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Maryunani, Khoiril Anwar. "Microfossil as proxy for palaeoclimate and palaeoceanography." Berita Sedimentologi 47, no. 3 (December 28, 2021): 77–78. http://dx.doi.org/10.51835/bsed.2021.47.3.363.
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Recent global warming has been addressed due to human activity that causes increased greenhouse gases. However, there are inherent uncertainties in the statement, one of them is the level of natural variability inherent in the climate system. Climate data from measuring instruments are not long enough to evaluate climate variability and current climate evolution. Therefore, we need climate data that has a long back span. To get adequate past climate data, we need natural phenomena which are climate dependent. This natural phenomenon provides a proxy record of the climate. This study of proxy data is the foundation of palaeoclimatology and paleoceanography. Microfossils (i.e., foraminifera, palynomorphs, nannofossils) which in geology are used as a standard tool in biostratigraphy for both age determination and paleoenvironment and correlation, can also be used as a proxy for obtaining paleoclimate and paleoceanography data. Using microfossil as a proxy to study past climate and paleoceanography, we need an understanding of the type of proxy data available and methods used in their analysis.In addition to the dating method (biostratigraphy), there are many climate and oceanography parameters that can be obtained from microfossil proxies such as: sea surface temperature (SST), sea surface salinity, (SST) climate (warm, cold, dry, wet), precipitation, productivity, oxygen content and organic carbon level, deep sea current and ventilation/upwelling, thermocline and mixed layer, variability deep water properties, CCD, bathymetry, sea level change and dissolution. The methods to obtain data fall into some categories e.g., faunal/floral displacement, morphology changes, transfer function/modern analog and isotopic content. Another method that can be used is observing microfossil assemblages and link them to ecological changes associated with climate change and its paleoceanography.A paleoclimate and paleoceanography study using microfossil proxies has been conducted in the Cendrawasih bay, Papua, Indonesia. The study shows that climate in the tropical west Pacific margin (Cendrawasih bay) during Late Pleistocene to Holocene shows high variability. There are nineteen climate changes occurred during Holocene. Early Holocene dated as ca. 11,800-year BP marked by rapid warming with SST differences to last glacial is about 4oC. Early to Middle Holocene (ca. 5960-year BP) marked by increasing temperature up to 2oC, interrupted by cooling at ca. 11230-, 8310- and 7120-years BP. At Middle Holocene temperature decreased rapidly and reached its peak at around ca. 3150-year BP. After cooling at ca. 3150-year BP, temperature increased and then decreased with its peak at ca. 1710-year BP. Since ca. 1710-year BP to Recent, temperature shows warming trend. SST from MAT indicates warming environment near to 1.5oC. The warming trend was interrupted by rapid cooling and warming at ca. 300-year BP. This last warming trend indicates that global warming had started before industrial era and rapid cooling, or warming can occur without anthropogenic gases influence. The typical Holocene climate of warm-wet, dry-cold reverse and become warm-dry, cold-wet during ca. 790-370-year BP and then reversed back to preceding state.Semi-restricted basin occurred since last glacial with anaerobic condition and estuarine circulation system. Warming during interstadial 1e-1a, causing reverse water circulation and basin become sub-aerobic with anti-estuarine circulation. A lot of terrestrial organic matter flow to the bay and increase acidity and carbonate dissolution. High sedimentation found occurred during glacial period especially at the end of glacial period. Rapid warming during late glacial to middle Holocene, rising relative sea level and the bay become more open marine with well oxygenated bottom water and high marine productivity. Warm temperature and deeper thermocline depth (~ 250 m) in west Pacific occurred up to ca. 5960-year BP. Decreasing Sea surface temperature at ca. 5960-year BP and drop of relative sea level causing sub-aerobic condition inside bay. The semi-restricted state with sub-aerobic condition occurred up to Recent.Distribution of Sphaeroidinella group in the tropical west Pacific shows strong correlation with thermocline depth and reflect El Niño frequency event. Early middle Holocene dominated by La Niña-like condition and since Middle Holocene (ca. 5960-year BP) frequent El Niño event began to occur.
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Lekscha, Jaqueline, and Reik V. Donner. "Detecting dynamical anomalies in time series from different palaeoclimate proxy archives using windowed recurrence network analysis." Nonlinear Processes in Geophysics 27, no. 2 (April 27, 2020): 261–75. http://dx.doi.org/10.5194/npg-27-261-2020.
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Abstract. Analysing palaeoclimate proxy time series using windowed recurrence network analysis (wRNA) has been shown to provide valuable information on past climate variability. In turn, it has also been found that the robustness of the obtained results differs among proxies from different palaeoclimate archives. To systematically test the suitability of wRNA for studying different types of palaeoclimate proxy time series, we use the framework of forward proxy modelling. For this, we create artificial input time series with different properties and compare the areawise significant anomalies detected using wRNA of the input and the model output time series. Also, taking into account results for general filtering of different time series, we find that the variability of the network transitivity is altered for stochastic input time series while being rather robust for deterministic input. In terms of significant anomalies of the network transitivity, we observe that these anomalies may be missed by proxies from tree and lake archives after the non-linear filtering by the corresponding proxy system models. For proxies from speleothems, we additionally observe falsely identified significant anomalies that are not present in the input time series. Finally, for proxies from ice cores, the wRNA results show the best correspondence to those for the input data. Our results contribute to improve the interpretation of windowed recurrence network analysis results obtained from real-world palaeoclimate time series.
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Bräuning, A. "Climate variability of the tropical Andes since the late Pleistocene." Advances in Geosciences 22 (October 13, 2009): 13–25. http://dx.doi.org/10.5194/adgeo-22-13-2009.
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Abstract. Available proxy records witnessing palaeoclimate of the tropical Andes are comparably scarce. Major implications of palaeoclimate development in the humid and arid parts of the Andes are briefly summarized. The long-term behaviour of ENSO has general significance for the climatic history of the Andes due to its impact on regional circulation patterns and precipitation regimes, therefore ENSO history derived from non-Andean palaeo-records is highlighted. Methodological constraints of the chronological precision and the palaeoclimatic interpretation of records derived from different natural archives, such as glacier sediments and ice cores, lake sediments and palaeo-wetlands, pollen profiles and tree rings are addressed and complementary results concerning former climatic conditions are discussed in terms of possible implications of former atmospheric circulation patterns and main climatic forcing factors. During the last years, increasing tree-ring information is getting available from the tropical Andes, providing high-resolution climate-sensitive records covering the past centuries for the study of climate variability.
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Marwan, Norbert, Jonathan F. Donges, Reik V. Donner, and Deniz Eroglu. "Nonlinear time series analysis of palaeoclimate proxy records." Quaternary Science Reviews 274 (December 2021): 107245. http://dx.doi.org/10.1016/j.quascirev.2021.107245.
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Herath, D., D. E. Jacob, H. Jones, and S. J. Fallon. "Potential of shells of three species of eastern Australian freshwater mussels (Bivalvia: Hyriidae) as environmental proxy archives." Marine and Freshwater Research 70, no. 2 (2019): 255. http://dx.doi.org/10.1071/mf17319.
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Freshwater mussels in Australia are rarely studied for their life history and potential as palaeoclimate proxy archives. Therefore, we studied three freshwater mussel species from the Williams River, Hunter Valley, Australia, namely Alathyria profuga, Cucumerunio novaehollandiae and Hyridella drapeta, to identify their potential as new environmental proxy archives from Australian freshwater bodies. Growth analysis revealed that A. profuga and C. novaehollandiae produce distinctive growth lines, which allow the first identification of age and growth structure of these species. The oxygen isotope ratio in A. profuga shells and high-resolution element concentrations in all three species show cyclic, annual variations. A high correlation between growth rates and the combined winter air temperature and annual rainfall, as well as accurate temperature reconstruction using oxygen isotope values in the shells suggest that A. profuga has good potential as an environmental proxy archive. However, the low correlation observed between the Sr:Ca ratio and temperature limited the usefulness of the Sr:Ca ratio in A. profuga shells as a water temperate proxy. In contrast, growth rates and element ratios of C. novaehollandiae do not indicate a significant relationship with environmental variables, suggesting that this species, together with H. drapeta, is probably not suitable for palaeoclimatic studies.
