A tidally driven fjord-like strait close to an amphidromic region

Abstract. The strait studied in this paper, “Sundalagið Norður”, is the northern part of a narrow body seawater separating two largest islands Faroe Islands (Faroes). It has shallow sills both ends and considerably deeper waters between. South southern end there an amphidromic region for semidiurnal tides so that tidal range much lower south than north it. resulting forcing generates periodically varying inflow across sill, but only manages to cross sill. Combined with large input freshwater, gives fjord-like character. To investigate how character affects circulation within its exchanges outside waters, pilot project was initiated simulate dynamics high-resolution ocean model month. simulations show clearly dominance over freshwater (estuarine) wind on timescales up day. On longer timescales, indicate systematic variations net flows (averaged diurnal period) through upper layers. These long-period flow are forced by sea level differences between generated dominant fortnightly monthly constituents (Mf, MSf, Mm, MSm). Harmonic analysis records from tide gauges located off each demonstrates behaviour not artefact it pronounced effects strait. Not does induce (mainly fortnightly) strait, also estuarine characteristics. According simulations, periods southward flow, typically lasting week, have strait-like almost everywhere. Periods northward contrast, more stronger salinity stratification counter-flow deep layer. This induces difference renewal rate water periods, which important consider human utilization especially local aquaculture plant. combination topographic, characteristics creating these rather unusual, known whether similar systems exist elsewhere, tend be masked may easily overlooked.