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- Comas-Bru, Laia, et al.
(författare)
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Evaluating model outputs using integrated global speleothem records of climate change since the last glacial
- 2019
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 15:4, s. 1557-1579
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Tidskriftsartikel (refereegranskat)abstract
- Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data-model comparisons. Here, we illustrate this using 456 globally distributed speleothem delta O-18 records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data-model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on delta O-18 values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.
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| 2. |
- Finné, Martin, 1981-, et al.
(författare)
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Rapid climatic shifts in southern Greece during Marine Isotope Stages 5a-3
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182 .- 1872-616X.
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Tidskriftsartikel (refereegranskat)abstract
- We present a speleothem based stable isotope (δ13C, δ18O) record from southern Greece covering a period from 79±5.8 ka to 37±3 ka, i.e. the end of Marine Isotope Stage (MIS) 5a and large parts of MIS 4 and MIS 3. The record from Glyfada Cave provides a U-Th dated proxy paleoclimate record from Greece, covering this time period, and shows that the climate over the Peloponnese rapidly responded to interstadial and stadial conditions over Greenland. During stadial (interstadial) conditions colder (warmer) and drier (wetter) conditions are reflected by depleted (enriched) δ13C-values in the speleothems from Glyfada Cave. Depositional hiatuses in Glyfada Cave correspond to periods of severe cold conditions in the northern Hemisphere and reduced precipitation over the Peloponnese most likely due to a southward displacement of Mediterranean cyclone tracks due to expanding northern ice sheets and increased snow cover over the European continent. By comparing our independently dated record with previously published pollen studies from Greece a time lag between the records from Ioannina and Megali Limni and Glyfada is evident. The match in time between the Glyfada speleothem record and the Tenaghi Philippon pollen record, when tuned to NGRIP, is rather precise.
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| 3. |
- Finné, Martin, et al.
(författare)
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Speleothem evidence for late Holocene climate variability and floods in Southern Greece
- 2014
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 81:2, s. 213-227
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Tidskriftsartikel (refereegranskat)abstract
- We present stable isotope data (delta O-18, delta C-13) from a detrital rich stalagmite from Kapsia Cave, the Peloponnese, Greece. The cave is rich in archeological remains and there are reasons to believe that flooding of the cave has directly affected humans using the cave. Using a combination of U-Th and C-14 dating to constrain a site-specific correction factor for (Th-232/U-238) detrital molar ratio, a linear age model was constructed. The age model shows that the stalagmite grew during the period from ca. 950 BC to ca. AD 830. The stable oxygen record from Kapsia indicates cyclical changes of close to 500 yr in precipitation amount, with rapid shifts towards wetter conditions followed by slowly developing aridity. Superimposed on this signal, wetter conditions are inferred around 850, 700, 500 and 400-100 BC, and around AD 160-300 and AD 770; and driest conditions are inferred to have occurred around 450 BC, AD 100-150 and AD 650. Detrital horizons in the stalagmite indicate that three major floods took place in the cave at 500 BC, 70 BC and AD 450. The stable carbon isotope record reflects changes in biological activity being a result of both climate and human activities. (c) 2014 University of Washington.
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