Downscaling Future Climate Scenarios

for the North Sea

2006 ROMS/TOMS Workshop, Alcalá de Henares, 6-8 November

Bjørn Ådlandsvik

Institute of Marine Research and

Bjerknes Centre for Climate Research

Contents

Background

Model tools

Analysis of control run

Preliminary results from climate projection

Conclusions

Motivation

Norway's two largest export industries,

petroleum activity and fisheries, are based on

the continental shelves and are heavily

influenced by climate.

It is therefore important to develop future

climate scenarios for shelf sea climate.

Global ocean models are not yet adequate for

shelf sea dynamics; lack of resolution and/or

physics

Dynamical downscaling

Force a shelf sea model with atmospheric input

and lateral boundary conditions from an

AOGCM.

Control run: CMIP 20C3M, (1970-1999)

Future scenario: SRES A1B, (2070-2099)

Bergen Climate Model (BCM)

Atmospheric model: ARPEGE

Ocean Model: MICOM

Coupler: OASIS

One of four European models in IPCC AR4

Reference: Furevik et al., 2003

Model domain

Model setup Atmospheric forcing

Daily averaged BCM surface fluxes

Ocean lateral boundary forcing

Monthly averaged BCM fields

8 tidal constituents

Boundary scheme: FRS + Flather

Fresh water

Climatological run-off modulated by BCM precipitation

Baltic = large river, salinity = 18

Relaxation of Sea Surface Salinity towards BCM

Model setup Atmospheric forcing

Daily averaged BCM surface fluxes

Ocean lateral boundary forcing

Monthly averaged BCM fields

8 tidal constituents

Boundary scheme: FRS + Flather

Fresh water

Climatological run-off modulated by BCM precipitation

Baltic = large river, salinity = 18

Relaxation of Sea Surface Salinity towards BCM

Sea surface temperature average for March 1978

BCM ROMS Climatology

Sea surface salinityaveraged over August 1978

BCM ROMS Climatology

Volume averaged temperature

Averaged sea surface temperature

Temperature – northern North Sea

Volume averaged salinity

Averaged sea surface salinity

Salinity – northern North Sea

Important climate process transporting heat and

salt into the North Sea

Important climate variable for ecological effects

as it controls import of nutrients and

zooplankton from the Norwegian Sea

To high degree controlled by regional wind field

Atlantic Inflow to the North Sea

Atlantic inflow

Results from downscaling of the

A1B scenario

Integrated temperature scenario

1972-95 vs. 2072-95

Downscaled inflow to the North Sea

20C3M vs. A1B

Conclusions I

BCM does a good job with integrated values for

the North Sea

Some problems due to low resolution but also

isopycnal coordinates on shallow shelf sea.

Downscaling works technically, with a factor ten

in resolution.

Conclusions II Downscaling provides added value by

improving the BCM results where most needed

Improved regional details, incl. Coastal Current

Improved Atlantic Inflow

Improved winter temperature

Improved vertical structure, incl. surface salinity:

Conclusions III

Future scenario:

Warming of the North Sea, maximum in winter

Yearly mean: BCM +1.0°C, ROMS +1.4°C

Increasing Atlantic Inflow,

max increase in August

Yearly mean: +0.2 Sv = +15 %