IMMEDIATE SCIENCE REPORT
K049 Holocene Climate History from Coastal Ice
Antarctica New Zealand
1 Popular Summary of Scientific Work Achieved
Victoria Valley is the northernmost and largest of the McMurdo Dry Valleys, which lie within the Transantarctic Mountains and between the Ross Sea and the East Antarctic Ice Sheet. Differences in moisture and temperature of air masses originating from either the East Antarctic Ice Sheet, the rocky area of the Dry Valleys or the Ross Sea form a sensitively balanced climate system where they meet in the Victoria Valley. Therefore a climate record of the Victoria/Valley provides an ideal opportunity to study rapid, high frequency climate variations.
During the 1999/2000 and 2000/2001 seasons firn cores and snow pit samples were collected from Victoria Lower Glacier, Baldwin Glacier and Wilson Piedmont Glacier. Their chemical and isotopic signals confirm the climate sensitivity of Victoria Valley, and verify the good preservation of this record in the ice of the surrounding low altitude, coastal glaciers.
During the 2001/2002 field season a 180m core was recovered from Victoria Lower Glacier. The ice was expected to provide a climate record for the last 8,000 to 10,000 years. The site was chosen for its location and for the glaciological characteristics of the site, which were determined with ground penetrating radar and mass balance measurements.
In addition, snow samples were collected from the polar plateau to complete our database along a transect from the coast to the East Antarctic Ice Sheet. The comparison of the chemical and isotopic record contained in the snow and firn at sites along this transect will allow us to distinguish between input from local and distant air masses
2 Proposed Programme
The 2001/2002 season focused on 'Holocene Glacial Ice - a Continuous Paleothermometer', the last of three dependent objectives addressed in this 3 year project.
- To recover a 200m deep ice core from Victoria Lower Glacier
- To re-visit GPS mass balance devices
- To record further weather observations from Victoria Lower Glacier
- To collect high resolution snow samples from the polar plateau
3 Scientific Endeavours and Achievements
The last field season of our project: Holocene Climate History from Coastal Ice was interesting and successful. Two sites were visited: Victoria Lower Glacier and the Polar Plateau (near Shapeless Mountain).
Victoria Lower Glacier S 77° 19′ 48.365″, E 162° 31′ 55.491″
Mass Balance Measurements
Mass balance measurements provide valuable information on glaciological characteristics that are important for the interpretation of the ice core record. A GPS base station (Fig.1) was installed (S 77° 20′ 38.109″, E 162° 35′ 37.592″) to revisit and measure mass balance devices (coffee can device) at Victoria Lower Glacier (Fig.2). Coffee can devices are used to measure the horizontal and vertical displacement of anchors placed at shallow depths (10′s of meters) in the glacier. While the horizontal flow indicates how 'active' the glacier is (how many cm/year the ice travels from its accumulation centre), the vertical change is the result of compaction and the mass balance of the glacier. The measurements can be used to calculate the net accumulation (or ablation) of the glacier in t/y. Three such mass balance devices have been installed at Victoria Lower Glacier during season 1999/2000 and 2000/2001.
Ice Core Drilling
In order to collect, store and process a 200m core, a field ice core laboratory / clean room was excavated (Fig.3). In the process 90m3 (?20t) of snow were moved. The temperature in the storage compartments had to be kept below –20°C, a temperature that guarantees that the chemical and isotopic characteristics of the cores are conserved. At a depth of 2.70m we reached this temperature, a remanent of the cold winter wave that travels from the glacier surface downwards.
Once the preparation for the drilling was completed, the drilling crew and the ICDS/NSF supplied electromechanical drill were flown to Victoria Lower Glacier. The drilling system worked well and we reached a depth of 180m (Fig.4). The processing crew extracted the core from the core barrel in the field laboratory in order to avoid contamination. The cores were then cleaned from cuttings (Fig.5), packed in "layflat" tubing, measured (Fig.6), and finally logged (Fig.7) before stored in the 'freezer' compartments of the snow pit. The ice cores were flown out to the transitional ice core facilities at McMurdo Station.page 3
The core quality deteriorated somewhat below 50m, a depth that coincides with a sharp boundary in the ground penetrating radar profile. This indicates that the ice below 50m could be older than first assumed, which makes the air enclosed in the ice potentially very interesting. The ICDS head ice core driller, Mr. Bruce Koçi, visited us in order to discuss possibilities to improve the core quality. Although some progress was made, in order to recover core material that is suitable for air bubble analysis a wet drilling system (electromechanical drill with drilling fluid) will have to be employed for this in future. The quality of the recovered core is sufficient for the proposed water and dust analysis. At Crary Laboratory the cores were split and sent to New Zealand and our collaboration partner, Prof. Paul Mayewski in the USA.
The drill hole was cased and capped (Fig. 8) to preserve the hole for future measurements, such as borehole temperature, magnetic susceptibility, transmissivity of light amongst others.
Basic weather observations have been recorded twice daily using a Scott Base meteorology kit. The measurements included: air temperature, wind direction, wind strength, air pressure, cloud cover and height and visibility.
Polar Plateau (near Shapeless Mountain) S 77° 21.092′, E 159° 52.226′
The climatic system of the Dry Valley area is complex. In order to interpret the climate record contained in the ice cores from Victoria Lower Glacier it is necessary to trace air mass trajectories and to distinguish between marine and continental influences. For this reason snow profiles have been sampled along a transect from the coast towards the East Antarctic Ice Sheet during the 2000/2001 season. To complete this transect a snow profile representative for the polar plateau has been sampled (Fig.9). The samples will be used to identify page 4 the characteristics of continental air masses and to quantify global dust input. The snow was sampled with 1cm resolution in 60ml HDPE Nalgene bottles (Fig.10). The snow profile temperatures will be compared with the measurements from Victoria Lower Glacier.
BERTLER N., MAYEWSKI P., BARRETT P., SHULMEISTER J., PYNE A., DICKINSON W., KREUTZ K. (in prep): Antarctic Response to Solar Activity – A guideline for policy makers?
BERTLER, N. (in prep): Changes in Climate and Ice Cover of the South Victoria Land Coast over the last 10,000 years. PhD thesis. Victoria University of Wellington.
- Peter Barrett, Alex Pyne, Jamie Shulmeister and Warren Dickinson for many useful discussions on scientific goals and field techniques
- Antarctic Research Centre, Victoria University for supporting this project
- Paul Mayewski for helpful discussions on ice core analysis and interpretation and for providing laboratory facilities in the United States
- Antarctica New Zealand for supporting this project
- NSF, Charlie Bentley and Bruce Koçi for supplying the drilling equipment and ice drilling expertise
- Webster Drilling for providing drilling expertise
- Scott Base staff, especially Jim Cowie and Keith Springer for logistical support
- Tim Haskell for providing freezer facilities in New Zealand
- Crary Laboratory for logistical and laboratory support at McMurdo Station
- FRST/PGSF for funding this project (grant VUW808)