Oceanic Nitrogen

The Pacific Ocean is the largest source of nitrogen to Puget Sound. The amount of nitrogen entering Puget Sound from the ocean is larger than local sources of nitrogen from wastewater treatment plants, rivers, and other sources combined.
The magnitude and month-to-month variability of oceanic nitrogen sources are determined by larger climatic and oceanic processes, such as Pacific Ocean upwelling, as well as local weather events.
This ocean influx of nitrogen is considered to be part of the ‘baseline’ nitrogen load to the Sound, and it cannot be controlled through local management activities. Local human nitrogen inputs add to this baseline of nitrogen inputs from the ocean.

Net exchange

Ocean water containing nitrogen enters the Salish Sea from the Pacific Ocean through the Strait of Juan de Fuca. This water combines with freshwater within the Sound and leaves the Salish Sea near the surface across this same boundary. On an annual basis, more nitrogen enters than leaves, resulting in a net nitrogen input to the Salish Sea (Mackas and Harrison, 1997), and Puget Sound. The main exchange of oceanic nitrogen to Puget Sound occurs across Admiralty Inlet.
 
The interaction of coastal upwelling, tides, and estuarine circulation govern this exchange of water. Each process varies seasonally or with phases of the moon and determines how well Puget Sound, the Salish Sea, and the ocean, are exchanging water in a process called estuarine circulation.