scholarly journals The Hans Tausen drill: design, performance, further developments and some lessons learned

2007 ◽  
Vol 47 ◽  
pp. 89-98 ◽  
Author(s):  
Sigfús J. Johnsen ◽  
Steffen Bo Hansen ◽  
Simon G. Sheldon ◽  
Dorthe Dahl-Jensen ◽  
Jørgen P. Steffensen ◽  
...  
Keyword(s):  
Mechanical Design ◽  
Ice Cores ◽  
Lessons Learned ◽  
Niels Bohr ◽  
Deep Drilling ◽  
Niels Bohr Institute ◽  
Design Performance ◽  
Ice Cap ◽  
Drill Design

AbstractIn the mid-1990s, excellent results from the GRIP and GISP2 deep drilling projects in Greenland opened up funding for continued ice-coring efforts in Antarctica (EPICA) and Greenland (NorthGRIP). The Glaciology Group of the Niels Bohr Institute, University of Copenhagen, was assigned the task of providing drilling capability for these projects, as it had done for the GRIP project. The group decided to further simplify existing deep drill designs for better reliability and ease of handling. The drill design decided upon was successfully tested on Hans Tausen Ice Cap, Peary Land, Greenland, in 1995. The 5.0m long Hans Tausen (HT) drill was a prototype for the ~11m long EPICA and NorthGRIP versions of the drill which were mechanically identical to the HT drill except for a much longer core barrel and chips chamber. These drills could deliver up to 4m long ice cores after some design improvements had been introduced. The Berkner Island (Antarctica) drill is also an extended HT drill capable of drilling 2 m long cores. The success of the mechanical design of the HT drill is manifested by over 12 km of good-quality ice cores drilled by the HT drill and its derivatives since 1995.

Comparison of 105 Years of Oxygen Isotope and Insoluble Impurity Profiles from the Devon Island and Camp Century Ice Cores

1979 ◽  
Vol 11 (3) ◽  
pp. 299-305 ◽  
Author(s):  
David A. Fisher
Keyword(s):  
Oxygen Isotope ◽  
Flow Line ◽  
Ice Cores ◽  
Devon Island ◽  
Ice Cap ◽  
Particulate Concentration ◽  
The Difference ◽  
Impurity Profiles ◽  
Level Lowering ◽  
Present Site

Oxygen-isotope profiles for the Devon Island ice cap and Camp Century Greenland are affected by a number of variables, some of which must have been the same for both sites. The two δ(18O) records spanning about 120,000 years are brought into relative alignment by comparison of major δ features, and subsequent verification that the insoluble particulate concentration records were also in phase for this alignment. The difference between the δ profiles is shown to be mainly a function of the altitude of the accumulation area for Camp Century. This altitude seems to have been higher than present for the last 100,000 years, suggesting the present flow line through the site has never been shorter. The maximum altitude for the Camp Century accumulation area is 1500 m above the present site and is almost synchronous with the maximum in particulate concentration that occurs at 16,000 yr B.P. The synchronism is likely due to the maximum sea-level lowering that exposed vast areas of continental shelf to wind erosion.

scholarly journals Glaciological Investigations of the Tropical Quelccaya Ice Cap, Peru

1980 ◽  
Vol 25 (91) ◽  
pp. 69-84 ◽  
Author(s):  
Lonnie G. Thompson
Keyword(s):  
Rainy Season ◽  
Ice Core ◽  
Ice Cores ◽  
Dry Season ◽  
Radioactive Material ◽  
Polar Regions ◽  
Near Surface ◽  
Ice Cap ◽  
Activity Measurements ◽  
Quelccaya Ice Cap

AbstractGlaciological results of the continuing investigations of the Quelccaya ice cap located at lat. 13° 56’ S., long. 70° 50’ W., in the Cordillera Oriental of southern Peru are presented. Ice cores to a depth of 15 m have been retrieved from the summit dome (5650 m), middle dome (5543 m), and south dome (5480 m) and sampled in detail for microparticle, oxygen-isotope, and total-β-activity measurements. Results of these core analyses indicate that although the summit of this ice cap is only 300 m above the annual snow line and the firn is temperate, an interpretable stratigraphic record is preserved. The marked seasonal ice stratigraphy is produced by the marked seasonal variation in regional precipitation. High concentrations of microparticles and β- radioactive material occur during the dry season (May-August). Microparticles deposited during the rainy season are larger than those deposited during the dry season. On the Quelccaya ice cap the most negative δ18O values occur during the warmer rainy season (the opposite occurs in polar regions). The near-surface mean δ value of – 21‰ is remarkably low for this tropical site where the measured mean annual air temperature is – 3°C The seasonality of the microparticles, total β activity, and isotope ratios offers the prospect of a climatic ice-core record from this tropical ice cap.

