Concentration of the tracer nitrate and dissolved oxygen (NO) on the S=33 isohaline in the Arctic. Each dot represents an observation. Higher NO values are associated with water masses originating from the Pacific while lower values originate from the Atlantic Ocean: the dashed red line marks the transition between the two sources. The blue dotted line marks the frontal transition from high to low Pacific water mass fractions when based on nutrient analysis. Credit: Alkier et al., 2019, Figure 3c
Source: Geophysical Research Letters

The accurate distinction of the original source of water masses in the central Arctic basin provides a key indicator as to how the circulation and trends of this climatically important region might be changing. In the past, the Arctic waters of Pacific Ocean origin have been distinguished from those of Atlantic Ocean origin primarily through the distribution of nutrient concentration. For example, high silicate and high phosphate relative to nitrate are generally indicative of Pacific water sources. However, recent changes to sea ice cover within the Arctic have resulted in the local denitrification of waters such that they become geochemically very similar to the Pacific waters. Alkire et al. [2019] demonstrate the utility of the semi-conservative tracer NO (nitrate and dissolved oxygen) to more accurately identify the fronts associated with water mass contributions of Pacific origin (red dashed line in figure) than identification based on traditional tracers (blue dotted lines).

Citation: Alkire, M. B., Rember, R., & Polyakov, I. [2019]. Discrepancy in the identification of the Atlantic/Pacific front in the central Arctic Ocean: NO versus nutrient relationships. Geophysical Research Letters, 46.

—Janet Sprintall, Editor, Geophysical Research Letters

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