The aim of this study is to produce high-resolution multi-proxy records of hydrological change, spanning the last c. 250 years, from nine ombrotrophic peatlands across the north of Ireland. The results provide important insights into the nature of recent climate change in the region. To quantify hydrological change, a combination of established proxy indicators are utilised, including testate amoebae, plant macrofossils and humification analysis. Reconstructions of water table change from testate-amoebae assemblages are undertaken using a transfer function previously developed for the north of Ireland. Chronological control is provided via tephrochronology and Spheroidal Carbonaceous Particle (SCP) analysis, supplemented by AMS 14C dating. Two important regional crypto-tephra's, the Hekla 1947 and Hekla 1510 tephra layers, are used to enhance the age-depth models. A new intermediate Hekla tephra layer is also described at six sites which is inferred to be sourced from the Hekla 1845 eruption event, from which tephra deposits have only previously. been established in Orkney and the Faroe Islands. The bog surface moisture records from the nine sites show a high degree of similarity, with synchronous changes occurring at all sites. Allogenic climate forcing rather than internal peatland dynamics, is thus suggested to be. driving the inferred hydrological changes. A phase of cool and wet conditions predominates in all the records from c. AD 1750 until the late 1800's/early 1900's, probably reflecting the end of the Little Ice Age (LIA). A phase of rapid drying is then recorded, although the timing of the onset varies locally between sites, it is prominent at all sites from c. AD 1940. The testate amoebae based records of hydrological change are validated through statistical comparisons with instrumental climate datasets from the region. Strong correlations are observed between the hydrological records and summer temperatures, and to a lesser extent summer precipitation, indicating that it is the interaction of summer seasonal temperature and precipitation which drives peatland hydrological change in the regional peatlands. Comparisons with other observed climate proxy records from elsewhere in northwest Europe suggest the recent drying in the peatlands from the north of Ireland is part of a climatic shift with wide spatial extent, although the exact timing shows minor variations. The acquisition of multiple intra-regional records preliminarily suggests that smaller bogs and those in lower topographic settings appear to be more sensitive to hydrological change than larger bogs and those in upland settings. This study thus contributes to the wider understanding of the character and impact of recent temperature/precipitation change on Irish peatlands and provides important baseline data for examining the response of future climate change on the region's peatlands.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:557646 |
| Date | January 2011 |
| Creators | Rea, Heidi Alice |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.002 seconds