Abstract
Broad embayment, such as some Fjords, can host the generation and
propagation of internal Kelvin waves should the ratio of their
stratification level to shelf-slope width be important. A number of high
latitude fjords fall under that category and were recently investigated
in relation to heat exchange with neighbouring shelf waters. Here, we
report on such a process in a broad, mid-latitude, fjord where the
upper-layer dynamics are dominated by sub-inertial baroclinic motions.
This fjord is of particular interest due to recent development of the
aquaculture industry and to being historical fishing grounds. Using a
fully non-linear, three-dimensional primitive equation numerical model
we show that the large majority of the thermocline vertical fluctuations
(80%) and much of the along-shore currents (50%) can be reproduced
with a flat-bottom assumption, i.e. the Kelvin wave assumption. We use
the model to determine the origin of the process, which is expressed by
upwelling and downwelling disturbances travelling cyclonically around
the bay. We find that the wind generates local and remote, from a large
and deep neighboring bay, responses which travel as forced and freely
propagating long, coastally trapped, internal waves into and around the
fjord. The resulting dynamics within the fjord can therefore be complex,
particularly in the fall season during which nearly continuous and
directionally variable winds occur. Under such forcing conditions and
given the irregularity of the regional coastline, signals combine to
form temporarily and spatially varying responses, enhancing or
diminishing transient upwelling or downwelling and their associated
along-shore current pulses.