Modelling the Effects of Holocene Primary Productivity Changes on Organic Carbon Accumulation and Storage in the Barents Sea

Irene Pathirana

"We investigate organic carbon sedimentation patterns linked to surface water primary productivity (PP) changes throughout the Holocene (last 10 ka) on the western Barents shelf between Svalbard and the Norwegian mainland through a multi-proxy geochemical and organic sedimentological approach coupled with organic facies modelling. The Barents Sea is a shallow (mean depth ca. 200 m) Arctic Ocean shelf sea which is partially covered by sea ice in the northeast in the winter. In spring and summer, ice melting leads to a stratified water column and a phytoplankton bloom that moves northward in the marginal ice zone (MIZ) (1). This high productivity regime in the MIZ is reflected in the surface sediments which are enriched in organic carbon (2). We use OF-Mod 3D, an organic facies modelling software developed by SINTEF Petroleum Research, to determine the organic carbon fractions and to reconstruct PP changes throughout the study region. OF-Mod 3D is a predictive, process-based, forward-modelling tool used to calculate organic matter preservation in a 3D grid throughout the modelled domain. We use an extensive set of surface sediment samples to calibrate the model to the present-day situation. Primary productivity is an input parameter in the model. We apply a low background PP and additional PP input in the MIZ region to represent the MIZ processes. The model is calibrated and able to reproduce the present-day regional distribution of the organic carbon fractions, including the high organic carbon content in the MIZ and on the flanks of Spitsbergenbanken. These calibrated results show the applicability of OF-Mod 3D to modelling organic carbon distribution, and show the reliability of the methodology. This is important when simulating ancient deposits for which not all input variables are as well-known as for the present day. We show results from the full 3D model in comparison to core data and discuss the reconstructed PP in the light of PP estimates from surface water modelling in the Barents Sea. We are also able to model the effects an ice-free Barents Sea region could have on organic carbon accumulation in this region. 1. E. Sakshaug, H. R. Skjoldal, 1989, Ambio, 18, 60-67. 2. J. Knies, P. Martinez, 2009, Norw J Geol, 89(1-2), 79-89. "

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013