Latitude (-68.5599 to -68.5599) Longitude (78.1958 to 78.1958)
Rationale For Indicator Selection
Deep Lake is the most saline of the lakes of the Vestfold Hills, and due to its salinity, has never been known to completely freeze. It is the only major lake in Antarctica with this characteristic, which makes it a prime candidate for monitoring water levels. This was recognised many years ago, and the water level has been monitored on a monthly basis since 1976. This 25-year long database is one of the longest non-weather records of the natural environment in Antarctica. Significant changes in the water level have been observed over this time.
The water level is related to water balance, that is the difference between inputs by direct precipitation or from melt of snow banks in the drainage basin, and losses, which include evaporation when the lake is ice free and ablation when it ice covered.
Net loss terms are thought to be relatively constant from year to year, and therefore water level is a measure of net precipitation. This may be direct (falling within the drainage basin) or indirect (initially falling elsewhere, but blown into the drainage basin by strong winds).
The water level of Deep Lake is a technologically simple measure of an important parameter. The long existing database should be continued, and means that all data collected can immediately be put into a long-term view.
Design and Strategy For Indicator Monitoring Program
Spatial scale: Deep Lake in the Vestfold Hills near Davis Station Antarctica.
Selection of Monitor. One member of the wintering group at Davis each year will be designated the Deep Lake monitor, preferably during pre-departure training. This person should discuss the project with the indicator custodian, and be comfortable with the requirements of the position prior to leaving for Antarctica. In the past, the person responsible for the measurements has often been a non-scientist who otherwise would not normally get off base regularly. This role provides a mechanism by which non-scientists can become involved in a long term scientific program.
If at all possible, there should be a joint visit to Deep Lake by the outgoing and incoming monitors over summer so that details of the location of the pole, method for reading and input of the data into SIMR can be passed on. It is recognised that this may not be possible during changeover, but if the monitors share a longer period together on base, such a visit to the lake should be made.
If the Deep Lake monitor has to leave Davis before winter, or no longer feels he or she is able to fulfil this role, another expeditioner should be designated to maintain continuity of the record.
Frequency: Readings of the surface level of Deep Lake should be taken monthly, preferably within the last few days of any month. A week prior the end of the month, an email will be sent to the Deep Lake monitor reminding him or her that a measurement is due. If no data has been input into the SIMR system by the end of the month, another email will be sent, which will be copied to the Station Leader. This formal monthly reading does not preclude other visitors to the lake recording data. Any expeditioners visiting the lake should be encouraged to record data and pass it on to the designated monitor for inclusion within SIMR. If readings input appear to be in error, the Indicator Custodian will contact the monitor and either work out the problem or request another measurement be made.
Technique: Water level is measured by use of a marked pole located near the edge of the lake, which is in turn tied in to a nearby, accurately surveyed, benchmark. The pole is marked in at 1 cm intervals, and should be read to the closest centimetre. At least two expeditioners should make independent estimates of the water level, which are then compared and a consensus reached. This value, which is a relative, rather than direct measure of the water level of Deep Lake, is input into the SIMR system. While at the lake, note should be taken of the state of the pole. If any change in the position of the pole has occurred since the last visit, an email should be sent to the Indicator Custodian, giving details.
The position of the pole should be checked on an annual basis over summer. This process can be done by surveyors, or, if none are available at Davis, by expeditioners after consultation with the Indicator Custodian and the Mapping Officer, Antarctic Division.
On the 22 Feb 2000, the base or zero reading of the "Tide Pole" at Deep Lake was 51.333 metres below sea level. To derive the water level of Deep Lake below mean sea level, the water level reading on the "Tide Pole" is added to -51.333. Note that this is a negative value so any water level readings will produce a smaller negative number.
The annual cycle in water level can be readily explained, but longer-term variations are more difficult.
The input and output terms are understood, but how these are controlled by the weather is less clear. Analysis of the water level data as well as weather data from Davis station currently underway should clarify the situation.
Temporal range of the available data, as described by the metadata record, is from
19-February-1977 to 30-August-2015
Number of data points
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Pole height at Deep Lake, Davis
Deep Lake: Water level
Data quality, interpretation and analysis of indicator data
Water level in closed lakes (i.e. those without a surface outlet) of the Vestfold Hills has varied markedly over the last thirty years. For example, the surface level of Ace Lake rose by about 2 metres between 1974 and 1994. Measurement of changes in the water level in most of the closed lakes is confounded by the presence of ice for approximately 11 months of the year. Retrieving actual water level in the presence of ice is possible, but difficult, and so only long-term changes can be identified.
The nature of the dataset makes it easy, at least at an initial level, to interpret. Changes in water level are clearly visible, and the graph of the data lends itself to presentation on the web, particularly due to the length of the dataset. There is an annual cycle in which the water level drops during winter, and increases again during summer. This is due to the cooling of the water, as well as decreased water input in winter. Relatively warm temperatures in summer result in thermal expansion of the water of the lake, as well as melt of snow banks in the drainage basins. Longer-term variations also occur. The lake rose by about 1 m between 1976 and 1988, when it began to fall again. This period of decrease in level may have ended in 2000.
