Middle to late Holocene paleoproductivity reconstructionsfor the western Barents Sea: a model-data comparison

In this study we focus on late Holocene primary productivity (PP) variability in the western Barents Sea and its response to variable sea ice coverage by combining PP reconstructed from several sediment cores with regional PP trends simulated with a well-constrained organic facies model, OF-Mod 3D. We find that modern production rates reconstructed from buried marine organic matter (“bottom-up”) resemble simulated export production at 50 m water depth inferred from numerical simulations of surface water PP in a 3D ocean model, SINMOD (“top-down”). Paleoproductivity rates in the northern Barents Sea are more variable and generally higher (30–150 gC m−2 year−1) than in the SW Barents Sea region (<75 gC m−2 year−1) throughout the last 6000 years BP. In the SW Barents Sea, PP rates and terrestrial organic matter (TOM) supply remain constantly low indicating present-day-like oceanographic conditions with only marginal influence of sea ice related processes during the last 6000 years BP. PP rates in the northern Barents Sea indicate a shift from stable modern-like conditions prior to 2800 BP to denser, more permanent sea ice coverage along the marginal ice zone (MIZ) between 2800 and 1000 years BP and low PP rates. PP rates increase around 1000 years BP indicating a northward shift of the MIZ and accelerated export towards the seabed. During the last 500 years a pronounced decline in PP rates towards the present day indicates reduced annual duration of the MIZ in the area due to global warming. Our results suggest that a combination of first-year ice and higher PP in a warming pan-Arctic may point to a potential Arctic carbon sink while sea ice is still present.