Synoptic reorganization of atmospheric flow during the Last Glacial Maximum

A coupled global atmosphere–ocean model of intermediate complexity is used to study the influence of glacial boundary conditions on the atmospheric circulation during the Last Glacial Maximum in a systematical manner. A web of atmospheric interactions is disentangled, which involves changes in the meridional temperature gradient and an associated modulation of the atmospheric baroclinicity. This in turn drives anomalous transient eddy momentum fluxes that feed back onto the zonal mean circulation. Moreover, the modified transient activity (weakened in the North Pacific and strengthened in the North Atlantic) leads to a meridional reorganization of the atmospheric heat transport, thereby feeding back onto the meridional temperature structure. Furthermore, positive barotropic conversion and baroclinic production rates over the Laurentide ice sheets and the far eastern North Pacific have the tendency to decelerate the westerlies, thereby feeding back to the stationary wave changes triggered by orographic forcing

Effect of sitagliptin on cardiovascular outcomes in type 2 diabetes

BACKGROUND: Data are lacking on the long-term effect on cardiovascular events of adding sitagliptin, a dipeptidyl peptidase 4 inhibitor, to usual care in patients with type 2 diabetes and cardiovascular disease. METHODS: In this randomized, double-blind study, we assigned 14,671 patients to add either sitagliptin or placebo to their existing therapy. Open-label use of antihyperglycemic therapy was encouraged as required, aimed at reaching individually appropriate glycemic targets in all patients. To determine whether sitagliptin was noninferior to placebo, we used a relative risk of 1.3 as the marginal upper boundary. The primary cardiovascular outcome was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina. RESULTS: During a median follow-up of 3.0 years, there was a small difference in glycated hemoglobin levels (least-squares mean difference for sitagliptin vs. placebo, -0.29 percentage points; 95% confidence interval [CI], -0.32 to -0.27). Overall, the primary outcome occurred in 839 patients in the sitagliptin group (11.4%; 4.06 per 100 person-years) and 851 patients in the placebo group (11.6%; 4.17 per 100 person-years). Sitagliptin was noninferior to placebo for the primary composite cardiovascular outcome (hazard ratio, 0.98; 95% CI, 0.88 to 1.09; P<0.001). Rates of hospitalization for heart failure did not differ between the two groups (hazard ratio, 1.00; 95% CI, 0.83 to 1.20; P = 0.98). There were no significant between-group differences in rates of acute pancreatitis (P = 0.07) or pancreatic cancer (P = 0.32). CONCLUSIONS: Among patients with type 2 diabetes and established cardiovascular disease, adding sitagliptin to usual care did not appear to increase the risk of major adverse cardiovascular events, hospitalization for heart failure, or other adverse events

Continuous record of microparticle concentration and size distribution in the central Greenland NGRIP ice core during the last glacial period

A novel laser microparticle detector used in conjunctionwith continuous sample melting has provided a more than 1500 mlong record of particle concentration and size distribution of theNGRIP ice core, covering continuously the period approx. from9.5-100kyr before present; measurements were at 1.65 m depthresolution, corresponding to approx. 35-200yr. Particleconcentration increased by a factor of 100 in the Last GlacialMaximum (LGM) compared to the Preboreal, and sharp variations ofconcentration occurred synchronously with rapid changes in thed18O temperature proxy. The lognormal mode &#956; of thevolume distribution shows clear systematic variations with smallermodes during warmer climates and coarser modes during colderperiods. We find &#956; ~ 1.7 &#956;m diameter during LGM and&#956; ~ 1.3 &#956;m during the Preboreal. On timescales belowseveral 100 years &#956; and the particle concentration exhibit acertain degree of independence present especially during warmperiods, when &#956; was also more variable. Using highlysimplifying considerations for the atmospheric transport anddeposition of particles we infer that (i) the observed changes of&#956; in the ice largely reflect changes in the size of airborneparticles above the ice sheet and (ii) changes of &#956; areindicative of changes in long range atmospheric transport time.From the observed size changes we estimate shorter transit timesby roughly 25% during LGM compared to the Preboreal. Theassociated particle concentration increase from more efficientlong range transport is estimated to less than one order ofmagnitude

Methanesulfonate in the Greenland Ice Sheet Project 2 Ice Core

In this paper we present measurements of methanesulfonate in the Greenland Ice Sheet Project 2 (GISP2) ice core. Methanesulfonate is an atmospheric oxidation product of dimethylsulfide. The GISP2 methanesulfonate record contains information about the atmospheric loading of biogenic sulfur over the past 110 kyr and its relationship to climate change. The GISP2 data set supports the inferences made from the Renland ice core from Greenland that the glacial atmosphere over Greenland had reduced concentrations of biogenic sulfur compared with the present day [Hansson and Saltzman, 1993]. We conclude that the flux of biogenic sulfur from the North Atlantic Ocean must have been lower during glacial times and speculate that this decrease may have been related to differences in phytoplankton speciation. The data suggest that changes in direct radiative forcing from biogenic sulfur aerosols would act as negative feedback to the glacial/interglacial climate cycles in this region