Past carbonate preservation events in the deep Southeast Atlantic Ocean (Cape Basin) and their implications for Atlantic overturning dynamics and marine carbon cycling

Micropaleontological and geochemical analyses reveal distinct millennial-scale increases in carbonate preservation in the deep Southeast Atlantic (Cape Basin) during strong and prolonged Greenland interstadials that are superimposed on long-term (orbital-scale) changes in carbonate burial. These data suggest carbonate oversaturation of the deep Atlantic and a strengthened Atlantic Meridional Overturning Circulation (AMOC) during the most intense Greenland interstadials. However, proxy evidence from outside the Cape Basin indicate that AMOC changes also occurred during weaker and shorter Greenland interstadials. Here we revisit the link between AMOC dynamics and carbonate saturation in the deep Cape Basin over the last 400 kyr (sediment cores TN057-21, TN057-10 and ODP Site 1089) by reconstructing centennial changes in carbonate preservation using mm-scale X-ray fluorescence (XRF) scanning data. We observe close agreement between variations in XRF Ca/Ti, sedimentary carbonate content and foraminiferal shell fragmentation, reflecting a common control primarily through changing deep-water carbonate saturation. We suggest that the high-frequency (sub-orbital) component of the XRF Ca/Ti records indicates the fast and recurrent redistribution of carbonate ions in the Atlantic basin via the AMOC during both long/strong- and short/weak North Atlantic climate anomalies. In contrast, the low- frequency (orbital) XRF Ca/Ti component is interpreted to reflect slow adjustments through carbonate compensation, and/or changes in the deep-ocean respired carbon content. Our findings emphasize the recurrent influence of rapid AMOC variations on the marine carbonate system during past glacial periods, providing a mechanism for transferring the impacts of North Atlantic climate anomalies to the global carbon cycle via the Southern Ocean.J.G. acknowledges support from the Swiss National Science Foundation (grant 200021_163003), the German Research Foundation (grant GO 2294/2-1) and the Gates Cambridge Trust. L.C.S. acknowledges the Royal Society, the Cambridge Isaac Newton Trust and NERC grant NE/J010545/1. S.L.J was funded by the Swiss National Science Foundation (grants PP00P2-144811 and PP002_172915)

Systematic analyses of radiocarbon ages of coexisting planktonic foraminifera

We compare radiocarbon (14C) ages of coexisting planktonic foraminifera species from sediment cores VM12-107 and KNR166-2-26JPC from the Equatorial Atlantic Ocean for three time periods (Holocene, Heinrich Stadial 1, last glacial maximum). We find a maximum inter-species difference of 1200 14C yr. On average, the 14C ages deviate by ∼300 yr between Globigerinoides ruber and other species. In most cases, this exceeds the analytical uncertainty range of the measurements and thus renders the choice of species for generating age models as important as sample weight. While modern stratified water-column profiles imply an increase in 14C ages with water depth, we observe an expected parallel increase of 14C ages and δ18O only at VM12-107. The mismatch between 14C ages and δ18O at KNR166-2-26JPC likely results from the effects of bioturbation and the hydrographic setting. The largest difference in 14C ages between mixed-layer versus thermocline-calcifying planktonic foraminifera are observed during Heinrich Stadial 1 despite a decrease in upper-ocean stratification at that time. This difference is likely the result of inconsistent increases in 14C reservoir ages during times of reduced overturning circulation masking the potential of 14C ages of coexisting planktonic foraminifera to reflect the density stratification of the water column

The German version of the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5): psychometric properties and diagnostic utility

Background: The Posttraumatic Stress Disorder (PTSD) Checklist (PCL, now PCL-5) has recently been revised to reflect the new diagnostic criteria of the disorder. Methods: A clinical sample of trauma-exposed individuals (N = 352) was assessed with the Clinician Administered PTSD Scale for DSM-5 (CAPS-5) and the PCL-5. Internal consistencies and test-retest reliability were computed. To investigate diagnostic accuracy, we calculated receiver operating curves. Confirmatory factor analyses (CFA) were performed to analyze the structural validity. Results: Results showed high internal consistency (α = .95), high test-retest reliability (r = .91) and a high correlation with the total severity score of the CAPS-5, r = .77. In addition, the recommended cutoff of 33 on the PCL-5 showed high diagnostic accuracy when compared to the diagnosis established by the CAPS-5. CFAs comparing the DSM-5 model with alternative models (the three-factor solution, the dysphoria, anhedonia, externalizing behavior and hybrid model) to account for the structural validity of the PCL-5 remained inconclusive. Conclusions: Overall, the findings show that the German PCL-5 is a reliable instrument with good diagnostic accuracy. However, more research evaluating the underlying factor structure is needed

Abrupt changes in the southern extent of North Atlantic Deep Water during Dansgaard–Oeschger events

