Younger Dryas and Holocene environmental change at the Atlantic fringe of Europe derived from lake‐sediment stable‐isotope records from western Ireland

Abstract

Western Ireland lies at the Atlantic fringe of Europe and is thus well positioned to record changes in climate linked to North Atlantic circulation. Lake‐sediment oxygen and carbon isotopes are sensitive to changes in the atmosphere, the lake catchment and the lake itself, and thus are valuable proxies for long‐term environmental change. Here we present Younger Dryas and Holocene stable‐isotope records from endogenic and biogenic carbonates from An Loch Mór, a karstic lake on Inis Oírr, Aran Islands, western Ireland. The bulk carbonate and ostracod‐derived stable‐isotope records are a complex response to regional climatic and local factors. Low oxygen‐isotope and high carbon‐isotope values in the Younger Dryas most likely reflect low air temperatures and dominance of bedrock‐derived carbon from the poorly vegetated catchment, but input of detrital carbonate cannot be ruled out. Holocene variations in oxygen‐isotope values are likely a response mainly to changes in the isotopic composition of rainfall, evaporative enrichment of lake water and, during the past millennium, incursion of seawater as a result of regional sea‐level rise. A reduction in carbon‐isotope values at the Younger Dryas/Early Holocene transition reflects increased input of soil‐derived carbon to the lake, modified by changes in aquatic productivity. During the past millennium a shift to less negative values is attributed mainly to increasing saline influence. Broad similarities with stable‐isotope records from other sites in western Ireland suggest regional climatic controls dominated by North Atlantic atmospheric circulation patterns, although abrupt events, that were possibly unique to An Loch Mór, point to local factors also being important.

Holocene Vegetation Dynamics, Landscape Change and Human Impact in Western Ireland as Revealed by Multidisciplinary, Palaeoecological Investigations of Peat Deposits and Bog-Pine in Lowland Connemara

“…The duration in DYR VI may be exaggerated due to weak chronological constraint of the upper part of this profile, and the dating as provided by the age/depth model in the case of both profiles is younger, by a century or more, than expected on the basis of the evidence from other sites in western Ireland. For example, in profile MOR1 (Inis Oírr, Aran Islands), where the record is chronologically tightly constrained (see [98], Figure 4), a LIAL-expressed by low NAP and a major expansion of Juniperus and Taxus in the final stages-spans the interval 1.86-1.45 ka, i.e., 90 BCE-500 CE [16]. In FRK II (Letterfrack), the LIAL is also well expressed but is centred on the early centuries CE, which is here regarded as the best available approximation for the dating of LIAL in Renvyle and Letterfrack.…”

Long-term human impact and environmental change in mid-western Ireland, with particular reference to Céide Fields – an overview

“…P. lanceolata or other anthropogenic pollen indicators (there are no records for cereal-type pollen) are poorly represented, so it is not possible to draw conclusions regarding human impact, apart from suggesting that it seems to have been unimportant. In subsequent investigations, chironomid, geochemical and geophysical analyses and 14 C dating (10 dates) were carried out on new cores, 6-7 m long, with a view to exploring impact of climate variability on long-term human activity (Holmes et al, 2013). At least half the core is pre-Holocene, so the resolution for the period of greatest interest, i.e.…”

A modern snapshot of the isotopic composition of lacustrine biogenic carbonates – records of seasonal water temperature variability

“…The oxygen and carbon isotopic compositions of biogenic carbonates from lake sediments are powerful tools for reconstructing past climatic and environmental changes. Despite the complex influences of climate, hydrology, catchment and lake processes, as well as biological effects, they may be interpreted, depending on the local context, as proxies of temperature, evaporation, the isotopic composition of atmospheric precipitation, or atmospheric circulation patterns (e.g., Holmes et al, 2020;Andersson et al, 2010;Jonsson et al, 2010;Hammarlund et al, 2003;Schwalb, 2003;Hammarlund et al, 2002;von Grafenstein et al, 1999a).…”