scholarly journals The Effects of Wind on δ(18O) and Accumulation Give an Inferred Record of Seasonal δ Amplitude From the Agassiz Ice Cap, Ellesmere Island, Canada

1988 ◽  
Vol 10 ◽  
pp. 34-37 ◽  
Author(s):  
D.A. Fisher ◽  
R.M. Koerner
Keyword(s):  
Flow Line ◽  
Conductivity Measurement ◽  
Ellesmere Island ◽  
Electrical Conductivity Measurement ◽  
Ice Caps ◽  
Devon Island ◽  
Ice Cap ◽  
Annual Layer ◽  
Winter Snow ◽  
Difference Series

Wind plays an important role in determining accumulation and δ(18O) on some ice caps. Three surface-to-bed cores spaced about 1 km apart have been taken on a flow line of the Agassiz Ice Cap, Ellesmere Island. The A84 core comes from the top of a local dome. The A79 core is 1200 m down the flow line, but very close to the ridge through the local dome. The A77 core is 1100m from A79 and well away from the ridge. The ridge causes wind turbulence, which removes or scours the soft winter snow from the A84 and A79 sites. No snow is scoured from the A77 site. Because of scour the retained accumulation and average δ(l8O) are different. The accumulations are 17.5, 11.5, 9.7 cm/a (ice equivalent) at A77, A79 and A84 respectively and the corresponding surface δs are –30.40, -27.90 and –27.05‰. The core records were dated by annual layer thicknesses and by identification of electrical conductivity measurement (ECM) acid peaks. With the three cores accurately aligned we examine the (δA84-δA77) and (δA84-δA79) time series. Significant variations in these difference series are interpreted as being caused by changes in the seasonal δ amplitude, which is then explained by changes in sea-ice cover. A seasonal δ amplitude series independently obtained from the Devon Island ice cap δ noise record is consistent with that from the Agassiz Ice Cap sites.

scholarly journals The Effects of Wind on δ(18O) and Accumulation Give an Inferred Record of Seasonal δ Amplitude From the Agassiz Ice Cap, Ellesmere Island, Canada

1988 ◽  
Vol 10 ◽  
pp. 34-37 ◽  
Author(s):  
D.A. Fisher ◽  
R.M. Koerner
Keyword(s):  
Flow Line ◽  
Conductivity Measurement ◽  
Ellesmere Island ◽  
Electrical Conductivity Measurement ◽  
Ice Caps ◽  
Devon Island ◽  
Ice Cap ◽  
Annual Layer ◽  
Winter Snow ◽  
Difference Series

Wind plays an important role in determining accumulation and δ(18O) on some ice caps. Three surface-to-bed cores spaced about 1 km apart have been taken on a flow line of the Agassiz Ice Cap, Ellesmere Island. The A84 core comes from the top of a local dome. The A79 core is 1200 m down the flow line, but very close to the ridge through the local dome. The A77 core is 1100m from A79 and well away from the ridge. The ridge causes wind turbulence, which removes or scours the soft winter snow from the A84 and A79 sites. No snow is scoured from the A77 site. Because of scour the retained accumulation and average δ(l8O) are different. The accumulations are 17.5, 11.5, 9.7 cm/a (ice equivalent) at A77, A79 and A84 respectively and the corresponding surface δs are –30.40, -27.90 and –27.05‰. The core records were dated by annual layer thicknesses and by identification of electrical conductivity measurement (ECM) acid peaks. With the three cores accurately aligned we examine the (δA84-δA77) and (δA84-δA79) time series. Significant variations in these difference series are interpreted as being caused by changes in the seasonal δ amplitude, which is then explained by changes in sea-ice cover. A seasonal δ amplitude series independently obtained from the Devon Island ice cap δ noise record is consistent with that from the Agassiz Ice Cap sites.

