Abstract. The flow regimes of glacier-fed rivers are sensitive to climate change due to
strong climate–cryosphere–hydrosphere interactions. Previous modelling
studies have projected changes in annual and seasonal flow magnitude but
neglect other changes in river flow regime that also have socio-economic and
environmental impacts. This study employs a signature-based analysis of
climate change impacts on the river flow regime for the deglaciating Virkisá
river basin in southern Iceland. Twenty-five metrics (signatures) are derived from
21st century projections of river flow time series to evaluate changes in
different characteristics (magnitude, timing and variability) of river flow
regime over sub-daily to decadal timescales. The projections are produced by
a model chain that links numerical models of climate and glacio-hydrology.
Five components of the model chain are perturbed to represent their
uncertainty including the emission scenario, numerical climate model,
downscaling procedure, snow/ice melt model and runoff-routing model. The
results show that the magnitude, timing and variability of glacier-fed river
flows over a range of timescales will change in response to climate change.
For most signatures there is high confidence in the direction of change, but
the magnitude is uncertain. A decomposition of the projection uncertainties
using analysis of variance (ANOVA) shows that all five perturbed model chain
components contribute to projection uncertainty, but their relative
contributions vary across the signatures of river flow. For example, the
numerical climate model is the dominant source of uncertainty for projections
of high-magnitude, quick-release flows, while the runoff-routing model is
most important for signatures related to low-magnitude, slow-release flows.
The emission scenario dominates mean monthly flow projection uncertainty, but
during the transition from the cold to melt season (April and May) the
snow/ice melt model contributes up to 23 % of projection uncertainty.
Signature-based decompositions of projection uncertainty can be used to
better design impact studies to provide more robust projections.
The river flow regime assessment model of bridge condition rating for preventive maintenance program
