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Effects of Global Climate Oscillations on Intermonthly to Interannual Variability of Sea levels along the English Channel Coasts (NW France)

Turki Imen, Massei Nicolas, Laignel Benoit, Shafiei Hassan

Oceanologia

2020

No. 62 (2)

226--242

This work examines the multiscale variability in sea level along the English Channel coasts (NW France) using a wavelet multiresolution decomposition of water level values and climate oscillations in order to gain insights in the connection between the global atmospheric circulation and the local-scale variability of the monthly extreme surges. Changes in surges have exhibited different oscillatory components from the intermonthly (~3-6-months) to the interannual scales (~1.5-years, ~2-4-years, ~5-8-years) with mean explained variances of ~40% and ~25% of the total variability respectively. The correlation between the multiresolution components of surges and 28 exceptional stormy events with different intensities has revealed that energetic events are manifested at all timescales while moderate events are limited to short scales. By considering the two hypotheses of (1) the physical mechanisms of the atmospheric circulation change according to the timescales and (2) their connection with the local variability improves the prediction of the extremes, the multiscale components of the monthly extreme surges have been investigated using four different climate oscillations (Sea Surface Temperature (SST), Sea-Level Pressure (SLP), Zonal Wind (ZW), and North Atlantic Oscillation (NAO)); results show statistically significant correlations with ~3-6-months, ~1.5-years, ~2-4-years, and ~5-8-years, respectively. Such physical links, from global to local scales, have been considered to model the multiscale monthly extreme surges using a time-dependent Generalized Extreme Value (GEV) distribution. The incorporation of the climate information in the GEV parameters has considerably improved the fitting of the different timescales of surges with an explained variance higher than 30%. This improvement exhibits their nonlinear relationship with the large-scale atmospheric circulation.

Early Vistulian climate oscillations in the light of pollen analysis of deposits from Dziadowa Kłoda (Silesian Lowland, Poland)

Kuszell T., Chmal R., Słychan K.

Geological Quarterly

2007

Vol. 51, No 3

319-328

The stratigraphy and palaeogeography of Quaternary deposits under lying the Oleoenica Plain were investigated during mapping of the Syców sheet of the De tailed Geo logical Map of Poland on the scale of 1:50 000. The Oleoenica Plain is part of the southern foreland of the Trzebnica Ridge, the latter representing a frontal moraine of the South and Middle Polish Glaciations. Neopleistocene deposits found at the Dziadowa Kłoda site were analyzed for their pollen content. These lacus trine to swamp deposits represent a continuous and undisturbed sequence spanning the Eemian Interglacial to Brörup Interstadial interval. The Early Vistulian deposits have been the subject of detailed palynological investigations. The reconstructed pattern of vegetation changes has allowed a precise determination of the upper boundary of the last interglacial as well as the recognition of stadial-interstadial horizons. Three climatic oscillations have been noted, corresponding to the Herning and Rederstallstadials and the Brörup Interstadial. In the climatic optimum of the interstadial, dense boreal pine-birch forests accompanied by a minor admixture of alder and spruce were predominant. Cold stadials were dominated by open vegetation with tundra and steppe elements.The pollen sequence from Dziadowa Kłoda is the first site on the Silesian Lowland that shows the first fully developed Early Vistulian warm oscillation that correlates with the Brörup Interstadial. A distinctive feature of this site is a long, continuous pollen sequence of the Eemian passing into deposits of the Vistulian Glaciation in the same profile.