease in residual temperature in years two and three after the event

Assessing recent climatic and human influences on chironomid communities from two moderately impacted lakes in western Ireland

This study assessed the influences of climate warming and human impacts on Irish lakes over the late nineteenth to early twenty-first centuries. High-resolution chironomid (Insecta: Diptera) stratigraphies were developed for two low- to mid-elevation lakes in northwest Ireland to determine if lakes with mild-to-moderate human impacts can be used to accurately reconstruct mean July air temperature. Application of an Ireland-based chironomid-inference model to quantitatively estimate July air temperature (r2jack = 0.60, RMSEP = 0.57�C) revealed that chironomids can reflect changes in Irish temperature, particularly post-1980 when warming accelerated, although this signal becomes compromised with intensified human impacts. A biotic response to nutrient enrichment and soil erosion from direct human activities was identified through a comparison of chironomid autecology with known catchment changes. Redundancy analysis and time seriescomparisons were used to identify when faunal turnover is a function of local (nutrient input, erosion) versus extra-regional (climate) drivers over the recent past, and identify any thresholds of human influence within the catchments. This study highlights the importance of careful site selection as moderately impacted sites do not follow a simple scheme, as well as multi-proxy analysis to assess catchment-based human activity for longer term chironomid-based temperature reconstructions in Ireland

The effects of aridity on conifer radial growth, recruitment, and mortality patterns in the eastern sierra nevada, california

Understanding natural variability in precipitation and drought, and the resulting effects on Sierra Nevada forests, is crucial for successful resource management in this environmentally sensitive area of California. This study assessed the species-specific influence of precipitation variations on radial growth, recruitment, and mortality patterns for three conifer species (Pinus jeffreyi, Juniperus occidentalis, and Pinus contorta) in two mid-elevation lake catchments over the past 550 years. The P. jeffreyi chronology was the most highly correlated with winter precipitation patterns, although the other two species also exhibited significant correlations. Ring-width patterns suggest the influence of the Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) on winter precipitation over the length of the records. Recruitment patterns displayed significant, though directionally distinct, correlations with winter drought: P. contorta exhibited increased recruitment during extended drought periods, while P. jeffreyi and J. occidentalis showed increased recruitment during wetter intervals. Finally, a ring of dead trees around both lakes is evidence of a late 20th century water level rise, likely caused by earlier snowmelt and/or wetter conditions. Moisture availability has exerted a strong influence on Sierra Nevada forests through time, but the strength of tree-growth response, and even the sign of tree population response, has been species-specific

The long-term temperature record from Markree Observatory, County Sligo, from 1842 to 2011

This study analysed long-term temperature patterns in the north-west of Ireland using a previously unexplored data-set from Markree Observatory, County Sligo. The Markree series extends back to 1842, making it one of the longest instrumental temperature records in Ireland and is renowned for holding the lowest recorded temperature for the island of Ireland, 198C on 16 January 1881. Despite its length, this record has been largely absent from past analyses of Ireland’s long-term temperature trends, rendering spatial coverage for the extended Irish climate chronology incomplete. Daily data stored in a variety of the historical archives were gathered and digitised and monthly records created. Calibrations to account for instrumentation, time of reading and exposure were applied where possible in order to standardise the record. Trends were subsequently investigated for seasonal averages of daily minimum, maximum and mean temperatures, and a comparison with previously published long Irish temperature records was carried out to situate the Markree record among the existing long-term series. Although the Markree series follows similar patterns to the other long-term temperature records, it displays more decadal variability, particularly in its minimum values which show a higher rate of late twentieth century warming compared to the other records. Due to its geographic location and surrounding topography shielding the site from direct ocean influences and prevailing south-westerly winds, Markree displays characteristic features of a more inland station (low minimum temperatures and large diurnal ranges) even though it is located only 7 km from the Atlantic Ocean. Such findings highlight the necessity of including the Markree data-set in future Irish climate change research

Carbon and nitrogen stable isotope ratios in surface sediments from lakes of western Ireland: Implications for inferring past lake productivity and nitrogen loading

We used statistical analyses to determine which subset of 36 environmental variables best explained variations in surface sediment δ C and δ N from 50 lakes in western Ireland that span a human-impact gradient. The factors controlling lake sediment δ C and δ N depended on whether organics in the lake sediment were mostly derived from the lake catchment (allochthonous) or from productivity within the lake (autochthonous). Lake sediments with a dominantly allochthonous organic source (high C:N ratio sediments) produced δ C and δ N measurements similar to values from catchment vegetation. δ C and δ N measurements from lake sediments with a dominantly autochthonous organic source (low C:N ratio sediments) were influenced by fractionation in the lake and catchment leading up to assimilation of carbon and nitrogen by lacustrine biota. δ C values from lake sediment samples in agricultural catchments were more negative than δ C values from lake sediment samples in non-impacted, bogland catchments. Hypolimnetic oxygen concentrations and methane production had a greater influence on δ C values than fractionation due to algal productivity. δ N from lake sediment samples in agricultural catchments were more positive than δ N in non-impacted bogland catchments. Lower δ N values from non-impacted lake catchments reflected δ N values of catchment vegetation, while higher δ N values in agricultural catchments reflected the high δ N values of cattle manure and inorganic fertilisers. The influence of changing nitrogen sources and lake/catchment fractionation processes were more important than early diagenesis for lake sediment δ N values in this dataset. The results from this study suggest a possible influence of bound inorganic nitrogen on the bulk sediment δ N values. We recommend using a suitable method to control for bound inorganic nitrogen in lake sediments, especially when working with clay-rich sediments. This study confirms the usefulness of δ C and δ N from bulk lake sediments, as long as we are mindful of the multiple factors that can influence these values. This study also highlights how stable isotope datasets from lake surface sediments can complement site-specific isotope source/process studies and help identify key processes controlling lake sediment δ C and δ N in a study area