scholarly journals Modelling of Quaternary Glacier Extent and Climate in Tasmania, Australia

2021 ◽  
Author(s):  
◽  
Rebecca Joan O'Donnell
Keyword(s):  
West Coast ◽  
Three Dimensional ◽  
Atmospheric Temperature ◽  
Coast Range ◽  
The West ◽  
Central Plateau ◽  
Climate Conditions ◽  
Temperature Reduction ◽  
Temperature And Precipitation ◽  
Central Highlands

<p>The aim of this study was to improve our understanding of Quaternary glaciations in Tasmania, and to assess their climatic significance. During the Quaternary, Tasmania experienced ice cap development in the West Coast Range and Central Plateau, with smaller cirque and valley glaciers developing on surrounding mountains. Geomorphic evidence indicates at least four glacial advances occurred. A 500 m resolution, three-dimensional thermomechanical ice-sheet model was used to reconstruct and simulate these glacier fluctuations. The model, while a simplification of reality, provided a framework in which to understand the genesis of contemporary landforms and former glacial climate conditions in Tasmania. Input specifications of basal topography, temperature and precipitation were required, with the latter two interpolated from present-day datasets. Numerous experiments were carried out, involving systematic alterations to temperature and precipitation, basal sliding and atmospheric temperature lapse-rates. Modelled output was compared to empirical evidence with the aim of optimizing the parameters (temperature, precipitation) from which model mismatch was minimised. An annual temperature reduction of 6' C is required for glaciers to form in Tasmania. When temperatures cool beyond this threshold, an ice mass develops over the Central Highlands, Central Plateau, West Coast Range and other mountains. In all but the most extensive glaciations, the Central Plateau ice field consists of a relatively thin carapace of ice, and the thickest and most dynamic glaciers develop in the deep valleys of the Central Highlands. The model shows that ice readily flows down the west-facing valleys from the Central Highlands to join with West Coast Range glaciers. A temperature reduction between 7 and 9' C, with corresponding regional precipitation changes of between +/-50% and an increase in orographic precipitation is required to simulate the Last Glacial Maximum (LGM) ice cover. Earlier glacial advances require larger coolings of up to 11.25' C depending on the regional precipitation conditions prescribed. Mismatches between geomorphic evidence and modelled reconstructions probably result from model grid size issues and parameters not accommodated by the model such as wind-blown snow redistribution. This means that temperature reductions derived from the model may have been overestimated. Despite these limitations, reconstructed temperatures compare well to some multi-proxy palaeo-temperature records from Tasmania, although the cooling identified was larger than that recorded in nearby ocean sediments.</p>

scholarly journals Modelling of Quaternary Glacier Extent and Climate in Tasmania, Australia

2021 ◽  
Author(s):  
◽  
Rebecca Joan O'Donnell
Keyword(s):  
West Coast ◽  
Three Dimensional ◽  
Atmospheric Temperature ◽  
Coast Range ◽  
The West ◽  
Central Plateau ◽  
Climate Conditions ◽  
Temperature Reduction ◽  
Temperature And Precipitation ◽  
Central Highlands

<p>The aim of this study was to improve our understanding of Quaternary glaciations in Tasmania, and to assess their climatic significance. During the Quaternary, Tasmania experienced ice cap development in the West Coast Range and Central Plateau, with smaller cirque and valley glaciers developing on surrounding mountains. Geomorphic evidence indicates at least four glacial advances occurred. A 500 m resolution, three-dimensional thermomechanical ice-sheet model was used to reconstruct and simulate these glacier fluctuations. The model, while a simplification of reality, provided a framework in which to understand the genesis of contemporary landforms and former glacial climate conditions in Tasmania. Input specifications of basal topography, temperature and precipitation were required, with the latter two interpolated from present-day datasets. Numerous experiments were carried out, involving systematic alterations to temperature and precipitation, basal sliding and atmospheric temperature lapse-rates. Modelled output was compared to empirical evidence with the aim of optimizing the parameters (temperature, precipitation) from which model mismatch was minimised. An annual temperature reduction of 6' C is required for glaciers to form in Tasmania. When temperatures cool beyond this threshold, an ice mass develops over the Central Highlands, Central Plateau, West Coast Range and other mountains. In all but the most extensive glaciations, the Central Plateau ice field consists of a relatively thin carapace of ice, and the thickest and most dynamic glaciers develop in the deep valleys of the Central Highlands. The model shows that ice readily flows down the west-facing valleys from the Central Highlands to join with West Coast Range glaciers. A temperature reduction between 7 and 9' C, with corresponding regional precipitation changes of between +/-50% and an increase in orographic precipitation is required to simulate the Last Glacial Maximum (LGM) ice cover. Earlier glacial advances require larger coolings of up to 11.25' C depending on the regional precipitation conditions prescribed. Mismatches between geomorphic evidence and modelled reconstructions probably result from model grid size issues and parameters not accommodated by the model such as wind-blown snow redistribution. This means that temperature reductions derived from the model may have been overestimated. Despite these limitations, reconstructed temperatures compare well to some multi-proxy palaeo-temperature records from Tasmania, although the cooling identified was larger than that recorded in nearby ocean sediments.</p>

Assessing potential climate change impacts on the seasonality of runoff in an Alpine watershed

