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 oceansensing instruments was deployed at 80.5N latitude to investigate the flux of seawater from the Arctic Ocean via Nares Strait, the pathway to the west of Greenland. Three-year measurements of current from this experiment provide, for the first time at periods longer than a single season, the seawater flux and its variability via this important pathway. Below 30-m depth the average flux of volume 2003–06 was 0.57±0.09 Sv (1 Sv = 106 m3 s–1) southward over a 38-km wide section reaching 360 m in depth. A linear trend, statistically significant at the 95% confidence level, indicates an increase in the sectionally averaged flow below 30-m depth of 20 ± 10% between 2003 and 2006. The flow is dominated by mixed diurnal and semi-diurnal tidal currents with kinetic energy an order of magnitude larger than that of the subtidal flow. The range of seasonal variation is 30–50% of the long-term mean flow. Variations in flow of daily to monthly period are comparable in magnitude to the average flow. The flow through the cross-section is the net result of a larger southward flux in the deep western two thirds of the strait and a small northward flux within about 5 km of Greenland. The latter is about 5% of the former. Spectral analyses indicates 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 a 33-day period with a phase lag consistent with a frictional response; at 3–7 day period the response is weaker (\u3c30%) with a phase relation suggestive of contributions by both friction and local acceleration