CAS ES 351 Chapter Notes - Chapter 11: Oxygen-18, Sintering, Foraminifera
26 Apr 2019
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Document Summary
The oldest ice sits under the middle of an ice sheet. There are dust layers that are deposited during cold, dry, windy winters. Layer count method works best where deposition is rapid. There are ice flow models based on the physical properties of the ice sheet, but not as accurate as layer counting. Sintering at about 50 meters depth, air can no longer circulate and is trapped in small bubbles. The age of the air in the bubble is younger than the surrounding ice in which they are trapped because the surrounding ice was deposited many years earlier. If deposition of ice is fast, the age difference between bubbles and surrounding ice will be a few hundred years, but when deposition is slow, it can be up to 2,000 years or more. During photosynthesis, plants prefer 12c so the organic matter they create has negative values of 13c.
