Palaeoclimate and climate systems facility
Mae'r cynnwys hwn ar gael yn Saesneg yn unig.
The facility comprises laboratories for processing marine sediment cores and sample preparation for geochemical analysis, a stable isotope laboratory and a high-resolution ICP-MS laboratory.
The labs house cold rooms suitable for storage of sediment cores; extensive wet areas equipped with fume hoods, DI water systems, and facilities for sediment sieving and generic geochemical processing; ample bench space with reflecting light microscopes for micropalaeontological analysis, and microbalances and further relevant equipment.
The stable isotope laboratory can provide analyses of the light isotopes D/H, 13C, 15N, and 18O in a range of materials. It is equipped with a Thermo MAT 253 with Kiel IV carbonate preparation device, a Thermo Delta V Advantage with Gasbench II and Flash EA CN analyser, and Picarro L2130-i analyser for liquid water.
High-resolution ICP-MS laboratory
The Palaeoclimate facility is equipped with a Thermo Scientific™ ELEMENT XR™ HR-ICP-MS in combination with an Elemental Scientific SC-E2 Autosampler. The Element XR is optimised for the analysis of trace metal elements in carbonate (e.g. foraminifera, molluscs) and sea water samples, but it can address applications from a wide range of disciplines. It is a double focusing mass analyser (magnetic sector and electrostatic sector) which benefits from high resolution, a large dynamic range and precise analysis at low concentrations (ppt-ppq).
There are three clean rooms for the preparation of the samples and standards to be analysed on the Element XR. These have fume cupboards, ELGA ultra-pure water systems delivering Type I water (up to 18.2 MΩ·cm) and laminar flow workstations fitted with HEPA and PTFE ULPA filters.
The lab is equipped with a Multisizer 4 Coulter Counter which uses the Coulter principle to detect particles via electrical zone sensing. It provides size distribution in number, volume and surface area in one measurement, with an overall sizing range of 0.4 μm to 1600 μm.
How it has helped
The PACS facility provides essential data on the physical and chemical composition of the world's oceans from which we can reconstruct past climate change, and investigate how the climate system has responded to rapid perturbations.
Large amplitude variations in atmospheric CO2 were associated with glacial terminations of the Late Pleistocene. We provided multiple lines of evidence suggesting that the ∼20 p.p.m.v. overshoot in CO2 at the end of Termination 2 (T2) ∼129 ka was associated with an abrupt (≤400 year) deepening of Atlantic Meridional Overturning Circulation (AMOC). In contrast to Termination 1 (T1), which was interrupted by the Bølling-Allerød (B-A), AMOC recovery did not occur until the very end of T2, and was characterized by pronounced formation of deep waters in the NW Atlantic. Considering the variable influences of ocean circulation change on atmospheric CO2, we suggest that the net change in CO2 across the last 2 terminations was approximately equal if the transient effects of deglacial oscillations in ocean circulation are taken into account.
We showed the presence of centennial cycles in ocean temperature and salinity from a sediment core South of Iceland for the period AD818 to 1780 that correlate with variability in total solar irradiance (sunspot cycles). We find a similar correlation in a simulation of climate over the past 1,000 years. We infer that the hydrographic changes probably reflect variability in the strength of the subpolar gyre associated with changes in atmospheric circulation. Specifically, in the simulation, low solar irradiance promotes the development of a quasi-stationary high-pressure system in the eastern North Atlantic, which modifies the flow of the westerly winds. We conclude that this process could have contributed to the consecutive cold winters documented in Europe during the Little Ice Age.
The ~100 k.y. cyclicity of the late Pleistocene ice ages started during the mid-Pleistocene transition (MPT), as ice sheets became larger and persisted for longer. We presented benthic foraminiferal stable isotope (d18O, d13C) and trace metal records (Cd/Ca, B/Ca, U/Ca) from Deep Sea Drilling Project Site 607 in the North Atlantic. We showed that the respired carbon content of Atlantic deep water during glacial intervals increased across the MPT, which would have raised mean ocean alkalinity and lowered atmospheric pCO2. However, the change in dissolved carbon was not mirrored by changes in nutrient content. We interpret this in terms of air-sea CO2 exchange effects, which changed the d13C signature of dissolved inorganic carbon in the deep water mass source regions. Increased sea ice cover or ocean stratification during glacial times may have reduced CO2 outgassing in the Southern Ocean, providing an additional mechanism for reducing glacial atmospheric pCO2. Conversely, following the establishment of the ~100 k.y. glacial cycles, d13C of interglacial northern-sourced waters increased, perhaps reflecting reduced invasion of CO2 into the North Atlantic following the MPT.