scholarly journals Bore-Hole Video and Photographic Cameras

1981 ◽  
Vol 2 ◽  
pp. 34-38 ◽  
Author(s):  
R.M. Koerner ◽  
D.A. Fisher ◽  
M. Parnandi
Keyword(s):  
Cross Section ◽  
Basal Slip ◽  
Flow Line ◽  
Ellesmere Island ◽  
Elliptical Cross Section ◽  
Polar Ice ◽  
Elliptical Cross ◽  
Ice Caps ◽  
Ice Cap ◽  
One Year

35 mm still and television techniques are shown to be of great value in following changes at the bedrock/ice interface and along borehole walls during closure over one or more years in polar or sub-polar ice caps. We have found no evidence of basal slip over a one year period in a 137 m hole at the top of the flow line on an ice cap in northern Ellesmere Island, However, the bore hole has deformed to an elliptical cross-section near the bed and some pronounced extrusion-like layers have developed within 3 m of the bed in dirty ice in the year since drilling.

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 CryoSat-2 delivers monthly and inter-annual surface elevation change for Arctic ice caps

2015 ◽  
Vol 9 (3) ◽  
pp. 2821-2865 ◽  
Author(s):  
L. Gray ◽  
D. Burgess ◽  
L. Copland ◽  
M. N. Demuth ◽  
T. Dunse ◽  
...  
Keyword(s):  
Snow Accumulation ◽  
Surface Elevation ◽  
Radar Altimeter ◽  
Elevation Change ◽  
Ice Caps ◽  
Ice Cap ◽  
Winter Snow ◽  
Surface Elevation Change ◽  
Devon Ice Cap ◽  
Arctic Ice

Abstract. We show that the CryoSat-2 radar altimeter can provide useful estimates of surface elevation change on a variety of Arctic ice caps, on both monthly and yearly time scales. Changing conditions, however, can lead to a varying bias between the elevation estimated from the radar altimeter and the physical surface due to changes in the contribution of subsurface to surface backscatter. Under melting conditions the radar returns are predominantly from the surface so that if surface melt is extensive across the ice cap estimates of summer elevation loss can be made with the frequent coverage provided by CryoSat-2. For example, the average summer elevation decreases on the Barnes Ice Cap, Baffin Island, Canada were 2.05 ± 0.36 m (2011), 2.55 ± 0.32 m (2012), 1.38 ± 0.40 m (2013) and 1.44 ± 0.37 m (2014), losses which were not balanced by the winter snow accumulation. As winter-to-winter conditions were similar, the net elevation losses were 1.0 ± 0.2 m (winter 2010/2011 to winter 2011/2012), 1.39 ± 0.2 m (2011/2012 to 2012/2013) and 0.36 ± 0.2 m (2012/2013 to 2013/2014); for a total surface elevation loss of 2.75 ± 0.2 m over this 3 year period. In contrast, the uncertainty in height change results from Devon Ice Cap, Canada, and Austfonna, Svalbard, can be up to twice as large because of the presence of firn and the possibility of a varying bias between the true surface and the detected elevation due to changing year-to-year conditions. Nevertheless, the surface elevation change estimates from CryoSat for both ice caps are consistent with field and meteorological measurements. For example, the average 3 year elevation difference for footprints within 100 m of a repeated surface GPS track on Austfonna differed from the GPS change by 0.18 m.

scholarly journals Reconnaissance of a Small Ice Cap Near St Patrick Bay, Robeson Channel, Northern Ellesmere Island, Canada

1973 ◽  
Vol 12 (66) ◽  
pp. 417-421 ◽  
Author(s):  
G. Hattersley-Smith ◽  
H. Serson
Keyword(s):  
Ellesmere Island ◽  
Direct Result ◽  
Ice Caps ◽  
Ice Cap

A reconnaissance was made of one of two small ice caps near the Robeson Channel coast of northern Ellesmere Island. It is shown that, after a period of net wastage, this ice cap is now thickening slightly and extending its margins. The present regime of the ice cap is a direct result of generally cooler summers in the last decade.

