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Immediate report of Victoria University of Wellington Antarctic Expedition 1989-90: VUWAE 34
THE HYDROLOGY, GLACIOLOGY, AND SEDIMENT TRANSPORT PROCESSES OF THE MIERS VALLEY (K046)
THE HYDROLOGY, GLACIOLOGY, AND SEDIMENT TRANSPORT PROCESSES OF THE MIERS VALLEY (K046)
Abstract
This project involved the second year of a hydrological, glaciological, and sediment transport monitoring programme in the Miers Valley. Information required to study and quantify the energy and mass balances of the glacier-river-bake system have been collected.
Data with significant implications to our understanding of the controls of stream flow in the Antarctic were collected. Evidence that direct solar radiation rather than temperature controls the stream flow has considerable importance to the current discussion of global warming and conflicts with many of the "popular" theories being advanced.
Fluvial sediment transport appears to be highly variable both through time and in space. Movement is of sand-sized particles (and smaller) and commences at very low flows and velocities. Coarser material forms a "lag" deposit on the bed and appears to be essentially immobile except under high flow regimes.
Once stream flow begins for the season there is usually sufficient energy available to mobilise any available sand-sized sediment. The fact that sediment is not continuously in motion suggests that the system is supply constrained. The sand is supplied from erosion of the stream banks and importantly from material present in water drained from the glaciers.
The different surficial materials throughout the valley reflect different proportions of the incoming solar radiation. As expected the "lighter" surfaces reflect a greater proportion than the darker surfaces. Data collected, but still to be analysed, should allow the absolute amounts of incoming radiation and the proportion reflected from each surface type to be quantified.
The change in albedo affects the temperature profiles under the various pavements, the depth to permafrost, the thickness of the active layer, and consequently the degree of development of the "patterns".
Resurvey of the three rows of five ablation poles on the Adams and Miers glaciers indicates, from the observed angles only, a movement of the upper portions of the glaciers of the order of 1 m.
No changes were evident in the appearance of the aprons or glacier snouts between seasons. Some spalling of material had obviously occurred but even the close spacing of survey points of 10 m made it difficult to detect any changes with "simple" survey techniques.
Over 100 photographs, carefully controlled for position and orientation, were taken to provide a stereoscopic coverage of the glacier snouts. These will allow a terrestrial photogrammetric survey of both the Miers and Adams glacier fronts. This should allow relatively small changes to be detected and quantified.
Proposed Programme
Work in the Miers has focused on quantifying various components of the energy balance for the valley. This work has significant implications to the current discussion of global warming and its likely impact on world sea levels. The Miers was chosen for this study as ft is a relatively small and simple valley with few inputs and outputs, all of which can be readily monitored.
Besides monitoring various climatic parameters and their control on the stream flow the affects of the available energy on geomorphic processes were also measured. The Miers valley provided a study area in which several experiments could be undertaken and replicated without the need for laboratory flume studies and the confusion caused by soils and vegetation in more temperate regions.
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| 1. | Continuation of the monitoring of stream flow and various climatic parameters which may be controlling its timing and volume. |
| 2. | Monitoring and attempting to quantify the fluvial sediment transport processes. |
| 3. | An attempt to quantify the albedo of the various surficial materials (including glacier and lake ice, and water) and relating this to the distinctive "patterned" ground found throughout the valley. |
| 4. | Measurement of changes in the Miers and Adams glaciers and testing the practicality of using "terrestrial" photogrammetric techniques to monitor changes in the terminal faces of the glaciers. |
The Miers Valley was chosen for this study because it has only two contributing glaciers, the Miers and Adams, each of which drains from a different aspect. This work builds on field work in the area by two members of the research team during the previous field season.
| 1. | The evaluation of the seasonal variability of glacier behaviour and surface water hydrology. |
| 2. | An improved understanding of the energy and mass balances of the glacier-river-lake system in the Miers Valley, which typifies such systems in the Dry Valleys region. |
| 3. | The development of a water balance for the Miers Valley hydrologic system. |
| 4. | The quantification of sediment sources, the relative importance of sediment transporting media, and how these vary both spatially and temporally. |
| 5. | Quantification of the albedo (reflective) properties of the various surficial materials found throughout the valley. |
Although some of these areas of study have been attempted in other areas of Antarctica (e.g., the Wright Valley) these studies have tended to be inconclusive because of the intensity of sampling and the complexity of the systems investigated.