More detailed analysis of the dataset to 2000 is currently underway. It is relatively straightforward to remove the annual variation mathematically to get a less noisy curve. The annual cycle in water level can be readily explained, but the longer-term variations are more difficult. The input and output terms are understood, but how these are controlled by the weather is less clear. Analysis of the water level data as well as weather data from Davis currently underway should clarify the situation.
Data usage constraints
' This data set conforms to the PICCCBY Attribution License (http://creativecommons.org/licenses/by/3.0/). '
Data access constraints
' These data are publicly available for download from the URL given below. '
5 Sep 2002
Deep Lake is the most saline of the large lakes of the Vestfold Hills, East Antarctica. The lake was formed when an arm of the sea was cut off due to post-glacial isostatic rebound. It has a small drainage basin and no outlet, and net evaporation over the thousands of years since isolation has resulted in the high salinity. The water level of the lake is now a balance between evaporation, and direct and indirect input of precipitation. The lake does not freeze during winter, so water level is measured easily. The level of Deep Lake has been recorded regularly (approximately monthly) since the mid-1970s. The data show an annual trend, with water level decreasing in autumn and winter, and increasing in spring. This is partly due contraction of the water during cooling in autumn and winter, and expansion during spring and summer. Sufficient temperature data exist for two years to estimate these affects, and to allow recovery of the true annual cycle of net precipitation (ie precipitation - evaporation). A longer term cycle is also evident in the data by comparing data from the same period each year. Such an analysis indicates that the water level in the lake increased from the mid-1970s until 1987, but then began to drop. This general trend was also observed in many other lakes in the Vestfold Hills. What do these trends imply? The annual water balance of Deep Lake became positive in the late 1990s or early 2000s, and water level is now increasing. This is consistent with an apparent increase in precipitation at Davis Station in recent years. The precise timing of the change in annual water balance from negative to positive is uncertain due to a gap in the data during this period. A note of caution in interpreting data in recent years must be added. There are problems at present with the 'tide pole' used to measure the water level of Deep Lake, and until this problem can be corrected during the 2002-2003 summer, recent data must be viewed with some caution. However, the general trend of increasing water level at present is likely to be true.
The precise controlling factors of the water level have yet to be determined, but, as evaporation is expected to be near constant from year to year, it is likely that the water level is a recorder of net precipitation. This is unlikely to be true precipitation (ie direct snowfall), but rather a measure of the amount of snow that accumulates in the drainage basin of the lake during blizzards, which then melts during summer. The precise nature of the controlling factors are the subject of on-going research. However, given the length of the record from Deep Lake, it is one of the most important indicators of climate change currently available from East Antarctica.
7 Nov 2002
Condition scale - 7 - the environment is pristine, in perfect condition, no anthropogenic influences
1 - the environment degraded to the point where rehabilitation is impossible
7 - the environment is pristine, in perfect condition, no anthropogenic influences
SOE_deep_lake - Water levels of Deep Lake, Vestfold Hills
Project 2323 - Applying e-science to evaluating antarctic lakes as indicators of climate change
Publication 1205 - Burton, H.R., Campbell, P.J., (1980) The climate of the Vestfold Hills, Antarctica, with a note on its effects on the hydrology of hypersaline Deep Lake. ANARE Report 129. .
Publication 1210 - Barker, R.J., (1980) Physical and chemical parameters of Deep Lake, Vestfold Hills, Antarctica. ANARE Reports 130.
Publication 2327 - Ferris, J.M., Burton, H.R., (1988) The annual cycle of heat content and mechanical stability of hypersaline Deep Lake, Vestfold Hills, Antarctica. Biology of the Vestfold Hills, Antarctica. Hydrobiologia 165. 115-128
Scientific Bibliography 110
- Edwards, R. (1991 ) Limnological studies of Deep Lake, Antarctica. MSc Thesis, Melbourne University
Scientific Bibliography 111
- Edwards, R. , Finlayson, B.L. (1991 ) The water balance of an Antarctic hypersaline lake. Proceedings, International Hydrology and Water resources Symposium, Perth, October 2-4, 1991, 699-703
Scientific Bibliography 17340
- Gibson, J.A.E., & Burton, H.R. (1996) Meromictic Antarctic Lakes as Recorders of Climate Change: The Structure of Ace and Organic Lakes, Vestfold Hills, Antarctica. Papers and Proceedings of the Royal Society of Tasmania, Vol 130, pp73-78.
SOE Indicator 1
- Monthly mean air temperatures at Australian Antarctic Stations
SOE Indicator 7
- Monthly mean of three-hourly wind speeds (m/s)
SOE Indicator 8
- Monthly mean atmospheric pressure at Australian Antarctic Stations
SOE Indicator 16
- Extent of summer surface glacial melt (sq km)
The properties link can be used to view details of the parameters measured for this indicator.