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Abstract:
Climate change impact studies for the Northwest European Shelf (NWES)
make use of various dynamical downscaling strategies in the experimental
setup of regional ocean circulation models. Projected change signals
from coupled and uncoupled downscalings with different domain sizes and
forcing global and regional models show substantial uncertainty. In this
paper, we investigate influences of the downscaling strategy on
projected changes in the physical and biogeochemical conditions of the
NWES. Our results indicate that uncertainties due to different
downscaling strategies are similar to uncertainties due to the choice of
the parent global model and the downscaling regional model. Downscaled
change signals reveal to depend stronger on the downscaling strategy
than on the model skills in simulating present-day conditions. Uncoupled
downscalings of sea surface temperature (SST) changes are found to be
tightly constrained by the atmospheric forcing. The incorporation of
coupled air-sea interaction, by contrast, allows the regional model
system to develop independently. Changes in salinity show a higher
sensitivity to open lateral boundary conditions and river runoff than to
coupled or uncoupled atmospheric forcings. Dependencies on the
downscaling strategy for changes in SST, salinity, stratification and
circulation collectively affect changes in nutrient import and
biological primary production.