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Schollaen, K., C. Karamperidou, P. Krusic, E. Cook, and G. Helle. "ENSO flavors in a tree-ring δ<sup>18</sup>O record of <i>Tectona grandis</i> from Indonesia." Climate of the Past 11, no. 10 (October 8, 2015): 1325–33. http://dx.doi.org/10.5194/cp-11-1325-2015.
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Abstract. Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900–2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific) El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics, as well as the potential of palaeoclimate proxy records from appropriately selected tropical regions for reconstructing past variability of. ENSO flavors.
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Breitenbach, S. F. M., K. Rehfeld, B. Goswami, J. U. L. Baldini, H. E. Ridley, D. Kennett, K. Prufer, et al. "COnstructing Proxy-Record Age models (COPRA)." Climate of the Past Discussions 8, no. 3 (June 19, 2012): 2369–408. http://dx.doi.org/10.5194/cpd-8-2369-2012.
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Abstract. Reliable age models are fundamental for any palaeoclimate reconstruction. Interpolation procedures between age control points are often inadequately reported, and available modeling algorithms do not allow incorporation of layer counted intervals to improve the confidence limits of the age model in question. We present a modeling approach that allows automatic detection and interactive handling of outliers and hiatuses. We use Monte Carlo simulation to assign an absolute time scale to climate proxies by conferring the dating uncertainties to uncertainties in the proxy values. The algorithm allows us to integrate incremental relative dating information to improve the final age model. The software package COPRA1.0 facilitates easy interactive usage.
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Emile-Geay, J., and M. Tingley. "Inferring climate variability from nonlinear proxies: application to palaeo-ENSO studies." Climate of the Past 12, no. 1 (January 15, 2016): 31–50. http://dx.doi.org/10.5194/cp-12-31-2016.
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Abstract. Inferring climate from palaeodata frequently assumes a direct, linear relationship between the two, which is seldom met in practice. Here we simulate an idealized proxy characterized by a nonlinear, thresholded relationship with surface temperature, and we demonstrate the pitfalls of ignoring nonlinearities in the proxy–climate relationship. We explore three approaches to using this idealized proxy to infer past climate: (i) methods commonly used in the palaeoclimate literature, without consideration of nonlinearities; (ii) the same methods, after empirically transforming the data to normality to account for nonlinearities; and (iii) using a Bayesian model to invert the mechanistic relationship between the climate and the proxy. We find that neglecting nonlinearity often exaggerates changes in climate variability between different time intervals and leads to reconstructions with poorly quantified uncertainties. In contrast, explicit recognition of the nonlinear relationship, using either a mechanistic model or an empirical transform, yields significantly better estimates of past climate variations, with more accurate uncertainty quantification. We apply these insights to two palaeoclimate settings. Accounting for nonlinearities in the classical sedimentary record from Laguna Pallcacocha leads to quantitative departures from the results of the original study, and it markedly affects the detection of variance changes over time. A comparison with the Lake Challa record, also a nonlinear proxy for El Niño–Southern Oscillation, illustrates how inter-proxy comparisons may be altered when accounting for nonlinearity. The results hold implications for how univariate, nonlinear recorders of normally distributed climate variables are interpreted, compared to other proxy records, and incorporated into multiproxy reconstructions.
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Williams, Charles J. R., Maria-Vittoria Guarino, Emilie Capron, Irene Malmierca-Vallet, Joy S. Singarayer, Louise C. Sime, Daniel J. Lunt, and Paul J. Valdes. "CMIP6/PMIP4 simulations of the mid-Holocene and Last Interglacial using HadGEM3: comparison to the pre-industrial era, previous model versions and proxy data." Climate of the Past 16, no. 4 (August 6, 2020): 1429–50. http://dx.doi.org/10.5194/cp-16-1429-2020.
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Abstract. Palaeoclimate model simulations are an important tool to improve our understanding of the mechanisms of climate change. These simulations also provide tests of the ability of models to simulate climates very different to today. Here we present the results from two brand-new simulations using the latest version of the UK's physical climate model, HadGEM3-GC3.1; they are the mid-Holocene (∼6 ka) and Last Interglacial (∼127 ka) simulations, both conducted under the auspices of CMIP6/PMIP4. This is the first time this version of the UK model has been used to conduct palaeoclimate simulations. These periods are of particular interest to PMIP4 because they represent the two most recent warm periods in Earth history, where atmospheric concentration of greenhouse gases and continental configuration are similar to the pre-industrial period but where there were significant changes to the Earth's orbital configuration, resulting in a very different seasonal cycle of radiative forcing. Results for these simulations are assessed firstly against the same model's pre-industrial control simulation (a simulation comparison, to describe and understand the differences between the pre-industrial – PI – and the two palaeo simulations) and secondly against previous versions of the same model relative to newly available proxy data (a model–data comparison, to compare all available simulations from the same model with proxy data to assess any improvements due to model advances). The introduction of this newly available proxy data adds further novelty to this study. Globally, for metrics such as 1.5 m temperature and surface rainfall, whilst both the recent palaeoclimate simulations are mostly capturing the expected sign and, in some places, magnitude of change relative to the pre-industrial, this is geographically and seasonally dependent. Compared to newly available proxy data (including sea surface temperature – SST – and rainfall) and also incorporating data from previous versions of the model shows that the relative accuracy of the simulations appears to vary according to metric, proxy reconstruction used for comparison and geographical location. In some instances, such as mean rainfall in the mid-Holocene, there is a clear and linear improvement, relative to proxy data, from the oldest to the newest generation of the model. When zooming into northern Africa, a region known to be problematic for models in terms of rainfall enhancement, the behaviour of the West African monsoon in both recent palaeoclimate simulations is consistent with current understanding, suggesting a wetter monsoon during the mid-Holocene and (more so) the Last Interglacial, relative to the pre-industrial era. However, regarding the well-documented “Saharan greening” during the mid-Holocene, results here suggest that the most recent version of the UK's physical model is still unable to reproduce the increases suggested by proxy data, consistent with all other previous models to date.
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Verma, Poonam, and Abha Singh. "Palynology of Cenozoic successions of Kerala Basin: a review from the perspective of biostratigraphy and palaeoclimatic studies." Journal of Palaeosciences 67, no. (1-2) (December 31, 2018): 99–111. http://dx.doi.org/10.54991/jop.2018.51.
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The Kerala Basin is only onshore opportunity to study Cenozoic palaeoclimate and palaeoenvironment of southwest India encompassing Neogene global events such as Mid Miocene Climate Optimum (MMCO) and even older times of Palaeogene. The global warming during ~17–15 Ma (MMCO), enhanced annual surface temperature 3–4° C higher than the present, is equivalent to the warming predicted for the next century. Since the palaeogeographical and other general conditions have not been much changed from the Miocene Period, Neogene palaeoclimate of Kerala Basin can be considered as a possible analogue for future climate. Many workers have studied the Cenozoic sedimentary successions of surface and subsurface for stratigraphic classification of the rocks, but still, discrepancy persists in the chronostratigraphic relationship in sedimentary successions. The palynological investigations have also been limited mainly to palynofloral and palaeoecological inferences except a few in which palynostratigraphy, correlation and age have been attempted on the basis of spore–pollen only. Major three Cenozones namely, Triangulorites bellus and Crassoretitriletes vanraadshooveni (Eocene–Oligocene) and Malvacearumpollis bakonyensis (Miocene) have been established. The palynological studies done in the region broadly suggest warm and humid climate with heavy rainfall. However, the recent quantitative studies have highlighted the complexity of palaeoclimatic evolution in the tropics in terms of monsoon. A time–constrained quantitative palaeovegetation and palaeoclimate reconstructions on the basis of palynology is required for evaluation of response and changes in the tropical flora of northwestern India across the major climate events. For that, the biostratigraphy of finer resolution based on systematic and integrated multi–biotic proxy is needed to establish an age model for these sedimentary successions.
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Eaves, Shaun R., Andrew N. Mackintosh, Brian M. Anderson, Alice M. Doughty, Dougal B. Townsend, Chris E. Conway, Gisela Winckler, Joerg M. Schaefer, Graham S. Leonard, and Andrew T. Calvert. "The Last Glacial Maximum in the central North Island, New Zealand: palaeoclimate inferences from glacier modelling." Climate of the Past 12, no. 4 (April 15, 2016): 943–60. http://dx.doi.org/10.5194/cp-12-943-2016.
