Details

Autor(en) / Beteiligte

• Severinghaus, Jeffrey P.
• Beaudette, Ross
• Headly, Melissa A.
• Taylor, Kendrick
• Brook, Edward J.

Titel

Oxygen-18 of O 2 Records the Impact of Abrupt Climate Change on the Terrestrial Biosphere

Ist Teil von

• Science (American Association for the Advancement of Science), 2009-06, Vol.324 (5933), p.1431-1434

Erscheinungsjahr

2009

Quelle

American Association for the Advancement of Science

Beschreibungen/Notizen

• Planted Evidence To understand the spatial patterns and consequences of past climate change requires the identification of reliable proxies that reflect specific aspects of those changes, such as temperature or rainfall in a given location. Also of interest are proxies for broader categories of change, such as methane production or the sources of carbon dioxide. Severinghaus et al. (p. 1431 ) present a 100,000-year-long record of the oxygen isotopic composition of atmospheric O 2 (δ 18 O atm ) extracted from air from polar ice cores. δ 18 O atm is a general measure of the strength of low-latitude terrestrial photosynthesis and thus of local rainfall because plant metabolism is controlled in large part by water availability. δ 18 O atm changes were related to Heinrich and Dansgaard-Oeschger events, two modes of abrupt climate change common over that interval, and δ 18 O atm was controlled mostly by the strength of the Asian and North African monsoons. The rapid changes observed should also help to synchronize ice core records. Ice core studies show that changes in low-latitude rainfall accompanied abrupt climate change over the past 100,000 years. Photosynthesis and respiration occur widely on Earth’s surface, and the 18 O/ 16 O ratio of the oxygen produced and consumed varies with climatic conditions. As a consequence, the history of climate is reflected in the deviation of the 18 O/ 16 O of air (δ 18 O atm ) from seawater δ 18 O (known as the Dole effect). We report variations in δ 18 O atm over the past 60,000 years related to Heinrich and Dansgaard-Oeschger events, two modes of abrupt climate change observed during the last ice age. Correlations with cave records support the hypothesis that the Dole effect is primarily governed by the strength of the Asian and North African monsoons and confirm that widespread changes in low-latitude terrestrial rainfall accompanied abrupt climate change. The rapid δ 18 O atm changes can also be used to synchronize ice records by providing global time markers.