Climate development and its effect on the North Sea environment during the Late Holocene

Abstract

In this study, the climate development of the Late Holocene as well as effects on the environment within the North Sea region were investigated in the two main accumulation areas of the North Sea: the Helgoland mud area (German Bight) and the Skagerrak. Sediment cores from either area served to reconstruct the Late-Holocene development within the North Sea area. The methods used included analyses on grain-size distribution, stable isotopes and foraminifera. In the geological past primarily natural components were forcing climate change. As one of the most important natural processes affecting the marine environment of the southern North Sea the storm-flood activity is considered. Albeit, the disintegration of the island of Helgoland seems to play a key role in the earlier depositional history. From measured sea-surface temperature and salinity (SSS) data we were able to evaluate and calibrate a stable oxygen isotope (d18O) record of a sediment core from the Helgoland mud area. The analyses reveal a dependence of the d18O signal on SSS, a parameter which is mainly driven by the Elbe discharge. Since the d18O series is covering the previous 800 years, a reconstruction of the parameters salinity and discharge further back in time became possible as well. An increased freshwater input via the Elbe River is a consequence of relatively higher precipitation rates in the Elbe catchment area. The variation of precipitation in Central Europe is thus also mirrored in the Helgoland isotope data. The onshore precipitation pattern also appears to be displayed in the sediments of the Skagerrak. There, relatively cool climatic periods are characterized by high productivity, which may have resulted from pronounced precipitation supplying nutrients via the main rivers of Northern and Central Europe into this area. To investigate this coherence, stable oxygen and carbon isotopes were analyzed in addition to benthic and planktonic foraminifera data.