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Abstract. Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers, constrained by moraine mapping, afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2-D coupled energy balance–ice flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in the central North Island, New Zealand. We find that the former ice limits can be simulated when present-day temperatures are reduced by between 4 and 7 °C, if precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The majority of catchments targeted require temperature decreases of 5.1 to 6.3 °C to simulate the former glaciers, which represents our best estimate of the temperature anomaly in the central North Island, New Zealand, during the Last Glacial Maximum. A decrease in precipitation of up to 25 % from present, as suggested by proxy evidence and climate models, increases the magnitude of the required temperature changes by up to 0.8 °C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial ( < 15 ka) volcanism generally increased the magnitude of cooling required to simulate the former ice limits by up to 0.5 °C. Our palaeotemperature estimates expand the spatial coverage of proxy-based quantitative palaeoclimate reconstructions in New Zealand. Our results are also consistent with independent, proximal temperature reconstructions from fossil groundwater and pollen assemblages, as well as similar glacier modelling reconstructions from the central Southern Alps, which suggest air temperatures were ca. 6 °C lower than present across New Zealand during the Last Glacial Maximum.
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Breitenbach, S. F. M., K. Rehfeld, B. Goswami, J. U. L. Baldini, H. E. Ridley, D. J. Kennett, K. M. Prufer, et al. "COnstructing Proxy Records from Age models (COPRA)." Climate of the Past 8, no. 5 (October 31, 2012): 1765–79. http://dx.doi.org/10.5194/cp-8-1765-2012.
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Abstract. Reliable age models are fundamental for any palaeoclimate reconstruction. Available interpolation procedures between age control points are often inadequately reported, and very few translate age uncertainties to proxy uncertainties. Most available modeling algorithms do not allow incorporation of layer counted intervals to improve the confidence limits of the age model in question. We present a framework that allows detection and interactive handling of age reversals and hiatuses, depth-age modeling, and proxy-record reconstruction. Monte Carlo simulation and a translation procedure are used to assign a precise time scale to climate proxies and to translate dating uncertainties to uncertainties in the proxy values. The presented framework allows integration of incremental relative dating information to improve the final age model. The free software package COPRA1.0 facilitates easy interactive usage.
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Helama, Samuli, Thomas M. Melvin, and Keith R. Briffa. "Regional curve standardization: State of the art." Holocene 27, no. 1 (July 28, 2016): 172–77. http://dx.doi.org/10.1177/0959683616652709.
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Tree rings are commonly used proxy data for past climate variability. Probably the simplest practical solution for transforming raw tree-ring data into proxy estimates and retaining information on low-frequency tree-growth forcing is the regional curve standardization (RCS). This paper reviews the RCS concept and the development of this standardization method over the past 25 years. Tree-ring based estimation of low-frequency climate variability is illuminated with a growing diversification of the original concept. The RCS-type methods are seen to remain as essential tools in palaeoclimate research while the RCS chronologies of tree-ring and other incremental proxy data remain the only source for calendar year dated short-to-long timescale climate variations.
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Dätwyler, Christoph, Martin Grosjean, Nathan J. Steiger, and Raphael Neukom. "Teleconnections and relationship between the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium." Climate of the Past 16, no. 2 (April 22, 2020): 743–56. http://dx.doi.org/10.5194/cp-16-743-2020.
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Abstract. The climate of the Southern Hemisphere (SH) is strongly influenced by variations in the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Because of the limited length of instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability over time. Using proxy-based reconstructions and last-millennium climate model simulations, we find that ENSO and SAM indices are mostly negatively correlated over the past millennium. Pseudo-proxy experiments indicate that currently available proxy records are able to reliably capture ENSO–SAM relationships back to at least 1600 CE. Palaeoclimate reconstructions show mostly negative correlations back to about 1400 CE. An ensemble of last-millennium climate model simulations confirms this negative correlation, showing a stable correlation of approximately −0.3. Despite this generally negative relationship we do find intermittent periods of positive ENSO–SAM correlations in individual model simulations and in the palaeoclimate reconstructions. We do not find evidence that these relationship fluctuations are caused by exogenous forcing nor by a consistent climate pattern. However, we do find evidence that strong negative correlations are associated with strong positive (negative) anomalies in the Interdecadal Pacific Oscillation and the Amundsen Sea Low during periods when SAM and ENSO indices are of opposite (equal) sign.
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Campbell, Rochelle, Danny McCarroll, Neil J. Loader, Håkan Grudd, Iain Robertson, and Risto Jalkanen. "Blue intensity in Pinus sylvestris tree-rings: developing a new palaeoclimate proxy." Holocene 17, no. 6 (September 2007): 821–28. http://dx.doi.org/10.1177/0959683607080523.
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Amesbury, M. J., D. J. Charman, R. M. Newnham, N. J. Loader, J. P. Goodrich, J. Royles, D. I. Campbell, T. P. Roland, and A. Gallego-Sala. "Carbon stable isotopes as a palaeoclimate proxy in vascular plant dominated peatlands." Geochimica et Cosmochimica Acta 164 (September 2015): 161–74. http://dx.doi.org/10.1016/j.gca.2015.05.011.
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Dowsett, Harry J., Marci M. Robinson, Danielle K. Stoll, Kevin M. Foley, Andrew L. A. Johnson, Mark Williams, and Christina R. Riesselman. "The PRISM (Pliocene palaeoclimate) reconstruction: time for a paradigm shift." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 2001 (October 28, 2013): 20120524. http://dx.doi.org/10.1098/rsta.2012.0524.
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Global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change, but single-temperature representations of the oceanic mixed layer for data–model comparisons are outdated, and the time for a paradigm shift in marine palaeoclimate reconstruction is overdue. The new paradigm in marine palaeoclimate reconstruction stems the loss of valuable climate information and instead presents a holistic and nuanced interpretation of multi-dimensional oceanographic processes and responses. A wealth of environmental information is hidden within the US Geological Survey's P liocene R esearch, I nterpretation and S ynoptic M apping (PRISM) marine palaeoclimate reconstruction, and we introduce here a plan to incorporate all valuable climate data into the next generation of PRISM products. Beyond the global approach and focus, we plan to incorporate regional climate dynamics with emphasis on processes, integrating multiple environmental proxies wherever available in order to better characterize the mixed layer, and developing a finer time slice within the Mid-Piacenzian Age of the Pliocene, complemented by underused proxies that offer snapshots into environmental conditions. The result will be a proxy-rich, temporally nested, process-oriented approach in a digital format—a relational database with geographic information system capabilities comprising a three-dimensional grid representing the surface layer, with a plethora of data in each cell.
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Sun, Zhong-Xiu, Qiu-Bing Wang, Chun-Lan Han, Qing-Jie Zhang, and Phillip R. Owens. "Clay mineralogical characteristics and the palaeoclimatic significance of a Holocene to Late Middle Pleistocene loess–palaeosol sequence from Chaoyang, China." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 106, no. 3 (September 2015): 185–97. http://dx.doi.org/10.1017/s1755691016000098.
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ABSTRACTChanges in soil chemistry in response to varying climatic regimes can alter the equilibria of soil systems and result in different clay minerals. Variations in phyllosilicate clay composition can reflect temporal and spatial climatic changes, such as summer/winter monsoon cycles. The objective of this research was to investigate the mineralogy of the clay fractions as a proxy for determining variations in the East Asian monsoon climate, based on a section at Chaoyang in China spanning the last 0.423 Ma BP. The clay mineralogy record in the Chaoyang section was compared with other proxies as recorded in this section and with other palaeoclimatic indicators, including oxygen isotopes from oceanic sediments and loess–palaeosol sections on the Chinese Loess Plateau (CLP). The results from clay mineralogy and related climatic studies show that the summer monsoon has a trend of four increased stages and four decreased stages; whereas the winter monsoon displays the opposite trend. During the last 0.423 Ma BP, the strongest winter monsoon occurred around 0.243–0.311 Ma BP. During this period, which included an intense winter monsoon, the soil in the section had the least illite, one of the smallest kaolinite and illite/Chlorite (I/C) indices and an overall decreasing clay content. The period 0.225–0.243 Ma BP had the strongest summer monsoon over the last 0.423 Ma BP. This period had the greatest amount of illite, the highest I/C index, greater overall clay content and the strongest magnetic susceptibility signal. Additionally, this section contained the smallest mean grain size. The multi-monsoon climate cycles of alternating cold-dry and warm-moist conditions as recorded in the Chaoyang section corresponded well with multiple glaciation cycles based on deep sea sediments. This indicates that the Chaoyang section provides a record of palaeoclimate changes in northeast China that can be linked to mineralogical suites to assist in reconstructing the palaeoclimate over the Late Middle Pleistocene, and complements the global palaeoclimate records in the CLP.
