| Data Tables, Images, and Other Entities: |
| Data Table: | Units_And_Column_Descriptions
View Table Metadata |
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Short Name: | icethickness |
| Online Distribution Info: |
| Download File: |
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| Data Set Owner(s): |
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Individual: | John Priscu |
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Address: |
| Department of Biology, |
| 309 Lewis Hall, |
| Montana State University , |
| Bozeman, MT 59717 USA |
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Phone:
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Email Address:
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| Metadata Provider(s): |
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Organization: | McMurdo Dry Valleys LTER |
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Address: |
| Byrd Polar Research Center , |
| 108 Scott Hall, |
| 1090 Carmack Rd, |
| Columbus, OH 43210-1002 USA |
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Phone:
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Email Address:
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| Associated Party: |
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Individual: | Chiuchiolo Amy |
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Address: |
| Department of Land Resources and Environmental Sciences, |
| Montana State University , |
| Bozeman, MT 59717 USA |
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Email Address:
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Role:
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| Abstract: |
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Ice thickness was measured from the bottom of the ice cover to the piezometric
water level and to the top of the ice cover.
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| Keywords: |
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- lake
(theme)
- ice thickness
(theme)
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| Additional Information: |
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| Comments |
Problems with the Kovacs drill prevented the limnological sampling team from
attaining more than one "unbiased" measurement at Lake Fryxell during the 1996-97
season.
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| Citations |
| Notes about 04-05 season |
Because sampling at Lake Vanda was done as a day trip, the Aqua-Vu system
was not brought to this sampling location, and the ice thickness measurement was done using
the method employed in previous years. A 30 cm brass rod, with nylon cord attached to one end,
was fastened to a 10 m tape measure and lowered through the newly drilled ice hole. Once
through the ice, the tape measure was slowly pulled upward allowing the brass rod to catch on
the bottom of the ice cover. The distances from the bottom of the ice cover to the piezometric
water level (z-water), and to the top of the ice cover (z-ice), were recorded.
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| Notes |
Data contained in these files has been subjected to quality control standards
imposed by the investigator. The user of this data should be aware that, while efforts have
been taken to ensure that these data are of the highest quality, there is no guarantee of
perfection for the data contained herein and the possibility of errors exists. If you
encounter questionable data, please contact the MCM LTER data manager corrected or qualified.
Thus, these data may be modified and future data will be appended.
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| License and Usage Rights: |
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| MCM LTER data may be used freely with the following restrictions: |
The Principal Investigator be sent a notice stating reasons for acquiring any
data and a description of the publication intentions.
The Principal Investigator of the data set be sent a copy of the report or
manuscript prior to submission and be adequately cited in any resultant
publications.
A copy of any resultant publications should be sent to the McMurdo data
manager and principal investigator.
The end-user follow the guidelines set forth in the LTER Network Data Access
Policy, Data Access Requirements, and General Data Use Agreement found at
http://www.mcmlter.org/data_guidelines.htm
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| Geographic Coverage: |
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Geographic Description: | Measurements were taken from East Lake Bonney, West Lake Bonney, Lake
Hoare, Lake Fryxell, Lake Joyce, and Lake Miers in the McMurdo Dry Valleys of Antarctica. |
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Bounding Coordinates:
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| West: | 162 degrees
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| East: | 163.6 degrees
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| North: | -77.2 degrees
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| South: | -77.8 degrees
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Mimimum Altitude: | 0 meter |
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Maximum Altitude: | 1000 meter |
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| Temporal Coverage: |
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Begin:
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End:
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| Maintenance: |
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Description:
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The 1995/96 data from this table was submitted to INSTAAR by Ray Kepner at the
Desert Research Institute. It was included in several e-mail messages sent in August 1997.
Denise Steigerwald, the data manager used the information in these messages to create a file
called thckness.dat.
The 1996/97 and 1997/98 data was submitted to INSTAAR by John Priscu's
team at Montana State University. The former is a Microsoft Excel version 6.0 file
(icethk.xls), and the latter is an ascii text file.
Upon arrival at INSTAAR, the data manager fine-tuned the files to allow them to be merged for use on the MCM LTER web site. Adjustments
included the following:
Lake Descriptions" file. added to the "Limno Holes, Dive Holes, Lake
Level Measurement Locations" file.
