IMMEDIATE SCIENCE REPORT
K 015 B Holocene Climate History from Coastal Ice
Antarctica New Zealand 1999/2000
Holocene Climate History from Coastal Ice - K015B
1. Popular Summery of Scientific Work Achieved
This study investigates the regional Holocene climate of the South Victoria Land coast, using the snow and ice of the Wilson Piedmont Glacier as an archive. Ice cores are being recovered and will be analysed to obtain a detailed, continuous record of past climate. The principal idea behind ice core analyses is, that as snow accumulates, it preserves information about climate, by trapping atmospheric gas, dust particles, and freezing the isotopic composition of water and air molecules. Analysis of these parameters can be used as proxies to quantify past temperature, precipitation, sea ice extent, wind direction, and storm frequency.
The purpose of this year's study was to test the quality of the paleoclimatic signal, recorded in the WPG and to establish transfer functions between meteorological data, satellite images and the ice core parameters. For this reason six shallow ice cores (varying from 7 to 33m) were recovered from Lower Victoria and Baldwin Glacier (Fig.:1). Due to their different characteristics in catchment, altitude, and topography, a comparison between the cores from the two areas will allow the effect of local influences to be separated from the regional climatic signal. To help interpret the ice core record, a mass balance measurement device has been installed, borehole temperature measured and snow profiles investigated and sampled. The area has been surveyed using differential GPS.
The results of this year's investigations are two-fold: firstly, they enable us to judge the quality of an ice record retrieved from that area and hence are the basis for the decision to drill a deeper 200m core during the coming season. Secondly, they will enable us to establish transfer functions for the deeper core, to calculate absolute values for paleoproxies, such as temperature, precipitation and sea ice extent, beyond the time covered by meteorological measurements and into the geological past.
2. Proposed Programme
Is the Wilson Piedmont Glacier suitable for reconstructing Holocene Climate of the Dry Valley area?
The study of aerial photographs and satellite images enabled us to identify suitable drilling sites to answer such a question at Victoria Lower Glacier and Baldwin Glacier. Due to their different characteristics in catchment, altitude, page 3 and topography, a comparison between the cores from the two areas will allow the effect of local influences to be separated from the regional climatic signal.
In help interpret the ice core record, we installed a mass balance measurement device (Hamilton & Whillans, 1995), measured borehole temperature and sampled snow profiles. The glacier topography in the vicinity of the drilling sites has been surveyed using differential GPS. The mass balance device will record from next year on the actual state of mass balance of the Victoria Lower Glacier. The borehole temperature will be used to calculate mean annual air temperature and the investigations of the snow samples will help to understand the acting processes during snow – firn – ice metamorphism.
What are the transfer functions between meteorological data, satellite images and the ice core proxies?
In order to calculate absolute temperature, precipitation and sea ice values, it is necessary to calibrate the ice core record with the measured climatic parameters of the area. For that reason meteorological data and satellite images, quantifying sea ice extent in the McMurdo Sound area, will be used to convert isotopic ratios and methane sulphuric acid percentages into temperature, precipitation and sea ice extent values. Once these transfer functions have been established, they can be used to convert ice core data beyond such records.
3. Scientific Endeavours and Achievements
Victoria Lower Glacier S77°19.810′, E162°31.991′
During the season 1999/2000 four shallow cores have recovered from the glacier (7.0m, 9.9m, 12.5m, 33.6m). While the 7.0m and 9.9m cores have been used to measure density profiles in the field, the 12.5 and 33.6m cores have been taken for further analyses to New Zealand and USA. All four cores have been logged to test for intrasite variability. The topography of the glacier surface in the vicinity of the drilling site has been surveyed applying differential GPS, with the base station employed at the Cape Roberts tide gauge.
To accomplish the ice/firn core record, snow profiles from 0 – 3m depth have been cut and investigated. The analyses include visual logging, density measurement and sampling for determining isotopic and chemistry characteristics. A mean annual temperature of −22.3°C has been calculated by recording the borehole temperatures of the 9.9 and 33.6m drilling holes (fig.).
Continuous meteorological data, such as temperature, wind speed and direction and insolation, have been recorded and will help to correlate between longterm page 5 weather records from Marble Point and the actual weather systems at Victoria Lower Glacier, where no such records are available.
In order to determine the present-day state of mass balance, a 'coffee can' device has been installed, following the instructions of Hamilton & Whillans (1995). The first readings can be expected from the coming season onwards.
Investigations of the Lower Victoria Glacier snout indicated an overall positive mass balance and led to a better understanding of the general ice flow directions and catchment characteristics. The sand dunes, west of the glacier snout, have been studied as a possible source for the dust found in the cores.
Baldwin Valley Glacier S77°19.836′, E162°32.019′
Two firn cores have been recovered from Baldwin Glacier (12.2m and 31.1m). While the 12.2m core has been used to establish a density record, the longer core has been taken to NZ and USA for further analyses. A snow profile from 0 – 1.8m has been cut, visually logged and the density measured. Samples for iso-topic measurements and chemistry have been taken.
The mean annual air temperature was calculated to be −23°C by measuring borehole temperatures. Investigations of the vicinity of the drilling site gave insides of the ice flow structures and catchment characteristics.
All cores chosen to be taken back for further analyses have been logged in more detail at Crary laboratory, using a light table. The 12.5m core from Victoria Lower Glacier has been prepared for ?-activity measurements and sent off. All cores have been split and packed for the transport to NZ and USA.
Ice Core Drilling
For the ice core drilling the PICO (Polar Ice Coring Office) Hand Auger has been used. Despite the loss of one drilling bit, the coring went smoothly with only minor problems. A few modifications have been carried out for safety and convenience.
Borehole Temperature Measurement
Coupled conductivity wire were used to read temperature. The meter displayed a high sensitivity to the air temperature and had to be keptabove 0°C.
Snow Profiling and Samplingpage 6
A hand saw and in places a chain saw were used to cut the snow profiles. No modifications were necessary.
The weather station used was hired from NIWA. Since it had been employed in Antarctica before, no modifications were necessary.
Differential GPS Measurements
The GPS system used (Trimble X PRO) has been employed in Antarctica before so that no modifications were necessary. In order to derive differential data, the measurements have been linked with the data from the base station located at the Cape Roberts tide gauge.
The results will be published in peer reviewed papers in co-authorship with Warren Dickinson, Peter Barrett, Alex Pyne, Paul Mayewski, Eric Saltzman, Gordon Hamilton, and Ian Whillans.
- Scott Base Staff
- CR Team, especially:
- Peter Barrett
- Alex Pyne
- John Alexander
- Jim Cowie
- Nick Jackson
- Mike Avey
- Richard Stutters
- PICO, especially:
- Dave Giles
- Crary Laboratory, especially:
- Robbie Score
- Berg Field Center, especially:
- Mimi Fujinomi
- NSF, especially
- Julie Palais
- Prof. Paul Mayewski
- Dr. Mark Twickler
- Dr. Gordon Hamilton
- Prof. Ian Whillans
- Dr. Tim Haskell
- NIWA, especially
- Tony Bromley
- Errol Lewthwaite
- Scripps Institution of Oceanography, especially
- Dan Lubin
- Bob Whritner
- Steve Hart
- and I acknowledge Victoria University for funding this project.