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

Irene Pathirana,Maarten Felix,Jochen Knies,Ute Mann,Ingrid Ellingsen

doi:10.1007/s41063-015-0002-z

Irene Pathirana, Maarten Felix + Show 3 more

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https://doi.org/10.1007/s41063-015-0002-z

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Abstract

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.

Highlights

The recent decline in Arctic sea ice cover has been attributed to numerous factors including Arctic temperature rise, changes in atmospheric circulation patterns, and enhanced warm water advection
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 (‘‘bottomup’’) resemble simulated export production at 50 m water depth inferred from numerical simulations of surface water PP in a 3D ocean model, simulated with a 3D ocean model (SINMOD) (‘‘top-down’’)

Summary

Introduction

The recent decline in Arctic sea ice cover has been attributed to numerous factors including Arctic temperature rise, changes in atmospheric circulation patterns, and enhanced warm water advection Primary production refers to the generation of organic carbon through photosynthesis by algae in the upper water column and is generally light and nutrient limited New production is production based on allochthonous nutrients from outside the euphotic zone (e.g. from upwelling, admixture of nutrient-rich deep water, windinduced mixing). The flux of organic matter that sinks out of the euphotic zone and is potentially available for burial in the sediments is referred to as export production and is limited by the amount of new production. Primary production reconstructed from sedimentary parameters (‘‘bottom-up’’) refers usually to total primary production at the sea surface. Primary production from biological and oceanographic parameters (‘‘top-down’’) is usually presented for the euphotic zone whose depth varies with season and follows the halocline/pycnocline (deep winter layer, shallow spring and summer layer)

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