• European Marine Science
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Much of our understanding of Earth's past climate states comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, major intervals in those records that lack the temporal resolution and/or age control required to identify climate forcing and feedback mechanisms. Here we document 66 million years of global climate by a new high-fidelity Cenozoic global reference benthic carbon and oxygen isotope dataset (CENOGRID). Using recurrence analysis, we find that on timescales of millions of years Earth's climate can be grouped into Hothouse, Warmhouse, Coolhouse and Icehouse states separated by transitions related to changing greenhouse gas levels and the growth of polar ice sheets. Each Cenozoic climate state is paced by orbital cycles, but the response to radiative forcing is state dependent.

High-resolution atmospheric carbon dioxide (CO2) and methane (CH4) records derived from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core covering Marine Isotope Stage (MIS) 9e - 12a (~330 - 450 ka BP). The majority of the CO2 data were measured at an average temporal resolution of ~300 years using a novel dry-extraction device called the Centrifugal Ice Microtome (CIM) employed at Climate and Environmental Physics (CEP), Physics Institute, University of Bern, Switzerland. Additional 33 data points were measured at the Institut des Géosciences de l'Environnement (IGE), Univ. Grenoble Alpes, France using the Ball Mill dry-extraction system. The CH4 data were measured at both CEP and IGE, improving the temporal resolution of existing data previously published by the same laboratories to ~350 years on average. These ice core records are complemented by high-resolution planktic and benthic stable isotope (δ18O and δ13C) records from the International Ocean Discovery Program (IODP) Site U1385 located on the Iberian Margin off the coast of Portugal (Shackleton Site) covering MIS 9e - 11c (~330 - 410 ka BP). All marine sediment data were measured at an average temporal resolution of ~150 years at the Godwin Laboratory of Palaeoclimate Research, University of Cambridge, UK.

In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate dependent DCF values. For M1-5 an average DCF of 56.2 ± 3.4 % is observed between 27 and 18 kyr BP. Such high DCF values indicate a high influence of aged soil organic matter (SOM) and nearly completely closed system carbonate dissolution conditions. Towards the end of the last glacial period decreasing Mg/Ca ratios suggest an increase in precipitation which caused a marked change in the soil carbon cycling as indicated by sharply decreasing DCF. This is in contrast to the relation of soil infiltration and reservoir age observed in stalagmites from temperate zones. For Socotra Island, which is influenced by the East African-Indian monsoon, we propose that more humid conditions and enhanced net-infiltration after the LGM led to denser vegetation and thus lowered the DCF by increased 14CO2 input into the soil zone. The onset of the Younger Dryas (YD) is represented in the record by the end of DCF decrease with a sudden change to much higher and extremely variable reservoir ages. Our study highlights the dramatic variability of soil carbon cycling processes and vegetation feedback on Socotra Island manifested in stalagmite reservoir ages on both long-term trends and sub-centennial timescales, thus providing evidence for climate influence on stalagmite radiocarbon. This is of particular importance for studies focussing on 14C calibration and atmospheric reconstruction through stalagmites which relies on largely climate independent soil carbon cycling above the cave.

One and two metre snow pit accumulation, density, peroxide and conductivity on a depth and age scale from summer 2019 obtained at 7 ice core drilling sites; NEEM, B16, B19, B22 as well as 3 sites in the vicinity of EastGRIP representing the years 2014 to summer 2019. The data was analysed by means of continuous flow using the Light weight In Situ Analysis (LISA) box (Kjær et al, 2021).

The past 3.2 Myr have seen drastic climate changes with the development, waxing and waning of huge continental ice sheets over the Northern Hemisphere. These striking phenomena have been observed in various records from ice cores, as well as marine and terrestrial sediments. These proxy records showed periodicities associated with the three orbital parameters that affect our planet's insolation, namely eccentricity, obliquity and precession. Until recently, these periodicities were considered as the canonical ones for the Quaternary Period and beyond. However, the improvement of the time resolution of available records has allowed one to describe climate changes occurring abruptly and with periodicities that are not related to those of the orbital parameters. The present datasets are those used to demonstrate that, in fact, these abrupt climate changes may still be related, albeit indirectly, to the astronomical theory of climate. They correspond to: 1- the statistics of the recurrence analysis of for North Atlantic core U1308 benthic δ18O representing the global temperature and the volume of continental ice sheet, U1308 bulk carbonate δ18O representing the ice-rafted debris released in the ocean(Hodell and Channell, 2016) covering the past 3.2 Myr and Greenland ice core NGRIP δ18O representing the temperature over Greenland (Rasmussen et al., 2014) covering the last 110 Kyr. These statistics correspond to changes in the variability regime present in the studied records with the identification of key transitions related to the variations in the Northern Hemisphere ice sheets; 2- the comparison of the main steps detected by Hodell and Channell (2016) from U1308 marine records with those deduced from the Recurrence Plot of the benthic δ18O and bulk carbonate δ18O data of the same record; 3-the thresholds identified in the recurrence plot of NGRIP δ18O record and their correspondence in the marine isotope stratigraphy of the last climate cycle stratigraphy from Bassinot et al., 1994 and Lisiecki and Raymo, 2005, showing a link between the length of the Greenland interstadials and the variations in the global sea level record.

