Existing reconstructions of the winter North Atlantic Oscillation (WNAO) are based on terrestrial proxies and historical documents. No direct high-resolution, long-term records from marine settings are available for this major climate-dictating phenomenon, which severely affects a variety of economic aspects of our society. Here we present a 245 yr proxy WNAO index based on shells of the long-lived marine bivalve mollusk Arctica islandica. Variations in annual rates of shell growth are positively correlated with WNAO-related changes in the food supply. Maximum amplitudes in frequency bands of 7-9 and 5-7 yr fall exactly within the range of instrumental and other proxy WNAO indices. These estimates were obtained for specimens collected live, 2000 km apart, in the central North Sea and on the Norwegian Shelf. Hence, the WNAO influences hydrographic regimes of large regions of the ocean. Our study demonstrates that A. islandica can reliably reconstruct WNAO dynamics for time intervals and regions without instrumental records. Our new tool functions as a proxy for the WNAO index prior to the twentieth-century greenhouse forcing and has the potential to further validate other proxy-based WNAO records.

Geological mapping, definition of facies distributions and reconstruction of platform-interior growth geometries of the Messinian Cariatiz carbonate platform (Sorbas basin, South Spain), were performed to evaluate the controlling factors in platform growth and to test a 3-D computer simulation program. For the simulation with the program REPRO, five platform-related facies were modelled: (1) the reef crest facies by the numerical solution of a Fisher equation; (2) the lagoonal facies by a function of water depth-dependent carbonate production; (3) the proximal and middle slope facies (breccia and block facies, calcarenite facies) by a subroutine simulating gravity-driven particle export from the reef crest; (4) a distal slope; and (5) a basinal facies by a pelagic rain function. Development of a fan delta conglomeratic system is simulated by using a siliciclastic point source and gravity-driven particle redistribution. A best fit between the observed platform growth geometries and modelling results is achieved by assuming that high-frequency sea-level changes superimposed onto a longer term sea-level fall controlled platform growth. For the modelling, a relative sea-level curve was reconstructed, which is based on a deep-sea benthic foraminiferal stable oxygen isotope record at ODP Site 926 with a 45 m eustatic sea-level fall, and a tectonic uplift component of 20 m. The consistency of 3-D simulation results is corroborated by the coral growth rates provided by the Fisher-equation subroutine. These rates of 2-8 mm year )1 compare well to the coral growth rates in Recent fringing reefs. We propose that during the early stage of platform evolution the high-frequency fluctuations were obliquity-modulated precessional cycles, whereas precessional cycles control later stages of platform growth. REPRO provides a separate visualization of the different facies bodies as a function of time and space, showing the intrinsic pattern of facies distribution in the platform. This is the result of a combination of platform growth and syndepositional subaerial erosion. For example, only the youngest stages of reef framework facies in the development of the Cariatiz carbonate platform are preserved.