Ocean Current Observations From Nares Strait to the West of Greenland: Interannual to Tidal Variability and Forcing

During 2003-06, as part of the Arctic Sub-Arctic Ocean Flux (ASOF) experiment, an array of ocean-sensing instruments was deployed at 80.5N latitude to investigate the flux of seawater from the Arctic Ocean via the pathway to the west of northern Greenland. Full-depth current profiles data from this experiment provide, for the first time at periods longer than a single season, the seawater flux and its variability via this important channel through the Canadian Archipelago. The average flux of volume during this three-year period was 0.57±0.09 Sv (1 Sv=106m3s-1) southward over a section 300 m deep and 37 km wide. A linear trend of the along-channel flow, statistically significant at the 95% confidence level, indicates an increase in the volume flux of 20±10% between 2003 and 2006. The flow is, however, dominated by mixed diurnal and semi-diurnal tidal currents with kinetic energy an order of magnitude larger than that of the sub-tidal flow. Seasonal variation is an order of magnitude weaker than the long-term mean flow: the largest southward flow occurs in mid-March when the ice cover is land-fast and the smallest southward flow occurs in November when a mobile ice cover responds directly to wind. Variations in flow of daily to monthly period are comparable in magnitude to the average flow. The net flow over the cross-section is the result of a larger southward flux in the deep main channel occupying the western two thirds of the strait and a northward flux within about 5 km of Greenland. The latter is about 8% of the former. Spectral analyses indicated that the cross-channel pressure gradient is highly correlated with the sectionally averaged flow consistent with geostrophy. Along-channel pressure gradient explains 70% of the variance at 33-day period with a phase lag consistent with a frictional response; at 3-7 day period the response is weaker (<30%) with a phase relation suggestive of contributions by both friction and local acceleration.