Abstract
Abstract. The flow of Pacific water to the North Atlantic exerts a globally significant control on nutrient balances between the two ocean basins and strongly influences biological productivity in the northwest Atlantic. Nutrient ratios of nitrate (NO3-) versus phosphate (PO43-) have previously been used to complement salinity characteristics in tracing the distribution of Pacific water in the North Atlantic. We expand on this premise and demonstrate that the fraction of Pacific water as determined by NO3- : PO43- ratios can be quantitatively predicted from the isotopic composition of sub-euphotic nitrate in the northwest Atlantic. Our linear model thus provides a critically important framework for interpreting δ15N signatures incorporated into both modern marine biomass and organic material in historical and paleoceanographic archives along the northwest Atlantic margin.
Highlights
Pacific water from the Bering Strait constitutes a major fraction of the polar outflow to the northwest Atlantic Ocean (McLaughlin et al, 1996; Jones et al, 2003; Aksenov et al, 2010)
We evaluate the preservation of δ15NNO3 and δ18ONO3 signatures during southward advection of Pacific water from the Arctic Archipelago to the Labrador Shelf and present a linear relationship between δ15NNO3 and Fraction Pacific water (fPW) for the northwest Atlantic margin
The 25 stations that were sampled for this study are distributed along this net transport pathway of Pacific water and are ideally situated for investigating the distribution of NO−3 isotopic ratios with respect to fPW
Summary
Pacific water from the Bering Strait constitutes a major fraction of the polar outflow to the northwest Atlantic Ocean (McLaughlin et al, 1996; Jones et al, 2003; Aksenov et al, 2010). Pacific water has relatively high nutrient concentrations (Macdonald et al, 2010). These nutrients support high productivity on the Bering and Chukchi shelves (Arrigo and van Dijken, 2011), which in turn fuels high rates of sedimentary denitrification both in the shelf regions and along the Bering continental slope (Devol et al, 1997; Lehmann et al, 2005, 2007; Chang and Devol, 2009; Granger et al, 2011; Brown et al, 2015). The excess PO34− supports N2 fixation in the Atlantic, thereby helping to balance the global oceanic nitrogen budget (Yamamoto-Kawai et al, 2006)
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