Constraining Lateglacial and early Holocene environmental changes in Wales and Germany using tephrochronology.

Evidence for the abrupt Lateglacial climatic changes is observed in many palaeorecords, however the mechanisms and triggers behind these changes are still unknown. The preferred hypothesis is thought to be linked with the disruption in the North Atlantic Ocean circulation, therefore palaeoclimatic records from maritime regions are needed to investigate the impact of these abrupt changes. The Greenland ice-core records provide high-resolution evidence of these changes, in addition to many marine and terrestrial records throughout the North Atlantic. However, there is a lack of studies on sites in the south western coastal regions of the British Isles that are well-constrained by robust chronologies. The latter, in particular, hampers our understanding of the mechanisms driving the rapid climate changes of the Lateglacial due to the difficulties of integrating and comparing the climatic response in diverse proxy records. In an attempt to resolve these challenges tephrochronology was employed as a precise correlation technique to investigate three Lateglacial sequences from Wales (Llyn Llech Owain, Cors Carmel and Pant- y-Llyn). An additional site from north Germany (Lake Hämelsee) was also included in this study and chosen due to its potential to preserve tephra from more than one volcanic region and develop a European tephra framework or stratotype for the Lateglacial.Twenty-one tephra deposits were identified across the network of sites. Twelve deposits have been correlated to known eruptions and in most cases have extended the geographical distribution of their respective ash dispersal. Icelandic tephra deposits of Lateglacial age such as the Askja-S Tephra have been discovered in Welsh sites for the first time highlighting the potential of employing tephrochronology more widely in areas such as Wales, south England and perhaps France. Furthermore, three non-Icelandic deposits, that originate from the Cascade region, Alaska and Italy, have been discovered in the Llyn Llech Owain record, allowing the synchronisation of records across a trans-continental scale. The Askja-S Tephra, Ulmener Maar Tephra and Vedde Ash are added to the tephrostartigraphy of the Hämelsee record highlighting its importance as a key site within the European tephra lattice.Nine of the discovered tephra deposits in Llyn Llech Owain and Lake Hämelsee have not been correlated and may represent new eruptions and potentially new tephra isochrons for future studies. Tephra results are supplemented by multi-proxy palaeoenvironmental reconstructions including lithostratigraphic data, sediment geochemistry, palaeoecology and radiocarbon dating where possible.In addition to providing fix-points for potential age-models, the discovered tephra deposits allow the study sites to be independently synchronised with other tephra bearing sites. This allows investigations to be made between sites to constrain any leads or lags in the environmental response to climate change and in turn help determine the mechanisms that cause these abrupt climate changes

Identification of the Askja-S Tephra in a rare turlough record from Pant-y-Llyn, south Wales

Tephrochronology and especially crypto-tephrochronology is an established chronological technique employed in a range of depositional environments in Europe and beyond. During the late Quaternary, Icelandic cryptotephra deposits are widely found in palaeorecords across northern latitudes of Europe e.g. Scotland, Ireland, Norway, Sweden and the Faroe Islands but are sporadic in southerly latitudes as distance from Iceland increases. As yet, very few Icelandic cryptotephras have been identified in Wales or southern England which may well reflect the geographical limit of Icelandic tephra distribution. Here, however, we report the discovery of an Icelandic cryptotephra deposit within a sediment sequence retrieved from the Pant-y-Llyn turlough (Carmarthenshire, south Wales), the only known turlough in Britain. Turloughs are groundwater-fed ephemeral lakes associated with limestone bedrock and can accumulate sediments that may yield records suitable for palaeoreconstructions. A discrete peak of glass shards originating from the Askja-S eruption is identified in the sediment record. This discovery extends the distribution of this early Holocene eruption giving new insight into its dispersal patterns and also indicates that sedimentary sequences from sites in these more southerly latitudes are valuable repositories for ash preservation. Furthermore, its discovery within a carbonate-rich sequence provides a minimum age constraint on the timing of sediment accumulation and provides an alternative tool for what is typically a problematic dating environment

A first chronology for the East Greenland Ice-core Project (EGRIP) over the Holocene and last glacial termination

This paper provides the first chronology for the deep ice core from the East Greenland Ice-core Project (EGRIP) over the Holocene and the late last glacial period. We rely mainly on volcanic events and common peak patterns recorded by dielectric profiling (DEP) and electrical conductivity measurement (ECM) for the synchronization between the EGRIP, North Greenland Eemian Ice Drilling (NEEM) and North Greenland Ice Core Project (NGRIP) ice cores in Greenland. We transfer the annual-layer-counted Greenland Ice Core Chronology 2005 (GICC05) from the NGRIP core to the EGRIP ice core by means of 381 match points, typically spaced less than 50 years apart. The NEEM ice core has previously been dated in a similar way and is only included to support the match-point identification. We name our EGRIP timescale GICC05-EGRIP-1. Over the uppermost 1383.84 m, we establish a depth–age relationship dating back to 14 967 years b2k (years before the year 2000 CE). Tephra horizons provide an independent validation of our match points. In addition, we compare the ratio of the annual layer thickness between ice cores in between the match points to assess our results in view of the different ice-flow patterns and accumulation regimes of the different periods and geographical regions. For the next years, this initial timescale will be the basis for climatic reconstructions from EGRIP high-resolution proxy data sets, e.g. stable water isotopes, chemical impurity or dust records

Synchronous vegetation response to the last glacial-interglacial transition in northwest Europe

