Downscaling future climate scenarios for the North Sea

Bjørn Ådlandsvik
Institute of Marine Research, Bergen, Norway

The ROMS ocean model is used in the North Sea to dynamically downscale
climate scenarios from the global coupled ocean-atmosphere model Bergen Climate Model (BCM). The objective is to produce input to marine climate impact studies.

As a validation, a hindcast run for 6 years has been performed with atmospheric forcing from NCAR/NCEP and climatology at the lateral boundaries. The Flow Relaxation Scheme (FRS) is used as the lateral boundary scheme, while a flux-based parameterization is used for the atmosphere. The model output is compared with hydrographic sections and time series from costal stations. The results show that the model is able to reproduce much of the annual and interannual climate variability, even with relatively coarse input.

For the actual downscaling, both atmospheric and lateral boundary forcing are taken from the BCM model. This one-way nesting approach works, in that the region model provides increased regional details while staying consistent with the global model. In particular, the Norwegian Coastal Current, which is absent in the global model, is created within the regional domain.