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Batehup, R., S. McGregor, and A. J. E. Gallant. "The influence of non-stationary teleconnections on palaeoclimate reconstructions of ENSO variance using a pseudoproxy framework." Climate of the Past 11, no. 12 (December 18, 2015): 1733–49. http://dx.doi.org/10.5194/cp-11-1733-2015.
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Abstract. Reconstructions of the El Niño–Southern Oscillation (ENSO) ideally require high-quality, annually resolved and long-running palaeoclimate proxy records in the eastern tropical Pacific Ocean, located in ENSO's centre of action. However, to date, the palaeoclimate records that have been extracted in the region are short or temporally and spatially sporadic, limiting the information that can be provided by these reconstructions. Consequently, most ENSO reconstructions exploit the downstream influences of ENSO on remote locations, known as teleconnections, where longer records from palaeoclimate proxies exist. However, using teleconnections to reconstruct ENSO relies on the assumption that the relationship between ENSO and the remote location is stationary in time. Increasing evidence from observations and climate models suggests that some teleconnections are, in fact, non-stationary, potentially threatening the validity of those palaeoclimate reconstructions that exploit teleconnections. This study examines the implications of non-stationary teleconnections on modern multi-proxy reconstructions of ENSO variance. The sensitivity of the reconstructions to non-stationary teleconnections were tested using a suite of idealised pseudoproxy experiments that employed output from a fully coupled global climate model. Reconstructions of the variance in the Niño 3.4 index representing ENSO variability were generated using four different methods. Surface temperature data from the GFDL CM2.1 were used as pseudoproxies for these reconstruction methods. As well as sensitivity of the reconstruction to the method, the experiments tested the sensitivity of the reconstruction to the number of non-stationary pseudoproxies and the location of these proxies. We find that non-stationarities can act to degrade the skill of ENSO variance reconstructions. However, when global, randomly spaced networks (assuming a minimum of approximately 20 proxies) were employed, the resulting pseudoproxy ENSO reconstructions were not sensitive to non-stationary teleconnections. Neglecting proxies from ENSO's centre of action still produced skilful reconstructions, but with a lower likelihood. Different reconstruction methods exhibited varying sensitivities to non-stationary pseudoproxies, which affected the robustness of the resulting reconstructions. The results suggest that caution should be taken when developing reconstructions using proxies from a single teleconnected region, or those that use less than 20 source proxies.
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Webb, Julia C., Julia McCarroll, Frank M. Chambers, and Tim Thom. "Evidence for the Little Ice Age in upland northwestern Europe: Multiproxy climate data from three blanket mires in northern England." Holocene 32, no. 5 (February 15, 2022): 451–67. http://dx.doi.org/10.1177/09596836221074036.
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The Little Ice Age (LIA) is a well-recognised palaeoclimatic phenomenon, although its causes, duration and severity have been matters of debate and dispute. Data from a wide range of archives have been used to infer climate variability before, during and after the LIA. Some published proxy-climate data from peatlands imply that two particularly severe episodes within the LIA may be contemporaneous between hemispheres; these echo a previous climatic downturn ca. 2800 cal BP of similar severity but lesser duration. Here, we present palaeoclimate data from the mid- to late-Holocene, reconstructed from three blanket peats in Yorkshire: Mossdale Moor, Oxenhope Moor and West Arkengarthdale. Multiproxy techniques used for palaeoclimatic reconstruction were plant macrofossil, pollen and humification analyses. Dating was provided by a radiocarbon-based chronology, aided by spheroidal carbonaceous particles (SCPs) for all sites, and 210Pb dates for one. The LIA presents as a distinct climatic event within each palaeoenvironmental record at the three sites. These indications are compared with terrestrial datasets from northwest Europe and elsewhere. A broad degree of synchronicity is evident, signifying that the LIA is one of the most pronounced downturns in global climate in the last ca. 6000 years, and arguably the most routinely recorded within the Holocene.
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Butler, Paul. "The application of proxy data from high resolution marine archives to palaeoclimate models." Quaternary International 279-280 (November 2012): 77. http://dx.doi.org/10.1016/j.quaint.2012.07.337.
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Obreht, Igor, Christian Zeeden, Ulrich Hambach, Daniel Veres, Slobodan B. Marković, and Frank Lehmkuhl. "A critical reevaluation of palaeoclimate proxy records from loess in the Carpathian Basin." Earth-Science Reviews 190 (March 2019): 498–520. http://dx.doi.org/10.1016/j.earscirev.2019.01.020.
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Dixon, Bronwyn C., Jonathan J. Tyler, Andrew M. Lorrey, Ian D. Goodwin, Joëlle Gergis, and Russell N. Drysdale. "Low-resolution Australasian palaeoclimate records of the last 2000 years." Climate of the Past 13, no. 10 (October 26, 2017): 1403–33. http://dx.doi.org/10.5194/cp-13-1403-2017.
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Abstract. Non-annually resolved palaeoclimate records in the Australasian region were compiled to facilitate investigations of decadal to centennial climate variability over the past 2000 years. A total of 675 lake and wetland, geomorphic, marine, and speleothem records were identified. The majority of records are located near population centres in southeast Australia, in New Zealand, and across the maritime continent, and there are few records from the arid regions of central and western Australia. Each record was assessed against a set of a priori criteria based on temporal resolution, record length, dating methods, and confidence in the proxy–climate relationship over the Common Era. A subset of 22 records met the criteria and were endorsed for subsequent analyses. Chronological uncertainty was the primary reason why records did not meet the selection criteria. New chronologies based on Bayesian techniques were constructed for the high-quality subset to ensure a consistent approach to age modelling and quantification of age uncertainties. The primary reasons for differences between published and reconstructed age–depth models were the consideration of the non-singular distribution of ages in calibrated 14C dates and the use of estimated autocorrelation between sampled depths as a constraint for changes in accumulation rate. Existing proxies and reconstruction techniques that successfully capture climate variability in the region show potential to address spatial gaps and expand the range of climate variables covering the last 2000 years in the Australasian region. Future palaeoclimate research and records in Australasia could be greatly improved through three main actions: (i) greater data availability through the public archiving of published records; (ii) thorough characterisation of proxy–climate relationships through site monitoring and climate sensitivity tests; and (iii) improvement of chronologies through core-top dating, inclusion of tephra layers where possible, and increased date density during the Common Era.
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Hlavatskyi, D. V., N. P. Gerasimenko, V. G. Bakhmutov, O. S. Bonchkovskyi, I. B. Poliachenko, V. V. Shpyra, S. V. Mychak, I. V. Kravchuk, and S. I. Cherkes. "Significance of the Ukrainian loess-palaeosol sequences for Pleistocene climate reconstructions: rock magnetic, palaeosol and pollen proxies." Geofizicheskiy Zhurnal 43, no. 3 (July 28, 2021): 3–26. http://dx.doi.org/10.24028/gzh.v43i3.236378.