The North Atlantic region experienced abrupt high-amplitude cooling at the onset of the Younger Dryas stadial. However, due to chronological uncertainties in the available terrestrial records it is unclear whether terrestrial ecosystem response to this event was instantaneous and spatially synchronous, or whether regional or time-transgressive lags existed. Here we use new palynological results from a robustly dated lake sediment sequence retrieved from lake Hämelsee (north Germany) to show that vegetation change started at 12,820 cal. yr BP, concurrent with the onset of changes in local climate. A comparison of the Hämelsee results to a compilation of precisely dated palynological records shows instant and, within decadal-scale dating uncertainty, synchronous response of the terrestrial plant community to Late-Glacial climate change across northwest Europe. The results indicate that the environmental impact of climate cooling was more severe than previously thought and illustrates the sensitivity of natural terrestrial ecosystems to external forcing. © 2022, The Author(s)

Cryptotephra preserved in Lake Suigetsu (SG14 core) reveals the eruption timing and distribution of ash fall from Japanese volcanoes during the Late-glacial to early Holocene

Long sedimentary successions extracted for palaeoclimate research regularly preserve volcanic ash (tephra) fall from explosive eruptions and are increasingly used to elucidate the timing and scale of past events. This study investigates the non-visible tephra (cryptotephra) layers preserved in the annually laminated and intensively 14C dated sediments of Lake Suigetsu (SG14 core), Japan. The cryptotephra investigations reported here focus on the Late-glacial to early Holocene sediments that were deposited between two visible tephra layers, the Ulleungdo (U)-Oki (10.2 ka) and the Sambe ‘Sakate’ (19.6 ka), and consequently span an interval of abrupt climate change making any newly identified cryptotephra layers invaluable chrono-stratigraphic markers. Using major and trace element volcanic glass compositions the cryptotephra are used to assign provenance to chrono-stratigraphically relevant eruption units. Five new cryptotephra layers are identified within this time interval. Three cryptotephra layers are from Kyushu volcanoes (SG14-1337 and SG14-1554 [Sakurajima]; and SG14-1806 [Kirishima]), all of which offer important chronological constraints on archaeological (Jomon) cultural transitions in southern Japan during the last termination. Another cryptotephra (SG14-1579), is assigned to activity on Niijima Island providing the first known distal occurrence and age of the eruption. Finally, the SG14-1798 cryptotephra precisely dated at 16,619 ± 74 IntCal20 yrs BP (2σ) is linked to Asama (As) volcano and more precisely the later phases of the As-YKU eruption. This discovery greatly expands the distribution of ash fall from this multi-phased eruption at Asama volcano, which affected an area in the region of 120,000 km2. Refining the timing of the eruption and the distribution of As-YKU ash fall is important as it offers an excellent chrono- and climato- stratigraphic marker suitable for assessing spatial variability in environmental response to past climate change during the termination of the last glacial

Synchronous vegetation response to the last glacial-interglacial transition in northwest Europe

The North Atlantic region experienced abrupt high-amplitude cooling at the onset of the Younger Dryas stadial. However, due to chronological uncertainties in the available terrestrial records it is unclear whether terrestrial ecosystem response to this event was instantaneous and spatially synchronous, or whether regional or time-transgressive lags existed. Here we use new palynological results from a robustly dated lake sediment sequence retrieved from lake Hämelsee (north Germany) to show that vegetation change started at 12,820 cal. yr BP, concurrent with the onset of changes in local climate. A comparison of the Hämelsee results to a compilation of precisely dated palynological records shows instant and, within decadal-scale dating uncertainty, synchronous response of the terrestrial plant community to Late-Glacial climate change across northwest Europe. The results indicate that the environmental impact of climate cooling was more severe than previously thought and illustrates the sensitivity of natural terrestrial ecosystems to external forcing

Haemelsee: late-glacial pollen counts

This dataset provides the raw pollen counts for the late-glacial sediment sequence retrieved from Lake Haemelsee (Germany) in 2013. The counts are presented against both depth (cm core depth) and time (cal. yr BP) and cover the time interval from ca 15.200 to 10.400 cal yr BP. A total of 106 samples were counted, with higher sampling resolution around the onset and end of the Younger Dryas, and lower sampling resolution elsewhere in the core. The pollen record provides information about both regional vegetation change as well as changes in the within-lake flora. It was produced to inform on the exact age and duration of major palynological transitions during the late-glacial Cores were retrieved from the lake using a 3-m long UWITEC piston corer deployed from a floating coring platform during field work in July 2013. Volumetric samples were obtained from splits of the core and processed in the laboratory (University of Amsterdam, the Netherlands) using standard protocols

Synchronous vegetation response to the last glacial-interglacial transition in northwest Europe

AbstractThe North Atlantic region experienced abrupt high-amplitude cooling at the onset of the Younger Dryas stadial. However, due to chronological uncertainties in the available terrestrial records it is unclear whether terrestrial ecosystem response to this event was instantaneous and spatially synchronous, or whether regional or time-transgressive lags existed. Here we use new palynological results from a robustly dated lake sediment sequence retrieved from lake Hämelsee (north Germany) to show that vegetation change started at 12,820 cal. yr BP, concurrent with the onset of changes in local climate. A comparison of the Hämelsee results to a compilation of precisely dated palynological records shows instant and, within decadal-scale dating uncertainty, synchronous response of the terrestrial plant community to Late-Glacial climate change across northwest Europe. The results indicate that the environmental impact of climate cooling was more severe than previously thought and illustrates the sensitivity of natural terrestrial ecosystems to external forcing.</jats:p