A Model Study of the Copper River Plume and its Effects on the Northern Gulf of Alaska

• Main Author: Wang, Yuan
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2013
• Subjects: Copper River Delta (Alaska); Alaska; Gulf of (Alaska); Computer simulation; Oceanography; Gulf of Alaska; Montague; glacier
• Online Access: https://digitalcommons.library.umaine.edu/etd/2017; https://digitalcommons.library.umaine.edu/context/etd/article/3052/viewcontent/WangY2013_OCR.pdf

Using a three-level nested Regional Ocean Modeling System coupled with the Carbon, Silicate, Nitrogen Ecosystem model, this study examined the seasonal evolution of the Copper River (CR) plume and how it influences the along- and across-shore transport in the northern Gulf of Alaska (NGoA). A passive tracer was introduced in the model to delineate the growth and decay of the plume and to diagnose the spread of the CR discharge in the shelf, into Prince William Sound (PWS) and offshore. Furthermore, a model experiment with doubled discharge was conducted to investigate potential impacts of accelerated glacier melt in future climate scenarios. The 2010 and 2011 simulation revealed that the upstream (eastward) transport in the NGoA is almost nil. About 60% of the passive tracer released in the CR discharge is transported southwestward on the shelf, while another one third goes into PWS with close to 60% of which exiting PWS to the shelf from Montague Strait. The rest few percent is transported across the shelf break and exported to the GoA basin. The downstream transport and the transport into PWS are regulated by the downwelling- favorable wind, while the offshore transport is related to the accumulation of plume water in the shelf, frontal instability and the Alaskan Stream. The CR plume appears to decay much faster than its formation. It takes weeks for the buoyancy to accumulate so that a bulge forms outside of the CR estuary. If the wind remains calm as in the summer of 2010, the bulge continues growing to trigger frontal instability. These frontal features can interact with the Alaskan Stream to send intense transport pulses across the shelf break. Alternatively as in 2011, a downwelling-favorable wind event in early August (near the peak discharge) accelerates the southwestward coastal current and produces an intense downstream transport event. Both processes result in fast drains of the buoyancy and the plume content, thereby rapid disintegration of the plume in the shelf. The plume in the doubled discharge ...