The Arctic Ocean carbon sink

G.A Macgilchrist,A.C Naveira Garabato,T Tsubouchi,S Bacon,S Torres-Valdés,K Azetsu-Scott

doi:10.1016/j.dsr.2014.01.002

G.A Macgilchrist, A.C Naveira Garabato + Show 4 more

Open Access

https://doi.org/10.1016/j.dsr.2014.01.002

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Abstract

We present observation based estimates of the transport of dissolved inorganic carbon (DIC) across the four main Arctic Ocean gateways (Davis Strait, Fram Strait, Barents Sea Opening and Bering Strait). Combining a recently derived velocity field at these boundaries with measurements of DIC, we calculated a net summertime pan-Arctic export of 231±49TgCyr−1. On an annual basis, we estimate that at least 166±60TgCyr−1 of this is due to uptake of CO2 from the atmosphere, although time-dependent changes in carbon storage are not quantified. To further understand the region's role as a carbon sink, we calculated the volume-conserved net DIC transport from beneath a prescribed mixed layer depth of 50m, referred to as ‘interior transport’, revealing an export of 61±23TgCyr−1. Applying a carbon framework to infer the sources of interior transport implied that this export is primarily due to the sinking and remineralisation of organic matter, highlighting the importance of the biological pump. Furthermore, we qualitatively show that the present day Arctic Ocean is accumulating anthropogenic carbon beneath the mixed layer, imported in Atlantic Water.

Highlights

The fate of the Arctic Ocean carbon cycle in the face of rapid climate change is of global importance
Transports across the main Arctic Ocean gateways are derived by combining a velocity field with measurements of dissolved inorganic carbon (DIC)
It is likely that inflowing waters would have a similar degree of undersaturation as those in the outflows we identify, since many of them were ventilated in similar regions, resulting in a lower net effect on the transport of the components than that derived by our calculations

Summary

Introduction

The fate of the Arctic Ocean carbon cycle in the face of rapid climate change is of global importance. High levels of primary production over extensive shelf seas (Fransson et al, 2001; Kaltin and Anderson, 2005), surface water cooling (Kaltin et al, 2002; Murata and Takizawa, 2003), and sea–ice dynamics (Anderson et al, 2004; Rysgaard et al, 2007; Else et al, 2011) have all been observed to induce locally significant CO2 uptake These processes are already undergoing measurable change as a consequence of regional warming (Bates et al, 2006; Arrigo et al, 2008; Lalande et al, 2009a; Cai et al, 2010; Brown and Arrigo, 2012), while further changes such as greater wind-induced mixing (Mathis et al, 2012) and higher inputs of terrigenous organic matter (McGuire et al, 2009) perturb the region0s carbon cycle in unquantified ways.

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