scholarly journals Apparent discrepancy of Tibetan ice core <i>δ</i><sup>18</sup>O records may be attributed to misinterpretation of chronology

2019 ◽  
Vol 13 (6) ◽  
pp. 1743-1752 ◽  
Author(s):  
Shugui Hou ◽  
Wangbin Zhang ◽  
Hongxi Pang ◽  
Shuang-Ye Wu ◽  
Theo M. Jenk ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Warming Trend ◽  
The Tibetan Plateau ◽  
Apparent Discrepancy ◽  
Ice Cap ◽  
Guliya Ice Core ◽  
Cooling Trend ◽  
Instrumental Period

Abstract. Ice cores from the Tibetan Plateau (TP) are widely used for reconstructing past climatic and environmental conditions that extend beyond the instrumental period. However, challenges in dating and interpreting ice core records often lead to inconsistent results. The Guliya ice core drilled from the northwestern TP suggested a cooling trend during the mid-Holocene based on its decreasing δ18O values, which is not observed in other Tibetan ice cores. Here we present a new high-resolution δ18O record of the Chongce ice cores drilled to bedrock ∼30 km away from the Guliya ice cap. Our record shows a warming trend during the mid-Holocene. Based on our results as well as previously published ice core data, we suggest that the apparent discrepancy between the Holocene δ18O records of the Guliya and the Chongce ice cores may be attributed to a possible misinterpretation of the Guliya ice core chronology.

scholarly journals Some comments on climatic reconstructions from ice cores drilled in areas of high melt

1997 ◽  
Vol 43 (143) ◽  
pp. 90-97 ◽  
Author(s):  
Roy M. Koerner
Keyword(s):  
Time Scales ◽  
Ice Core ◽  
Ice Cores ◽  
The Holocene ◽  
Ice Caps ◽  
Ice Cap ◽  
Thermal Maximum ◽  
Devon Ice Cap ◽  
Seasonal Signals ◽  
Cross Correlations

AbstractPoor consideration has been given in many Arctic circum-polar ice-core studies to the effect of summer snow melt on chemistry, stable-isotope concentrations and time-scales. Many of these corps are drilled close to the firn line where melt is intense. Some come from below the firn line where accumulation is solely in the form of super-imposed ice. In all cases, seasonal signals are reduced or removed and, in some, time gaps develop during periods of excessive melting which situate the drill site in the ablation zone. Consequently, cross correlations of assumed synchronous events among the cores are invalid, so that time-scales along the same cores differ between authors by factors of over 2. Many so-called climatic signals are imaginary rather than real. By reference to published analyses of cores from the superimposed ice zone on Devon Ice Cap (Koerner, 1970) and Meighen Ice Cap (Koerner and Paterson, 1974), it is shown how melt affects all the normally well-established ice-core proxies and leads to their misinterpretation. Despite these limitations, the cores can give valuable low-resolution records for all or part of the Holocene. They show that the thermal maximum in the circum-polar Arctic occurred in the early Holocene. This maximum, effected negative balances on all the ice caps and removed the smaller ones. Cooler conditions in the second half of the Holocene have caused the regrowth of these same ice caps.

Late-Glacial and Holocene Glacier Fluctuations and Environmental Change on South Georgia, Southern Ocean

1989 ◽  
Vol 31 (2) ◽  
pp. 210-228 ◽  
Author(s):  
Chalmers M. Clapperton ◽  
David E. Sugden ◽  
Jacqueline Birnie ◽  
Mandy J. Wilson
Keyword(s):  
Environmental Change ◽  
Ice Cores ◽  
Late Glacial ◽  
Environmental Indicators ◽  
Temperature Changes ◽  
South Georgia ◽  
Ice Cap ◽  
Late Glacial And Holocene ◽  
Climatic Cooling ◽  
The Antarctic

