Hourly wave measurement data were collected at 2 sites off the coast of Barrow, at 5 meter and 10 meter depths, from 12 August - 30 September, 2003 and from 16 July - 13 September 2004. Evans-Hamilton, Inc. was contracted for data collection by the U.S. Army Corps of Engineers, Waterways Experiment Station, Coastal and Hydraulics Lab for the Barrow Coastal Storm Damage Reduction Project.
Acoustic Doppler Current Profiler (ADCP) Instrumentation
Figure 1. Graphic from the RD Instrument's Waves User's Guide
10. Theory of Operation
10.1 Principles of ADCP Wave Measurement
The basic principle behind wave measurement is that the wave orbital
velocities below the surface can be measured by the highly accurate ADCP. The
ADCP is bottom mounted, upward facing and has a pressure sensor for measuring
tide and mean water depth. Time series of velocities are accumulated and from
these time series, velocity power spectra are calculated. To get a surface
height spectrum the velocity spectrum is translated to surface displacement
using linear wave kinematics. The depth of each bin measured and the total water
depth are used to calculate this translation. To calculate directional spectra,
phase information must be preserved. Each bin in each beam is considered an
independent sensor in an array. The cross-spectrum is then calculated between
each sensor and every other sensor in the array. The result is a cross-spectral
matrix that contains phase information in the path between each sensor and every
other sensor at each frequency band. The cross-spectrum at a particular
frequency is linearly related to the directional spectrum at a particular
frequency. By inverting this forward relation, we solve for the directional
spectrum.
[ From the
Waves User's Guide, RD Instruments April 2001, page 65 ]
For more details about the instrumentation visit the RDI ADCP Waves Array web page.
ADCP Data for Barrow
Figure 2. Location of ADCP Instruments near Barrow, AK.
View 2003 and 2004 Reports
Monthly Summary File Format Description
October 2003 Service and Data Report
March 2004 Recovery and Data Report
View Summarized Data
2 August - 30 September, 2003
Wave and current data summary plots are presented in a monthly format with decimal day of the year being the common reference. A cross-reference table for conversion of non leap year calendar day to decimal (Julian) day can be accessed at: http://amsu.cira.colostate.edu/julian.html. The Data reports above contain more details about the plots below.
The October - November 2003 summary data plots present clear evidence of two storm events
where wave height (Hs) reached 2 meters. While these two events dominate this data collection period, the single most significant wave height event for the entire data collection period (Aug – Nov, 2003) remains from day 251 through 255 (Sept. 8 – 12). Maximum wave period (Tp) during storm events was again 9 to 10 seconds and direction remained predominantly from the west.Water level data present curious fluctuations in the Oct – Nov plots, when compared with the Aug – Sept plots. When correlated to wave and current data plots, it appears WL decreases may be associated with suspected wind events from the east. These suspect wind events have little to no effect on Hs, Tp & Dp, due to lack of fetch (instrument locations vs. shoreline), yet significantly increase and alter surface current and direction, plots Ss and Ds.
Diurnal tidal data are evident as the continuous small sine wave (or saw tooth pattern)
embedded through all WL plots. These data have not been statistically compared to NOAA predicted or verified levels yet appear consistent in magnitude to the published data plots.The current summary plots no longer present such predominant flow direction to the
northeast when compared to previous (Aug-Sept) data. Flow direction to the southwest nearly equals northeasterly flow in these Oct - Nov data. Again, this may be evidence of sustained east wind causing seawater movement westward, with enough force and duration to overcome the predominant northerly current flow; through an unknown mechanism such as large scale cyclonic effect or a purely wind-driven water flow. Further evidence supporting wind related southerly current events may also be indicated by surface velocity (Ss) rising to the highest level of the project at the 10m depth site, spanning days 279 – 281 (October 6-8). This surface velocity data peak also coincides with the largest water level (WL) drop, of nearly one meter at both sites, recorded from Aug. – Nov. 2003.Theories offered in the previous paragraphs, referencing presently unknown wind events,
may be solidified through acquisition and correlation of digital wind data. Additional useful data may be obtained by comparison of WL data available from the Prudhoe, AK NOAA weather/tide station. Inclusion of Prudhoe WL data may direct Barrow current flow direction interpretation toward a more regional / seasonal phenomena. These additional data, both wind and WL could be plotted in the same format, for immediate use by the interpreter.An interesting correlation may also be produced if seawater salinity data were collected
during the 2004 data collection period. The correlation being – easterly wind has weak correlation to cyclonic effect as the cause of the southerly flow at these sites, considering both data points close proximity to shore. It is more likely that sustained east wind pushes enough water westward to cause a dip in WL and subsequent in-flow of water from the north around Point Barrow. The significant number of rivers on the North Slope, east of Barrow, may produce enough fresh water to be detected as a drop in salinity at these sites. If this salinity change could not be detected, then cyclonic effect may predominate theories as to the cause of southerly flow.2003 - 5 Meter Depth
August September October November
2003 - 10 Meter Depth
August September October November
16 July - 13 September 2004
No data analyses were reported for 2004.
2004 - 5 Meter Depth
July
2004 - 10 Meter Depth
July August September
Each 2003 hourly dataset contains a flat text file (sample can be viewed here) named with the date and hour (GMT) and an accompanying .gif graph (shown below).
Figure 3. Graph showing the first hour of data collected (2003).
Download All Data (840MB)
2003 Data Download
Download WINzipped file (right click) containing all 5-meter depth text files and graphs here (26 MB). WINzipped 5-meter and 10-meter depth summary files are here (673 KB).
2004 Data Download
Download WINzipped file (right click) containing 5- meter and 10-meter depth summarized text files and graphs here (516 KB). Final ASCII data has not been released. WAVES formatted data has been released but is not included here.
Acknowledgements
Use Constraints: Dataset credit required. Use at your own risk. Users assume responsibility to determine the usability of the dataset, as well as dataset resolution and accuracy, for their purposes.
Data credits: The Civil Works Program of the Alaska District of the Army Corps of Engineers, Elmendorf Air Force Base, Anchorage, Alaska.
Data distribution: Leanne Lestak, University of Colorado - CIRES, 216 UCB, Boulder, Colorado 80309. Funding from the National Science Foundation's program for Arctic System Science (ARCSS) Program (NSF Award OPP-0100120).