Results from six firn cores obtained during a 426 km long northern Greenland traverse in 2015 between the NEEM and the EGRIP deep drilling stations situated on the Western and Eastern side of the Greenland ice sheet, respectively. The cores (9 to 14 m long) are analysed for chemical impurities by means of Continuous Flow Analysis (CFA); Insoluble dust, ammonium, calcium, acid, conductivity and peroxide. The data was dated by means of annual layer counting of mainly peroxide supplemented by calcium seasonal cycles and spans 18 to 53 years (±3 yrs) depending on local snow accumulation that decreases from west to east. Insoluble dust, ammonium, and calcium concentrations in the 6 firn cores overlap, and also the seasonal cycles are similar in timing and magnitude across sites, while peroxide (H2O2) and conductivity both have spatial variations. H2O2 is driven by the accumulation pattern and conductivity is likely influenced by sea salt. Data is published as part of Kjær et al. 2022, Climate of the past, https://doi.org/10.5194/cp-2021-99

The RECAP ice core was drilled on Renland ice cap, coastal East Greenland, in May-June 2015. This dataset presents the first complete timescale for the ice core record, based on impurity (dust and chemistry) as well as gas content measurements. The underlying dust particle and gas (CH4, d15N and d18Oair) data are presented. Strontium and Neodymium measurements of potential dust source samples collected from exposed terrain in central East Greenland are also presented. The timescale is called 'RECAP GICC05modelext Time Scale (version 1/3-2018)' and has been synchronized to the existing GICC05modelext timescale. All synchronization tiepoints are presented.

Loess sequences are a particular record of paleoenvironments and paleoclimates and show regional peculiarities. Among those, European loess sequences show the occurrence of paleosols and other pedogenic units that have been demonstrated to correspond to the Greenland Interstadials (GIS) or Dansgaard-Oeschger events (DO), for the last climate cycle (Moine et al. 2017), of GIS-like for the penultimate climate cycle (Rousseau et al. 2020). During the last climate cycle, these paleosols developed synchronously over Europe along a wide longitude transect eastward in Ukraine (Rousseau et al., 2017). More interesting the development of these paleosols or pedogenic units, occurred during a stop of the dust deposition from the top of the most recently deposited eolian unit. Taking into consideration this point in our manuscript, we revisited the stratigraphy of the European loess sequences by considering the paleodust units, equivalent to Greenland Stadials (GS), as associating the lower loess unit and the overlying paleosol or pedogenic unit. Moreover, the close correlation that we established between the paleosols or pedogenic units with GIs, allows us to consider that the paleosol development occurred during the related GI in Greenland (Rousseau et al., 2017). Having the GI durations published by Rasmussen et al (2014), we propose therefore new timescales for the European loess sequences. Moreover, we have assigned the paleosol-loess units doublets to the corresponding Bond cycles defined by Broecker (1994). These cycles group several DO events, of increasing cold amplitude, and end with a Heinrich event that some literature interpreted as the coldest and dustiest time interval over Europe, an interpretation that we are testing in our paper. In our manuscript, we demonstrate our new method by applying it to the reference sequence of Nussloch that we have investigated for decades. We present a revised detailed record of sedimentation and mass accumulation rates over the 60 ka to 15 ka b2k time interval (TAB. 1). We also apply our method to other key European sequences that we investigated previously at high resolution, allowing us to propose new estimates for the SR and MARs of the most recent Bond cycles, i.e. e. between GI4 and GS3 (29 to 23.2ka b2k) and between GI8 and GS5 (38.2 to 29ka b2k) (TAB. 2). We conclude the LGM as the dustiest interval with the highest values, and presenting a longitudinal pattern along the studied European transect, with the highest values westward. Another finding is that for every Bond cycle, the dustiest interval always happened in the GS prior the last ones corresponding to Heinrich stadials. Expanding the comparison with high-resolution sequences from the Chinese loess plateau (TAB. 3) for the same Bond cycles, our study shows that Europe was dustier than China. A final test of our new method is by considering the SR and MARs for the various grain size categories measured in three key reference sequences. Considering the finest grain size category, which can be assimilated as the closest the mineral aerosols, our estimates fit the dust deposition reconstructed for the LGM in Europe by Earth System models opening new perspectives for future data-model comparisons (TAB. 4).

Summary statistics of posterior marginal distribution of the onset of abrupt warming transitions located in the last glacial age of the NGRIP record, based on both the d18O and Ca2+ proxy. Includes both statistics for the onset depth as well as age transition. Onset depth is found by applying a linear ramp function (Erhardt et al. 2019) which is combined with a probabilistic age-depth model to infer the onset age of the transition.