Neoglacial cooling culminates in rapid sea ice oscillations in eastern Fram Strait

EGU2011-407 The spatial and temporal distribution of sea ice in the subpolar North Atlantic is mainly controlled by the advection of warm Atlantic Water via the Norwegian and West Spitsbergen Current in eastern Fram Strait. Simultaneously, polar water and sea ice from the Arctic Ocean is transported southward by the East Greenland Current. Hence, variations in the strength of this oceanic circulation regime may either stimulate or reduce the sea ice extent. Based on organic geochemical studies of a high-resolution sediment core from eastern Fram Strait we provide new evidence for the highly variable character of the sea ice conditions in this area. The combination of the sea ice proxy IP25 (Belt et al., 2007) with phytoplankton derived biomarkers (e.g. brassicasterol, dinosterol; Volkman 2006) enables a reliable reconstruction of sea surface and sea ice conditions, respectively (Müller et al., 2009; 2010). By means of these biomarkers, we trace gradually increasing sea ice occurrences from the Mid to the Late Holocene – consistent with the neoglacial cooling trend. Throughout the past ca. 3,000 years (BP) we observe a significant short-term variability in the biomarker records, which points to rapid advances and retreats of the sea ice cover at the continental margin of West Spitsbergen. The co-occurrence of IP25 and phytoplankton markers, however, suggests that the primary productivity benefits from these sea ice surges. As such, higher amounts of open-water phytoplankton biomarkers together with peak abundances of IP25 indicate recurring periods of enhanced ice-edge phytoplankton blooms at the core site. To what extent a seesawing of temperate Atlantic Water may account for these sea ice fluctuations requires further investigation. Concurrent variations in Siberian river discharge (Stein et al., 2004) or Norwegian glacier extents (Nesje et al., 2001), however, strengthen that these fluctuations may be assigned to variations in the North Atlantic/Arctic Oscillation (NAO/AO) and (hence) a weakened/accelerated Atlantic Water input and Arctic sea ice export

Modern spatial sea-ice variability in the central Arctic Ocean and adjacent marginal seas: Reconstruction from biomarker data

Sea ice is a fundamental component of Earth’s climate system, contributing to heat reduction (albedo) and deep-water formation. In order to understand processes controlling the recent dramatic reduction in Arctic sea-ice cover, it is essential to determine spatial and temporal changes in sea-ice occurrence and its natural variability in the present and past. Here, we present biomarker data from surface sediments and related to the modern spatial (seasonal) sea-ice variability in the central Arctic Ocean and adjacent marginal seas (i.e., Bering, Chukchi, Laptev and Kara seas) as well as the Fram Strait/Yermak Plateau area. We determined concentrations of the sea-ice diatom-derived biomarker “IP25″ (highly-branched isoprenoid – HBI – with 25 carbon atom; Belt et al., 2007), phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and Î_-sitosterol) to estimate recent sea-ice conditions in the study area. A combined phytoplankton-IP25 biomarker approach (“PIP25 index”; Müller et al., 2009, 2011) is used to reconstruct the modern sea-ice distribution more quantitatively. In addition, the distribution pattern of HBI-diene/IP25 ratios has been determined to test a proposed relationship between the diene/IP25 ratio and sea-surface temperatures in Arctic marginal ice-zone environments (Fahl and Stein, 2012; Stein et al., 2012). Assessment of sea-ice conditions based on these biomarker data display that a quite stable marginal ice zone exists along the continental shelf/slope of Kara and Laptev seas during summer/early fall. Elevated IP25 as well as brassicasterol and dinosterol values occurring in the central Kara and Laptev seas are related to extended sea-ice-cover and higher primary production (close to ice-edge situation). Further to the north and the central Arctic Ocean, lower IP25 and phytoplankton biomarker concentrations point to a more close sea-ice cover situation

Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30 000 years

The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are scarce, rarely exceed the Holocene, and contain sparse information about past richness and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA (sedaDNA) metabarcoding. Amplifying a short, partial rbcL marker from samples of sediment core MSM05/5-712-2 resulted in 95.7 % of our sequences being assigned to diatoms across 18 different families, with 38.6 % of them being resolved to species and 25.8 % to genus level. Independent replicates show a high similarity of PCR products, especially in the oldest samples. Diatom sedaDNA richness is highest in the Late Weichselian and lowest in Mid- and Late Holocene samples. Taxonomic composition is dominated by cold-water and sea-ice-associated diatoms and suggests several reorganisations – after the Last Glacial Maximum, after the Younger Dryas, and after the Early and after the Mid-Holocene. Different sequences assigned to, amongst others, Chaetoceros socialis indicate the detectability of intra-specific diversity using sedaDNA. We detect no clear pattern between our diatom sedaDNA record and the previously published IP25 record of this core, although proportions of pennate diatoms increase with higher IP25 concentrations and proportions of Nitzschia cf. frigida exceeding 2 % of the assemblage point towards past sea-ice presence

Homozygous CREM-IbΔC-X Overexpressing Mice Are a Reliable and Effective Disease Model for Atrial Fibrillation

