The last 18 kyr fluctuations in Norwegian Sea surface conditions and implications for the magnitude of climatic change: Evidence from the North Sea

A combined record of three cores spanning the last 18 kyr from the northern North Sea is investigated for content of benthic and planktonic foraminife ra and stable oxygen isotopes. The paleoenvironmental development through t his time period shows an early deglaciation (18-14.4 ka) and the Younger Dr yas (12.7-11.5 ka) characterized by arctic/ polar conditions and increased ice rafting in the Norwegian Channel. During the Bolling-Allerod period, wa rm sea surface temperature (9 degreesC) conditions similar to present condi tions are inferred, while bottom waters stayed cold (0-1 degreesC) with nor mal salinity. The Bolling-Allerod period is interrupted twice at 13.9-13.6 ka (Older Dryas) and at 13.0-12.8 ka (Inter-Allerod Cooling Period) by redu ctions in sea surface temperatures and increased sea ice cover. The beginni ng of the Holocene period is marked by increases in surface and bottom wate r temperature. Superimposed on the broad climatic changes through the Holoc ene, a series of short-lived oscillations in the ocean circulation are reco rded. The amplitude of these Holocene events appears larger in the early Ho locene (prior to 8 ka) than compared with the remaining part of the Holocen e. This amplification can possibly be attributed to a general increased fre shwater budget in the North Atlantic at this time during the final stages o f the deglaciation of the Laurentide and Scandinavian ice sheets.