The WAIS-Divide deep ice core WD2014 chronology – Part 2: Methane synchronization (68–31 ka BP) and the gas age-ice age difference

Abstract. The West Antarctic Ice Sheet (WAIS)-Divide ice core (WAIS-D) is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ∼68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we present a chronology for the deep part of the core (67.8–31.2 ka BP), which is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WAIS-D gas age-ice age difference (Δage) using a combination of firn densification modeling, ice flow modeling, and a dataset of δ15N-N2, a proxy for past firn column thickness. The largest Δage at WAIS-D occurs during the last glacial maximum, and is 525 ± 100 years. Internally consistent solutions can only be found when assuming little-to-no influence of impurity content on densification rates, contrary to a recently proposed hypothesis. We synchronize the WAIS-D chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard-Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu speleothem record. The small Δage at WAIS-D provides valuable opportunities to investigate the timing of atmospheric greenhouse gas variations relative to Antarctic climate, as well as the interhemispheric phasing of the bipolar "seesaw"

The WAIS-Divide deep ice core WD2014 chronology – Part 2: Methane synchronization (68–31 ka BP) and the gas age-ice age difference

Abstract. The West Antarctic Ice Sheet (WAIS)-Divide ice core (WAIS-D) is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ∼68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we present a chronology for the deep part of the core (67.8–31.2 ka BP), which is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WAIS-D gas age-ice age difference (Δage) using a combination of firn densification modeling, ice flow modeling, and a dataset of δ15N-N2, a proxy for past firn column thickness. The largest Δage at WAIS-D occurs during the last glacial maximum, and is 525 ± 100 years. Internally consistent solutions can only be found when assuming little-to-no influence of impurity content on densification rates, contrary to a recently proposed hypothesis. We synchronize the WAIS-D chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard-Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu speleothem record. The small Δage at WAIS-D provides valuable opportunities to investigate the timing of atmospheric greenhouse gas variations relative to Antarctic climate, as well as the interhemispheric phasing of the bipolar "seesaw"

Diurnal patterns of salivary cortisol and DHEA in adolescent anorexia nervosa

Although there is well-documented evidence for hyperactivity of hypothalamic–pituitary–adrenal (HPA) axis function in anorexia nervosa (AN), there has been little research into secretory patterns of salivary cortisol and dehydroepiandrosterone (DHEA) in this condition. The cortisol awakening response (CAR), a prominent and discrete feature of the cortisol cycle, has not been extensively explored in adolescent AN. Saliva samples were collected at awakening, 30 min and 12 h post-awakening on two consecutive weekdays from eight female adolescents with clinically diagnosed AN and 41 healthy control (HC) age-matched females. Adolescent AN patients had greater salivary cortisol and DHEA concentrations than HC girls at all points. Increased hormone secretion was unrelated to body mass index. However, despite hypersecretion of both hormones, the circadian pattern including the CAR paralleled that of the HC group. Findings from this preliminary study confirm dysregulation of HPA axis function in adolescent AN as evidenced by hypersecretion of both cortisol and DHEA, which share the common secretagogue adrenocorticotropic hormone. However, the parallel diurnal profiles for AN and HC participants, including the CAR, may indicate hypersecretion per se rather than differential regulation of the diurnal pattern of these two adrenal steroids in AN