Hudson Riverkeeper Monthly CTD Surveys

Project PIs:

Philip Orton

Bruce Huber

Martin Visbeck

Caption: Summary of all CTD transects, where colors indicate date, while years are shown alongside each colored line. Lines show the range of conditions from the first to last day spent on each transect, in terms of the semi-diurnal (D2) tidal range and mean flow past Poughkeepsie. The mean Poughkeepsie flow for the period 2001-present is shown with a dotted line.

Project Summary

Since 2001, monthly along channel CTD transects have been run during ice-free months from The Battery to Green Island, NY, by John Lipscomb and the Hudson Riverkeeper. Ongoing monthly transects will provide another ~8 transects every year.  A Seabird SBE-19 CTD is used for profiling salinity, conductivity and temperature, which is done in the thalweg (deepest cross-sectional location) to best track the salt intrusion up the Hudson. To present these data in the context of along-channel depth variations, we have constructed a latitudinal profile of thalweg depth from bathymetric survey data (NOAA-NOS, 2006) by seeking maximum depths in 0.0005 degree latitude (~50 m) increments from the Battery to Poughkeepsie.

Individual transect plots are available following the link below. There are also "climatology" figures summarizing how the Hudson's salinity, temperature, density and stratification vary over differing tidal and riverflow forcing.  Spring tides have the largest range in water level, because the gravitational effects of the sun and moon act constructively, whereas neap tides have the smallest range because their gravitational effects act in opposition.  Riverflow forcing is highly variable for the Hudson; flow past Green Island dam averages 400 m3 s-1, but in a typical year varies over a factor of 25, with 1980-2004 means for annual minimum and maximum riverflow of 90 m3 s-1 and 2340 m3 s-1.