Nontidal Currents

There are many other processes not considered here that give rise to currents that can have magnitudes of the same order as the tidal currents shown in this atlas. Some of these are:

• Local wind forcing. This will depend on the force, direction and duration of the wind. It is not uncommon to see magnitudes of 5 to 15 cm ^. s ^-1.
• Distant meteorological forcing. Even though the Harbour seems calm, distant weather systems can give rise to sea level changes at the mouth of the Harbour influencing the inner Harbour currents to the same degree as the local winds for periods of hours to days .
• Resonance. Halifax Harbour can be rung like a bell from passing weather systems or big waves at the Harbour entrance. The period of this resonant ringing is about 2.1 hours and the currents can be 5 to 10 cm ^.s^-1 [5]. The resonance has been observed to be stronger and more frequent in winter.
• Estuarine circulation. The fresh water flowing out on the surface is compensated for by a deeper saltier flow into the harbour. The currents (5 - 15 cm ^. s^-1) are stronger at times of strong runoff, but are seen at all times of the year [6].