Non-linear regime shifts in Holocene Asian monsoon variability: potential impacts on cultural change and migratory patterns
Summary: Paleoclimate records from cave deposits allow the reconstruction of Holocene dynamics of the Asian monsoon system, an important tipping element in Earth's climate. Employing recently developed techniques of nonlinear time series analysis reveals several robust and continental-scale regime shifts in the complexity of monsoonal variability. These regime shifts might have played an important role as drivers of migration, cultural change, and societal collapse during the past 10,000 years.
Clim. Past, 11, 709-741, doi:10.5194/cp-11-709-2015, 2015
A 2000-year annual record of snow accumulation rates for Law Dome, East Antarctica
Summary: The Law Dome, East Antarctica snow accumulation record is extended back to 22 BCE using a power-law vertical strain rate model. The periods of 380-442, 727-783 and 1970-2009 CE show above-average snow accumulation rates, while 663-704, 933-975 and 1429-1468 CE were below average. The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates and significant spatial correlation over a wide expanse of East Antarctica.
Clim. Past, 11, 697-707, doi:10.5194/cp-11-697-2015, 2015
Subsurface North Atlantic warming as a trigger of rapid cooling events: evidence from the early Pleistocene (MIS 31–19)
Summary: This manuscript presents new Mg/Ca and previously published δ18O measurements of Neogloboquadrina pachyderma sinistral for MIS 31-19, from a sediment core from the subpolar North Atlantic. The mechanism proposed here involves northward subsurface transport of warm and salty subtropical waters during periods of weaker AMOC, leading to ice-sheet instability and IRD discharge. This is the first time that these rapid climate oscillations are described for the early Pleistocene.
Clim. Past, 11, 687-696, doi:10.5194/cp-11-687-2015, 2015
Carbon isotope (δ13C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic
Summary: A sediment core collected from a pockmark field on the Vestnesa Ridge (~80N) in the Fram Strait is presented. Our results show an undisturbed sedimentary record for the last 14 ka BP and negative carbon isotope excursions (CIEs) during the Bølling-Allerød interstadials and during the early Holocene. Both CIEs relate to periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere, suggesting an apparent correlation with warm climatic events.
Clim. Past, 11, 669-685, doi:10.5194/cp-11-669-2015, 2015
The bivalve Glycymeris planicostalis as a high-resolution paleoclimate archive for the Rupelian (Early Oligocene) of central Europe
Clim. Past, 11, 653-668, doi:10.5194/cp-11-653-2015, 2015
Late Pleistocene–Holocene ground surface heat flux changes reconstructed from borehole temperature data (the Urals, Russia)
Clim. Past, 11, 647-652, doi:10.5194/cp-11-647-2015, 2015
A new approach for modeling Cenozoic oceanic lithium isotope paleo-variations: the key role of climate
Summary: We develop here a new approach that couples the carbon and lithium cycles for reconstructing the Cenozoic Li isotope record. We show that this record does not provide persuasive, unique evidence for Cenozoic change in erosional forcing as it could, alternatively, be consistent with climatic control on soil production rates. The Li storage in continental secondary phases plays a key role, in particular, during the Early Cenozoic.
Clim. Past, 11, 635-645, doi:10.5194/cp-11-635-2015, 2015
High-resolution leaf wax carbon and hydrogen isotopic record of the late Holocene paleoclimate in arid Central Asia
Clim. Past, 11, 619-633, doi:10.5194/cp-11-619-2015, 2015
Interannual climate variability seen in the Pliocene Model Intercomparison Project
Summary: Previously, model ensembles have shown little consensus in the response of the El Niño–Southern Oscillation (ENSO) to imposed forcings – either for the past or future. The recent coordinated experiment on the warm Pliocene (~3 million years ago) shows surprising agreement that there was a robustly weaker ENSO with a shift to lower frequencies. Suggested physical mechanisms cannot explain this coherent signal, and it warrants further investigation.
Clim. Past, 11, 605-618, doi:10.5194/cp-11-605-2015, 2015
Late Weichselian and Holocene palaeoceanography of Storfjordrenna, southern Svalbard
Summary: Storfjordrenna was deglaciated about 13,950 cal yr BP. During the transition from the sub-glacial to glaciomarine setting, Arctic Waters dominated its hydrography. However, the waters were not uniformly cold and experienced several warmer spells. Atlantic Water began to flow onto the shelves off Svalbard and into Storfjorden during the early Holocene, leading to progressive warming and significant glacial melting. A surface-water cooling and freshening occurred in late Holocene.
