The orbital‐scale transition from the last interglacial to glacial climate corresponds to the progressive organization of global millennial‐scale climate variability. Here, we investigate the ...structure and the global fingerprint of the first warming event occurring during the last glacial inception, the Greenland InterStadial 25 (GIS 25). Using centennial to decadal‐resolution measurements ofδ18O and δD in the ice together with δ15N, δ18O2 and CH4in the trapped air, we show that GIS 25 does not coincide with large environmental changes at lower latitudes. Such an equivocal fingerprint questions whether GIS 25 is simply a smaller amplitude version of later rapid events or whether it reflects a more regional northern hemisphere origin for the initiation of the millennial‐scale climatic variability. After this ambiguous first rapid event, the onset of the global millennial‐scale variability ‐characteristic of the last glacial period‐ occurs as a short (300 years) event ending GIS 25.
Key Points
A 3 degree C abrupt warming ending the last interglacial in Greenland
Potentially, a regional origin for the initiation of rapid climate variability
Interplay between orbitally‐driven glacial inception and abrupt climate change
Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores and the estimation of the age-scale uncertainty are essential to interpret the climate and ...environmental records that they contain. It is, however, a complex problem which involves different methods. Here, we present IceChrono1, a new probabilistic model integrating various sources of chronological information to produce a common and optimized chronology for several ice cores, as well as its uncertainty. IceChrono1 is based on the inversion of three quantities: the surface accumulation rate, the lock-in depth (LID) of air bubbles and the thinning function. The chronological information integrated into the model are models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice- and air-dated horizons, ice and air depth intervals with known durations, Δdepth observations (depth shift between synchronous events recorded in the ice and in the air) and finally air and ice stratigraphic links in between ice cores. The optimization is formulated as a least squares problem, implying that all densities of probabilities are assumed to be Gaussian. It is numerically solved using the Levenberg–Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono follows an approach similar to that of the Datice model which was recently used to produce the AICC2012 (Antarctic ice core chronology) for four Antarctic ice cores and one Greenland ice core. IceChrono1 provides improvements and simplifications with respect to Datice from the mathematical, numerical and programming point of views. The capabilities of IceChrono1 are demonstrated on a case study similar to the AICC2012 dating experiment. We find results similar to those of Datice, within a few centuries, which is a confirmation of both IceChrono1 and Datice codes. We also test new functionalities with respect to the original version of Datice: observations as ice intervals with known durations, correlated observations, observations as air intervals with known durations and observations as mixed ice–air stratigraphic links. IceChrono1 is freely available under the General Public License v3 open source license.
Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near‐surface snow between precipitation events. These changes have ...been linked to isotopic exchange with atmospheric water vapor and sublimation‐induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes are crucial to both the interpretation of ice core climate proxies and the formulation of isotope‐enabled general circulation models. Here, we present continuous measurements of the water isotopic composition in surface snow and atmospheric vapor together with near‐surface atmospheric turbulence and snow‐air latent and sensible heat fluxes, obtained at the East Greenland Ice‐Core Project drilling site in summer 2016. For two 4‐day‐long time periods, significant diurnal variations in atmospheric water isotopologues are observed. A model is developed to explore the impact of this variability on the surface snow isotopic composition. Our model suggests that the snow isotopic composition in the upper subcentimeter of the snow exhibits a diurnal variation with amplitudes in δ18O and δD of ~2.5‰ and ~13‰, respectively. As comparison, such changes correspond to 10–20% of the magnitude of seasonal changes in interior Greenland snow pack isotopes and of the change across a glacial‐interglacial transition. Importantly, our observation and model results suggest, that sublimation‐induced fractionation needs to be included in simulations of exchanges between the vapor and the snow surface on diurnal timescales during summer cloud‐free conditions in northeast Greenland.
