Author: Christopher Lee JarosPublisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 182
Book Description
Temperature-elevation Effect on Glacial Meltwater Generation in McMurdo Dry Valleys, Antarctica
Author: Christopher Lee JarosPublisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 182
Book Description
Spatial and Temporal Variability of Glacier Melt in the McMurdo Dry Valleys, Antarctica
Author: Matthew James HoffmanPublisher:
ISBN:
Category : Ablation (Aerothermodynamics)
Languages : en
Pages : 296
Book Description
In the McMurdo Dry Valleys, Victoria Land, East Antarctica, melting of glacial ice is the primary source of water to streams, lakes, and associated ecosystems. To better understand meltwater production, three hypotheses are tested: 1) that small changes in the surface energy balance on these glaciers will result in large changes in melt, 2) that subsurface melt does not contribute significantly to runoff, and 3) that melt from 25-m high terminal cliffs is the dominant source of baseflow during cold periods. These hypotheses were investigated using a surface energy balance model applied to the glaciers of Taylor Valley using 14 years of meteorological data and calibrated to ablation measurements. Inclusion of transmission of solar radiation into the ice through a source term in a one-dimensional heat transfer equation was necessary to accurately model summer ablation and ice temperatures. Results showed good correspondence between calculated and measured ablation and ice temperatures over the 14 years using both daily and hourly time steps, but an hourly time step allowed resolution of short duration melt events and melt within the upper 15 cm of the ice. Resolution of short duration melt events was not important for properly resolving seasonal ablation totals. Across the smooth surfaces of the glaciers, ablation was dominated by sublimation and melting was rare. Above freezing air temperatures did not necessarily result in melt, and low wind speed was important for melt initiation. According to the model, subsurface melt between 5 and 15 cm depth was extensive and lasted for up to six weeks in some summers. The model was better able to predict ablation if some subsurface melt was assumed to drain, lowering ice density, consistent with observations of a low density weathering crust that forms over the course of the summer on Dry Valley glaciers. In extreme summers, drainage of subsurface melt may have contributed up to half of the observed surface lowering through reduction of ice density and possibly through collapse of highly weathered ice. When applied spatially, the model successfully predicted proglacial streamflow at seasonal and daily time scales. This was despite omitting a routing scheme, and instead assuming that all melt generated exits the glacier on the same day, suggesting refreezing is not substantial. Including subsurface melt as runoff improved predictions of runoff volume and timing, particularly for the recession of large flood peaks. Because overland flow was rarely observed over much of these glaciers, these model results suggest that runoff may be predominantly transported beneath the surface in a partially melted permeable layer of weathered ice. According to the model, topographic basins, particularly the low albedo basin floors, played a prominent role in runoff production. Smooth glacier surfaces exhibited low melt rates, but were important during high melt conditions due to their large surface area. Estimated runoff contributions from cliffs and cryoconite holes was somewhat smaller than suggested in previous studies. Spatial and temporal variability in albedo due to snow and debris played a dominant role in flow variations between streams and seasons. In general, the model supported the existing assumption that snowmelt is insignificant, but in extreme melt years snowmelt in the accumulation area may contribute significantly to runoff in some locations.
Ecosystem Dynamics in a Polar Desert
Author: Glacial Meltwater Modeling to Simulate Lake Water Budget (1996-2013) in Taylor Valley, Antarctica
Author: Publisher:
ISBN:
Category : Hydrologic models
Languages : en
Pages : 100
Book Description
The McMurdo Dry Valleys (MDV), the largest ice-free region (4,500 km2) in Antarctica, are a polar desert with an average annual temperature of -18°C. In Taylor Valley, one of the MDV, closed-basin, perennially ice-covered lakes occupy the valley floor. Their water balance is controlled by inflow from glacial meltwater runoff and loss due to sublimation, making them sensitive indicators of climate. In this study, a physically-based model of glacier meltwater and lake ice sublimation is adapted to explain modern (1996 to 2013) lake-level variations. Meltwater model results were improved by the inclusion of MODIS remotely-sensed albedo measurements (E = 0.47; nRMSE = 0.73). After 2008 the meltwater model significantly under-predicted streamflow and only through decreasing albedo by -30% (equivalent to a decrease of -0.18 on average) did the results match observations (E = 0.79; nRMSE = 0.45). This study provides the first estimate of direct (unmeasured) glacier inflow to the lakes, 69%, 73% and 28%, and sublimation loss rates, 0.37 m yr−1, 0.24 m yr−1 and 0.16 m yr−1, for lakes Bonney, Hoare and Fryxell, respectively. Despite similar meltwater volumes entering lakes Bonney and Fryxell, the difference in basin hypsometry results in a much faster lake rise at Bonney from 2002-13. If future climate conditions match current (1996-2013) conditions, all lakes will rise through the end of the century.
