Abrupt Climatic Changes During Younger Dryas in the NE Nordic Seas

New, detailed stratigraphical analyses, from sediment core JM99-1200, based on the planktic foraminiferal fauna, oxygen isotopic measurements, the content of ice rafted debris and the relative proportions of marine organic carbon and biogenic carbonate have been carried out. The aim is to reconstruct abrupt climatic variability during the Younger Dryas (YD) and during the Allerod (AL)/YD and YD/Preboreal (PBO) - transitions to discuss the causes of the abrupt climatic changes. The core is located in a glacial trough, Andfjorden, northern Norway at 476m water depth. This is an open marine location, which can provide us with a high resolution of climate records due to high sedimentation rates. The core site is influenced by two watermasses. The relatively warm Atlantic Water from the North Atlantic Current and the less saline coastal water from the Norwegian Coastal Current. The chronology of the core is based on seven AMS 14C datings performed on macrofossils. The AMS datings have been calibrated to calendar years by using INTCAL 98. The sedimentationrate in YD is calculated by linear interpolation between the dated levels. This is implying an average of eight years/centimeter. Sea surface temperatures (SST) were calculated by using the SIMMAX method developed by Plaumann et al., (1996) based on the modern analogue technique. The estimated SST varies from 1.5 to 10 degrees celcius and the duration of a production low during Younger Dryas is about 1200 years, which correlates very good with the chronology of the Greenland icecores. It is cold during YD except in two levels in the early part of the period which shows warming peaks of 8 degrees celcius. The AL/YD transition last about 30 yr. with a temperature change of 3.5 degrees celcius. The transition YD/PBO is decadal with a temperature change of 2 degrees celcius. The planktic foraminiferas correlates also well to variations in temperatures from Greenland ice core. Variable inflow of Atlantic water masses can be a controlling mechanism in changes of the climate in the investigated area.