Geomagnetic field intensity variations in Western Europe over the past 1100 years

International audienceTen archeointensity results have been obtained from brick and ceramic fragments collected in France and precisely dated to between the tenth and eighteenth centuries. Intensity experiments were performed using the Triaxe protocol taking into account cooling rate and thermoremanent magnetization anisotropy effects. Together with our previous results from France and Belgium, we computed a geomagnetic field intensity variation curve for Western Europe covering the past 1100 years. This curve is characterized by a general decreasing trend at the millennial timescale punctuated by three short intensity peaks, during the twelfth century, around 1350–1400 AD and $1600 AD. A similar evolution but with smoother variations due to data scatter is also observed in Western Europe and to a lesser extent in Eastern Europe when all available archeointensity data fulfilling quality criteria are used. Comparison of our archeointensity variation curve with the climatic record derived from fluctuations in length of the Swiss glaciers shows a good temporal concordance between all geomagnetic field intensity maxima detected in Western Europe over the past millennium and colder episodes. A comparison is further discussed between these intensity maxima and episodes of low rates of 14 C production. A common pattern of variations between both records is recognized between the middle of the tenth and of the beginning of eighteenth centuries. If significant, such coincidences suggest a dual geomagnetic and solar origin for the century-scale climate and radionuclide production variations during at least the past millennium