Flow, thermal structure, and subglacial conditions of a surge-type glacier

1984 ◽  
Vol 21 (2) ◽  
pp. 232-240 ◽  
Author(s):  
Garry K. C. Clarke ◽  
Sam G. Collins ◽  
David E. Thompson
Keyword(s):  
Energy Source ◽  
Heat Flux ◽  
Thermal Structure ◽  
Drainage System ◽  
Temperature Measurements ◽  
Bottom Temperature ◽  
Water Percolation ◽  
Geothermal Flux

Temperature measurements in a subpolar surge-type glacier reveal a distinctive thermal structure associated with the boundary between the ice reservoir and receiving areas. In the receiving area the glacier is cold based, but bottom temperature has increased as much as 0.5 °C between 1981 and 1982, and the basal heat flux is roughly 10 times the expected geothermal flux. Water percolation through permeable subglacial material is the probable energy source. Deformation of the substrate could destroy this drainage system and trigger a surge.

scholarly journals Borehole Temperature Measuring Equipment and the Geothermal Flux in Tasmania

1953 ◽  
Vol 6 (4) ◽  
pp. 480 ◽  
Author(s):  
G Newstead ◽  
A Beck
Keyword(s):  
Heat Flux ◽  
Measuring Equipment ◽  
Bridge Circuit ◽  
Temperature Measurements ◽  
Temperature Measuring ◽  
A Value ◽  
Borehole Temperature ◽  
Geothermal Flux

An instrument, using a thermistor and an A.C. bridge circuit, is described by which temperature measurements in boreholes can be made to 0�01 �C. Results of temperature measurements in Tasmania are given and a value of 2 cal cm?2 sec?1 is obtained for the heat flux (uncorrected for recent glaciation).

scholarly journals The thermal structure of Israel

2011 ◽  
Vol 3 (1) ◽  
pp. 431-452 ◽  
Author(s):  
E. Shalev ◽  
V. Lyakhovsky ◽  
Y. Weinstein ◽  
Z. Ben-Avraham
Keyword(s):  
Heat Flux ◽  
Thermal Structure ◽  
Local Heating ◽  
Arabian Shield ◽  
Supporting Evidence ◽  
Hydrologic Models ◽  
Average Value ◽  
Water Wells ◽  
Shear Heating ◽  
Deep Seismicity

Abstract. Heat flux at the Arabian Shield is a significant component in reconstructing tectonic, seismic, and hydrologic models. In this paper we analyze temperature data from all the available oil and water wells in Israel. We show that the average heat flux in Israel is 40–45 mW m−2. A supporting evidence for the low heat flux is the relatively deep seismicity, extending almost to the mantle in the region. A Heat flux anomaly that exists in Northern Israel and Jordan could be attributed to groundwater flow or young magmatic activity (~100 000 years) that is common in this area. Xenoliths that yield relatively steep geothermal gradients could be the result of local heating by magmas or by lithospheric necking and shear heating. The higher Heat flux in Southern Israel and Jordan probably reflects the opening of the Red Sea and the Gulf of Eilat and does not reflect the average value of the Arabian Shield.

scholarly journals Pure rotational-Raman channels of the Esrange lidar for temperature and particle extinction measurements in the troposphere and lower stratosphere

2013 ◽  
Vol 6 (1) ◽  
pp. 91-98 ◽  
Author(s):  
P. Achtert ◽  
M. Khaplanov ◽  
F. Khosrawi ◽  
J. Gumbel
Keyword(s):  
Lower Stratosphere ◽  
Thermal Structure ◽  
Atmospheric Temperature ◽  
Temperature Measurements ◽  
Integration Time ◽  
Aerosol Extinction ◽  
Temperature Profiles ◽  
Backscatter Coefficient ◽  
Upper Troposphere ◽  
532 Nm

Abstract. The Department of Meteorology at Stockholm University operates the Esrange Rayleigh/Raman lidar at Esrange (68° N, 21° E) near the Swedish city of Kiruna. This paper describes the design and first measurements of the new pure rotational-Raman channel of the Esrange lidar. The Esrange lidar uses a pulsed Nd:YAG solid-state laser operating at 532 nm as light source with a repetition rate of 20 Hz and a pulse energy of 350 mJ. The minimum vertical resolution is 150 m and the integration time for one profile is 5000 shots. The newly implemented channel allows for measurements of atmospheric temperature at altitudes below 35 km and is currently optimized for temperature measurements between 180 and 200 K. This corresponds to conditions in the lower Arctic stratosphere during winter. In addition to the temperature measurements, the aerosol extinction coefficient and the aerosol backscatter coefficient at 532 nm can be measured independently. Our filter-based design minimizes the systematic error in the obtained temperature profile to less than 0.51 K. By combining rotational-Raman measurements (5–35 km height) and the integration technique (30–80 km height), the Esrange lidar is now capable of measuring atmospheric temperature profiles from the upper troposphere up to the mesosphere. With the improved setup, the system can be used to validate current lidar-based polar stratospheric cloud classification schemes. The new capability of the instrument measuring temperature and aerosol extinction furthermore enables studies of the thermal structure and variability of the upper troposphere/lower stratosphere. Although several lidars are operated at polar latitudes, there are few instruments that are capable of measuring temperature profiles in the troposphere, stratosphere, and mesosphere, as well as aerosols extinction in the troposphere and lower stratosphere with daylight capability.

