Lecture 14

Lecture 14 - SIO 40 Life and Climate on Earth Nov 2, 2009...

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SIO 40 – Life and Climate on Earth Nov 2, 2009 Lecture 14 – Pleistocene Glaciations Ice cores like the one shown here are valuable archives of past climate.
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Outline - Proxies for studying glacial cycles - Milankovitch cycles as a forcing function - Glacial climate feedbacks
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Quaternary period - includes two epochs: The Pleistocene (~ 2 million years ago to 10,000 years ago) and the Holocene (10,000 years ago to today). This time has in general been characterized by regular cycles of growth and decay of Northern Hemisphere ice sheets. Although Antarctica has been covered with ice sheets for tens of millions of years, only during the past 2.5 million years or so have ice sheets extended from the Arctic into the northern and mid-latitudes. Where are we in time?
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Methods of determining climate change vary depending on the timescale being considered. For climate change during the Quaternary Period, there are a variety of proxies to take advantage of. We will focus first on ocean sediment cores.
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Forams in deep-sea sediment cores Foraminefera are tiny marine organisms that secrete a shell made out of CaCO 3 . They can be found in ocean surface waters, and in benthic environments on the sea floor. Scientists can use the shells of forams deposited in ocean sediment cores to tell things about ancient climate. The ratio of the stable isotopes 18 O and 16 O in the CaCO 3 skeletons of forams depends on the temperature of the water the organisms grew in – the colder the water, the greater the tendency for the mineral shell to incorporate 18 O. Thus, analysis of the 18 O/ 16 O ratio (ie. the δ 18 O) in foram shells in ocean sediment cores should tell us something about the history of temperature fluctuations in the ocean. However, the δ 18 O signal in forams is also affected by the growth and decline of the glacial ice sheets….
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Glacial mass balance in the global water cycle H 2 16 O H 2 18 O H 2 18 O H 2 16 O ocean enriched in H 2 18 O Throughout Earth's history, changes in the relative sea level have occurred over glacial/interglacial cycles because of the mass balance of water between the oceans and glaciers. Changes in sea level
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This note was uploaded on 10/23/2010 for the course SIO SIO 40 taught by Professor Barbeau during the Fall '10 term at UCSD.

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Lecture 14 - SIO 40 Life and Climate on Earth Nov 2, 2009...

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