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Variations of rock magnetic parameters in loess-palaeosol sequences, related to climatic and environmental conditions during their formation, are a powerful tool for palaeoclimate reconstruction. Combined enviromagnetic study of loess deposits in Ukraine and its assessment for the palaeoreconstruction purposes are carried out in the framework of the National Research Foundation of Ukraine project 2020.02/0406 ‘Magnetic proxies of palaeoclimatic changes in the loess-palaeosol sequences of Ukraine’. Environmental/climatic reconstructions of the past are fulfilled using a significant number of palaeoindicators: morphology and lithological properties of palaeosols and loesses, their pollen assemblages and a wide range of magnetic characteristics. In this paper, we present a multi-proxy approach to palaeoenvironmental reconstructions, and introduce preliminary results obtained from magnetic susceptibility of loess-palaeosol sequences in the northern (at Vyazivok), central (Stari Kaydaky) and southern (Roksolany) parts of the Ukrainian loess belt. The amplitudes of palaeoclimate change established using magnetic proxies are well correlated with the lithological, palaeopedological and palynological patterns of the sites, and with the global oxygen-isotope scale (MIS). Ongoing studies of the Stari Kaydaky section confirm the correlation of the Upper Zavadivka (S3) soil unit and Lower Zavadivka (S4) soil unit with MIS 9 and MIS 11, respectively (this was proved earlier at the Vyazivok and Roksolany sites). The underlying Lubny (S5) pedocomplex likely corresponds to MIS 13, and the Martonosha (S6) pedocomplex to MIS 15. Palaeomagnetic investigations at Stari Kaydaky have not so far reached the Lower Shyrokyne unit, in which the Matuyama—Brunhes boundary has been detected at Roksolany and Vyazivok. The Upper Shyrokyne (S7S1) palaeosol unit has normal polarity and is preliminarily correlated with MIS 17.
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Stone, Abi E. C. "Last Glacial Maximum conditions in southern Africa." Progress in Physical Geography: Earth and Environment 38, no. 5 (April 8, 2014): 519–42. http://dx.doi.org/10.1177/0309133314528943.
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The Last Glacial Maximum (LGM) (21±2 ka) is an important period for which to understand past climatic and environmental conditions. In particular it is a key time-slice for evaluating the performance of numerical climate model simulations of glacial palaeoclimates using palaeoenvironmental data sets. However, our palaeoenvironmental data sets and reconstructions of climatic conditions at the LGM are still debated in certain regions. This is the case for southern Africa, despite more than half a century of research since early conceptual models of palaeoclimate were proposed. The greatest debates are about the spatial patterning of relatively wetter and drier conditions than present and the position of the mid-latitude westerlies at the LGM. Different patterns emerge from: separate syntheses of palaeoenvironmental proxies, from different numerical model simulations and from comparisons of the two. In this review of the progress over half a century of research in southern Africa: (1) a brief historical review of key conceptual models is given, (2) key points of conflict that emerge in synthesis of palaeoenvironmental proxy records are outlined and (3) numerical model simulations are considered. From these, some points for future progress are suggested.
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Ackerley, D., A. Lorrey, J. A. Renwick, S. J. Phipps, S. Wagner, S. Dean, J. Singarayer, et al. "Using synoptic type analysis to understand New Zealand climate during the Mid-Holocene." Climate of the Past Discussions 7, no. 2 (April 19, 2011): 1301–37. http://dx.doi.org/10.5194/cpd-7-1301-2011.
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Abstract. Diagnosing the climate of New Zealand from low-resolution General Circulation Models (GCMs) is notoriously difficult due to the interaction of the complex topography and the Southern Hemisphere (SH) mid-latitude westerly winds. Therefore, methods of downscaling synoptic scale model data for New Zealand are useful to help understand past climate. New Zealand also has a wealth of palaeoclimate-proxy data to which the downscaled model output can be compared, and to provide a qualitative method of assessing the capability of GCMs to represent, in this case, the climate 6000 years ago in the Mid-Holocene. In this paper, a synoptic weather and climate regime classification system using Empirical Orthogonal Function (EOF) analysis of GCM and reanalysis data, was used. The climate regimes are associated with surface air temperature and precipitation anomalies over New Zealand. From the analysis in this study, we find that increased trough activity in summer and autumn led to increased precipitation, with an increased north-south pressure gradient ("zonal events") in winter and spring leading to drier conditions. Opposing effects of increased (decreased) temperature are also seen in spring (autumn) in the South Island, which are associated with the increased zonal (trough) events. Evidence from the palaeoclimate-proxy data suggests that the Mid-Holocene was characterized by increased westerly wind events in New Zealand, which agrees with the preference for trough and zonal regimes in the models.
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Campbell, Rochelle, Danny McCarroll, Iain Robertson, Neil J. Loader, Håkan Grudd, and Björn Gunnarson. "Blue Intensity In Pinus sylvestris Tree Rings: A Manual for A New Palaeoclimate Proxy." Tree-Ring Research 67, no. 2 (July 2011): 127–34. http://dx.doi.org/10.3959/2010-13.1.
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Spicer, Robert A., Jian Yang, Teresa E. V. Spicer, and Alexander Farnsworth. "Woody dicot leaf traits as a palaeoclimate proxy: 100 years of development and application." Palaeogeography, Palaeoclimatology, Palaeoecology 562 (January 2021): 110138. http://dx.doi.org/10.1016/j.palaeo.2020.110138.
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Lehejček, Jiří, Allan Buras, Miroslav Svoboda, and Martin Wilmking. "Wood anatomy of Juniperus communis: a promising proxy for palaeoclimate reconstructions in the Arctic." Polar Biology 40, no. 5 (August 2, 2016): 977–88. http://dx.doi.org/10.1007/s00300-016-2021-z.
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Hall, Grant, Lyn Wadley, and Stephan Woodborne. "Past Environmental Proxies from the Middle Stone Age at Sibudu, Kwazulu-Natal, South Africa." Journal of African Archaeology 12, no. 1 (November 1, 2014): 7–24. http://dx.doi.org/10.3213/2191-5784-10246.
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Middle Stone Age technological and behavioural developments in southern Africa are central to understanding the emergence of modern humans, and elucidating the role of environmental change in this trajectory is dependent on emerging palaeoclimatic reconstructions. Climate proxies from Middle Stone Age sites are often poorly preserved, coarsely resolved or subject to anthropogenic selection and are not considered in favour of global environmental proxies despite the fact that the modern climate regimes at the relevant archaeological sites differ profoundly. Sibudu has a well-preserved Middle Stone Age sequence that has yielded abundant palaeoclimate proxy data. Isotopic analysis of charcoal, charcoal anatomy and species representation, macro- and micro-faunal remains, sediment texture, mineralogy and magnetic susceptibility, pollen and macrobotanical remains provide evidence for the environmental succession specific to this site. The isotopic data suggest that archaeological charcoal was not significantly post-depositionally altered. During the Howiesons Poort (65–62 ka) the local environment was thickly forested, moist and more humid than during the 58 ka occupations. The environment changes during the post-Howiesons Poort occupation (~58 ka) into the late MSA occupation (~48 ka); conditions became drier and colder than present with vegetation shifting to open savanna grassland or woodlands.
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Modarres, Mohammad Hadi, Hamid Alizadeh Ketek Lahijani, Nasser Keshavarz, Yann Lahaye, Kira Rehfeld, Irmeli Manttari, Abdolmajid Naderi-Beni, Antti Ojala, and Mehran Moradpour. "Late Tortonian – Piacenzian multi-proxy record of Asian southwest monsoon intensification: evidence from Coastal Makran, southeast Iran." Canadian Journal of Earth Sciences 56, no. 4 (April 2019): 347–62. http://dx.doi.org/10.1139/cjes-2018-0071.
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This study presents a long-term, multi-proxy reconstruction of the Asian southwest monsoon during the Tortonian to Piacenzian, based on a 4.78 Ma record from Coastal Makran, northwestern Gulf of Oman, southeast Iran. The integration of humidity proxies (clay minerals, Th/K, volume magnetic susceptibility, and grain size analysis), marine redox sensitivity (Th/U), total organic matter, carbonate content, 87Sr/86Sr ratio, and spectral gamma-ray data conducted here provide valuable information that fill the existing gap in marine palaeoclimate records. The results show that a strong winter monsoon condition associated with relatively low precipitation and subsequently low physical and chemical weathering dominated the region during late Tortonian – late Messinian (7.65–5.83 Ma). However, a few episodes of intense physical and chemical weathering related to high precipitation are observed during this period (6.23–6.01 Ma), which is consistent with increased organic matter input from continental reservoirs to the oceans. In addition, the data indicate that from the latest Messinian (5.82–5.33 Ma) to Zanclean–Piacenzian (5.33–2.87 Ma), a strong summer monsoon accompanied by a relatively wetter condition and higher physical and chemical weathering resulted in a high detrital input into the basin. This higher weathering period is associated with the highest rate of Himalayan uplift, causing enhanced precipitation. Wavelet analysis of spectral gamma-ray data revealed notable periodicities at 750 Ka and 1.7 Ma, with significant periodicities centered around 5.75–6.03 Ma over the latest Messinian – Zanclean. Comparison with palaeoclimate records from other sites indicates a teleconnection with respect to precipitation, weathering, and productivity, especially during the Messinian–Zanclean transition.
