Key personnel and responsibilities:
Bjørn Ådlandsvik (IMR):
Principal investigator, regional
high resolution modelling.
Harald Loeng (IMR): Field work in Bjørnøyrenna, scientific
links to ASOF.
Ilker Fer (Bjerknes): Field work in Storfjordrenna, plume physics including
Trond Dokken and Eystein Jansen (Bjerknes): Sediment interaction and isotope
Svein Østerhus (Bjerknes): Moorings, scientific links to Greenland-Scotland
Tor Eldevik (NERSC): Very high resolution outflow modelling.
Field work 2003-2006: Trawl-proof ADCPs will be deployed in Storfjordrenna
and Bjørnøyrenna, recovered and redeployed, in order to
provide near continuous time series of cold outflows. Ship-mounted ADCP
will add information on the ambient currents. Samples for oxygen and carbon
isotope studies will be collected in conjunction with CTD surveys. The
nature of intermittency and turbulent mixing within the overflow will
be resolved using a profiling microstructure measuring system (to be purchased).
Similar measurements will take place in both outflows. Personnel from
Bjerknes will take part in cruises organized by IMR and vice versa.
Modelling: The regional modelling will use the ice-ocean model
(ROMS) focussing on flow of dense water from the shelf to deep water.
High resolution atmospheric forcing fields to be produced in WP2
will be used. The effects of topography on mixing will be examined through
idealized very high-resolution experiments with the MITgcm (Marshall et
al., 1997). Parameter studies of the topographic drag based on non-resolved
bottom-roughness statistics will be performed. The established parameterizations
will be used in the ROMS and the MITgcm models that will subsequently
be used to simulate the outflow of dense bottom water from the two study
Discussion, description and motivation:
Bottom boundary layers through which dense overflows contribute to the
world ocean circulation are poorly represented in large scale models.
A large group of today's state-of-the-art ocean models systematically
underestimates the cascade, and an improved parameterization of topographic
effects is desirable. Recent profiling of the Storfjordrenna outflow (Fer
et al., 2002) has demonstrated an internal two-layer structure with implications
for the understanding of entrainment and mixing. Detailed structural analysis
and long term measurements are required.
Most of the dense water produced in the central Barents Sea leaves the
Barents Sea via the northern part of Bjørnøyrenna south
of Bjørnøya. As the outflow may be episodic, it is desirable
to monitor the outflow for several years. The outflow of Arctic water
south of Bjørnøya was not successfully measured during VEINS
because the moorings twice were taken by fishing vessels. Also, a mooring
in Storfjordrenna deployed during NOClim
phase I was lost due to trawling. It is therefore necessary to use
trawl proof bottom mounted ADCPs of the same type that have been used
with great success during the WOCE experiment and later in the Faroe-Shetland
Channel. The EU-funded ASOF-N project measures currents in the deepest
part of Bjørnøyrenna and southwards. ADCP measurements from
the slope will be an important contribution both to the EU-project and
to the international ASOF programme.
High precision temperature and pressure will also be recorded at the ADCP
Ongoing projects at NERSC aiming at better turbulence modeling in boundary
layers will underpin activities proposed here. Other activities like the
planned principal module 2 in RegClim
phase III, focussing on downscaling and Atlantic inflow, will benefit
from this work package by improved handling of the export of dense water
from the Barents Sea in the ROMS model.
Fer, I., R. Skogseth, P.M. Haugan, and P. Jaccard. 2002. Observations
of the Storfjord outflow. submitted to Deep-Sea Res. Part I.
Marshall, J., C. Hill, L. Perelman, and A. Adcroft, 1997: Hydrostatic,
quasi-hydrostatic, and nonhydrostatic ocean modelling. J. Geophys. Res.,
102, C3, 5733-5752.