Climatic dependence of the organic matter contributions in the north eastern Norwegian Sea over the last 15,000 years

Abstract

Lipids are used for the evaluation of the different organic matter contributions in the north eastern Norwegian Sea (M23258 site, 75°N, 14°E) over the last 15,000 years. Development of a mass balance model based on the down-core quantification of the C37 alkenones, the odd carbon numbered n-alkanes (Aodd) and the unresolved complex mixture of hydrocarbons (UCM) has allowed three main organic matter inputs involving marine, continental and ancient reworked organic matter to be recognized. The model shows good agreement between measured and reconstructed TOC values. Similarly, a strong parallelism is observed between predicted components such as marine TOC and carbonate content, which was determined independently. Representation of the model results within a time scale based on 15 AMS-14C measurements shows that the main changes in organic matter constituents are coincident with the major climatic events of the last 15,000 years. Thus, the predominance of reworked organic matter is characteristic of Termination Ia (up to 70%), continental organic matter was dominant during the Bølling-Allerød (B-A) and Younger Dryas (YD) periods (about 85%) and a strong increase of marine organic matter occurred in the Holocene (between 50 and 75%). This agreement reflects the main hydrographic changes that determined the deposition of sedimentary materials between 0 and 15 cal ka: ice-rafted detritus from the Barents continental platform, ice-melting waters from the Arctic fluvial system discharging into the Barents Sea and dominance of North Atlantic currents, respectively. In this respect, the high-resolution down-core record resulting from the mass balance and lipid measurements allows for the identification of millennial scale events such as the increase of reworked organic matter at the final retreat of the Barents ice sheet at the end of the deglaciation period (Termination Ib).