Key Points
Data show evidence of isotopic fractionation during vapor exchange between the snow surface and atmosphere
Model simulations suggest diurnal variation in the snow surface isotopic composition
We propose an enhanced effective isotopic exchange between the surface of the snow grain and its interior
The stratospheric degradation of chlorofluorocarbons (CFCs) releases chlorine, which is a major contributor to the destruction of stratospheric ozone (O3). A recent study reported strong chlorine ...isotope fractionation during the breakdown of the most abundant CFC (CFC-12, CCl2F2, Laube et al., 2010a), similar to effects seen in nitrous oxide (N2O). Using air archives to obtain a long-term record of chlorine isotope ratios in CFCs could help to identify and quantify their sources and sinks. We analyse the three most abundant CFCs and show that CFC-11 (CCl3F) and CFC-113 (CClF2CCl2F) exhibit significant stratospheric chlorine isotope fractionation, in common with CFC-12. The apparent isotope fractionation ( epsilon app) for mid- and high-latitude stratospheric samples are respectively -2.4 (0.5) and -2.3 (0.4) ppt for CFC-11, -12.2 (1.6) and -6.8 (0.8) ppt for CFC-12 and -3.5 (1.5) and -3.3 (1.2) ppt for CFC-113, where the number in parentheses is the numerical value of the standard uncertainty expressed in per mil. Assuming a constant isotope composition of emissions, we calculate the expected trends in the tropospheric isotope signature of these gases based on their stratospheric 37Cl enrichment and stratosphere-troposphere exchange. We compare these projections to the long-term delta (37Cl) trends of all three CFCs, measured on background tropospheric samples from the Cape Grim air archive (Tasmania, 1978-2010) and tropospheric firn air samples from Greenland (North Greenland Eemian Ice Drilling (NEEM) site) and Antarctica (Fletcher Promontory site). From 1970 to the present day, projected trends agree with tropospheric measurements, suggesting that within analytical uncertainties, a constant average emission isotope delta ( delta ) is a compatible scenario. The measurement uncertainty is too high to determine whether the average emission isotope delta has been affected by changes in CFC manufacturing processes or not. Our study increases the suite of trace gases amenable to direct isotope ratio measurements in small air volumes (approximately 200 mL), using a single-detector gas chromatography-mass spectrometry (GC-MS) system.
During the last glacial cycle, Greenland temperature showed many rapid temperature variations, the so-called Dansgaard–Oeschger (DO) events. The past atmospheric methane concentration closely ...followed these temperature variations, which implies that the warmings recorded in Greenland were probably hemispheric in extent. Here we substantially extend and complete the North Greenland Ice Core Project (NGRIP) methane record from the Preboreal Holocene (PB) back to the end of the last interglacial period with a mean time resolution of 54 yr. We relate the amplitudes of the methane increases associated with DO events to the amplitudes of the local Greenland NGRIP temperature increases derived from stable nitrogen isotope (δ15N) measurements, which have been performed along the same ice core (Kindler et al., 2014). We find the ratio to oscillate between 5 parts per billion (ppb) per °C and 18 ppb °C−1 with the approximate frequency of the precessional cycle. A remarkably high ratio of 25.5 ppb °C−1 is reached during the transition from the Younger Dryas (YD) to the PB. Analysis of the timing of the fast methane and temperature increases reveals significant lags of the methane increases relative to NGRIP temperature for DO events 5, 9, 10, 11, 13, 15, 19, and 20. These events generally have small methane increase rates and we hypothesize that the lag is caused by pronounced northward displacement of the source regions from stadial to interstadial. We further show that the relative interpolar concentration difference (rIPD) of methane is about 4.5% for the stadials between DO events 18 and 20, which is in the same order as in the stadials before and after DO event 2 around the Last Glacial Maximum. The rIPD of methane remains relatively stable throughout the full last glacial, with a tendency for elevated values during interstadial compared to stadial periods.
The climate of the last glacial Marine Isotopic Stage 3 (MIS3) period is characterized by strong millennial-scale variability with a succession of Dansgaard–Oeschger events first identified in ...Greenland ice cores and associated with variations of the Atlantic Meridional Overturning Circulation (AMOC). These abrupt events have a smooth and lagged counterpart in water stable isotopes from Antarctic ice cores. In this study we aim at depicting and understanding the circum-Antarctic expression of this millennial-scale variability. To illustrate the mechanisms potentially at work in the response of the southern high latitudes to an abrupt decrease of the AMOC, we first present results from experiments performed with the IPSL-CM4 atmosphere-ocean coupled model under glacial boundary conditions. When the AMOC is perturbed by imposing an additional freshwater flux in the North Atlantic, our model produces the classical bipolar seesaw mechanism generally invoked to explain the warming of the Southern Ocean/Antarctic region. However, this mechanism can be locally offset by faster atmospheric teleconnections originating from the tropics, even though the precise location of this fast response is not coherent among different climate models. Our model results are confronted with a synthesis of Antarctic records of ice core stable isotope and sea-salt sodium, including new data obtained on the TALDICE ice core. The IPSL-CM4 produces a dipole-like pattern around Antarctica, with warming in the Atlantic/Indian sectors contrasting with an unexpected cooling in the East-Pacific sector. The latter signal is not detected in our data synthesis. Both ice core data and simulations are consistent in depicting a more rapid response of the Atlantic sector compared to the Indian sector. This feature can be explained by the gradual impact of ocean transport on which faster atmospheric teleconnections are superimposed. Detailed investigations of the sequence of events between different proxies are conducted in three ice cores. Earlier shifts in deuterium excess and significant changes in sea-salt sodium fluxes in the most coastal sites (TALDICE and EDML) compared to EDC suggest reorganizations in local moisture sources, possibly linked with sea-ice cover. This study demonstrates the added value of circum-Antarctic ice core records to characterize the patterns and mechanisms of glacial climate variability.
