Interpretation and representation of the synoptic features in the Iceland-Faeroe-Shetland region

Abstract

The kinematic structure of the sub-inertial fluctuations of measured current and temperature fields from 6 moorings deployed during the June

1989 Icelandic Current Experiment (ICE) cruise is analyzed and interpreted. The field of operations encompassed the Iceland-Faeroe Front (IFF) where high temperature and salinity gradients exist together with mesoscale activity. The currentmeter records were found to be highly contaminated by tidal signals and contain evidence of 2-5 day oscillations (the mesoscale events) embedded in a long period signal of about 10-15 days (synoptic events). The currentmeter data is analyzed for vertical and horizontal coherence. The variability of the IFF is highly energetic and mainly due to baroclinic instability of the frontal flow. Satellite images of the region show that in the vicinity of the front mesoscale features are present with horizontal scales of 15 to 50 km. Ocean currents were calculated from hydrography data with a diagnostic model. The model assumes geostrophic and hydrostatic balances and uses CTD measurements taken in the region during the interval of currentmeter measurements. It is found that the model reproduces the large scale current structures of the region but underestimates the velocity magnitude of the upper ocean. This is attributed to the simplified physics that is incorporated into the formalism.