National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2007

A transect of Glacier Bay ocean currents measured by acoustic Doppler current profiler (ADCP)

Cokelet, E.D., A.J. Jenkins, and L.L. Etherington

In Proceedings of the Fourth Glacier Bay Science Syposium, 2004, U.S. Geological Survey Scientific Investigations Report 2007-5047, J.F. Piatt and S.M. Gende (eds.), U.S. Geological Survey, Washington, DC, 26–28 October 2004, 80–83 (2007)

We present one of the first shipboard acoustic Doppler current profiler (ADCP) transects of ocean current in Glacier Bay and Muir Inlet. The water temperature, salinity, nitrate plus nitrite concentration and chlorophyll fluorescence also were sampled underway at 5 m depth from the research vessel. These data were combined with conductivity-temperature-depth (CTD) sections made a fortnight later to provide a composite data set. The measurements show that the tidal flow accelerates over Glacier Bay’s shallow entrance sill to speeds of 180 cm/s and then slows to a few cm/s in the deeper basin beyond. The near-surface salinity was ~32 psu in Icy Strait and Sitakaday Narrows but freshened up the estuary to ~20 psu in patches, owing to glacial melt water. The nitrate plus nitrite concentration followed a similar pattern with enrichment (~19 µM) in the mixed water over the sill but then depletion (0-2 µM) in Glacier Bay, presumably due to phytoplankton consumption. We postulate that turbulence generated by strong currents over the shallow entrance sill to Glacier Bay mixes deeper, nutrient-rich water into the surface layers and fertilizes the fjord.

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