Scientific Endeavours and Achievements
Hydrology
| 1. | Stream flow is directly controlled by the amount, and intensity, of solar radiation striking the glaciers. Such is the level of this control that clouds passing in front of the sun can be identified in the hydrographs. |
| 2. | Temperature has only a minor affect on stream flow, determining to a slight degree the "baseflow" when there is no direct sunlight. |
| 3. | There is a maximum amount of melt able to be generated, if there is no cloud when the sun is at a particular azimuth. This is indicated by "flat" peaks on the hydrographs. |
| 4. | The maximum amount of melt possible on any day during the season (if there is no cloud) is cyclic and increases as the angle of the sun gets higher. Essentially maximum stream flows are cyclic around the "longest day".page 15 |
| 5. | Periods with several "clear days in a row had higher flows as a result of gradually increasing "baseflows". |
Fluvial sediment Transport
| 1. | High spatial and temporal variability as found in other studies. |
| 2. | Movement of sand sized and smaller particles. Particles larger than this appear to form a "pavement" or lag deposit" on the bed. These larger particles tended to roll only when the sand around them was removed under high flow regimes. |
| 3. | Movement tends to be via migrating ripples although movement commences at very low flows and very low velocities. This ease of movement appears to be a result of particle shape (predominately spherical) and the generally smooth and regular bed. |
| 4. | The fluvial transport system appears to be supply constrained. That is, there always appears to be sufficient energy available to shift any sand sized particles present. On occasion, however, both temporally and spatially these particle sizes are absent. |
Albedo Studies
Distinctive differences were found between the albedo (reflective) properties of the various surficial deposits in the valley.
| 1. | The glaciers had the highest reflective properties (except when covered with silt) followed by lake ice, marble dominated pavement, granite pavement, and lastly volcanic dominated pavement. |
| 2. | The change in albedo affects the temperature profiles under the pavement, the depth to permafrost, the thickness of the active layer, and consequently the degree of development of the "patterns". |
| 3. | The degree of development of the patterns appears to be related to the availability of moisture and the cryergic activity at the site. Variation in the rate of this activity in the valley is largely controlled by the albedo of the different surfaces. |
Ground Survey and Photogrammetry
Considerable survey work was again undertaken during the past season. Tying into the various benchmarks established in 1988-89 and completion of the survey network during the past season allowed the following work to be undertaken.
| 1. | A resurvey of the three rows of five ablation poles on the Adams and Miers glaciers. The observed angles suggest movement of the upper portions of the glaciers to be of the order of 1 m. |
| 2. | A resurvey of the glacier snouts and their associated aprons. No changes are evident in the preliminary calculations of the measurements of the aprons or glacier snouts between the two seasons. Some spalling of material had obviously occurred but even the close spacing of survey points of 10 m made it difficult to detect any changes. |
Ablation of the "fallen" ice also makes it difficult to establish amounts of ice lost from the system. To precisely measure the stability or shift of the glacier fronts and to assess the glacier ice lost from the snout, a terrestrial photogrammetric survey of both the Miers and Adams Glaciers was undertaken this season. Approximately 100 photographs were taken to provide a stereoscopic coverage of the glacier snouts. Each photograph position was accurately set up with respect to a known geometry. Foreground and background survey marks were established using "terrier bolts" which were flagged with coloured discs mounted on special fittings for
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photography. With this "height" control it is intended to map the glacier fronts using the floating mark of the photogrammetric plotter. This will result in very accurate profiling and contouring which will allow minor changes in the morphology and volume of the glacier snouts to De quantified very accurately.
