T-3 Ice Island One Hour Navigation: May 14, 1962 to September 15, 1974

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Frequently anticipated questions:

What does this data set describe?

T-3 Ice Island One Hour Navigation: May 14, 1962 to September 15, 1974
The T-3 (Fletcher's) Ice Island in the Arctic Ocean was the site of a scientific research station re-established by the Naval Arctic Research Laboratory starting in 1962. Lamont Geological Observatory (LGO; now Lamont-Doherty Earth Observatory) and the U.S. Geological Survey, along with other organizations, ran research laboratories on the island during the 1960s and early 1970s as the island drifted in the Amerasian Basin. LGO compiled navigational data, measured gravity and magnetic data, and conducted seismic surveys to image the seafloor. This data release provides the edited LGO-compiled 1 hour navigational data for T-3 from May 1962 until September 1974, along with gravity and magnetic data and calculated anomalies on the same hourly intervals.
  1. How might this data set be cited?
    Hall, John K., and Ruppel, Carolyn D., 2019, T-3 Ice Island One Hour Navigation: May 14, 1962 to September 15, 1974: data release DOI:10.5066/P97EPU2F, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Ruppel, Carolyn D., Hutchinson, Deborah R., Lachenbruch, Arthur H., and Hall, John K., 2019, Thermal Data and Navigation for T-3 (Fletcher's) Ice Island Arctic Ocean Heat Flow Studies, 1963-1973: data release DOI:10.5066/P97EPU2F, U.S. Geological Survey, Reston, VA.

    Online Links:

    Ruppel, C.D., Hutchinson, D.R., Lachenbruch, A.H., and Hall, J.K., 2019, Thermal data and navigation for T-3 (Fletcher's) Ice Island Arctic Ocean heat flow studies, 1963-73: USGS data release, https://doi.org/10.5066/P97EPU2F.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -176.792
    East_Bounding_Coordinate: -73.580
    North_Bounding_Coordinate: 86.330
    South_Bounding_Coordinate: 74.288
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5d10eb1ae4b0941bde550208?name=T3navigationgraphic.jpg (JPEG)
    T-3 Ice Island navigation track labelled with a selection of dates. The background bathymetry is from: Jakobsson, M. and others (2012), The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0, Geophys. Res. Lett., 39, L12609, doi:10.1029/2012GL052219. Inset shows the Arctic Ocean and surrounding land masses, with the red box indicating the approximate area corresponding to the larger map.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 14-May-1962
    Ending_Date: 15-Sep-1974
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: tabular digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.001. Longitudes are given to the nearest 0.001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.978698214.
      Depth_Datum_Name: Not known, but likely was water's surface below the ice.
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: attribute values
  7. How does the data set describe geographic features?
    Excel 2013 file (XLSX) containing data. (Source: Producer Defined)
    Number of day within month at Greenwich meridian. (Source: Producer Defined)
    Range of values
    Number of month in year at Greenwich meridian. (Source: Producer Defined)
    Range of values
    Last two digits of year of measurement, with year designating the one at the Greenwich meridian. Years are in 20th century. For example, "64" corresponds to 1964. (Source: Producer Defined)
    Range of values
    Hour (0 to 23) multiplied by 100 at Greenwich meridian (GMT). For example, 0800 corresponds to 8 in the morning. (Source: Producer Defined)
    Range of values
    North latitude for position (Source: Producer Defined)
    Range of values
    Units:Decimal degrees
    West longitude for position (Source: Producer Defined)
    Range of values
    Units:Decimal degrees
    Direction of island's motion; "0" means no azimuth data available (Source: Producer Defined)
    Range of values
    Water Depth (m)
    Measured water depth to seafloor beneath the ice (m); "0" means no water depth available (Source: Producer Defined)
    Range of values
    Total gravity (mgal)
    Total gravity measurement in milligal. "0.00" means no value. The following was taken from the report of Hunkins and Tiemann (1977; see cross-reference): "Gravity measurements were made several times a day with a Lacoste and Romberg Model G (No. 27) geodetic gravity meter. The meter was mounted on a wooden post which projected through the laboratory floor and was securely frozen into the ice. The meter height was approximately 4 meters above sea level. Ice vibrations generally did not interfere with the observations. In order to record its instrumental drift, this meter was used in comparison measurements at the University of Wisconsin pundulum [sic] station at Barrow, Alaska, 30 times between 1962 and 1970. The base station was located in the furnace room attached to side of the old quonset main building of the Naval Arctic Research Laboratory. The site is marked by a brass disk set in the concrete floor. Abrupt changes in drift occurred in late 1964 and 1969, but these have been accounted for and the data corrected. Elsewhere, a linear drift has been assumed between calibrations." (Source: Producer defined)
    Range of values
    Units:milligal (10^(-10) m^2/s)
    Free Air anomaly (mgal)
    To determine the free-air gravity anomaly, Hunkins and Tiemann (1977; see cross-references) state that "the gravity observations were reduced to sea level, and corrected for the acceleration due to east-west motion (Eotvos correction) by the reduction program. This correction seldom exceeded +1 milligal. Maximum errors are considered to be less than 1 milligal for most observations, but possibly as much as +5 milligals during the severest storms." No data valus are represented as 0.00. (Source: Producer Defined)
    Range of values
    Bouguer anomaly (mgal)
    From Hunkins and Tiemann (1977; see cross-reference): "Simple Bouguer anomalies were computed for each observation by adding the attraction of a horizontally infinite plate, of density 1.64 g/cc [1640 kg/m^3] and thickness equal to the water depth, to the free air anomaly." No value denoted as "0.00." (Source: Producer Defined)
    Range of values
    Total Magnetic Field (gamma)
    Total magnetic field in gamma (1 gamma = 1 nanoTesla (nT)). The following is taken from the Hunkins and Tiemann (1977) report (see cross-reference): "The total intensity of the earth's magnetic field was measured almost continuously with a proton precession magnetometer built at the Lamont-Doherty Geological Observatory. Readings were made every six seconds and recorded on a strip chart. Magnetic total intensity was calculated from precession frequency according to the relation H = 23.487386*f where H is the total field in gammas (10^-5 Gauss) and f is the proton precession frequency in Hertz. The precession frequency measurements were made with a frequency counter, whose crystal oscillator time base was checked periodically against other frequency standards. The individual measurements are accurate to better than +/- 10 gammas. Diurnal variations of the earth's magnetic field in polar regions commonly exceed one hundred gammas. The periodic nature of these variations was used to eliminate them by averaging the observations over 24 hour periods. The records were read every hour, and the filtered field strength computed at each observation point by taking an average of the twenty-four hourly readings centered about that time." No value denoted as "0.00." (Source: Producer defined)
    Range of values
    Magnetic Anomaly (gamma)
    Magnetic anomaly (gammas). The following is taken from the Hunkins and Tiemann (1977) in the cross-reference: "The value of the earth's regional field was removed by the use of a Taylor series expansion of third degree, fitted by least squares to the regional field in this area by the Dominion Observatory of Canada...The area of this investigation lies near the center of their aeromagnetic survey. The magnetic total intensity anomalies presented here are defined as the difference between the observed total magnetic field and the computed regional field at the point of observation." No value denoted as "0.0". The Fortran output file provided by John Hall had no space between this column and the previous one when the values for magnetic anomaly required 6 or more spaces (including the decimal). The file was hand-edited and quality controlled by Carolyn Ruppel to separate these columns, but problems may remain. (Source: Producer defined)
    Range of values

