scholarly journals Basal melt at NorthGRIP modeled from borehole, ice-core and radio-echo sounder observations

2003 ◽  
Vol 37 ◽  
pp. 207-212 ◽  
Author(s):  
Dorthe Dahl-Jensen ◽  
Niels Gundestrup ◽  
S. Prasad Gogineni ◽  
Heinz Miller
Keyword(s):  
Heat Flow ◽  
Flow Model ◽  
Flow Line ◽  
Ice Core ◽  
Time Dependent ◽  
Surface Velocity ◽  
Geothermal Heat ◽  
The North ◽  
Annual Layer ◽  
Dependent Flow

AbstractFrom temperature measurements down through the 3001 m deep borehole at the North Greenland Icecore Project (NorthGRIP) drill site, it is now clear that the ice at the base, 3080 m below the surface, is at the pressure-melting point. This is supported by the measurements on the ice core where the annual-layer thicknesses show there is bottom melting at the site and upstream from the borehole. Surface velocity measurements, internal radio-echo layers, borehole and ice-core data are used to constrain a time-dependent flow model simulating flow along the north-northwest-trending ice-ridge flow-line, leading to the NorthGRIP site. Also time-dependent melt rates along the flowline are calculated with a heat-flow model. The results show the geothermal heat flow varies from 50 to 200 mW m–2 along the 100km section of the modeled flowline. The melt rate at the NorthGRIP site is 0.75 cm a–1, but the deep ice in the NorthGRIP core originated 50 km upstream and has experienced melt rates as high as 1.1 cm a–1.

scholarly journals Greenland Geothermal Heat Flow Database and Map (Version 1)

2021 ◽  
Author(s):  
William Colgan ◽  
Agnes Wansing ◽  
Kenneth Mankoff ◽  
Mareen Lösing ◽  
John Hopper ◽  
...  
Keyword(s):  
Heat Flow ◽  
Flow Model ◽  
Horizontal Resolution ◽  
Geothermal Heat ◽  
Flow Measurements ◽  
Flow Models ◽  
The North ◽  
Marine Areas ◽  
Heat Flow Model

Abstract. We compile, analyse and map all available geothermal heat flow measurements collected in and around Greenland into a new database of 419 sites and generate an accompanying spatial map. This database includes 290 sites previously reported by the International Heat Flow Commission (IHFC), for which we now standardize measurement and metadata quality. This database also includes 129 new sites, which have not been previously reported by the IHFC. These new sites consist of 88 offshore measurements and 41 onshore measurements, of which 24 are subglacial. We employ machine learning to synthesize these in situ measurements into a gridded geothermal heat flow model that is consistent across both continental and marine areas in and around Greenland. This model has a native horizontal resolution of 55 km. In comparison to five existing Greenland geothermal heat flow models, our model has the lowest mean geothermal heat flow for Greenland onshore areas (44 mW m–2). Our model’s most distinctive spatial feature is pronounced low geothermal heat flow (< 40 mW m–2) across the North Atlantic Craton of southern Greenland. Crucially, our model does not show an area of elevated heat flow that might be interpreted as remnant from the Icelandic Plume track. Finally, we discuss the substantial influence of paleoclimatic and other corrections on geothermal heat flow measurements in Greenland. The in-situ measurement database and gridded heat flow model, as well as other supporting materials, are freely available from the GEUS DataVerse (https://doi.org/10.22008/FK2/F9P03L; Colgan and Wansing, 2021).

scholarly journals Ice thinning, upstream advection, and non-climatic biases for the upper 89% of the EDML ice core from a nested model of the Antarctic ice sheet

2007 ◽  
Vol 3 (4) ◽  
pp. 577-589 ◽  
Author(s):  
P. Huybrechts ◽  
O. Rybak ◽  
F. Pattyn ◽  
U. Ruth ◽  
D. Steinhage
Keyword(s):  
Flow Model ◽  
Ice Core ◽  
Age Distribution ◽  
Ice Sheet ◽  
Glacial Cycles ◽  
Thermomechanical Model ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
Annual Layer ◽  
Dronning Maud Land

