Abdelfettah Sifeddine

Coastal cooling and increased productivity in the main upwelling zone off Peru since the mid-twentieth century

[1]xa0We reconstructed a high-resolution, alkenone-based sea surface temperature (SST) record spanning the last ca. 150 years, from a sediment core retrieved within the main upwelling zone off Peru. A conspicuous SST decline is evidenced since the 1950s despite interdecadal SST variability. Instrumental SST data and reanalysis of ECMWF ERA 40 winds suggest that the recent coastal cooling corresponds mainly to an intensification of alongshore winds and associated increase of upwelling in spring. Consistently, both proxy and instrumental data evidence increased productivity in phase with the SST cooling. Our data expand on previous reports on recent SST cooling in other Eastern Boundary upwelling systems and support scenarios that relate coastal upwelling intensification to global warming. Yet, further investigations are needed to assess the role of different mechanisms and forcings (enhanced local winds vs. spin-up of the South Pacific High Pressure cell).

South Tropical Atlantic anti-phase response to Holocene Bond Events

Records of the climatic impacts of the North Atlantic Bond cycles over the subtropical Southern Hemisphere re-main scarce, and their mechanism is a topic of active discussion. We present here an alkenone-based reconstruct-ed sea surface temperature (SST) of a sediment core retrieved from the Brazilian Southwestern Tropical Atlantic (SWTA), Rio de Janeiro, together with a sediment SST record from the Cariaco Basin. The sediment cores span the period 2,100 B.P. – 11,100 B.P. Morlet-wavelet analysis detected marked periodic signals of ~ 0.8, ~ 1.7 and ~2.2 kyr, very similar and with comparable phases to the hematite-stained-grain time series from the Northern North Atlantic in which the cyclic pattern was recognized as Bond cycles. Our result corroborates the modeled surface ocean anti-phase thermal relation between the North and the South Atlantic. We attribute this behavior to the slowing of the Atlantic Meridional Overturning Circulation. The relative SST warming at Rio de Janeiro and the relative cooling at Cariaco were comparatively more pronounced during the early Holocene (from 11 to 5 kyr B.P.) than in more recent time.

Assessment of Climate and Land Use Changes: Impacts on Groundwater Resources in the Souss-Massa River Basin

This work investigates the current climate situation in Souss-Massa river basin (southwestern Morocco) and the impacts of climate change and land use on groundwater resources in Morocco. The annual rainfall amount ranges from 100 mm in the plains to 600 mm in the High Atlas Mountains. However, climate data indicate an overall decrease of precipitation during the three last decades, coupled with an increase of temperature. This recent climate situation, faced with growing population and increasing water demands, results in depletion of surface and subsurface water resources. Indeed, recurrent droughts and decreasing recharge of aquifers affect groundwater levels. Moreover, the overexploitation of groundwater resources explains the witnessed water crisis in the study area, which is predicted to be particularly more affected by climate change in the future. The depletion of groundwater level induced by limited recharge and overexploitation has induced degradation of water quality in the Souss-Massa plain aquifer. The climatic change effect coupled with the pressure of human activities manifested in the intensification of agricultural activities using fertilizers highly affects the water quality with high nitrate contents.