scholarly journals An Analysis of the Relation Between the Surface and Bedrock Profiles of Ice Caps

1971 ◽  
Vol 10 (59) ◽  
pp. 197-209 ◽  
Author(s):  
W.F. Budd ◽  
D.B. Carter
Keyword(s):  
Flow Line ◽  
Smooth Curve ◽  
Small Scale ◽  
Ice Thickness ◽  
Damping Factor ◽  
Gravitational Acceleration ◽  
Ice Caps ◽  
Ice Cap ◽  
The Mean ◽  
Image Position

AbstractResults art, presented of spectral analyses of the surface and bedrock profiles along a flow line of the Wilkes ice cap and the surface along the Greenland E.G.I.G. profile. Although the bedrock appears irregular over all was velengths studied, the ice-cap surface is typically characterized by a smooth curve with small-scale surface undulations superimposed on it. The following relations of Budd (1969, 19701 are confirmed. The “damping factor" or ratio of the bedrock amplitude to the surface amplitude is a minimum for wavelengths λ about 3.3 times the ice thickness. The surface lags the bed in the direction of motion by λ/4. The magnitude of the minimum damping factor φmis typically least near the coast, and increases inland depending on the ice thicknessZ, the velocityV, and the mean ice viscosityη(which is a function of stress and temperature) according towherepis the mean ice density andgis the gravitational acceleration. Thus the determination of the damping factors provides a valuable means of estimating the ice flow parameterη.

scholarly journals Natural and anthropogenic levels of tritium in a Canadian Arctic ice core, Agassiz Ice Cap, Ellesmere Island, and comparison with other radionuclides

2000 ◽  
Vol 46 (152) ◽  
pp. 35-40 ◽  
Author(s):  
Thomas G. Kotzer ◽  
Akira Kudo ◽  
James Zheng ◽  
Wayne Workman
Keyword(s):  
Ice Core ◽  
Canadian Arctic ◽  
Fission Products ◽  
Ellesmere Island ◽  
Anthropogenic Radionuclides ◽  
Ice Caps ◽  
Nuclear Bomb ◽  
Ice Cap ◽  
Nuclear Weapons Testing ◽  
Arctic Ice

AbstractNumerous studies of the ice caps in Greenland and Antarctica have observed accumulations of transuranic radionuclides and fission products from nuclear weapons testing, particularly during the period 1945–75. Recently, the concentrations of radionuclides in the annually deposited surface layers of Agassiz Ice Cap, Ellesmere Island, Canadian Arctic, from 1945 to the present have been measured and have demonstrated a continuous record of deposition of 137Cs and 239,240Pu in ice and snow. In this study, 3He-ingrowth mass spectrometry has been used to measure the low levels of tritium (3H) in some of these samples. Pre-nuclear-bomb tritium levels in ice-core samples were approximately 12 TU in high-latitude meteoric waters and 3–9 TU in mid-latitude meteoric waters. Comparisons of 3H levels and 3H/137Cs + 239,240Pu ratios, which were quite low during the earliest fission-bomb detonations (1946–51) and substantially higher during thermonuclear hydrogen-fusion bomb testing (1952–64), provide a clear indication of the type of nuclear device detonated. This finding accords with the results from other ice-core studies of the distribution of anthropogenic radionuclides from bomb fallout.

