The characteristics and trends of observed river discharge into the Hudson, James, and Ungava Bays (HJUBs) for the period 1964–2000 are investigated. Forty-two rivers with outlets into these bays contribute on average 714 km3 yr−1 [= 0.023 Sv (1 Sv ≡ 106 m3 s−1)] of freshwater to high-latitude oceans. For the system as a whole, discharge attains an annual peak of 4.2 km3 day−1 on average in mid-June, whereas the minimum of 0.68 km3 day−1 occurs on average during the last week of March. The Nelson River contributes as much as 34% of the daily discharge for the entire system during winter but diminishes in relative importance during spring and summer. Runoff rates per contributing area are highest (lowest) on the eastern (western) shores of the Hudson and James Bays. Linear trend analyses reveal decreasing discharge over the 37-yr period in 36 out of the 42 rivers. By 2000, the total annual freshwater discharge into HJUBs diminished by 96 km3 (−13%) from its value in 1964, equivalent to a reduction...

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Characteristics and Trends of River Discharge into Hudson, James, and Ungava Bays, 1964–2000

Plumes of buoyant water produced by inflow from rivers and estuaries are common on the continental shelf. Typically they turn anticyclonically to flow alongshelf as buoyancy-driven coastal currents. During this passage, mixing with ambient shelf water gradually erodes the plume buoyancy so that its alongshelf penetration is finite. This paper addresses the extent of this penetration and how it is determined by fundamental dimensionless flow parameters. A three-dimensional numerical model is applied to an idealized flow regime. Ambient shelf conditions include tidal motion, but neither wind stress nor ambient alongshelf current. The alongshelf extent of penetration is evaluated after the plume reaches a stationary condition downshelf. A total of 66 model experiments are conducted, including variations in buoyant source and ambient shelf properties. Five dimensionless parameters determine the alongshelf and across-shelf penetration, the latter the coastal current width. The most critical of these i...

Penetration of Buoyant Coastal Discharge onto the Continental Shelf: A Numerical Model Experiment

This study describes the first year round observations of the outflow from Hudson Strait as obtained from a moored array deployed mid-strait from August 2004–2005, and from a high-resolution hydrographic section conducted in September 2005. The outflow has the structure of a buoyant boundary current spread across the sloping topography of its southern edge. The variability in the flow is dominated by the extreme semi-diurnal tides and by vigorous, mostly barotropic, fluctuations over several days. The fresh water export is seasonally concentrated between June and March with a peak in November–December, consistent with the seasonal riverine input and sea-ice melt. It is highly variable on weekly timescales because of synchronous salinity and velocity variations. The estimated volume and liquid fresh water transports during 2004–2005 are, respectively, of 1–1.2 Sv and 78–88 (28–29) mSv relative to a salinity of 34.8 (33). This implies that the Hudson Strait outflow accounts for approximately 15% of the volume and 50% of the fresh water transports of the Labrador Current. This larger than previously estimated contribution is partially due to the recycling, within the Hudson Bay System, of relatively fresh waters that flow into Hudson Strait, along its northern edge. It is speculated that the source of this inflow is the outflow from Davis Strait.

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The outflow from Hudson Strait and its contribution to the Labrador Current

REE in the Great Whale River estuary, northwest Quebec

The present study examines sources of the interannual variability in salinity on the Newfoundland continental shelf observed in a 40‐year time series from an oceanographic station known as Station 27. Specifically, we investigate, through lag‐correlation analysis, the a priori hypotheses that the salinity anomalies at Station 27 are determined by freshwater runoff anomalies from Hudson and Ungava bays and by ice‐melt anomalies in Hudson Bay and on the Labrador Shelf. Interannual variations of summer runoff into Hudson Bay were significantly negatively correlated with salinity anomalies on the Newfoundland Shelf with a lag (9 months) that is consistent with expected travel times based on known current velocities in Hudson Bay and along the Labrador Shelf. Sea‐ice extent over the Labrador and northern Newfoundland shelves was significantly negatively correlated with salinity at a lag of 3 to 4 months, corresponding to the time of minimum salinity at Station 27. It appears that ice‐melt over the Lab...

The influence of Hudson Bay runoff and ice‐melt on the salinity of the inner Newfoundland Shelf

The residual circulation in the western Labrador Sea is discussed in the light of recent current data combining information from moored instruments, satellite-tracked surface buoys, and geostrophic calculations. The characteristic features of the surface flow pattern observed near the mouth of Hudson Strait are explained qualitatively in terms of the response of the flow to the form of the coastline and to the nearshore bathymetry.

R. Goodman

Papers

Surface circulation in the Western Labrador Sea