Ocean Temperatures Surface and Abyssal

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4.2.2.b
Cenozoic, The Abyssal Ocean Temperature

In the course of the Cenozoic, the abyssal ocean temperature declined, usually slowly, but sudden major coolings occurred at the Eocene/Oligocene boundary and in the middle Miocene, indicating a change in the temperature of the earth’s atmosphere. In low latitudes, surface temperatures change little, but in the far south the Eocene saw a drastic drop from the Paleocene high of 15oC. Thereafter surface temperatures remained roughly constant. The temperature scale on the right holds true only until about 15 million years before present (mbp).

The shaded areas in Quaternary (Q) on the left, indicate the rapid large scale temperature fluctuations of the last two or three million years. The curves are based on oxygen isotope 18 concentrations found in the microscopic calcium carbonate shells of planktic (surface) and benthic (bottom) foraminifera. Formaninifera are relatives of the amoeba.

Greater contrast in temperature between the equator and the poles continued to develop. Colder oceans resulted in less global rainfall. The focus needs to be on atmospheric temperature change, concentration of Oxygen 18 and temperature change over time.

Activity
1. What is the difference in the surface temperatures of the low and mid latitudes at the Cretaceous/Paleocene boundary?
2. Describe the patterns of low and mid latitude surface temperatures. What are the maximums, minimums, trends?
3. Describe the patterns of the mid latitude surface and abyssal temperatures. What maximums, minimums, and trends
can you make about their temperatures?
4. What predictions can you make about climate change?

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