Publications
| 1. | Two papers for the New Zealand Antarctic Record: one on ground water hydrology and its importance in the Antarctic (a little reported area); and one on the instrumentation used during the season. |
| 2. | One paper for either Nature, the Journal of Hydrology, or the Journal of Glaciology on the results of the field season and their implications to the discussion of "global warming" and predicted consequent rises in sea level. |
| 3. | The sedimentological work will be initially reported as an Honours dissertation submitted in the Research School of Earth Sciences at Victoria University before possible publication in the Journal of Hydrology. |
| 4. | One paper on the aeolian sediment transport processes and landforms will be published in "Earth Surface Processes". |
| 5. | One paper on the albedo measurements and variations in the temperature profiles will be published in "Earth Surface Processes". |
| 6. | One paper on the work undertaken on the "patterned" ground will be published in "Earth Surface Processes". |
| 7. | At least one paper on the work undertaken on terrestrial photogrammetry will be published in a reputable "Photogrammetry Journal". |
| 8. | At least four conference papers should also come from the work of the past season. |
Environmental Impact
| 1. | The construction of the weirs resulted in minor channel modification and an overflow channel on the Adams stream was diverted to bring all the flow together above the weir. This diversion was constructed using a hessian embankment and the channel deepened itself naturally with the flow. So effective was this diversion in its first year (1988-89) that it appears to be unnecessary during the past season. Some sand bagging was also required to safeguard the integrity of the weirs and prevent erosion. While hessian sacks were in the main used some "blue" plastic rubbish bags were also used. The majority of these were removed at the end of last season and the five which remain are well buried. These remaining bags should, however, remain intact in the weirs and not present an environmental problem. They will be removed with the weirs once they are no longer needed. |
| 2. | The provision of permanent benchmarks around the margins of the glaciers required the installation of "terrier" bolts into prominent rocks. These sites are invisible except where cairns and other markers have been used to surveying purposes. |
| 3. | The only other evidence of our presence in the valley are the numerous foot prints left as we travelled to sites of specific interest. These, however, appear to be "softened" very rapidly by the high winds experienced during the winter The prints left after the 1989-90 season were hardly discernable after the past winter and certainly would not be visible after a further couple of winter seasons. |
Future Research
At this stage it is envisaged that a sufficient data base has been collected to allow many of the questions posed at the outset of this programme to be answered. Time is now required to analyse the data and to identify areas in which further work is required.
In one or two seasons time it is hoped to return to the Miers and to re-photograph and re-measure the glaciers so that the changes discussed above can be quantified. The changes are expected to be relatively small and therefore measurements are not required every year. These measurements should allow a good indication of the changes in the mass balance of the valley.
Management of Science In the Ross Dependency
This type of project is readily supported by Antarctic Division as it is largely self sufficient in the field and requires little by way of mechanical support.
Difficulties in field testing equipment under field conditions in New Zealand mean that at least two seasons are usually required to undertake any specific programme. The first is dedicated to field testing equipment and the second in collecting the required data base.
Acknowledgements
The success of the 1989/90 programme reflects the tremendous assistance received from many persons. The University Grants Committee provided the basic expedition funding and the Internal Research Committee of Victoria University funded all the prefabricated weirs and flumes, the data logging equipment, albedometer, and various sensors.
Graeme Hewitt and the staff of the Mechanical Workshop at Victoria University constructed all the weirs, flumes, sediment traps, and instrument mountings within a very short time frame. They also designed and constructed all the attachments for mounting the camera on the theodolite and for erecting the numerous benchmarks both on the glacier snout and on the rock pavement. A tribute to their work is the fact that all weirs survived the winter and are continuing to work. The quality of the data collected hung on their craftsmanship which could not be faulted.
Staff at Scott Base, but in particular the Operations Manager (Don Hammond), the Stores staff (John Lee and Doug Henderson), and radio operators assisted the project in many ways. Generally all the staff at Scott Base were more than willing to assist event personnel in any way they could.
This was a very productive season on the "Ice" and this is a credit to all those who have helped this event.