Showing papers by "Andrew C. Parnell published in 2009"

Erroneous behaviour of MixSIR, a recently published Bayesian isotope mixing model: a discussion of Moore & Semmens (2008)

Abstract: The application of Bayesian methods to stable isotopic mixing problems, including inference of diet has the potential to revolutionise ecological research. Using simulated data we show that a recently published model MixSIR fails to correctly identify the true underlying dietary proportions more than 50% of the time and fails with increasing frequency as additional unquantified error is added. While the source of the fundamental failure remains elusive, mitigating solutions are suggested for dealing with additional unquantified variation. Moreover, MixSIR uses a formulation for a prior distribution that results in an opaque and unintuitive covariance structure.

Timing and magnitude of recent accelerated sea-level rise (North Carolina, United States)

Abstract: We provide records of relative sea level since AD 1500 from two salt marshes in North Carolina to complement existing tide-gauge records and to determine when recent rates of accelerated sea-level rise commenced Reconstructions were developed using foraminifera-based transfer functions and composite chronologies, which were validated against regional twentieth century tide-gauge records The measured rate of relative sea-level rise in North Carolina during the twentieth century was 30–33 mm/a, consisting of a background rate of ~1 mm/a, plus an abrupt increase of 22 mm/a, which began between AD 1879 and 1915 This acceleration is broadly synchronous with other studies from the Atlantic coast The magnitude of the acceleration at both sites is larger than at sites farther north along the US and Canadian Atlantic coast and may be indicative of a latitudinal trend