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Ackerley, D., A. Lorrey, J. A. Renwick, S. J. Phipps, S. Wagner, S. Dean, J. Singarayer, et al. "Using synoptic type analysis to understand New Zealand climate during the Mid-Holocene." Climate of the Past 7, no. 4 (November 9, 2011): 1189–207. http://dx.doi.org/10.5194/cp-7-1189-2011.
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Abstract. Diagnosing the climate of New Zealand from low-resolution General Circulation Models (GCMs) is notoriously difficult due to the interaction of the complex topography and the Southern Hemisphere (SH) mid-latitude westerly winds. Therefore, methods of downscaling synoptic scale model data for New Zealand are useful to help understand past climate. New Zealand also has a wealth of palaeoclimate-proxy data to which the downscaled model output can be compared, and to provide a qualitative method of assessing the capability of GCMs to represent, in this case, the climate 6000 yr ago in the Mid-Holocene. In this paper, a synoptic weather and climate regime classification system using Empirical Orthogonal Function (EOF) analysis of GCM and reanalysis data was used. The climate regimes are associated with surface air temperature and precipitation anomalies over New Zealand. From the analysis in this study, we find at 6000 BP that increased trough activity in summer and autumn led to increased precipitation, with an increased north-south pressure gradient ("zonal events") in winter and spring leading to drier conditions. Opposing effects of increased (decreased) temperature are also seen in spring (autumn) in the South Island, which are associated with the increased zonal (trough) events; however, the circulation induced changes in temperature are likely to have been of secondary importance to the insolation induced changes. Evidence from the palaeoclimate-proxy data suggests that the Mid-Holocene was characterized by increased westerly wind events in New Zealand, which agrees with the preference for trough and zonal regimes in the models.
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Frisia, S., A. Borsato, R. N. Drysdale, B. Paul, A. Greig, and M. Cotte. "A re-evaluation of the palaeoclimatic significance of phosphorus variability in speleothems revealed by high-resolution synchrotron micro XRF mapping." Climate of the Past 8, no. 6 (December 14, 2012): 2039–51. http://dx.doi.org/10.5194/cp-8-2039-2012.
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Abstract. Phosphorus (P) is potentially a very important environmental proxy in speleothem palaeoclimate reconstructions. However, the transfer of P to a speleothem seems to vary between cave sites. Therefore, it is important to investigate the source of P and the way it is incorporated into a speleothem on a site-by-site basis before it can be used as a robust palaeoclimate proxy. In this paper, the distribution of P in one modern and two Early Pliocene speleothems formed in coastal caves on Christmas Island (Indian Ocean) and the Nullarbor Plain (southern Australia) is investigated using microscopy and ultra-high resolution chemical mapping. Phosphorus has been found to be both incorporated in the lattice and present as diverse P-rich phases. Monitoring data from Christmas Island suggest that co-precipitation of P-rich phases occurs when "prior calcite precipitation" decreases following recharge, even if the drip rate decreases. Microbial mediation may also play a role, which complicates a direct climate relationship between P and hydrology. We find that some P-enriched layers contain dissolution features, with possible involvement of microbial mats which colonise pores during reduced drip rates associated with prolonged dry spells. In the two Early Pliocene speleothems the relationship between P and microbial laminae is clearer. Both petrographic and chemical data suggest that phosphorus-rich phases in the microbial laminae mark intervals of reduced drip rates, which may indicate dry intervals during the otherwise wet palaeoclimate of the Early Pliocene. We develop a speleothem distribution coefficient for phosphorus (SKP) rather than the thermodynamic partition coefficient (KP) to account for the presence of crystalline phosphate inclusions. SKP describes P enrichment in speleothems regardless of the process, as similar mechanisms of phosphate co-precipitation may be in operation in biotic and abiotic conditions. The most important implication of our study is that variability in P concentration may be related to diverse processes which can be recognized through petrographic observations and chemical mapping. In particular, there may not be a direct relation between an increase in P concentration and seasonal infiltration as has been found in some previous studies, especially if the source of this element is not the labile phosphate released through leaching during seasonal vegetation dieback in temperate climates.
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Ufnar, David F., Luis A. Gonzalez, Greg A. Ludvigson, Robert L. Brenner, and Brian J. Witzke. "Diagenetic overprinting of the sphaerosiderite palaeoclimate proxy: are records of pedogenic groundwater delta18O values preserved?" Sedimentology 51, no. 1 (February 2004): 127–44. http://dx.doi.org/10.1046/j.1365-3091.2003.00615.x.
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HELAMA, S., J. K. NIELSEN, M. MACIAS FAURIA, and I. VALOVIRTA. "A fistful of shells: amplifying sclerochronological and palaeoclimate signals from molluscan death assemblages." Geological Magazine 146, no. 6 (July 15, 2009): 917–30. http://dx.doi.org/10.1017/s0016756809990033.
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AbstractA growing body of literature is using sclerochronological information to infer past climates. Sclerochronologies are based on series of skeletal growth records of molluscs that have been correctly aligned in time. Incremental series are obtained from a number of shells to assess the temporal control and improve the climate signal in the final chronology. Much of the sclerochronological theory has been adopted from tree-ring science, due to the longer tradition and more firmly established concepts of chronology construction in dendrochronology. Compared to tree-ring studies, however, sclerochronological datasets are often characterized by relatively small sample size. Here we evaluate how effectively palaeoclimatic signal can be extracted from such a suite of samples. In so doing, the influences of the very basic methods that are applied in nearly every sclerochronological study to remove the non-climatic growth variability prior to palaeoclimatic interpretations, are ranked by their capability to amplify the desired signal. The study is performed in the context of six shells that constitute a bicentennial growth record from annual shell increments of freshwater pearl mussel. It was shown that when the individual series were detrended using the models set by the mean or the median summary curves for ageing (that is, applying Regional Curve Standardization, RCS), instead of fitting the ageing mode statistically to each series, the resulting sclerochronology displayed more low-frequency variability. Consistently, the added low-frequency variability evoked higher proxy–climate correlations. These results show the particular benefit of using the RCS method to develop sclerochronologies and preserve their low-frequency variations. Moreover, calculating the ageing curve and the final chronology by median, instead of mean, resulted in an amplified low-frequency climate signal. The results help to answer a growing need to better understand the behaviour of the sclerochronological data. In addition, we discuss the pitfalls that may potentially disrupt palaeoclimate signal detection in similar sclerochronological studies. Pitfalls may arise from shell taphonomy, water chemistry, time-variant characters of biological growth trends and small sample size.
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Sundqvist, H. S., Q. Zhang, A. Moberg, K. Holmgren, H. Körnich, and J. Nilsson. "Northern high-latitude climate change between the mid and late Holocene – Part 1: Proxy data evidence." Climate of the Past Discussions 5, no. 4 (July 6, 2009): 1819–52. http://dx.doi.org/10.5194/cpd-5-1819-2009.
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Abstract. In this paper we try to develop a quantitative understanding of the absolute change in climate between the mid-Holocene ~6000 yr BP (6 ka) and the preindustrial period ~1750 AD (0 ka) in the northern high latitudes. This has been performed using available quantitative reconstructions of temperature and precipitation from proxy data. The main reason for comparing these two periods is that the summer insolation in the northern high latitudes was higher at 6 ka than 0 ka due to orbital forcing. Another reason is that it gives us the opportunity to quantitatively compare results from proxy data with results from several climate model simulations for the same periods by using data from the Palaeoclimate Modelling Intercomparison Project. Another aim has been to try and quantify the uncertainties in the proxy data reconstructions. The reconstructions indicate that the northern high latitudes were 0.96±0.42°C warmer in summer, 1.71±1.70°C warmer in winter and 2.02±0.72 warmer in the annual mean temperature at 6 ka compared to 0 ka. The warmer climate in summer around 6 ka BP was most likely directly related to the higher summer insolation whereas the warmer climate in annual mean and winter temperature may possibly be explained by internal physical mechanisms such as heat stored in the oceans during summer and released during the cold season or by changes in the vegetation causing albedo changes that may affect seasonal temperatures differentially. For the future there is a great need to reduce the errors of the predictions as well as improving our understanding of how a proxys respond to changes in environmental variables.