The icethk.xls file did not contain variables for latitude
and longitude, but records for each "location" represented in this dataset were added to the
"Limno Holes, Dive Holes, Lake Level Measurement Locations" file (leaving the latitude and
longitude fields blank). The links made possible by doing this will allow users to call up
further information about a given lake (thru the link with the "McMurdo Dry Valley Lake
Descriptions" file), and/or about a given sampling location on the lake (thru the link with
the "Limno Holes, Dive Holes, Lake Level Measurement Locations" file).
icethk.xls file had variables for z-water, z-ice, and z-diff. After consulting with Craig Wolf (at Montana State
University), the ice thickness variable was renamed to z-ice. project (S025) which is still
taking place. John Priscu requested to have these records removed from the MCM LTER web site
in an August, 1998 e-mail message. Any location codes containing a "C" followed by a number
(eg. C01) were removed from this file.
Each of these adjustments allowed the all of the ice
thickness measurements to be represented in one data file on the MCM LTER web site. The file
was imported into Microsoft Access on INSTAAR's Unix system, and can currently be found
there. The file was then exported in ascii, comma delimited text and MS-DOS text (table
layout) to present on the MCM LTER web site. Both of these files are linked to this web page
above.
Information for the metadata was obtained from the icethick.metadata.txt and
Metaicethick9697.rtf files. The".rtf" file was called up using Microsoft Word version 6.0,
and a simple text editor was used for the icethick.metadata.txt file. Text from these files
was used to create this page in html format.
In 2006, Chris Gardner added Latitude and Longitude columns to the Ice Thickness table. He also deleted and reloaded
seasons 2001-2002 through 2003-2004 as some errors were found. Lat/Longs were added to these dates as well.
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Frequency:
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| Contact: |
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Organization: | McMurdo Dry Valleys LTER |
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Position: | Data Manager |
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Address: |
| Byrd Polar Research Center , |
| 108 Scott Hall, |
| 1090 Carmack Rd, |
| Columbus, OH 43210-1002 USA |
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Phone:
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Email Address:
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| Publisher: |
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Organization: | McMurdo Dry Valleys LTER |
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Address: |
| Byrd Polar Research Center , |
| 108 Scott Hall, |
| 1090 Carmack Rd, |
| Columbus, |
| Columbus, OH 43210-1002 USA |
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Phone:
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| Methods Info: |
| Step 1: |
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Description:
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A 30 cm brass rod, with nylon string attached to one end, was fastened to a 10
m tape measure and lowered through a newly drilled ice hole. Once through the ice, the tape
measure was slowly pulled upward allowing the brass rod to catch on the bottom of the ice
cover. The distances from the bottom of the ice cover to the piezometric water level
(z-water), and to the top of the ice cover (z-ice) were then recorded. The difference between
these two measurements (z-difference) or "freebore" provides some insight into the
topographical features of the ice cover as well as density of the ice. Ice thickness
measurements are typically performed on each hole drilled through the ice cover. Because most
limnological sampling holes are drilled in low-lying areas, ice thickness measurements have
been biased. Therefore, random ice thickness measurements were performed in a 1000 m2
sampling grid on each lake. At Lakes Fryxell, Hoare, East and West Bonney the sampling grids
are located along a 100 m baseline due south of the blue instrument boxes. Prior to sampling,
two sets of random numbers between 0 and 100 were generated as south and east coordinates in
this 100x100m grid. For example, if the sampling coordinates were (56S, 72E), the hole would
be located 56 m due south along the baseline, then similarly, 72 m due east of that
baseline.
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| Step 2: |
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Description:
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A new method for measuring ice thickness was employed in the 04-05 season using the
Aqua-Vu underwater viewing system, which allows us to see the exact point where the bottom of
the ice cover is located. The Aqua-Vu underwater camera is lowered through a newly drilled ice hole,
and the camera lowered until the bottom of the ice cover is viewed through the above-water viewing system.
The distances from the bottom of the ice cover to the piezometric water level (z-water), and to the top of the
ice cover (z-ice), are marked on the viewing system cord and measured with a tape measure once the
viewing system is brought out of the ice hole. The difference between these two measurements (z-difference)
or 'freebore' provides some insight into the topographical features of the ice cover as well as density of the ice.
Ice thickness measurements are typically performed on each hole drilled through the ice cover. Because
most limnological sampling holes are drilled in low-lying areas, it was thought that ice thickness
measurements were biased. Therefore, random ice thickness measurements were performed in a 1000 m2
sampling grid on each lake in past years. However, statistical analyses by Dr. Priscu have shown that
measurements from three ice holes are representative of the ice thickness measured by this grid system.
This season, ice thickness measurements were done on the two holes drilled for limnological sampling,
plus one additional hole. In addition, notes were taken to describe the topography of the ice surrounding
the ice hole (see comments section of data file).
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