Clim. Past, 11, 587-603, doi:10.5194/cp-11-587-2015, 2015
The impact of Sahara desertification on Arctic cooling during the Holocene
Clim. Past, 11, 571-586, doi:10.5194/cp-11-571-2015, 2015
Diminished greenhouse warming from Archean methane due to solar absorption lines
Summary: High methane concentrations are thought to have helped sustain warm surface temperatures on the early Earth (~3 billion years ago) when the sun was only 80% as luminous as today. However, radiative transfer calculations with updated spectral data show that methane is a stronger absorber of solar radiation than previously thought. In this paper we show that the increased solar absorption causes a redcution in the warming ability of methane in the Archaean atmosphere.
Clim. Past, 11, 559-570, doi:10.5194/cp-11-559-2015, 2015
Inferring palaeo-accumulation records from ice-core data by an adjoint-based method: application to James Ross Island's ice core
Clim. Past, 11, 547-557, doi:10.5194/cp-11-547-2015, 2015
Technical Note: Probabilistically constraining proxy age–depth models within a Bayesian hierarchical reconstruction model
Summary: We present a Bayesian approach to simultaneously constrain the age models associated with time-uncertain proxies and inferring past climate in space and time. For the sake of exposition, the discussion focuses on annually resolved climate archives, such as varved lakes, corals, and tree rings, with dating by layer counting. Numerical experiments show that updating the probabilities associated with an ensemble of possible age models reduces uncertainty in the inferred climate.
Clim. Past, 11, 533-545, doi:10.5194/cp-11-533-2015, 2015
Evidence for the non-influence of salinity variability on the Porites coral Sr/Ca palaeothermometer
Summary: The influence of salinity on the Porites Sr/Ca palaeothermometer is still poorly documented. We test the salinity effect on Porites Sr/Ca-based SST reconstructions using a large spatial compilation of published Porites data from the Pacific, Indian Ocean, and the Red Sea. We find no evidence of a salinity bias in the Sr/Ca SST proxy at monthly and interannual timescales using two different salinity products. This result is in agreement with laboratory experiments on coral species.
Clim. Past, 11, 523-532, doi:10.5194/cp-11-523-2015, 2015
A high-resolution δ18O record and Mediterranean climate variability
Summary: The key to gaining information on climate over the last millennia is the study of proxy records in ice and sediment cores, trees, etc. We measured the oxygen isotopic ratio in planktonic foraminifera of a high-resolution, well-dated central Mediterranean core. The comparison between the variability detected in this core and that characterizing the Northern Hemisphere allows for local and global (hemispheric) climate variations to be distinguished.
Clim. Past, 11, 509-522, doi:10.5194/cp-11-509-2015, 2015
Freshwater discharge controlled deposition of Cenomanian–Turonian black shales on the NW European epicontinental shelf (Wunstorf, northern Germany)
Summary: Based on the chemistry and microfossils preserved in sediments deposited in a shallow sea, in the current Lower Saxony region (NW Germany), we conclude that changes in Earth’s orbit around the Sun led to enhanced rainfall and organic matter production. The additional supply of organic matter, depleting oxygen upon degradation, and freshwater, inhibiting the mixing of oxygen-rich surface waters with deeper waters, caused the development of oxygen-poor waters about 94 million years ago.
Clim. Past, 11, 495-508, doi:10.5194/cp-11-495-2015, 2015
Early Paleogene variations in the calcite compensation depth: new constraints using old borehole sediments from across Ninetyeast Ridge, central Indian Ocean
Clim. Past, 11, 473-493, doi:10.5194/cp-11-473-2015, 2015
Global climate simulations at 3000-year intervals for the last 21 000 years with the GENMOM coupled atmosphere–ocean model
Clim. Past, 11, 449-471, doi:10.5194/cp-11-449-2015, 2015
Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium – Part 3: Practical considerations, relaxed assumptions, and using tree-ring data to address the amplitude of solar forcing
Summary: Experiments with climate models can help to understand causes of past climate changes. We develop a statistical framework for comparing data from simulation experiments with temperature reconstructions for the last millennium. A combination of several external factors is found to explain a significant part of the observed variations, but our selection of data cannot tell which of two alternative choices of past solar forcing gives the best fit between simulations and reconstructions.
Clim. Past, 11, 425-448, doi:10.5194/cp-11-425-2015, 2015