Bathymetry/depth measurements made at Long Fjord, Vestfold Hills by drilling through sea ice
Methodology: A line reel was rigged up to sit on the back a quad (see picture in download file) to allow measurements to be taken without the need to touch the wet cord (a problem, even for gloved hands, in sub-zero temperatures). The measuring cord is nylon blind cord marked every metre with red he...
| Other Authors: | , |
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| Format: | Dataset |
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Australian Ocean Data Network
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| Online Access: | https://researchdata.ands.org.au/bathymetrydepth-measurements-long-sea-ice/685303 https://data.aad.gov.au/metadata/records/Long_Fjord_Depth_Measurements_2007 https://data.aad.gov.au/eds/1530/download https://data.aad.gov.au/metadata/records/VH_bathy_99 https://data.aad.gov.au/metadata/records/long_tryne_bathy http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=Long_Fjord_Depth_Measurements_2007 |
| Summary: | Methodology: A line reel was rigged up to sit on the back a quad (see picture in download file) to allow measurements to be taken without the need to touch the wet cord (a problem, even for gloved hands, in sub-zero temperatures). The measuring cord is nylon blind cord marked every metre with red heat shrink and then every ten metres with yellow heat shrink. There is some stretch in the cord but not much, (roughly 300mm over 100 metres with about 10kg of weight applied). Two weights were made up, one at 2 kg and one a little over 4 kg (the hope was to be able to use the lighter weight to reduce line stretch, but it may be affected more by currents, and cause the line to drift). A gen-set was also available on the quad bike and was used to power a drill for making holes in the sea ice. In total, 60 holes were drilled at 100 metre intervals (using the odometer on the quad bike), and the location of each hole was recorded on a GPS. The line was then dropped, any slack was taken up and the bottom established before taking the measurement. The time was also recorded in case tidal variations need to be checked. We followed the travel routes up the Fjord to Brookes Hut taking cross measurements every 500 metres. The setup worked well and took about 2 to 4 minutes per hole depending on water depth. Water depths varied from 3.6 metres between islands to 141.6 metres out from the entrance to the Fjord. There was very little sediment coming up with the weight and what did come up was either dark green vegetation or grey silt. GPS measurements were collected using the WGS84 horizontal datum. Water depth measurements were taken in Long Fjord during early winter in 2007. The measurements were collected by Graham Cook, station leader at Davis Station in the Australian Antarctic Territory. The measurements were made by dropping a weighted line off the back of a quad bike, after drilling a hole through the sea ice. Measurements were made approximately every 100 metres. The download file contains a csv spreadsheet which lists each waypoint, plus the corresponding water depth and any comments. The text file contains the waypoint information collected by the Garmin GPS unit. Data in the text file are comma separated and are interpreted as follows: WP,D,001 (waypoint) , -68.51341000, 78.06903000,(Latitude and Longitude) 05/25/2007, 10:25:35, (Date and time Downloaded to Computer) 24-MAY-07 11:40:42 (Date and time of reading). Time is in local time. Vegetation was found on the weight that we used when we first started at the seaward end of the Fjord and then again in shallow water between Brookes Hut and a small island 800 or 900 metres out from Brookes. The weight is quite smooth and does not pick up a lot. The reference given below provides some further information about previously collected bathymetry data in Long Fjord. Furthermore, also see the metadata records: 'Bathymetric data of Long and Tryne Fjords at Vestfold Hills, Antarctica, collected in December 1999 [VH_bathy_99]' 'Interpolated bathymetry of Long and Tryne Fjords, Vestfold Hills, Antarctica [long_tryne_bathy]' The fields in this dataset are: Waypoint Latitude Longitude Water Depth Date Time |
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