International audienceConsiderable climatic variability on decadal to millennial timescales has been documented for the past 11,500 years of interglacial climate1, 2, 3. This variability has been particularly pronounced at a frequency of about 1,500 years, with repeated cold intervals in the North Atlantic1, 3. However, there is growing evidence that these oscillations originate from a cluster of different spectral signatures4, ranging from a 2,500-year cycle throughout the period to a 1,000-year cycle during the earliest millennia. Here we present a reappraisal of high-energy estuarine and coastal sedimentary records from the southern coast of the English Channel, and report evidence for five distinct periods during the Holocene when storminess was enhanced during the past 6,500 years. We find that high storm activity occurred periodically with a frequency of about 1,500 years, closely related to cold and windy periods diagnosed earlier1, 2, 3. We show that millennial-scale storm extremes in northern Europe are phase-locked with the period of internal ocean variability in the North Atlantic of about 1,500 years4. However, no consistent correlation emerges between spectral maxima in records of storminess and solar irradiation. We conclude that solar activity changes are unlikely to be a primary forcing mechanism of millennial-scale variability in storminess

New high-quality multibeam and seismic data image the western slope of the Great Bahama Bank and the adjacent fl oor of the Straits of Florida. The extensive survey reveals several unexpected large-and small-scale morphologies. These include bypass areas, channel-leveelobe systems, gullied slopes, and products of slope instabilities at various scales, including long slump scars at the lower slope and mass transport complexes that extend ~30 km into the adjacent basin fl oor. The toe of the slope is irregularly covered with deep-water carbonate mounds. The abundance of the individual morphological features varies from north to south. From 26°00′N to 25°20′N, the slope is dissected by numerous deep canyons that abruptly end southward, where the slope is characterized by a smooth lower portion and small regularly spaced furrows in its upper part. Further south, two long (25-50 km) scars document instability at the lower slope. One of these scars is the source area of a large mass transport complex. In addition to this large-scale feature, several types of gravity-induced sedimentary processes are revealed. Most of the morphologies and inferred processes of this carbonate system are similar to those observed in siliciclastic systems, including mass transport complexes, gravity currents initiated by density cascading, and overspilling channeled turbidity currents. For the fi rst time, a clear asymmetric channel-levee system has been identifi ed along the slope, suggesting similitude in sorting processes between carbonate and siliciclastic systems and enhancing the reservoir-bearing potential of carbonate slopes. Notable differences with siliciclastic systems include: the lack of connection with the shallow and emerged part of the system (i.e., bank top), and the small size of the sedimentary system.

International audienceThe impacts of rapid climate changes during the Holocene are well documented in deep oceanic and lacustrine sediments. Until now, no studies have shown the effects of rapid climate change on tidal successions in coastal wedges formed during the late Holocene transgression. Cores and very high resolution seismic data collected in Mont-Saint-Michel Bay, France, a macrotidal setting, demonstrate that rapid climate changes, with ~1500 year periodicity, are recorded in the sedimentary successions that constitute the late Holocene infill of the bay. The sedimentary expressions of rapid climate changes vary according to the different subenvironments within Mont-Saint-Michel Bay; cycles, a few meters thick, can be correlated throughout the bay, and radiocarbon dating suggests that they have a millennial time scale. The various changes reflect an increase in wave dynamics in association with Bond cold events, possibly in conjunction with long-term (1800 year periodicity) tidal cycle