Abstract. A nested ice flow model was developed for eastern Dronning Maud Land to assist with the dating and interpretation of the EDML deep ice core. The model consists of a high-resolution higher-order ice dynamic flow model that was nested into a comprehensive 3-D thermomechanical model of the whole Antarctic ice sheet. As the drill site is on a flank position the calculations specifically take into account the effects of horizontal advection as deeper ice in the core originated from higher inland. First the regional velocity field and ice sheet geometry is obtained from a forward experiment over the last 8 glacial cycles. The result is subsequently employed in a Lagrangian backtracing algorithm to provide particle paths back to their time and place of deposition. The procedure directly yields the depth-age distribution, surface conditions at particle origin, and a suite of relevant parameters such as initial annual layer thickness. This paper discusses the method and the main results of the experiment, including the ice core chronology, the non-climatic corrections needed to extract the climatic part of the signal, and the thinning function. The focus is on the upper 89% of the ice core (appr. 170 kyears) as the dating below that is increasingly less robust owing to the unknown value of the geothermal heat flux. It is found that the temperature biases resulting from variations of surface elevation are up to half of the magnitude of the climatic changes themselves.

scholarly journals Ice thinning, upstream advection, and non-climatic biases for the upper 89% of the EDML ice core from a nested model of the Antarctic ice sheet

2007 ◽  
Vol 3 (3) ◽  
pp. 693-727 ◽  
Author(s):  
P. Huybrechts ◽  
O. Rybak ◽  
F. Pattyn ◽  
U. Ruth ◽  
D. Steinhage
Keyword(s):  
Flow Model ◽  
Ice Core ◽  
Age Distribution ◽  
Ice Sheet ◽  
Glacial Cycles ◽  
Thermomechanical Model ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
Annual Layer ◽  
Dronning Maud Land

Abstract. A nested ice flow model was developed for eastern Dronning Maud Land to assist with the dating and interpretation of the EDML deep ice core. The model consists of a high-resolution higher-order ice dynamic flow model that was nested into a comprehensive 3-D thermomechanical model of the whole Antarctic ice sheet. As the drill site is on a flank position the calculations specifically take into account the effects of horizontal advection as deeper ice in the core originated from higher inland. First the regional velocity field and ice sheet geometry is obtained from a forward experiment over the last 8 glacial cycles. The result is subsequently employed in a Lagrangian backtracing algorithm to provide particle paths back to their time and place of deposition. The procedure directly yields the depth-age distribution, surface conditions at particle origin, and a suite of relevant parameters such as initial annual layer thickness. This paper discusses the method and the main results of the experiment, including the ice core chronology, the non-climatic corrections needed to extract the climatic part of the signal, and the thinning function. The focus is on the upper 89% of the ice core (appr. 170 kyears) as the dating below that is increasingly less robust owing to the unknown value of the geothermal heat flux. It is found that the temperature biases resulting from variations of surface elevation are up to half of the magnitude of the climatic changes themselves.

scholarly journals Critical Tectonic Limits for Geothermal Aquifer Use: Case Study from the East Slovakian Basin Rim

Resources ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 31
Author(s):  
Stanislav Jacko ◽  
Roman Farkašovský ◽  
Igor Ďuriška ◽  
Barbora Ščerbáková ◽  
Kristína Bátorová
Keyword(s):  
Heat Flow ◽  
Pannonian Basin ◽  
Open Fractures ◽  
Water Type ◽  
Geothermal Heat ◽  
The North ◽  
Heat System ◽  
Volcanic Chain ◽  
Saline Solutions

