Seasonably variable estuarine exchange through inter-connected channels
in the Salish Sea
Abstract
The Salish Sea is a semi-enclosed estuary whose largest basin (Strait of
Georgia) is connected to the north-eastern Pacific Ocean through regions
with tight constructions and sills that cause intense tidal mixing. The
estuarine circulation is complicated through the tidally mixed region
around the San Juan and Gulf Islands (SJGI), which consists of three
different straits: Haro Strait, Rosario Strait, and San Juan Channel.
Haro Strait, as the largest and deepest of the channels, is the dominant
pathway; however, we determine that Rosario Strait also has an important
influence in this region. To examine the differences in water transport
through the different channels, Lagrangian particle tracking simulations
were performed for a 4-year hindcast (from 2018-2022) using the
3-dimensional numerical model SalishSeaCast. While Haro Strait has
southward surface flow and northward deep flow, there is primarily
southward flow at all depths through Rosario Strait and San Juan
Channel. The proportion of the total southward flow through these two
channels is higher from May – October and this increase is attributed
to the influence of both the Fraser River and the river discharge from
Puget Sound. Rosario Strait is the dominant pathway of southward
exchange from the Strait of Georgia to Puget Sound, while the majority
of deep northward flow to the Strait of Georgia is through Haro Strait.