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Hansen Klünder, Maiken, Dorothee Hippler, Rob Witbaard, and Dirk Frei. "Laser ablation analysis of bivalve shells – archives of environmental information." Geological Survey of Denmark and Greenland (GEUS) Bulletin 15 (July 10, 2008): 89–92. http://dx.doi.org/10.34194/geusb.v15.5052.
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Reconstructing past secular environmental variations is an important issue in palaeoclimate research. However, most key variables for palaeoclimate reconstructions cannot be measured directly, and reconstructions are therefore based on proxy data. Here, we demonstrate the potential of bivalve shells as an archive of environmental parameters. The Geological Survey of Denmark and Greenland (GEUS) has developed a fast and reliable method for chemical analyses of shell material by laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS), and here we present some ex amples of the use of this method. In tropical and subtropical waters, corals can provide century-long archives of past water chemistry with annual resolution. A comparable archive for temperate and Arctic waters would be highly useful in climate research, and therefore it has been examined whether this can be provided by bivalve shells (e.g. Schoene et al. 2005). Long-lived species may provide archives with annual resolution extending over several hundred years, whereas short-lived, fast-growing species can provide archives with a seasonal or in some cases daily resolution over a period of a few years. Most bivalves are sessile, and shells are commonly preserved as fossils. There are, however, a number of challenges related to the use of bivalves as proxy archives: (1) many proxies show species specific behaviour (Seed 1980); (2) only very few proxies are dependent on a single variable (Wefer et al. 1999); and (3) the effects of biology and ontogeny on the uptake of trace elements and stable isotope fractionation in shell carbonate are largely unknown and have to be evaluated empirically. Therefore, any potential proxy must be calibrated individually for each species of interest before it can be used. A large number of chemical analyses are needed to calibrate a proxy. These are commonly obtained by solution ICP-MS, in which sample preparation is time-consuming and labour-intensive. The use of LA-ICP-MS is therefore a considerable advance in bivalve shell proxy research, as it greatly reduces the effort needed for sample preparation. At the same time, the method requires less material for analysis, thus providing better spatial and hence temporal resolution. Proxies based on bivalve shell carbonate can be used in present-day environmental monitoring, and for environmental reconstructions from shells found as fossils. Shells from museum collections and shells found in archaeological middens can give information on historic and prehistoric environmental conditions (e.g. Carrell et al. 1987), and fossil shells can be used as archives of environmental parameters on geological timescales (e.g. Hendry et al. 2001).
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Luoto, Tomi P., Antti E. K. Ojala, and Marek Zajaczkowski. "Proxy-based 300-year High Arctic climate warming record from Svalbard." Polar Record 55, no. 3 (May 2019): 132–41. http://dx.doi.org/10.1017/s0032247419000275.
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AbstractWe used fossil Chironomidae assemblages and the transfer function approach to reconstruct summer air temperatures over the past 300 years from a High Arctic lake in Hornsund, Svalbard. Our aims were to compare reconstructed summer temperatures with observed (last 100 years) seasonal temperatures, to determine a potential climate warming break point in the temperature series and to assess the significance and rate of the climate warming trend at the study site. The reconstructed temperatures were consistent with a previous proxy record from Svalbard and showed good correlation with the meteorological observations from Bjørnøya and Longyearbyen. From the current palaeoclimate record, we found a significant climate warming threshold in the 1930s, after which the temperatures rapidly increased. We also found that the climate warming trend was strong and statistically significant. Compared with the reconstructed Little Ice Age temperatures in late eighteenth century cooling culmination, the present day summer temperatures are >4°C higher and the temperature increase since the 1930s has been 0.5°C per decade. These results highlight the exceptionally rapid recent warming of southern Svalbard and add invaluable information on the seasonality of High Arctic climate change and Arctic amplification.
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Ruffell, Alastair, Jennifer M. McKinley, and Richard H. Worden. "Comparison of clay mineral stratigraphy to other proxy palaeoclimate indicators in the Mesozoic of NW Europe." Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 360, no. 1793 (April 15, 2002): 675–93. http://dx.doi.org/10.1098/rsta.2001.0961.
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Poole, Imogen, David Cantrill, and Torsten Utescher. "A multi-proxy approach to determine Antarctic terrestrial palaeoclimate during the Late Cretaceous and Early Tertiary." Palaeogeography, Palaeoclimatology, Palaeoecology 222, no. 1-2 (June 2005): 95–121. http://dx.doi.org/10.1016/j.palaeo.2005.03.011.
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Mehrotra, Nivedita, Santosh K. Shah, and Amalava Bhattacharyya. "Review of palaeoclimate records from Northeast India based on pollen proxy data of Late Pleistocene–Holocene." Quaternary International 325 (March 2014): 41–54. http://dx.doi.org/10.1016/j.quaint.2013.10.061.
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Riechelmann, Dana F. C., and Marjolein T. I. J. Gouw-Bouman. "A review of climate reconstructions from terrestrial climate archives covering the first millennium AD in northwestern Europe." Quaternary Research 91, no. 1 (October 8, 2018): 111–31. http://dx.doi.org/10.1017/qua.2018.84.
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AbstractLarge changes in landscape, vegetation, and culture in northwestern (NW) Europe during the first millennium AD seem concurrent with climatic shifts. Understanding of this relation requires high-resolution palaeoclimate reconstructions. Therefore, we compiled available climate reconstructions from sites across NW Europe (extent research area: 10°W–20°E, 45°–60°N) through review of literature and the underlying data, to identify supraregional climatic changes in this region. All reconstructions cover the period from AD 1 to 1000 and have a temporal resolution of ≤50 yr. This resulted in 22 climate reconstructions/proxy records based on different palaeoclimate archives: chironomids (1), pollen (6), Sphagnum mosses (1), stalagmites (8), testate amoebae (4), and tree rings (2). Comparing all temperature reconstructions, we conclude that summer temperatures between AD 1 and 250 were relatively high, and the period between AD 250 and 700 was characterised by colder summer conditions. The period from AD 700 to 1000 was again characterised by warmer summers. These temperature shifts occurred in the whole of NW Europe. In contrast, the compilation of precipitation reconstructions does not show a common pattern across NW Europe either as a result of a heterogeneous precipitation pattern or the lack of suitable and consistent precipitation proxies.
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Mutz, Sebastian G., Todd A. Ehlers, Martin Werner, Gerrit Lohmann, Christian Stepanek, and Jingmin Li. "Estimates of late Cenozoic climate change relevant to Earth surface processes in tectonically active orogens." Earth Surface Dynamics 6, no. 2 (April 6, 2018): 271–301. http://dx.doi.org/10.5194/esurf-6-271-2018.
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Abstract. The denudation history of active orogens is often interpreted in the context of modern climate gradients. Here we address the validity of this approach and ask what are the spatial and temporal variations in palaeoclimate for a latitudinally diverse range of active orogens? We do this using high-resolution (T159, ca. 80 × 80 km at the Equator) palaeoclimate simulations from the ECHAM5 global atmospheric general circulation model and a statistical cluster analysis of climate over different orogens (Andes, Himalayas, SE Alaska, Pacific NW USA). Time periods and boundary conditions considered include the Pliocene (PLIO, ∼ 3 Ma), the Last Glacial Maximum (LGM, ∼ 21 ka), mid-Holocene (MH, ∼ 6 ka), and pre-industrial (PI, reference year 1850). The regional simulated climates of each orogen are described by means of cluster analyses based on the variability in precipitation, 2 m air temperature, the intra-annual amplitude of these values, and monsoonal wind speeds where appropriate. Results indicate the largest differences in the PI climate existed for the LGM and PLIO climates in the form of widespread cooling and reduced precipitation in the LGM and warming and enhanced precipitation during the PLIO. The LGM climate shows the largest deviation in annual precipitation from the PI climate and shows enhanced precipitation in the temperate Andes and coastal regions for both SE Alaska and the US Pacific Northwest. Furthermore, LGM precipitation is reduced in the western Himalayas and enhanced in the eastern Himalayas, resulting in a shift of the wettest regional climates eastward along the orogen. The cluster-analysis results also suggest more climatic variability across latitudes east of the Andes in the PLIO climate than in other time slice experiments conducted here. Taken together, these results highlight significant changes in late Cenozoic regional climatology over the last ∼ 3 Myr. Comparison of simulated climate with proxy-based reconstructions for the MH and LGM reveal satisfactory to good performance of the model in reproducing precipitation changes, although in some cases discrepancies between neighbouring proxy observations highlight contradictions between proxy observations themselves. Finally, we document regions where the largest magnitudes of late Cenozoic changes in precipitation and temperature occur and offer the highest potential for future observational studies that quantify the impact of climate change on denudation and weathering rates.
