PNWTOX simulations

results - freshwater influence on productivity

freshwater sources

In the Pacific Northwest, the coastal waters are strongly influenced by freshwater inputs from the Strait of Juan de Fuca (fed by the Fraser River and the rivers of Puget Sound) and the Columbia River. These rivers act as a conduit for land-derived nutrients and as a facilitator for entraining ocean-derived nutrients into the coastal euphotic zone. Riverine delivery of nutrients to the coastal ocean may play an important role in winter and spring phytoplankton blooms along the Washington and Oregon coasts. In the Strait of Juan de Fuca, freshwater flow influences estuarine exchange, where deep, high-nutrient waters are upwelled from a submarine canyon and entrained into surface waters. Additionally, the Columbia River plume modifies flow on the shelf and can play a significant role in the retention and transport of phytoplankton communities along the coast.

Figure 1. Freshwater influences

Three snapshots of a passive dye tracer in the Columbia (left) and Fraser (right) rivers to visualize the presence of riverine water from these two different sources on the coast. Results are from a 2005 hindcast simulation where the dye concentration input at the river mouths is 1.

Figure 2. Upwelling

Cross-sections of modeled nitrate along the LAB Line and Line 47N for 28-30 August 2005 during a period of upwelling-favorable winds. The horizontal axis is longitude, z axis is depth. These cross section lines are marked on the map at the right.

Figure 3. Upwelling

Snapshots of modeled surface chlorophyll-a, a proxy for phytoplankton, throughout the year 2005.