Bridging the low nitrogen Pacific with the high nitrogen Atlantic using Arctic N2/Ar and N* measurements

The Pacific and Atlantic Oceans can easily be considered opposites with regards to their role in the marine nitrogen cycle. The Atlantic Ocean acts as a net source of fixed nitrogen, while the Pacific Ocean acts as a net sink. The Arctic Ocean allows Pacific water to flow across several major denitrifying shelves and into the North Atlantic. We present new N₂/Ar and N* measurements from the subarctic North Pacific, Beaufort Sea, Canadian Archipelago, and Labrador Sea focusing on the Pacific water layer. N₂/Ar and N* work well together as they both describe the net state of the nitrogen cycle in a water mass, but they approach the question from opposite sides of the cycle and have different inherent sources of error. N₂/Ar considers the saturation of N₂ gas in comparison with a physical proxy, and is increased by the addition of N₂ by fixed nitrogen removal processes. The primary concerns with this tracer are the variabilities caused by air-sea gas exchange, and the difficulty of measuring it. As a result, the N₂/Ar data presented here are the first measurements of their kind, to our knowledge, from the Arctic. N* is easy to measure and focuses on fixed nitrogen availability in comparison with phosphate availability. Its primary downside is that it can be affected by variations in the Redfield ratio and therefore is not always an accurate proxy for the net state of the nitrogen cycle.This study presents new data from two complimentary methods describing the role of the Arctic Ocean in the global nitrogen cycle.