AbstractSouth Georgia provides a terrestrial record of postglacial environmental change from a largely oceanic zone of the Earth. The record is representative of the southern westerlies and provides a link between Antarctica and the temperate zones of southern South America. Evidence from glacial geomorphology, slope stratigraphy, and analyses of environmental indicators in peat and lake cores is used to interpret this record. Wastage of the full-glacial ice cap was interrupted by a late-glacial stade of the outlet and valley glaciers before ca. 10,000 yr B.P. Plant growth had begun at low altitude (<50 m) on the sheltered (lee side) northeast coast within the late-glacial moraine limits by 9700 yr B.P. Environmental conditions on slopes above 80 m probably were too rigorous for a stable vegetation cover until ca. 6400 yr B.P. This was followed by a period from 5600 to 4800 yr B.P. when conditions were warmer than at present by up to 0.6°C. Periods of climatic cooling occurred at ca. 4800-3800 yr B.P., ca. 3400-1800 yr B.P., and within the last 1400 yr. The most extensive Holocene advance of South Georgia glaciers culminated just before 2200 yr B.P. These Holocene temperature changes of between 0.5 and 1.0°C are comparable in scale and timing to those identified from recent analyses of Vostok ice cores from the Antarctic ice sheet.

Exposure age chronology of the last glaciation in the eastern Pyrenees

2008 ◽  
Vol 69 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Magali Delmas ◽  
Yanni Gunnell ◽  
Régis Braucher ◽  
Marc Calvet ◽  
Didier Bourlès
Keyword(s):  
Ice Cores ◽  
Sampling Strategy ◽  
Large Change ◽  
Equilibrium Line Altitude ◽  
Ice Cap ◽  
Eastern Pyrenees ◽  
Relative Chronology ◽  
Geomorphological Map ◽  
Glacial Landforms

We present a chronology of ice recession in the eastern Pyrenees based onin situ-produced10Be data obtained from the Têt paleoglacier complex. The sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms. Results indicate that the last maximum ice advance occurred late (i.e., during Marine Isotope Stage 2) compared to the chronology currently established for the rest of the Pyrenees. Despite debatable evidence for a glacial readvance during the Oldest Dryas stade, ice-cap melt-out was rapid, residual cirque glaciers having disappeared by the Allerød interstade. This is consistent both with North Atlantic excursions established by the Greenland ice cores and paleoenvironmental data for the region. The rapid response of the east-Pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger Pyrenean ice fields, to the dry Mediterranean climate, and to topography-related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass. Possible sources of age uncertainty are discussed in the context of sampling design for single-nuclide (10Be) dating of landform sequences in formerly glaciated landscapes.

scholarly journals Community change of microorganisms in the Muztagata and Dunde glacier and climatic and environmental implications

2016 ◽  
Author(s):  
Yong Chen ◽  
Xiang-Kai Li ◽  
Jing Si ◽  
Guang-Jian WU ◽  
Li-De Tian ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Cell Density ◽  
Ice Core ◽  
Ice Cores ◽  
Community Change ◽  
Rrna Gene ◽  
Environmental Implications ◽  
Depth Profiles ◽  
Ice Cap ◽  
Glacier Ice

Abstract. Microorganisms are continuously blown onto the glacier snow, and thus the glacial depth profiles provide excellent geographic archives of the microbial communities. However, it is uncertain about how the microbial communities respond to the climatic and environmental changes over the glacier ice. In the present study, the live microbial density, stable isotopic ratios, 18O/16O in the precipitation, and mineral particle concentrations along the glacial depth profiles were collected from ice cores from the Muztagata glacier and the Dunde ice cap. Six bacterial 16S rRNA gene clone libraries were established from the Dunde ice core. The Muztagata ice core presented seasonal response patterns for both live and total cell density with high cell density occurring in the warming spring and summer. Both ice core data showed a frequent association of dust and microorganisms in the ice. Genera Polaromas sp., Pedobacter sp, Flavobacterium sp., Cryobacteriium sp., and Propionibacterium/Blastococcus sp. frequently appeared at the six tested ice layers, and constituted the dominant species endemic to the Dunde ice cap, whereas some genera such as Rhodoferax sp., Variovorax sp., Sphingobacterium sp., Cyanobacterium sp., Knoellia sp., and Luteolibacter sp. rarely presented in the ice. In conclusion, data present a discrete increase of microbial cell density in the warming seasons and biogeography of the microbial communities associated with the predominance of a few endemic groups in the local glacial regions. This reinforces our hypothesis of dust-borne and post-deposition being the main agents interactively controlling microbial load in the glacier ice.

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