The Pannonian basin is a major geothermal heat system in Central Europe. Its peripheral basin, the East Slovakian basin, is an example of a geothermal structure with a linear, directed heat flow ranging from 90 to 100 mW/m2 from west to east. However, the use of the geothermal source is limited by several critical tectono-geologic factors: (a) Tectonics, and the associated disintegration of the aquifer block by multiple deformations during the pre-Paleogene, mainly Miocene, period. The main discontinuities of NW-SE and N-S direction negatively affect the permeability of the aquifer environment. For utilization, minor NE-SW dilatation open fractures are important, which have been developed by sinistral transtension on N–S faults and accelerated normal movements to the southeast. (b) Hydrogeologically, the geothermal structure is accommodated by three water types, namely, Na-HCO3 with 10.9 g·L−1 mineralization (in the north), the Ca-Mg-HCO3 with 0.5–4.5 g·L−1 mineralization (in the west), and Na-Cl water type containing 26.8–33.4 g·L−1 mineralization (in the southwest). The chemical composition of the water is influenced by the Middle Triassic dolomite aquifer, as well as by infiltration of saline solutions and meteoric waters along with open fractures/faults. (c) Geothermally anomalous heat flow of 123–129 °C with 170 L/s total flow near the Slanské vchy volcanic chain seems to be the perspective for heat production.

scholarly journals A 60 000 year Greenland stratigraphic ice core chronology

2008 ◽  
Vol 4 (1) ◽  
pp. 47-57 ◽  
Author(s):  
A. Svensson ◽  
K. K. Andersen ◽  
M. Bigler ◽  
H. B. Clausen ◽  
D. Dahl-Jensen ◽  
...  
Keyword(s):  
North Atlantic ◽  
Time Scale ◽  
Ice Core ◽  
Ice Cores ◽  
The North ◽  
Annual Layer ◽  
Zone Ii ◽  
Absolute Age ◽  
Age Estimates ◽  
New Time

Abstract. The Greenland Ice Core Chronology 2005 (GICC05) is a time scale based on annual layer counting of high-resolution records from Greenland ice cores. Whereas the Holocene part of the time scale is based on various records from the DYE-3, the GRIP, and the NorthGRIP ice cores, the glacial part is solely based on NorthGRIP records. Here we present an 18 ka extension of the time scale such that GICC05 continuously covers the past 60 ka. The new section of the time scale places the onset of Greenland Interstadial 12 (GI-12) at 46.9±1.0 ka b2k (before year AD 2000), the North Atlantic Ash Zone II layer in GI-15 at 55.4±1.2 ka b2k, and the onset of GI-17 at 59.4±1.3 ka b2k. The error estimates are derived from the accumulated number of uncertain annual layers. In the 40–60 ka interval, the new time scale has a discrepancy with the Meese-Sowers GISP2 time scale of up to 2.4 ka. Assuming that the Greenland climatic events are synchronous with those seen in the Chinese Hulu Cave speleothem record, GICC05 compares well to the time scale of that record with absolute age differences of less than 800 years throughout the 60 ka period. The new time scale is generally in close agreement with other independently dated records and reference horizons, such as the Laschamp geomagnetic excursion, the French Villars Cave and the Austrian Kleegruben Cave speleothem records, suggesting high accuracy of both event durations and absolute age estimates.

scholarly journals Temperature profiles for the barnes ice cap surge zone

1977 ◽  
Vol 18 (80) ◽  
pp. 391-405 ◽  
Author(s):  
D. F. Classen
Keyword(s):  
Heat Flow ◽  
Flow Line ◽  
Temperature Measurements ◽  
Temperature Profiles ◽  
Baffin Island ◽  
Geothermal Heat ◽  
Ice Cap ◽  
Marginal Areas ◽  
Thermal Drilling

AbstractThermal drilling and deep ice-temperature measurements along a flow line in a surge area of the Barnes Ice Cap, Baffin Island, N.W.T., Canada revealed a layer of basal temperate ice 30 m thick. Marginal areas were determined to be frozen to bedrock and geothermal heat flow estimated to be 1.02 μcal/cm2s (42 mW/m2).

