High-resolution Holocene Paleooceanographic and Paleoclimatic Records from Iceland: Land Sea Correlation

The region around Iceland is highly sensitive climatically because of its location with respect to atmospheric and oceanographic fronts. Detailed studies of foraminiferal assemblages and stable isotopes on marine cores off West and Northwest Iceland reveal major changes in oceanographic conditions since the last Deglaciation and through Holocene. Today the core site on the western shelf of Iceland is bathed by the warm and saline Irminger Current, whereas at the northwestern site the oceanography is controlled by the boundary between the Irminger Current and the cold and fresh E-Greenland Current. We trace the northward migration of the Polar Front bringing Atlantic water to the shelf during Bolling/Allerod, simultaneously as meltwater flooded the shelf area. A rapid return to more Arctic conditions as the Polar Front moved south at the onset of the Younger Dryas. Low surface δ18O shows maximum cooling before 12.3 kyr BP followed by a trend toward warming starting just before the fall of the Vedde ash. Higher sedimentation rates in the northwestern core feature the warming signal as three step appearance. The full establishment of the Irminger Current is distinguished by a high abundance of Boreal species. Maximum Holocene warmth, attributed to a stronger Irminger Current, occurred between 8.3 and 4.7 kyr BP. Over the past 4.3 kyr BP a general cooling trend is seen in the fauna on the West shelf. Superimposed on this cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf. These millennial-scale climate fluctuations through Holocene are also seen in the lacustrine records from South and West Iceland. To compare terrestrial and marine records in a significant way requires an independent correlation tool. Here we use regional scale changes in the geomagnetic field (PSV) preserved within magnetic minerals to synchronize the marine and terrestrial sediment cores. The paleomagnetic correlations are then further tested and confirmed by a complete tephrachronology. The detailed paleomagnetic study and the paleoclimatic data presented here can thus be used for detecting mechanisms and forcing factors behind the reconstructed climate variations and to study leads and lags in the Icelandic oceanographic and climate system.