The Increase of Particle Flux in the Deep Canada Basin: Provenance, Resilience and Implications
Arctic Research Initiative
2010 Funded Project
It has been predicted that anthropogenically-driven climate change will have far more rapid and amplified consequences for the Arctic relative to other regions (IPCC, 2001; 2007), and there is compelling evidence that marked changes are indeed already underway. Two of the most blatant manifestations of this change are a reduction in sea-ice cover and destabilization of permafrost soils, both of which will likely alter the Arctic carbon cycle, including the carbon cycling in the Arctic Ocean. In anticipation of these changes, we incorporated sediment traps into moorings supported through an existing NSF-sponsored physical oceanography observation program in the central Canada Basin. A major objective was to test our hypothesis that the central Arctic Ocean is poised for an invigoration of the biological pump. Examination of the most recent samples collected during Aug 2008-Aug 2009 indicated a 2-fold increase in annual particle flux over prior years (2004-5; 2007-8), with the emergence of a new period of mass flux during the late summer. This increased particle flux delivered to the deep basin may have been triggered by an activation of the biological pump fueled by increased surface ocean productivity, consistent with our hypothesis, but there are alternative explanations. We also do not know if this change in behavior truly represents a shift in the Arctic Ocean carbon cycle. Our ARI funding request focuses on 2 objectives regarding the functionality of the Arctic Ocean carbon pump that will fill looming information crucial for assessing future change, and will provide important leverage for future federally-funded in-depth investigations. Specifically, we seek to determine the origin of the summer flux maximum and to evaluate whether the increased fluxes represents a shift or trend, or a transient feature. We propose to:
1. Collect 2 additional years of sediment trap samples (2010-2011; 2011-2012) in order to establish whether the observed increase in particle flux in 2008-9 is a resilient feature.
The additional time-series samples will provide crucial data for assessing whether there has been a shift in the behavior of the biological pump.
2. Explore new geochemical tracers for assessing the provenance of margin-derived particulate matter intercepted in the deep Canada Basin.
In order to establish the provenance of laterally transported material we propose to exploit anticipated differences in the Nd isotopic composition of particles emanating from the dominant terrestrial source (the Mackenzie River) versus those entering the basin via the Chukchi Sea. The timing and outcome of the WHOI-ARI call for proposals is such that, if successful, we will be able to install sediment traps this coming field season (Sept 2010) in order to insure only a l-year gap in the particle flux time-series and to extend the sediment trap study for a further 2 years (until 2012). In addition, we will be able to assess the Nd isotope approach using the sediment trap samples that are already in hand. We plan to use findings from our current NSF project, together with the acquisition of new time-series particle flux samples, and a successful demonstration of the utility of Nd isotopes as a particle provenance tracer in order to justify additional support from NSF-OPP in order to build upon and sustain biogeochemical flux studies in the Arctic Ocean.