Recent variations in the general circulation as related to glacier retreat in northern Scandinavia

Summary A review is given of the investigations on variations in the general circulation in middle latitudes made byWillett andPetterssen. According toWillett a «high-index» type of circulation pattern with a strong zonal flow has probably caused the recent climatic improvement in the northern latitudes while the «low-index» type with meridional flow would create a cooling off in the same areas. According toPetterssen an other type of «low-index» pattern with a weak zonal flow and strong meridional exchange of air has been the essential cause of the warming up of the northern latitudes in Europe. This implies that the definition of the «low-index» type is not clear and gives rise to misunderstanding. Making use of our experience on glacier retreat in northern Scandinavia it is concluded that thePetterssen type of circulation more probably than the «high-index» type has caused the warming-up in the North Atlantic area from which the retreat of the glaciers has followed.