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| 2. |
- Askebjer, P., et al.
(författare)
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Optical properties of deep ice at the South Pole : Absorption
- 1997
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Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 36:18, s. 4168-4180
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Tidskriftsartikel (refereegranskat)abstract
- We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At depths of 800-1000 m scattering is dominated by residual air bubbles, whereas absorption occurs both in ice itself and in insoluble impurities. The absorption coefficient increases approximately exponentially with wavelength in the measured interval 410-610 nm. At the shortest wavelength our value is approximately a factor 20 below previous values obtained for laboratory ice and lake ice; with increasing wavelength the discrepancy with previous measurements decreases. At ∼415 to ∼500 nm the experimental uncertainties are small enough for us to resolve an extrinsic contribution to absorption in ice: submicrometer dust particles contribute by an amount that increases with depth and corresponds well with the expected increase seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The laser pulse method allows remote mapping of gross structure in dust concentration as a function of depth in glacial ice.
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| 3. |
- Askebjer, P., et al.
(författare)
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UV and optical light transmission properties in deep ice at the South Pole
- 1997
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 24:11, s. 1355-1358
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Tidskriftsartikel (refereegranskat)abstract
- Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in the South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wavelengths the absorption lengths exceeded 200 meters - an order of magnitude longer than has been reported for laboratory ice. The absorption shows a strong wavelength dependence while the scattering length is found to be independent of the wavelength, consistent with the hypothesis of a residual density of air bubbles in the ice. The observed linear decrease of the inverse scattering length with depth is compatible with an earlier measurement by the AMANDA collaboration (at ∼515 nanometers).
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| 4. |
- Askebjer, P, et al.
(författare)
-
Optical properties of deep ice at the South Pole: Absorption
- 1997
-
Ingår i: APPLIED OPTICS. - : OPTICAL SOC AMER. - 0003-6935. ; 36:18, s. 4168-4180
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At dep
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| 5. |
- Askebjer, P, et al.
(författare)
-
UV and optical light transmission properties in deep ice at the South Pole
- 1997
-
Ingår i: GEOPHYSICAL RESEARCH LETTERS. - : AMER GEOPHYSICAL UNION. - 0094-8276. ; 24:11, s. 1355-1358
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in tile South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wa
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