Surface Temperature Reconstructions for the Last 2,000 Years (2006) / Chapter Skim
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6 Ice Isotopes
6 Ice Isotopes
Pages 65-70
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From page 65... ...
Measurements of oxygen and hydrogen isotopic ratios in ice cores, or ice isotopic ratios, are an important temperature proxy, providing high-resolution continuous records of climatic temperature change at locations with persistent snow accumulation and low temperatures.1 The isotopic record provides information about climate because atmospheric moisture transported onto cold glaciers is distilled by the precipitation process as the air mass cools. This distillation combines with the temperature dependence of isotopic separations 1In this context, ice isotopic ratio refers to the oxygen and hydrogen stable isotopic composition of water molecules composing the ice itself.
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From page 66... ...
Ice isotopic ratio records are geographically limited to locations of significant ice thickness, namely, polar regions and high-altitude mountain ranges elsewhere. It is remarkably fortuitous that the high Andes, the Tibetan and Himalayan ranges, and the great volcanoes of eastern equatorial Africa offer any ice records at all for Earth's low latitudes.
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From page 67... ...
Most glaciers in the midlatitude mountains cannot provide long records of this sort because the ice mass is too rapidly removed by flow. RESULTS FROM ICE ISOTOPIC RATIO RECORDS The four available ice cores from Tibet (Figures 6-1 and 6-2)
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From page 68... ...
. Higher isotopic values generally indicate warmer conditions, but the records from the Andes may be dominated by hydrologic factors such as precipitation in Amazonia.
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From page 69... ...
In each -1.0 -1.0 plot, data are shown as -1.5 -1.5 point measurements and a -2.0 -2.0 TIBETAN ICE CORES COMPOSITE smoothed version is super -2.5 -2.5 800 1000 1200 1400 1600 1800 2000 imposed for clarity of trends. The central Green 2.5 2.5 land and Taylor Dome series 2.0 2.0 are smoothed using a 100 1.5 1.5 year triangular filter, while 1.0 1.0 the composite series uses a ichment 0.5 0.5 50-year triangular filter.
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From page 70... ...
and coastal Antarctica, ice isotopic ratio records clearly shows 20th century warming, a Little Ice Age, and earlier warmth. In Greenland, this earlier warmth is centered at about A.D.
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