The glacial climate system transitioned rapidly between cold (stadial) and warm (interstadial) conditions in the Northern Hemisphere. This variability, referred to as Dansgaard–Oeschger variability, is widely believed to arise from perturbations of the Atlantic Meridional Overturning Circulation. Evidence for such changes during the longer Heinrich stadials has been identified, but direct evidence for overturning circulation changes during Dansgaard–Oeschger events has proven elusive. Here we reconstruct bottom water [CO32−] variability from B/Ca ratios of benthic foraminifera and indicators of sedimentary dissolution, and use these reconstructions to infer the flow of northern-sourced deep water to the deep central sub-Antarctic Atlantic Ocean. We find that nearly every Dansgaard–Oeschger interstadial is accompanied by a rapid incursion of North Atlantic Deep Water into the deep South Atlantic. Based on these results and transient climate model simulations, we conclude that North Atlantic stadial–interstadial climate variability was associated with significant Atlantic overturning circulation changes that were rapidly transmitted across the Atlantic. However, by demonstrating the persistent role of Atlantic overturning circulation changes in past abrupt climate variability, our reconstructions of carbonate chemistry further indicate that the carbon cycle response to abrupt climate change was not a simple function of North Atlantic overturning

factor structure and symptom profiles

Background: The proposed ICD-11 criteria for trauma-related disorders define posttraumatic stress disorder (PTSD) and complex posttraumatic stress disorder (cPTSD) as separate disorders. Results of previous studies support the validity of this concept. However, due to limitations of existing studies (e.g. homogeneity of the samples), the present study aimed to test the construct validity and factor structure of cPTSD and its distinction from PTSD using a heterogeneous trauma-exposed sample. Method: Confirmatory factor analyses (CFAs) were conducted to explore the factor structure of the proposed ICD-11 cPTSD diagnosis in a sample of 341 trauma-exposed adults (n = 191 female, M = 37.42 years, SD = 12.04). In a next step, latent profile analyses (LPAs) were employed to evaluate predominant symptom profiles of cPTSD symptoms. Results: The results of the CFA showed that a six-factor structure (i.e. symptoms of intrusion, avoidance, hyperarousal and symptoms of affective dysregulation, negative self-concept, and interpersonal problems) fits the data best. According to LPA, a four-class solution optimally characterizes the data. Class 1 represents moderate PTSD and low symptoms in the specific cPTSD clusters (PTSD group, 30.4%). Class 2 showed low symptom severity in all six clusters (low symptoms group, 24.1%). Classes 3 and 4 both exhibited cPTSD symptoms but differed with respect to the symptom severity (Class 3: cPTSD, 34.9% and Class 4: severe cPTSD, 10.6%). Conclusions: The findings replicate previous studies supporting the proposed factor structure of cPTSD in ICD-11. Additionally, the results support the validity and usefulness of conceptualizing PTSD and cPTSD as discrete mental disorders

Confirmatory factor analysis of the Clinician-Administered PTSD Scale (CAPS-5) based on DSM-5 vs. ICD-11 criteria

Introduction Many studies have investigated the latent structure of the DSM-5 criteria for posttraumatic stress disorder (PTSD). However, most research on this topic was based on self-report data. We aimed to investigate the latent structure of PTSD based on a clinical interview, the Clinician-Administered PTSD Scale (CAPS-5). Method A clinical sample of 345 participants took part in this multi-centre study. Participants were assessed with the CAPS-5 and the Posttraumatic Stress Disorder Checklist (PCL-5). We evaluated eight competing models of DSM-5 PTSD symptoms and three competing models of ICD-11 PTSD symptoms. Results The internal consistency of the CAPS-5 was replicated. In CFAs, the Anhedonia model emerged as the best fitting model within all tested DSM-5 models. However, when compared with the Anhedonia model, the non-nested ICD-11 model as a less complex three-factor solution showed better model fit indices. Discussion We discuss the findings in the context of earlier empirical findings as well as theoretical models of PTSD

Biological and physical controls in the Southern Ocean on past millennial-scale atmospheric CO2 changes

Millennial-scale climate changes during the last glacial period and deglaciation were accompanied by rapid changes in atmospheric CO2 that remain unexplained. While the role of the Southern Ocean as a 'control valve' on ocean–atmosphere CO2 exchange has been emphasized, the exact nature of this role, in particular the relative contributions of physical (for example, ocean dynamics and air–sea gas exchange) versus biological processes (for example, export productivity), remains poorly constrained. Here we combine reconstructions of bottom-water [O2], export production and 14C ventilation ages in the sub-Antarctic Atlantic, and show that atmospheric CO2 pulses during the last glacial- and deglacial periods were consistently accompanied by decreases in the biological export of carbon and increases in deep-ocean ventilation via southern-sourced water masses. These findings demonstrate how the Southern Ocean's 'organic carbon pump' has exerted a tight control on atmospheric CO2, and thus global climate, specifically via a synergy of both physical and biological processes

