Seminar 31/03/17: Modelling of the stratified flow circulation in Greenland fjords

Modelling of the stratified flow circulation in Greenland fjords
Violeta Moloney
Swansea University
Friday 31 March 2017
2pm, Room KE2-008, 2nd Floor, Main Building, DIT Kevin Street

Abstract:

The glacier/fjord/ocean is a unique complex system. The seasonal changes in atmospheric temperatures and constant interaction with ambient waters affect the salinity and temperature balance in the fjords and that has an impact on the glacier melt rate. The subject of investigation is the physical processes in Sermilik Fjord, Greenland.

This research investigates the effects of the subglacial discharge, Coriolis force, wind and tidal forcing on the stratification and circulation in the fjord using the three-dimensional model TELEMAC-3D. Firstly, in order to avoid large horizontal pressure gradients at an open boundary, the matching conditions for temperature and salinity between coastal and fjord domains had to be found before the other forces such as wind, tide and fresh water discharge were applied. Secondly, measured wind speed, tidal levels and velocities, and a representation of the subglacial discharge have been implemented to reproduce an analysis of seasonal conditions. After calibration, the tidal model produced matching results with the measured tides. The tidal analysis shows that the strength and direction of the tidal currents are sensitive to any changes in the width and shape of the domain. The effect of Coriolis force, the wind stress and the tidal propagation has been shown to play an important role on the fjord circulation, and particularly the stratification. However, the wind forcing has the strongest effect on the velocities, temperature and salinity profiles through the water column. The addition of the subglacial discharge has produced the turbulent flow that affects stratification near the glacier front, but it has little effect on the fjord dynamics further away from the source. When all forces are combined the winter conditions have shown the biggest changes in the fjord dynamics, as strong winds drive the circulation in fjord and that in turn delivers the coastal waters to the glacier.