scholarly journals Ice motion over Lake Vostok, Antarctica: constraints on inferences regarding the accreted ice

2000 ◽  
Vol 46 (155) ◽  
pp. 689-694 ◽  
Author(s):  
R. Kwok ◽  
M.J. Siegert ◽  
F. D. Carsey
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Maximum Velocity ◽  
Sar Interferometry ◽  
Surface Velocity ◽  
Parabolic Profile ◽  
Lake Vostok ◽  
The North ◽  
Regional Flow ◽  
Overlapping Data

AbstractIce motion over Lake Vostok, Antarctica, is measured using repeat-pass synthetic-aperture radar (SAR) interferometry. The coverage of the lake and the components of the vector field are resolved using 10 overlapping data takes from ascending and descending look directions. Seventy-day temporal baselines provide the sensitivity required to observe the range of ice motion (0–6 m a−1) over the lake and the adjacent ice sheet. It is remarkable that the scattering field remained coherent over these time separations. This is critical for interferometric analysis and can be attributed to the low surface accumulation and low air temperature at this elevation. The regional flow of the ice sheet around Lake Vostok is from west to east, perpendicular to the surface elevation contours. As the ice flows past the grounding line, a southward component of motion develops that is correlated with the north–south surface slope along the length of the lake. The surface velocity increases slowly from the northern tip of the lake and then more rapidly south of 77° S. At Vostok station, the ice motion is 4.2 m a−1. Across the lake and away from boundary effects, the down-lake flow pattern takes on a parabolic profile with maximum velocity close to the center line of the lake. The overall influence of the subglacial lake is the addition of a down-lake motion component to the prevailing west–east motion of the ice sheet. As a result, we estimate 10% of the mass flowing onto the lake is diverted south. Reconstructions based on the Vostok ice core indicate that the ice was grounded up-glacier from the core site approximately 5000 years ago. This suggests a minimum freezing rate of 40 mm a−1 for the subglacial accretion ice, 10 times greater than that inferred from thermodynamic modeling of the upper 2 km of the ice core.

scholarly journals Temperature profiles for the barnes ice cap surge zone

1977 ◽  
Vol 18 (80) ◽  
pp. 391-405 ◽  
Author(s):  
D. F. Classen
Keyword(s):  
Heat Flow ◽  
Flow Line ◽  
Temperature Measurements ◽  
Temperature Profiles ◽  
Baffin Island ◽  
Geothermal Heat ◽  
Ice Cap ◽  
Marginal Areas ◽  
Thermal Drilling

AbstractThermal drilling and deep ice-temperature measurements along a flow line in a surge area of the Barnes Ice Cap, Baffin Island, N.W.T., Canada revealed a layer of basal temperate ice 30 m thick. Marginal areas were determined to be frozen to bedrock and geothermal heat flow estimated to be 1.02 μcal/cm2s (42 mW/m2).

An LPG Pipeline Break Flow Model

1983 ◽  
Vol 105 (3) ◽  
pp. 379-387 ◽  
Author(s):  
T. B. Morrow ◽  
R. L. Bass ◽  
J. A. Lock
Keyword(s):  
Reaction Time ◽  
Flow Rate ◽  
Flow Model ◽  
Time Dependent ◽  
Vapor Layer ◽  
Model Predictions ◽  
Vapor Cloud ◽  
Dependent Flow

An LPG pipeline break flow model has been develped to evaluate the flammability hazards associated with a pipeline rupture. The model estimates the time-dependent flow rate of LPG from a pipeline rupture, the gravity spreading of the LPG vapor layer over the ground, and the dispersion of the vapor cloud downwind of the break location. Examples of model predictions are presented to illustrate the effects of pipeline isolation valve spacing, and shutdown reaction time on the flammable cloud boundaries that could result from a partial break in a propane pipeline.

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