Southern Ocean convection amplified past Antarctic warming and atmospheric CO 2 rise during Heinrich Stadial 4

Abstract: The record of past climate highlights recurrent and intense millennial anomalies, characterised by a distinct pattern of inter-polar temperature change, termed the ‘thermal bipolar seesaw’, which is widely believed to arise from rapid changes in the Atlantic overturning circulation. By forcing a suppression of North Atlantic convection, models have been able to reproduce many of the general features of the thermal bipolar seesaw; however, they typically fail to capture the full magnitude of temperature change reconstructed using polar ice cores from both hemispheres. Here we use deep-water temperature reconstructions, combined with parallel oxygenation and radiocarbon ventilation records, to demonstrate the occurrence of enhanced deep convection in the Southern Ocean across the particularly intense millennial climate anomaly, Heinrich Stadial 4. Our results underline the important role of Southern Ocean convection as a potential amplifier of Antarctic warming, and atmospheric CO2 rise, that is responsive to triggers originating in the North Atlantic

changes in PTSD prevalence in military personnel

Background: Recently, changes have been introduced to the diagnostic criteria for posttraumatic stress disorder (PTSD) according to the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD). Objectives: This study investigated the effect of the diagnostic changes made from DSM-IV to DSM-5 and from ICD-10 to the proposed ICD-11. The concordance of provisional PTSD prevalence between the diagnostic criteria was examined in a convenience sample of 100 members of the German Armed Forces. Method: Based on questionnaire measurements, provisional PTSD prevalence was assessed according to DSM-IV, DSM-5, ICD-10, and proposed ICD-11 criteria. Consistency of the diagnostic status across the diagnostic systems was statistically evaluated. Results: Provisional PTSD prevalence was the same for DSM-IV and DSM-5 (both 56%) and comparable under DSM-5 versus ICD-11 proposal (48%). Agreement between DSM-IV and DSM-5, and between DSM-5 and the proposed ICD-11, was high (both p < .001). Provisional PTSD prevalence was significantly increased under ICD-11 proposal compared to ICD-10 (30%) which was mainly due to the deletion of the time criterion. Agreement between ICD-10 and the proposed ICD-11 was low (p = .014). Conclusion: This study provides preliminary evidence for a satisfactory concordance between provisional PTSD prevalence based on the diagnostic criteria for PTSD that are defined using DSM-IV, DSM-5, and proposed ICD-11. This supports the assumption of a set of PTSD core symptoms as suggested in the ICD-11 proposal, when at the same time a satisfactory concordance between ICD-11 proposal and DSM was given. The finding of increased provisional PTSD prevalence under ICD-11 proposal in contrast to ICD-10 can be of guidance for future epidemiological research on PTSD prevalence, especially concerning further investigations on the impact, appropriateness, and usefulness of the time criterion included in ICD-10 versus the consequences of its deletion as proposed for ICD-11

Evolution of South Atlantic density and chemical stratification across the last deglaciation.

Explanations of the glacial-interglacial variations in atmospheric pCO2 invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected δ(18)O measurements on the benthic foraminifer Uvigerina spp. from deep and intermediate water-depth marine sediment cores to reconstruct the changes in density of sub-Antarctic South Atlantic water masses over the last deglaciation (i.e., 22-2 ka before present). We find that a major breakdown in the physical density stratification significantly lags the breakdown of the deep-intermediate chemical divide, as indicated by the chemical tracers of benthic foraminifer δ(13)C and foraminifer/coral (14)C. Our results indicate that chemical destratification likely resulted in the first rise in atmospheric pCO2, whereas the density destratification of the deep South Atlantic lags the second rise in atmospheric pCO2 during the late deglacial period. Our findings emphasize that the physical and chemical destratification of the ocean are not as tightly coupled as generally assumed.We are grateful to I. Mather, J. Rolfe, F. Dewilde and G. Isguder for preparing and performing isotopic analyses, as well as C. Daunt, S. Souanef-Ureta and M. Greaves for technical assistance in performing trace element analysis. J.R. was funded jointly by the British Geological Survey/British Antarctic Survey (Natural Environment Research Council) and the University of Cambridge. J.G. was funded by the Gates Cambridge Trust. L.C.S. acknowledges support from the Royal Society and NERC grant NE/J010545/1. C.W. acknowledges support from the European Research Council grant ACCLIMATE/no 339108. This is LSCE contribution 5514. This work was funded (in part) by the European Research Council (ERC grant 2010-NEWLOG ADG-267931 HE). N.V.R. acknowledges support from EU RTN NICE (no. 36127). We thank the captain and crew of the RRS James Clark Ross for facilitating the collection of the marine sediment core GC528.This is the author accepted manuscript. The final version is available from PNAS via http://dx.doi.org/10.1073/pnas.151125211