Fróðskaparrit - 01.01.2005, Page 147

NÝTT INNAN VÍSINDI 2004
145
Hjálmar Hátún
The Faroe Current
Ph.D.-thesis at the University of Bergen, Norway.
The Atlantic inflow is of key importance
for the marine ecology in the Nordic Seas
and for the climate in the countries sur-
rounding these waters. This thesis focuses
on the large inflow branch between Ice-
land and the Faroe Islands, but the inflow
between the Faroes and Scotland is also
discussed.
Comprehensive hydrographic and cur-
rent data, obtained along a north-south
standard section crossing the Faroe Cur-
rent to the north of the Faroes, have been
analyzed. The principal patterns of hydro-
graphic and current variation along this
section were identified. These represent a
pulsation in the near core current veloci-
ties, lateral fluctuations of the current core
and vertical movements of the main pyc-
nocline, which constitutes the sub-surface
signature of the Iceland-Faroe Front in the
region. A connection was found between
the current mode representing the lateral
fluctuations and the hydrographical pattern
linked to the vertical movement of the pyc-
nocline. Daily information on the tempera-
ture and the salinity fields was obtained
from the current field via this relation.
Combining the current data and the ad-
ditional hydrographic information, a rela-
tively accurate volume transport estimate
of the Atlantic inflow could be obtained.
The mean transport for the period July
1997 to June 2001 was estimated to be 3.5
± 0.5 Sv (1 Sv = 106 mV). The eastward
(downstream) current velocities are largest
in March-April, but the spatial coverage
of Atlantic water is also smallest during
this period, resulting in an Atlantic water
transport with only a weak seasonal signal.
Most transport variation was seen at time-
scales between a half and two months,
but a secondary peak in the spectrum was
found at five to seven days. A reversal of
the flow with transport towards the west
was not observed, illustrating the persist-
ency of the Faroe Current. The transport
was not found to be correlated to wind,
wind stress, or sea surface air pressure.
The potential of using sea level gradients
for transport estimation has been examined.
This approach was not found to be viable
unless other monitoring as e.g. seabed
pressure, inverted echo sounders or similar
is conducted concurrently. The possibility
of using the Nansen Center version of the
Miami Isopycnal Coordinate Ocean Model
(MICOM) for transport estimation was
likewise studied. Some of the observed
transport variability is correctly simulated,
but the model is not yet at the stage where
it can replace the current observations. The
relatively expensive current profilers are
thus the only option for reliable transport
estimation at present.
Regular fluctuations with periods be-
tween four and seven days are identified