► Review of glacial millennial-scale climate variability in Antarctic ice cores. ► Comparison between Antarctic ice core data and global coupled model simulations. ► Included new Talos Dome ice core climatic data. ► Regional differences of Southern Ocean and Antarctica climate are observed when North Atlantic Ocean circulation is weakened.
Abstract Objective Maternal antenatal depression and anxiety are associated with increased risk of childhood behavioural and emotional problems in offspring; it remains unclear to what extent this is ...due to a maternal biological impact on foetal development. Here, we compare associations between maternal and paternal antenatal depression and anxiety with offspring anxiety disorders, thus controlling for some genetic and shared environmental factors. Methods We used data from the ALSPAC population cohort including measures of antenatal parental depression and anxiety. At 18 years, offspring completed the CIS-R interview, yielding diagnoses for anxiety disorders. Results were adjusted for confounding variables including parental postnatal depression and anxiety. Results Children of women with antenatal depression (18 weeks gestation), had an increased risk of anxiety disorders at 18 years of age (11.1% vs. 6.2%; adj. OR 1.75 (1.19, 2.58); p =0.01). Children of women with antenatal anxiety had increased risk of co-morbid anxiety and depression (adj. OR 1.39 (1.06, 1.82); p =0.02). No such associations were found with paternal antenatal depression or anxiety. Limitations There was a high attrition rate from the original cohort to the CIS-R completion at 18 years postpartum. Parental mood was only assessed together at one time point during the antenatal period. Conclusions The differences in the association between maternal and paternal mood during pregnancy and child outcomes supports the hypothesis that foetal programming may account, at least in part, for this association. We highlight the potential opportunity for preventative intervention by optimising antenatal mental health.
Domestic violence and abuse is a considerable international public health problem, which is associated with mental disorders in both women and men. Nevertheless, victimization and perpetration remain ...undetected by mental health services. This paper reviews the evidence on mental health service responses to domestic violence, including identifying, referring, and providing care for people experiencing or perpetrating violence. The review highlights the need for mental health services to improve rates of identification and responses to domestic violence and abuse, through the provision of specific training on domestic violence and abuse, the implementation of clear information sharing protocols and evidence-based interventions, and the establishment of care referral pathways. This review also highlights the need for further research into mental health service users who perpetrate domestic violence and abuse.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We expand here the description of the Antarctic temperature variability during the long interglacial period occurring ~400 thousand years before the present (Marine Isotopic Stage, MIS 11). Our study ...is based on new detailed deuterium measurements conducted on the EPICA Dome C ice core, Antarctica, with a ~50 year temporal resolution. Despite an ice diffusion of a length reaching ~8 cm at MIS 11 depth, the data allow us to highlight a variability at multi-centennial scale for MIS 11, as it has already been observed for the Holocene period (MIS 1). The differences between MIS 1 and MIS 11 are analysed regarding the links between multi-millennial trends and sub-millennial variability. The EPICA Dome C deuterium record shows an increased variability and the onset of millennial to sub-millennial periodicities at the beginning of the final cooling phase of MIS 11. Our findings are robust with respect to sensitivity tests on the somewhat uncertain MIS 11 duration.
Interglacials, including the present (Holocene) period, are warm, low land ice extent (high sea level), end-members of glacial cycles. Based on a sea level definition, we identify eleven ...interglacials in the last 800,000years, a result that is robust to alternative definitions. Data compilations suggest that despite spatial heterogeneity, Marine Isotope Stages (MIS) 5e (last interglacial) and 11c (~400ka ago) were globally strong (warm), while MIS 13a (~500ka ago) was cool at many locations. A step change in strength of interglacials at 450ka is apparent only in atmospheric CO2 and in Antarctic and deep ocean temperature. The onset of an interglacial (glacial termination) seems to require a reducing precession parameter (increasing Northern Hemisphere summer insolation), but this condition alone is insufficient. Terminations involve rapid, nonlinear, reactions of ice volume, CO2, and temperature to external astronomical forcing. The precise timing of events may be modulated by millennial-scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere. A variety of temporal trends is observed, such that maxima in the main records are observed either early or late in different interglacials. The end of an interglacial (glacial inception) is a slower process involving a global sequence of changes. Interglacials have been typically 10-30ka long. The combination of minimal reduction in northern summer insolation over the next few orbital cycles, owing to low eccentricity, and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future. Key Points We have reviewed the occurrence, strength, shape, and timing of interglacials Despite spatial variability, MIS 5 and 11 stand out as strong/warm The current interglacial is expected to be longer than any of those reviewed
PDF