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • John K. Hall
    • Carolyn D. Ruppel
  2. Who also contributed to the data set?
    Original file compiled and processed by Lamont Geological Observatory (now Lamont-Doherty Earth Observatory). Digital data at 1 hour intervals were received in digital form by the U.S. Geological Survey from Dr. John K. Hall (Geological Survey of Israel, retired), who participated in the T-3 expeditions as Lamont staff member during parts of 1966, 1967, and 1968.
  3. To whom should users address questions about the data?
    Carolyn Ruppel
    U.S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Research Geophysicist
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700 x2339 (voice)
    (508) 457-2310 (FAX)

Why was the data set created?

To provide 1-hour navigational data and some gravity anomaly and magnetic anomaly data for the T-3 ice island circuit of the Amerasian Basin from 1962 to 1974.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 1977 (process 1 of 4)
    Hourly navigation for the T-3 Ice Island was determined by LGO by calculating positions between the actual location fixes. Hunkins and Tiemann (1977) report navigation at 12-hour intervals, but more frequent fixes were often available, especially after fixes from Navy satellites became available in 1967. Prior to that time, when navigation relied on the use of theodolites, John K. Hall reports that cloud cover and sun conditions (sun low on horizon in summer) sometimes prevented successful fixes for several days running. The longest period with no navigational fix during the theodolite navigation era was 22 days. The original fixes are no longer available. Hunkins and Tiemann (1977) describe the interpolation procedure between actual navigational fixes: "The interpolated drift track between fixes was constructed on the basis of wind data. Nansen's rule is that ice drifts 30 degrees to the right of the wind and at 1/50th of the wind speed. The ice motion between fixes was determined using speed factors and deviation angles calculated on the basis of the constraints of wind data and a given pair of observed positions. In the event that the computed speed factor exceeds 0.035 (75 percent above Nansen's value) or falls below 0.0075 (37 percent of Nansen's value), the motion is ascribed to both wind drift, using Nansen's constants, and to a steady current whose velocity is determined. This occurs when currents or the effects of winds at a distance cause small movements during periods of calm." Process date is unknown and assigned to 1977 based on date of the Hunkins and Tiemann (1977) report.
    Date: 1992 (process 2 of 4)
    Navigation and other data were interpolated to 1 hour intervals by LGO researchers using a Fortran program and a punch card system to enter satellite fixes. No other information is available. Process date is unknown and assigned to 1992 based on the oldest Fortran executable located on a hard drive provided to the U.S. Geological Survey by John K. Hall.
    Date: 2019 (process 3 of 4)
    Carolyn Ruppel edited the original text file provided by John K. Hall, fixing incorrect date designators across the yearly boundaries (usually in the last hours of each year), formatting into an Excel file, fixing data columns that were combined into one entry during the conversion to Excel, and adding appropriate headers. The resulting file is the one released here. The native Excel 2013 file was also exported to CSV format using the "save as" command.
    Date: 06-Aug-2020 (process 4 of 4)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
  3. What similar or related data should the user be aware of?
    Lachenbruch, Arthur H., Marshall, B. Vaughn, and Ruppel, C.D, 2019, Post-expedition report for USGS T-3 Ice Island heat flow measurements in the High Arctic Ocean, 1963-1973: data release DOI:10.5066/P91XQ3IS, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Lachenbruch, A.H., Marshall, B.V., and Ruppel, C.D., 2019, Post-expedition report for USGS T-3 Ice Island heat flow measurements in the High Arctic Ocean, 1963-1973: U.S. Geological Survey data release, https://doi.org/10.5066/P91XQ3IS.
    Hunkins, Kenneth, and Tiemann, Werner, 1977, Geophysical Data Summary for Fletcher's (T-3) Ice Island: May 1962 to September 1974: Lamont-Doherty Geological Observatory, Palisades, New York.

