Acceptance and utilization of LTER data requires that:
FILE NAME: PRINCIPAL INVESTIGATOR: OTHERS: KEYWORDS: lake, ice thickness
ABSTRACT: Ice thickness was measured from the bottom of the ice cover to
the piezometric water level and to the top of the ice cover.
VARIABLES: lake, location, date, z-water (m), z-ice (m), z-diff (m),
density, tool, comments, file name
RESEARCH LOCATION: 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. More complete descriptions of these
lakes can be found on the McMurdo Dry Valley
Lake Descriptions web page. More specifics of the sample sites on these lakes can be found on the Limno Holes, Dive Holes, Lake Level Measurement
Locations web page.
METHODS: 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 mē
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.
TIMING: Data collection occurred between December 1995 and December 1997.
Specific dates and lakes include the following:
CITATIONS:
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.
STATUS: Public Access (Type 1).
VARIABLE DESCRIPTION:
VARIABLE TYPE DESCRIPTION UNITS MISSING VALUE INDICATOR MINIMUM MAXIMUM PRECISION Lake Text Name of lake where measurement was made none Required entry n/a n/a n/a Location Text Specifics of ice hole site upon lake. Locations designated by numbers are distances in meters, south and east,respectively, from the blue box none Required entry n/a n/a n/a Date Date Date on which sample was gathered mm/dd/yy Required entry 01/01/93 12/31/99 dd Z-water (m) Number Distance from piezometric water level to bottom of ice (negative value) meters Required entry -10 0 0.01 Z-ice (m) Number Distance from bottom of ice to top of ice (total ice thickness) meters Null 0 10 0.01 Z-diff (m) Number Distance from piezometric water level to top of ice (positive value) meters Null 0 5 0.01 Density Number Density of ice Null 0 1 0.0001 Tool Text Tool used to gather sample Null n/a n/a n/a Comments Text Helpful hints about the ice thickness measurement Null n/a n/a n/a File Name Text Name of file in which data was submitted Null n/a n/a n/a LOG: 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:
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.
NOTE: 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
(; (303)492-4639) so that the data can be
corrected or qualified. Thus, these data may be modified and future
data will be appended.
Season East Bonney West Bonney Hoare Fryxell Joyce Miers
1995-1996 8-Jan-1996 11-Dec-1995 30-Dec-1995
18-Dec-1995 31-Dec-1995
20-Dec-1995 20-Jan-1996
22-Dec-1995 22-Jan-1996
24-Dec-1995
11-Jan-1996
15-Jan-1996
17-Jan-1996
18-Jan-1996
19-Jan-1996
1996-1997 29-Oct-1996 27-Nov-1996 10-Nov-1996 24-Oct-1996 14-Nov-1996 10-Dec-1996
27-Nov-1996 1-Dec-1996 25-Oct-1996 5-Dec-1996
3-Dec-1996 18-Nov-1996
8-Jan-1997 20-Nov-1996
1997-1998 8-Nov-1997 2-Dec-1997 14-Dec-1997 15-Dec-1997 9-Dec-1997 5-Dec-1997
30-Nov-1997 6-Dec-1997 17-Dec-1997
4-Dec-1997
1998-1999 9-Nov-1998 11-Nov-1998 31-Oct-1998 21-Nov-1998 23-Dec-1998
5-Dec-1998 8-Dec-1998 27-Nov-19988
1999-2000 8-Dec-1999 8-Dec-1999 17-Nov-1999 30-Oct-1999
14-Dec-1999 29-Nov-1999
none
none
none
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.