Radiocarbon levels in the Iceland Sea from 25-53 kyr and their link to the Earth's magnetic field intensity.

Abstract

By correlating the climate records and radiocarbon ages of the planktonic foraminifera N. pachyderma(s) of deep-sea core PS2644 from the Iceland Sea with the annual-layer chronology of the GISP2 ice core, we obtained 80 marine (super 14) C calibration points for the interval 11.4-53.3 ka cal BP. Between 27 and 54 ka cal BP the continuous record of (super 14) C/cal age differences reveals three intervals of highly increased (super 14) C concentrations coincident with low values of paleomagnetic field intensity, two of which are attributed to the geomagnetic Mono Lake and Laschamp excursions (33.5-34.5 ka cal BP with maximum 550 per mil marine Delta (super 14) C, and 40.3-41.7 ka cal BP with maximum 1215 per mil marine Delta (super 14) C, respectively). A third maximum (marine Delta (super 14) C: 755 per mil) is observed around 38 ka cal BP and attributed to the geomagnetic intensity minimum following the Laschamp excursion. During all three events the Delta (super 14) C values increase rapidly with maximum values occurring at the end of the respective geomagnetic intensity minimum. During the Mono Lake Event, however, our Delta (super 14) C values seem to underestimate the atmospheric level, if compared to the (super 36) Cl flux measured in the GRIP ice core (Wagner et al. 2000) and other records. As this excursion coincides with a meltwater event in core PS2644, the underestimation is probably caused by an increased planktonic reservoir age. The same effect also occurs from 38.5 to 40 ka cal BP when the meltwater lid of Heinrich Event 4 affected the planktonic record.