Background: Atrial fibrillation (AF) is a significant cause of morbidity and mortality with foreseeably increasing prevalence. While large animal models of the disease are well established but resource intensive, transgenic AF mouse models are not yet widely used to develop or validate novel therapeutics for AF. Hemizygous mice with a cardiomyocyte-specific overexpression of the human cAMP response element modulator (CREM) isoform IbΔC-X spontaneously develop AF on grounds of an arrhythmogenic substrate consisting of alterations in structure, conduction, and calcium handling.Objective: We investigated if homozygous expression of the CREM-IbΔC-X transgene in mice alters the time course of AF development, and if homozygous CREM-IbΔC-X transgenics could be suitable as a disease model of AF.Methods: Southern Blot, quantitative real-time PCR, and immunoblotting were used to identify and verify homozygous transgenics. Cardiac gravimetry, quantitative real-time RT-PCR, histology, survival analysis, and repeated ECG recordings allowed assessment of phenotypic development and effects of antiarrhythmic drugs.Results: Homozygous animals could be identified by Southern blot and quantitative PCR, showing a strong trend to increased transgenic protein expression. In homozygous animals, atrial hypertrophy appeared earlier and more pronounced than in hemizygous animals, going along with an earlier onset of spontaneous AF, while no increased early mortality was observed. Application of a rate-controlling drug (esmolol) led to the expected result of a decreased heart rate. Application of a rhythm-controlling drug (flecainide) showed effects on heart rate variability, but did not lead to a definitive conversion to sinus rhythm.Conclusion: We suggest homozygous CREM-IbΔC-X overexpressing mice as a reliable model of early onset, rapidly progressive AF

Impact of the Madden–Julian oscillation and equatorial waves on tracked mesoscale convective systems over southeast Asia

Southeast Asia is a region dominated by high-impact weather, but numerical weather prediction here is a challenge owing to the complex orography and interactions between small- and large-scale phenomena. Localised mesoscale convective systems (MCSs) can produce intense precipitation. Here, we track MCSs over a 5-year period in Himawari satellite data, characterise the distribution of MCSs in the region, and investigate how they are modulated by the Madden–Julian oscillation (MJO) and equatorial waves. Between 10°S and 10°N in southeast Asia, MCSs account for 45–70% of the precipitation during boreal extended winter (November–April). Over most of the region, the fractional MCS contribution to rainfall is higher than average on days with extreme rainfall (>55%). Long-lived (>12 hr) MCSs contribute disproportionately, providing 85% of the rainfall despite comprising only 34% of all MCSs. Variability in MCS rainfall accounts for >50% of the total rainfall variability during an MJO cycle, mostly due to larger numbers of MCSs in convectively active MJO phases. Variations in MCS size and mean rain rate due to shifts in the stratiform proportion provide compensating effects. In the west of the region, a shift to faster moving MCSs in active MJO phases and slower moving MCSs in inactive phases resulted in fast-moving MCSs having the greatest impact on the MJO-associated variability. Variability is larger in the west than in the east. Equatorial Kelvin waves modulate MCS rainfall, with MCSs accounting for 20–50% of local rainfall anomalies. This variability is again enhanced in the west. By contrast, rainfall anomalies due to westward-propagating mixed Rossby–gravity waves and Rossby-1 waves are dominated by tropical-cyclone-related rainfall. Skill at local scales may be extracted from forecasts of subseasonal drivers such as the MJO and Kelvin waves, by understanding how these modulate the number and characteristics of MCSs

Lactobacillus Acidophilus/Bifidobacterium Infantis Probiotics Are Beneficial to Extremely Low Gestational Age Infants Fed Human Milk

To evaluate the nutrition-related effects of prophylactic Lactobacillus acidophilus/ Bifidobacterium infantis probiotics on the outcomes of preterm infants <29 weeks of gestation that receive human milk and/or formula nutrition. We hypothesize that human-milk-fed infants benefit from probiotics in terms of sepsis prevention and growth. Methods: We performed an observational study of the German Neonatal Network (GNN) over a period of six years, between 1 January, 2013 and 31 December, 2018. Prophylactic probiotic use of L. acidophilus/B. infantis was evaluated in preterm infants <29 weeks of gestation (n = 7516) in subgroups stratified to feeding type: (I) Exclusively human milk (HM) of own mother and/or donors (HM group, n = 1568), (II) HM of own mother and/or donor and formula (Mix group, n = 5221), and (III) exclusive exposure to formula (F group, n = 727). The effect of probiotics on general outcomes and growth was tested in univariate models and adjusted in linear/logistic regression models. Results: 5954 (76.5%) infants received L. acidophilus/B. infantisprophylactically for the prevention of necrotizing enterocolitis (NEC). Probiotic use was associated with improved growth measures in the HM group (e.g., weight gain velocity in g/day: effect size B = 0.224; 95% CI: 2.82–4.35; p < 0.001) but not in the F group (effect size B = −0.06; 95% CI: −3.05–0.28; p = 0.103). The HM group had the lowest incidence of clinical sepsis (34.0%) as compared to the Mix group (35.5%) and the F group (40.0%). Only in the Mix group, probiotic supplementation proved to be protective against clinical sepsis (OR 0.69; 95% CI: 0.59–0.79; p < 0.001). Conclusion: Our observational data indicate that the exposure to L. acidophilus/B. infantis probiotics may promote growth in exclusively HM-fed infants as compared to formula-fed infants. To exert a sepsis-preventive effect, probiotics seem to require human milk

Primary headaches in patients with generalized anxiety disorder

Although anxiety disorders and headaches are comorbid conditions, there have been no studies evaluating the prevalence of primary headaches in patients with generalized anxiety disorder (GAD). The aim of this study was to analyze the lifetime prevalence of primary headaches in individuals with and without GAD. A total of 60 individuals were evaluated: 30 GAD patients and 30 controls without mental disorders. Psychiatric assessments and primary headache diagnoses were made using structured interviews. Among the GAD patients, the most common diagnosis was migraine, which was significantly more prevalent among the GAD patients than among the controls, as were episodic migraine, chronic daily headache and aura. Tension-type headache was equally common in both groups. Primary headaches in general were significantly more common and more severe in GAD patients than in controls. In anxiety disorder patients, particularly those with GAD, accurate diagnosis of primary headache can improve patient management and clinical outcomes