Papers from the International Symposium on Ice and Water Interactions
Author: Douglas R. MacAyealPublisher:
ISBN:
Category : Nature
Languages : en
Pages : 268
Book Description
Ecosystem Dynamics in a Polar Desert
Author: Publisher: American Geophysical Union
ISBN: 9780875905
Category : Desert ecology
Languages : en
Pages : 224
Book Description
Presents information from the primary abiotic forces defining the system, and from the present hydrology, biogeochemistry and physics of major sites of organic carbon production of the McMurdo Dry Valleys. Additionally, research on the physical, chemical, and biological properties of the dry valley soils is included. The role of environmental management in long-term ecological studies is also addressed. The accompanying CDROM provides details and scale to visualize the McMurdo Dry Valleys from an ecosystem perspective.
Hydrologic Controls of Nutrient Fluxes in Glacial Meltwater Streams at Inter-annual, Seasonal, and Daily Timescales in the McMurdo Dry Valleys, Antarctica
Author: Mitchell R. WeaverAntarctic Journal of the United States
Author: Polar Lakes and Rivers
Author: Warwick F. VincentPublisher: OUP Oxford
ISBN: 0191550183
Category : Science
Languages : en
Pages : 352
Book Description
This is the first book to describe the ecology of high latitude lakes, rivers and glacial environments in both the North and South polar regions. From the lake-rich floodplains of the Arctic to the deep, enigmatic waters of Lake Vostok, Antarctica, these regions contain some of the most extraordinary aquatic ecosystems on Earth. They provide a fascinating diversity of habitats for plant, animal and microbial communities, and are proving to be valuable model systems for exploring many ecological themes including landscape-lake interactions, adaptation of life to environmental extremes, and controls on the structure and functioning of aquatic ecosystems. Some of these waters also have direct global implications, including permafrost thaw lakes as sources of greenhouse gases, subglacial aquatic environments as a storehouse of ancient microbes, and Arctic rivers as major inputs of freshwater and organic carbon to the World Ocean. Given that many polar areas are experiencing greater climate warming than at lower latitudes, these ecosystems can also be viewed as sentinels of global change. This timely volume brings together many of the world's leading researchers in polar limnology to describe these diverse aquatic environments and their ecology. It introduces each major ecosystem type, examines the similarities and differences between Arctic and Antarctic systems as well as their responses to environmental change, and describes new frontiers for future research. A glossary of terms is provided for non-specialists, and a set of colour plates introduces the ecosystems and their biota. Polar Lakes and Rivers will be of value to students and specialist researchers alike, as well as to those with a more general interest in aquatic ecology, polar environments or global change who require an authoritative overview of this fast emerging topic.
Glacial and Periglacial Geomorphology of the McMurdo Dry Valleys, Antarctica
Author: Kate Mackenzie SwangerPublisher:
ISBN:
Category :
Languages : en
Pages : 498
Book Description
Abstract: Although the McMurdo Dry Valleys (MDV) of Antarctica lie within an archetypal cold-desert climate, research presented here shows that the MDV are best divided into a series of microclimatic zones, with each zone fostering a unique suite of landforms and geomorphic processes that are produced by, and in balance with, local summertime environmental conditions. To quantify better the relationship between microclimates and landforms, we conducted a series of field-based and numerical-modeling studies designed (1) to elucidate landform response to potential climate warming, (2) to determine past climate variation by reconstructing former ice-volume changes of outlet glaciers draining the East Antarctic Ice Sheet, and (3) to describe the range of processes that both produce and modify near-surface ice in each microclimatic zone. Results from a one dimensional heat diffusion equation coupled with a Mohr-Coulomb-based safety-factor model show that ice-cemented slope deposits in the upland microclimate zone would remain frozen, without failure from planar sliding, even if local summertime atmospheric temperatures were to warm by as much as 4 to 9°C. Given documented evidence for enduring geomorphic stability, the model results suggest that the maximum potential summertime warming in this zone since late Miocene time was 4 to 9°C. At lower elevations of the MDV, within the inland-mixed microclimatic zone, buried ice today experiences seasonal melting and modification via the formation of secondary ice; stream dissection, fan deposition, and active-layer cryoturbation also play major roles in modifying buried ice and overlying deposits. Finally, geomorphic analyses of nine moraines in Kennar Valley show that the East Antarctic Ice Sheet inland from the MDV has remained stable and robust ( -200 m of ice-elevation change) for at least the last -3.1 million years; chronologic control for the moraine sequence comes from cosmogenic 3 He analyses of surface boulders. Taken together, the results suggest that the modern microclimatic zonation of the MDV has persisted for at least the last 3.1 million years, making it one of the most climatically stable regions on Earth.