Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming

Methane seepage from the upper continental slopes of Western Svalbard has previously been attributed to gas hydrate dissociation induced by anthropogenic warming of ambient bottom waters. Here we show that sediment cores drilled off Prins Karls Foreland contain freshwater from dissociating hydrates. However, our modeling indicates that the observed pore water freshening began around 8 ka BP when the rate of isostatic uplift outpaced eustatic sea-level rise. The resultant local shallowing and lowering of hydrostatic pressure forced gas hydrate dissociation and dissolved chloride depletions consistent with our geochemical analysis. Hence, we propose that hydrate dissociation was triggered by postglacial isostatic rebound rather than anthropogenic warming. Furthermore, we show that methane fluxes from dissociating hydrates were considerably smaller than present methane seepage rates implying that gas hydrates were not a major source of methane to the oceans, but rather acted as a dynamic seal, regulating methane release from deep geological reservoirs.

Methane seepage from continental slopes has been attributed to gas hydrate dissociation induced by anthropogenic bottom water warming. Here, the authors show that hydrates dissociated before the Anthropocene when the isostatic rebound induced by deglaciation of the Arctic ice sheet outpaced eustatic sea-level rise.

Blink rate in childhood-onset schizophrenia: comparison with normal and attention-deficit hyperactivity disorder controls

Several lines of evidence have implicated central dopaminergic pathways in the modulation of blink rate. In the present study, blink rate during smooth pursuit was examined in 17 children with childhood-onset schizophrenia, on and off of clozapine, and compared to that of age-matched normal children and unmedicated children with attention-deficit hyperactivity disorder (ADHD). As has been observed in adolescent and adult schizophrenics, blink rate was significantly higher in schizophrenic children relative to normal and ADHD controls. Within the schizophrenic group, blink rate did not significantly change with the introduction of clozapine and was not related to clinical variables. Blink rate was positively correlated with deterioration in smooth pursuit in normal subjects.

Smooth pursuit eye movements in childhood-onset schizophrenia: comparison with attention-deficit hyperactivity disorder and normal controls

Abnormalities of the smooth pursuit eye movements of adults with schizophrenia have been well described. We examined smooth pursuit eye movements in schizophrenic children, contrasting them with normal and attention-deficit hyperactivity disorder (ADHD) subjects, to determine whether there is continuity of eye movement dysfunction between childhood- and adult-onset forms of schizophrenia. Seventeen schizophrenic children with onset of illness by age 12, 18 ADHD children, and 22 normal children were studied while engaged in a smooth pursuit eye tracking task. Eye tracking variables were compared across the three groups. Schizophrenic children exhibited significantly greater smooth pursuit impairments than either normal or ADHD subjects. Within the schizophrenic group, there were no significant relationships between eye tracking variables and clinical variables, or ventricular/brain ratio. Childhood-onset schizophrenia is associated with a similar pattern of smooth pursuit abnormalities to that seen in later-onset schizophrenia.