scholarly journals Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by ground penetrating radar

2011 ◽  
Vol 5 (1) ◽  
pp. 139-149 ◽  
Author(s):  
K. Bælum ◽  
D. I. Benn
Keyword(s):  
Ground Penetrating Radar ◽  
Thermal Structure ◽  
Drainage System ◽  
High Arctic ◽  
Differential Gps ◽  
Glacier Surface ◽  
Digital Elevation ◽  
Drainage Channels ◽  
Ground Penetrating ◽  
Subglacial Drainage

Abstract. Proglacial icings accumulate in front of many High Arctic glaciers during the winter months, as water escapes from englacial or subglacial storage. Such icings have been interpreted as evidence for warm-based subglacial conditions, but several are now known to occur in front of cold-based glaciers. In this study, we investigate the drainage system of Tellbreen, a 3.5 km long glacier in central Spitsbergen, where a large proglacial icing develops each winter, to determine the location and geometry of storage elements. Digital elevation models (DEMs) of the glacier surface and bed were constructed using maps, differential GPS and ground penetrating radar (GPR). Rates of surface lowering indicate that the glacier has a long-term mass balance of −0.6 ± 0.2 m/year. Englacial and subglacial drainage channels were mapped using GPR, showing that Tellbreen has a diverse drainage system that is capable of storing, transporting and releasing water year round. In the upper part of the glacier, drainage is mainly via supraglacial channels. These transition downglacier into shallow englacial "cut and closure" channels, formed by the incision and roof closure of supraglacial channels. Below thin ice near the terminus, these channels reach the bed and contain stored water throughout the winter months. Even though no signs of temperate ice were detected and the bed is below pressure-melting point, Tellbreen has a surface-fed, channelized subglacial drainage system, which allows significant storage and delayed discharge.

The dynamics and impact of compositionally originating provinces in a mantle convection model featuring rheologically obtained plates

2019 ◽  
Vol 220 (3) ◽  
pp. 1700-1716
Author(s):  
Sean M Langemeyer ◽  
Julian P Lowman ◽  
Paul J Tackley
Keyword(s):  
Heat Flux ◽  
Velocity Field ◽  
Mantle Convection ◽  
Surface Deformation ◽  
Thermal Structure ◽  
Dense Material ◽  
Surface Velocity ◽  
Material Surface ◽  
Mantle Component ◽  
High Topography

SUMMARY Previous geodynamic studies have indicated that the presence of a compositionally anomalous and intrinsically dense (CAID) mantle component can impact both core heat flux and surface features, such as plate velocity, number and size. Implementing spherical annulus geometry mantle convection models, we investigate the influence of intrinsically dense material in the lower mantle on core heat flux and the surface velocity field. The dense component is introduced into a system that features an established plate-like surface velocity field, and subsequently we analyse the evolution of the surface velocity as well as the interior thermal structure of the mantle. The distribution and mobility of the CAID material is investigated by varying its buoyancy ratio relative to the ambient mantle (ranging from 0.7 to 1.5), its total volume (3.5–10 per cent of the mantle volume) and its intrinsic viscosity (0.01–100 times the ambient mantle viscosity). We find at least three distinct distributions of the dense material can occur adjacent to the core–mantle boundary (CMB), including multiple piles of varying topography, a core enveloping layer and two diametrically opposed provinces (which can on occasion break into three distinct piles). The latter distribution mimics the morphology of the seismically observed large low shear wave velocity provinces (LLSVPs) and can occur over the entire range of CAID material viscosities. However, diametrically opposed provinces occur primarily in cases with CAID material buoyancy numbers of 0.7–0.85 (corresponding to contrasts in density between ambient and CAID material of 130 and 160 kg m−3, respectively) in our model (with an effective Rayleigh number of order 106). Steep and high topography piles are also obtained for cases featuring buoyancy ratios of 0.85 and viscosities 10–100 times that of the ambient mantle. An increase in relative density, as well as larger volumes of CAID material, lead to the development of a core enveloping layer. Our findings show that when two provinces are present core heat flux can be reduced by up to 50 per cent relative to cases in which CAID material is absent. Surface deformation quantified by Plateness is minimally influenced by variation of the properties of the dense material. Surface velocity is found to be reduced in general but mostly substantially in cases featuring high CAID material viscosities and large volumes (i.e. 10 per cent) or buoyancy ratios.

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