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Schollaen, K., C. Karamperidou, P. J. Krusic, E. R. Cook, and G. Helle. "ENSO flavors in a tree-ring δ<sup>18</sup>O record of <i>Tectona grandis</i> from Indonesia." Climate of the Past Discussions 10, no. 5 (October 2, 2014): 3965–87. http://dx.doi.org/10.5194/cpd-10-3965-2014.
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Abstract. Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño–Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900–2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific) El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics.
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Ashley, Kate E., Xavier Crosta, Johan Etourneau, Philippine Campagne, Harry Gilchrist, Uthmaan Ibraheem, Sarah E. Greene, et al. "Exploring the use of compound-specific carbon isotopes as a palaeoproductivity proxy off the coast of Adélie Land, East Antarctica." Biogeosciences 18, no. 19 (October 14, 2021): 5555–71. http://dx.doi.org/10.5194/bg-18-5555-2021.
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Abstract. The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas, where large phytoplankton blooms and drawdown of CO2 occur. Reconstruction of historical primary productivity changes and the associated driving factors could provide baseline insights on the role of these areas as sinks for atmospheric CO2, especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes (δ13C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ∼ 400 years and monitor changes in the concentrations and δ13C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C24 fatty acid δ13C predominantly reflects phytoplankton productivity in open-water environments, while C18 fatty acid δ13C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future palaeoclimate studies.
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Morée, Anne L., and Jörg Schwinger. "A Last Glacial Maximum forcing dataset for ocean modelling." Earth System Science Data 12, no. 4 (November 20, 2020): 2971–85. http://dx.doi.org/10.5194/essd-12-2971-2020.
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Abstract. Model simulations of the Last Glacial Maximum (LGM; ∼ 21 000 years before present) can aid the interpretation of proxy records, can help to gain an improved mechanistic understanding of the LGM climate system, and are valuable for the evaluation of model performance in a different climate state. Ocean-ice only model configurations forced by prescribed atmospheric data (referred to as “forced ocean models”) drastically reduce the computational cost of palaeoclimate modelling compared to fully coupled model frameworks. While feedbacks between the atmosphere and ocean and sea-ice compartments of the Earth system are not present in such model configurations, many scientific questions can be addressed with models of this type. Our dataset supports simulations of the LGM in a forced ocean model set-up while still taking advantage of the complexity of fully coupled model set-ups. The data presented here are derived from fully coupled palaeoclimate simulations of the Palaeoclimate Modelling Intercomparison Project phase 3 (PMIP3). The data are publicly accessible at the National Infrastructure for Research Data (NIRD) Research Data Archive at https://doi.org/10.11582/2020.00052 (Morée and Schwinger, 2020). They consist of 2-D anomaly forcing fields suitable for use in ocean models that employ a bulk forcing approach and are optimized for use with CORE forcing fields. The data include specific humidity, downwelling long-wave and short-wave radiation, precipitation, wind (v and u components), temperature, and sea surface salinity (SSS). All fields are provided as climatological mean anomalies between LGM and pre-industrial (PI) simulations. These anomaly data can therefore be added to any pre-industrial ocean forcing dataset in order to obtain forcing fields representative of LGM conditions as simulated by PMIP3 models. Furthermore, the dataset can be easily updated to reflect results from upcoming and future palaeo-model intercomparison activities.
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Hébert, Raphaël, Kira Rehfeld, and Thomas Laepple. "Comparing estimation techniques for temporal scaling in palaeoclimate time series." Nonlinear Processes in Geophysics 28, no. 3 (July 29, 2021): 311–28. http://dx.doi.org/10.5194/npg-28-311-2021.
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Abstract. Characterizing the variability across timescales is important for understanding the underlying dynamics of the Earth system. It remains challenging to do so from palaeoclimate archives since they are more often than not irregular, and traditional methods for producing timescale-dependent estimates of variability, such as the classical periodogram and the multitaper spectrum, generally require regular time sampling. We have compared those traditional methods using interpolation with interpolation-free methods, namely the Lomb–Scargle periodogram and the first-order Haar structure function. The ability of those methods to produce timescale-dependent estimates of variability when applied to irregular data was evaluated in a comparative framework, using surrogate palaeo-proxy data generated with realistic sampling. The metric we chose to compare them is the scaling exponent, i.e. the linear slope in log-transformed coordinates, since it summarizes the behaviour of the variability across timescales. We found that, for scaling estimates in irregular time series, the interpolation-free methods are to be preferred over the methods requiring interpolation as they allow for the utilization of the information from shorter timescales which are particularly affected by the irregularity. In addition, our results suggest that the Haar structure function is the safer choice of interpolation-free method since the Lomb–Scargle periodogram is unreliable when the underlying process generating the time series is not stationary. Given that we cannot know a priori what kind of scaling behaviour is contained in a palaeoclimate time series, and that it is also possible that this changes as a function of timescale, it is a desirable characteristic for the method to handle both stationary and non-stationary cases alike.
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Vossel, Hannah, Patricia Roeser, Thomas Litt, and Jane M. Reed. "Lake Kinneret (Israel): New insights into Holocene regional palaeoclimate variability based on high-resolution multi-proxy analysis." Holocene 28, no. 9 (June 11, 2018): 1395–410. http://dx.doi.org/10.1177/0959683618777071.
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The southern Levant is a Mediterranean climate zone of complex variability in which uncertainty remains in regional palaeoclimate reconstruction. In spite of the proven value of diatoms in circum-Mediterranean palaeoenvironmental research, their potential remains largely unexplored in the southern Levant region. In this study, we generate a new, high-resolution multi-proxy record for the last ca. 9000 cal. yr BP, supported by diatom data and key biological, mineralogical and geochemical indicators preserved in a 17.8-m-long sediment sequence recovered from Lake Kinneret (the Sea of Galilee), Israel. During the Holocene, well-correlated shifts in the diatom, minero-geochemical and palynological data indicate marked lake-level variation over time as well as changes in the trophic state of Lake Kinneret. Our results are particularly important in improving the reconstruction of Holocene lake-level variation, and thus past moisture availability. Diatom-inferred lake-level oscillations correlate well with the output from climatic models from the Levantine region and clarify previous uncertainty concerning regional variation in moisture availability. The Early Holocene (from ca. 9000 to 7400 cal. yr BP) was characterized by lake-level shifts due to fluctuating dry-wet climate conditions. During the mid-Holocene (from 7400 to 2200 cal. yr BP), a stable, deep lake-level phase persisted due to high humidity. The lake level of modern Lake Kinneret not only fluctuates seasonally with available moisture, but has also been influenced for ca. 2000 years by the impacts of water abstraction for human consumption and agriculture. Over the last 9000 cal. yr BP, the trophic state of Lake Kinneret has changed from an oligotrophic to a meso- to eutrophic environment, mainly triggered by increased human impact from around 2200 cal. yr BP onwards. The lake’s ecosystem status was not strongly affected by the documented major changes in human occupation patterns during the mid-Holocene, when a relatively stable environment persisted.
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Lorrey, Andrew, Paul Williams, Jim Salinger, Tim Martin, Jonathan Palmer, Anthony Fowler, Jian-xin Zhao, and Helen Neil. "Speleothem stable isotope records interpreted within a multi-proxy framework and implications for New Zealand palaeoclimate reconstruction." Quaternary International 187, no. 1 (August 2008): 52–75. http://dx.doi.org/10.1016/j.quaint.2007.09.039.
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Baker, Andrea, Joyanto Routh, and Alakendra N. Roychoudhury. "n-Alkan-2-one biomarkers as a proxy for palaeoclimate reconstruction in the Mfabeni fen, South Africa." Organic Geochemistry 120 (June 2018): 75–85. http://dx.doi.org/10.1016/j.orggeochem.2018.03.001.
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