Fine-scale estimations of bioclimatic change in the Valencia region, Spain

Recent advances in statistical downscaling have allowed the reconstruction of temperatures for the complete 1948–2011 period in a spatial resolution of 90 m and without gaps for the Valencian Community (Spain) and bordering areas. It presently enables analyses in this region, which allows the determination of recent temperature changes at subregional and local scales. The present work focuses on obtaining the thermicity index according to Rivas-Martínez, a well-known indicator of different thermotypes associated with bioclimatic horizons. The change in this index, which has happened in the region between 1948 and 2011, was calculated by generating fine-scale maps of the potential extension of different thermotypes. The results show a greater regression for the thermotypes in a finicolous position, e.g. Orotemperate, Supratemperate and Supramediterranean horizons, which herein indicate greater potential vulnerability in climate change. In the absence of, and given the need for, such fine-scale information, this work should be useful for specialized researchers to spatially limit the potentially most vulnerable biotopes to climate change.

Sea surface temperature reconstruction of a combined sediment record of the midlatitude North Pacific

Suborbital climate variability during the last glacial period is suggested to have involved a 1500-year pacing cycle, but the expression and spatial distribution of the ~1500-year oscillation during interglacials remains unclear. We generated a multidecade resolution record of alkenone sea surface temperature (SST) in the northwestern Pacific off central Japan during the Holocene. The SST record showed centennial and millennial variability with an amplitude of ~1 °C throughout the entire Holocene. Spectral analysis for SST variation revealed a statistically significant peak with 1470-year periodicity. The SST variation partly correlated with the variations of ice-rafted hematite-stained grain content in North Atlantic sediments. These findings indicate that the mean latitude of the Kuroshio Extension has varied on a 1500-year cycle, and suggest that a climatic link exists between the North Pacific gyre system and the high-latitude North Atlantic thermohaline circulation. The regular pacing at 1500-year intervals seen throughout both the Holocene and the last glacial period suggests that the oscillation was a response to external forcing.

A procedure for the reconstruction of a stochastic stationary temperature field

An iterative procedure is proposed for the reconstruction of a temperature field from a linear stationary heat equation with stochastic coefficients, and stochastic Cauchy data given on a part of the boundary of a bounded domain. In each step, a series of mixed well-posed boundary-value problems are solved for the stochastic heat operator and its adjoint. Well-posedness of these problems is shown to hold and convergence in the mean of the procedure is proved. A discretized version of this procedure, based on a Monte Carlo Galerkin finite-element method, suitable for numerical implementation is discussed. It is demonstrated that the solution to the discretized problem converges to the continuous as the mesh size tends to zero.