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Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats

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Polar ocean stratification in a cold climate.

Daniel M Sigman¹, Samuel L Jaccard, Gerald H Haug

¹Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA. sigman@princeton.edu

|March 6, 2004

Summary

Global cooling 2.7 million years ago increased ocean stratification in polar regions. This shift weakened temperature"s role in ocean density, enhancing stratification and potentially amplifying global cooling by trapping carbon dioxide.

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Area of Science:

Oceanography
Paleoclimatology
Marine Geology

Background:

Low-latitude oceans are surface-warm stratified, limiting deep ocean atmospheric exchange.
Polar oceans exhibit complex density structures influenced by temperature and salinity.
Seawater density sensitivity to temperature decreases near freezing, impacting ocean circulation in cold climates.

Purpose of the Study:

Investigate changes in polar ocean stratification during the late Pliocene.
Determine the impact of global cooling on ocean density structure and circulation.
Assess the feedback mechanisms between polar stratification and global climate.

Main Methods:

Analysis of deep-sea sediment cores from the Subarctic North Pacific and Southern Ocean.
Measurement of biogenic opal accumulation rates.
Examination of sedimentary nitrogen isotopic composition.

Main Results:

Increased vertical stratification observed in both hemispheres starting 2.7 million years ago.
Coincided with intensified Northern Hemisphere glaciation and global cooling.
Cooling weakened temperature

Conclusions:

Late Pliocene cooling enhanced polar ocean stratification by reducing temperature