    Hunkins, K., and W. Tiemann (1977), Geophysical data summary for Fletcher's Ice Island (T-3), 1962-1974, Technical Report, Lamont-Doherty Survey of the World Ocean Rep. CU-1-77, 219 pp, Lamont-Doherty Geological Observatory.
    Ruppel, Carolyn D., Lachenbruch, Arthur H., Hutchinson, Deborah R., Munroe, Robert, and Mosher, David C., 2019, Heat Flow in the Western Arctic Ocean (Amerasian Basin): Journal of Geophysical Research DOI:10.1029/2019JB017587, American Geophysical Union, Washington, D.C..

    Online Links:

    The Journal of Geophysical Research article relies on navigational information compiled in this dataset.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Lacking the original data acquired by LGO, no checks for accuracy were possible.
  2. How accurate are the geographic locations?
    Background on navigation is summarized in Hunkins and Tiemann (1977)--see cross-reference-- and in the Journal of Geophysical Research report by Ruppel and others (2019) associated with this release. Before 1967, navigation relied on theodolite fixes of the sun (summer) and stars (winter) coupled with a chronometer that was frequently checked for accuracy via radio. Hunkins and Tiemann (1977) estimate a positional error of up to 1 km during the summer and 0.5 km in the winter for this period. Starting in 1967, satellite data from the Navy Navigation Satellite System provided positional fixes, and Hunkins and Tiemann (1977) estimate that positions were known within 250 m. Based on the years of the island's occupation, the horizontal datum is assumed to be NAD27.
  3. How accurate are the heights or depths?
    This text is taken from the report of Hunkins and Tiemann (1977)--see cross-reference: "During the first year [1962] depths were obtained with explosive sources and a geophone detector with a pen-and-ink recorder operated with one channel for the geophone and one for chronometer ticks. In 1963 a Precision Depth Recorder was installed with a 12 kHz Gifft sonar transceiver driving an EDO AN/UQN transducer at a nominal pulsed power of 1000 watts. All soundings were made on a one-second (750 m) sweep with paper fed at approximately 1 cm/hr. The errors of timing and reading are about+ 2 m. These records were digitized at all extrema and slope changes. Corrections for sound velocity conditions in the Arctic Ocean were applied on the basis of Matthew's tables (1939)." The reference for the Matthews tables is: Matthews, D.J., 1939, Tables of the velocity of sound in pure water and sea water for use in echo sounding and sound ranging, Hydrographic Department Report 282 (2nd edition), United Kingdom Hydrographic Department.
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the observations, including topology?
    Each type of data within the dataset was tested for logical consistency by Carolyn Ruppel. Dates were corrected as needed in the last hours of each year. Where these errors occurred, the original data set received by the U.S. Geological Survey had a date indicator of "0" within January (month 1) for the last few hours of each year due to a presumed error in the interpolation code across year boundaries. The latitudes and longitudes all lie within the Amerasian Basin along a continuous track, as expected. Raw gravity data are of an appropriate and reasonable magnitude, as are the raw magnetic field data. Free air and Bouguer gravity anomalies and magnetic anomalies are also of an appropriate sign and of credible magnitude.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None. Please see 'Distribution Info' for details.
Not to be used for navigation. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? The dataset contains the data in both Excel XLSX format and CSV format (T3navigation.xlsx, T3navigation.csv), browse graphic of data locations (T3navigationgraphic.jpg), and CSDGM metadata in XML, TXT, and HTML formats.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 06-Aug-2020
Metadata author:
U.S. Geological Survey
Attn: Carolyn D. Ruppel
Research Geophysicist
384 Woods Hole Rd.
Woods Hole, MA

508-548-8700 x2339 (voice)
508-457-2310 (FAX)
Metadata standard:
Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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