2014 ◽  
Vol 6 (2) ◽  
pp. 263-277 ◽  
Author(s):  
Klaus Schneeberger ◽  
Christian Dobler ◽  
Matthias Huttenlau ◽  
Johann Stötter
Keyword(s):  
Climate Change ◽  
Full Range ◽  
Three Dimensional ◽  
Climate Change Impacts ◽  
Climate Change Scenarios ◽  
Discharge Data ◽  
Climate Conditions ◽  
Temperature And Precipitation ◽  
Alpine Watershed ◽  
Flood Peaks

The aim of this study is to investigate potential impacts of climate change on the seasonality of runoff in a mountainous watershed, located in the Austrian Alps. In order to consider the full range of possible climate variation, hypothetical climate change scenarios were used to force a hydrological model to simulate runoff time series for potential future climate conditions. The variation of runoff seasonality is illustrated with a three-dimensional representation of daily discharge data, directional statistics of annual flood peaks and the analysis of seasonal occurrence of runoff peaks. The results show that changes in temperature and precipitation patterns could have considerable effects on seasonal runoff variability in the investigated watershed. Generally, a possible increase in temperature may cause an increase in seasonal variability of runoff. Further, annual flood peaks are projected to occur throughout the entire year in the investigated Alpine watershed, whereas moderate high flows may increase in winter (December–February).

Glaciations of the West Coast Range, Tasmania

1985 ◽  
Vol 24 (1) ◽  
pp. 39-59 ◽  
Author(s):  
Eric A. Colhoun
Keyword(s):  
West Coast ◽  
Chemical Weathering ◽  
Early Pleistocene ◽  
Similar Distribution ◽  
Coast Range ◽  
Late Cenozoic ◽  
The West ◽  
Glacial Deposits ◽  
Ice Cap ◽  
Snow Line

Geomorphic, stratigraphic, palynologic and 14C evidence indicates that the West Coast Range, Tasmania, was glaciated at least three times during the late Cenozoic. The last or Margaret Glaciation commenced after 30,000 yr B.P., culminated about 19,000 yr B.P., and ended by 10,000 yr B.P. During this period a small ice cap, ca. 250 m thick, and cirque and valley glaciers covered 108 km2. The glacial deposits show little chemical weathering or erosional dissection. The snow line ranged from 690 to 1000 m with an average of 830 m for the ice cap. Mean temperature was 6.5°C below the present temperature. During the preceding Henty Glaciation a 300- to 400-m-thick ice cap and outlet glaciers exceeded 1000 km2. The glacial deposits are beyond 14C assay. They are more weathered chemically and more dissected than Margaret age deposits, and the degree suggests a pre-last interglaciation age (> 130,000 yr B.P.). The snow line of the ice cap lay at 740 m, and annual temperature was reduced by 7°C. Ice of the earliest Linda Glaciation slightly exceeded that of the Henty Glaciation but had a similar distribution. The glacial deposits are intensely weathered, have reversed magnetization, and overlie a paleosol containing pollen of Tertiary type. An early Pleistocene or Tertiary age is indicated.

Pleistocene glaciation of the King Valley, Western Tasmania, Australia

1991 ◽  
Vol 36 (2) ◽  
pp. 135-156 ◽  
Author(s):  
Sean J. Fitzsimons ◽  
Eric A. Colhoun
Keyword(s):  
Southern Hemisphere ◽  
West Coast ◽  
Chemical Weathering ◽  
Middle Latitude ◽  
Pleistocene Glaciation ◽  
Coast Range ◽  
The West ◽  
Last Glaciation ◽  
Late Tertiary ◽  
Pollen Types

AbstractAnalysis of the geomorphology, geology, and palynology of deposits in the King Valley permits the identification of four glaciations and two interglaciations and has led to a revision of the Pleistocene stratigraphy of the West Coast Range. The oldest late-Cenozoic deposits in the valley appear to predate glaciation, contain extinct pollen types, and are probably of late-Tertiary age. Overlying deposits of the Linda Glaciation show intense chemical weathering and have a reversed detrital remanent magnetization indicating deposition before 730,000 yr B.P. The highly weathered tills are conformably overlain by organic deposits of the Regency Interglaciation which show a transition from montane scrub rainforest to lowland temperate rainforest. Deposits formed during the later Moore Glaciation record advances of the King Glacier and glaciers from the West Coast Range. A pollen-bearing fluvial deposit records an interstade during this glaciation. On the basis of weathering rinds, amino acid dating, and palaeomagnetism the deposits are estimated to have formed between 730,000 and 390,000 yr B.P. The Moore Glaciation deposits are overlain by sediments of the Henty Glaciation which are believed to predate 130,000 yr B.P. These deposits record multiple advances of the King Glacier and the development of a large lake during an interstade. Deposits of the subsequent Pieman Interglaciation consist of organic fine sands and silts that record a lowland scrub rainforest. Deposits of the last (Margaret) glaciation are restricted to small areas in the northern part of the valley. Although the most recent ice advance culminated after 19,000 yr B.P., evidence of older deposits of the Margaret Glaciation suggests that an early last-glaciation ice advance may have occurred. When combined with earlier studies, the recent work in the King Valley has provided one of the more complete records of Pleistocene glaciation in the Southern Hemisphere. Comparison of the deposits with the record of glaciation in southern South America and Westland, New Zealand, suggests some similarities exist between pre-last-glaciation events and indicates that glacial events in Southern Hemisphere middle latitude areas were synchronous during the last glaciation.

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