Artificial radioactivity layers in the Devon Island ice cap, Northwest Territories

1976 ◽  
Vol 13 (9) ◽  
pp. 1251-1255 ◽  
Author(s):  
R. M. Koerner ◽  
H. Taniguchi
Keyword(s):  
Northwest Territories ◽  
Snow Accumulation ◽  
Polar Ice ◽  
Artificial Radioactivity ◽  
Ice Caps ◽  
Devon Island ◽  
Ice Cap ◽  
Positive Balance ◽  
Melt Water

Bomb-produced radioactive fall-out layers are evident in the firn at the top of the Devon Island ice cap and also lower down in a zone where accumulation is in the form of re-frozen melt-water. This allows 1963–1974 snow accumulation (positive balance) gradients for the same period to be determined on sub-polar ice caps in Canada.

scholarly journals On the Special Rheological Properties of Ancient Microparticle-Laden Northern Hemisphere Ice as Derived from Bore-Hole and Core Measurements

1986 ◽  
Vol 32 (112) ◽  
pp. 501-510 ◽  
Author(s):  
D.A. Fisher ◽  
R.M. Koerner
Keyword(s):  
Rheological Properties ◽  
Northern Hemisphere ◽  
Crystal Size ◽  
Ellesmere Island ◽  
Ice Age ◽  
Devon Island ◽  
Ice Cap ◽  
Density Flow ◽  
Density Enhancement ◽  
Flow Enhancement

AbstractIn the Northern Hemisphere, ice layers which have high microparticle concentrations (in particular late Wisconsin) are “softer” than modern or Holocene ice. Such ice deforms more readily in bore-hole tilt and closure measurements. This enhancement in flow, which is shownnotto be related toc-axis concentration, has a maximum of three for late Wisconsin ice. The closure and tilt of a bore hole in the Agassiz Ice Cap, Ellesmere Island, drilled in 1977, has been followed every year since its drilling and the flow enhancement observed has been compared to the following quantities measured in the cores: concentration, δ(18O), crystal size,c-axis, Ca, Na, conductivity, and density. Flow enhancement of the ice age and bottom ice was found to be unrelated toc-axis concentration and density. Enhancement of flow is best related to microparticle (or Ca) concentration which in turn seems to be inversely related to crystal size. The latter relationship also seems to hold for the Devon Island Ice Cap and Greenland. In future, modellers of northern ice ages should use model ice that is three times softer than modern or Holocene ice.

scholarly journals Accumulation variability, density profiles and crystal growth trends in ITASE firn and ice cores from West Antarctica

2004 ◽  
Vol 39 ◽  
pp. 101-109 ◽  
Author(s):  
Anthony J. Gow ◽  
Debra A. Meese ◽  
Robert W. Bialas
Keyword(s):  
Crystal Growth ◽  
Layer Structure ◽  
Conductivity Measurement ◽  
Ice Cores ◽  
Lapse Rate ◽  
Localized Deformation ◽  
Electrical Conductivity Measurement ◽  
Density Profiles ◽  
Annual Layer ◽  
West Antarctic

AbstractResults of analyses of snow annual accumulation variability, density and crystal growth measurements in firn and ice cores recovered from the upper layers of the West Antarctic ice sheet during the US component of the International Trans-Antarctic Scientific Expedition (ITASE) are presented. Annual-layer structure was analyzed on the basis of the visible stratigraphy and electrical conductivity measurement record in each core. Annual accumulation varied appreciably between core sites and within cores at individual sites where undulating surface topography appears to be exerting a significant impact on the magnitude of snow deposition. All density profiles except one exhibited densification that was normal with respect to snow annual accumulation and 10 m firn temperatures. Snow annual accumulation was determined stratigraphically, and 10m firn temperatures were either measured in the holes drilled for cores or inferred using elevation changes relative to Byrd Station, the 10m temperature at Byrd Station and an assumed lapse rate. Measurements at the one exceptional location indicated that the firn had undergone extremely rapid densification to ice, with the transition to ice occurring at 35–36m depth. Furthermore, thin-section measurements of grain-size show that the growth of crystals accelerated below the firn–ice transition. The behavior at this one site is attributed to localized deformation in the upper layers of firn and ice. Enhanced crystal growth was also observed at another site. At all other locations where grain-sizes were measured, the rates of crystal growth were in accord with age–temperature relationships observed by other researchers in Antarctica and Greenland. Profiles illustrating pore–crystal structure changes with increasing depth of burial are also presented.

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