dorsal/arxiv
View SchemaOptical Properties of Deep Ice at the South Pole - Absorption
| Authors | L. Bergstrom |
|---|---|
| Categories | |
| ArXiv ID | physics/9701025 |
| URL | https://arxiv.org/abs/physics/9701025 |
| DOI | 10.1364/AO.36.004168 |
| Journal | Appl.Opt.36:4168-4180,1997 |
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 to 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 to 610 nm. At the shortest wavelength our value is about a factor 20 below previous values obtained for laboratory ice and lake ice; with increasing wavelength the discrepancy with previous measurements decreases. At around 415 to 500 nm the experimental uncertainties are small enough for us to resolve an extrinsic contribution to absorption in ice: submicron 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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"abstract": "We discuss recent measurements of the wavelength-dependent absorption\ncoefficients in deep South Pole ice. The method uses transit time distributions\nof pulses from a variable-frequency laser sent between emitters and receivers\nembedded in the ice. At depths of 800 to 1000 m scattering is dominated by\nresidual air bubbles, whereas absorption occurs both in ice itself and in\ninsoluble impurities. The absorption coefficient increases approximately\nexponentially with wavelength in the measured interval 410 to 610 nm. At the\nshortest wavelength our value is about a factor 20 below previous values\nobtained for laboratory ice and lake ice; with increasing wavelength the\ndiscrepancy with previous measurements decreases. At around 415 to 500 nm the\nexperimental uncertainties are small enough for us to resolve an extrinsic\ncontribution to absorption in ice: submicron dust particles contribute by an\namount that increases with depth and corresponds well with the expected\nincrease seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The\nlaser pulse method allows remote mapping of gross structure in dust\nconcentration as a function of depth in glacial ice.",
"arxiv_id": "physics/9701025",
"authors": [
"L. Bergstrom"
],
"categories": [
"physics.optics",
"astro-ph",
"physics.geo-ph"
],
"doi": "10.1364/AO.36.004168",
"journal_ref": "Appl.Opt.36:4168-4180,1997",
"title": "Optical Properties of Deep Ice at the South Pole - Absorption",
"url": "https://arxiv.org/abs/physics/9701025"
},
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