An ice age in the tropics

Article Abstract:

The datable lavas overlying glacial deposits that were found in South Africa support the suggestion of a 'snowball' Earth during the Palaeoproterozoic era about 2.2 billion years ago. A 'snowball' Earth theory suggests that most of the planet was engulfed by ice. In light of the evidence that one other such severe glaciation also occurred more than a billion years later, the Earth is then believed to be a largely ice-free Precambrian Earth that was interrupted by two extreme ice ages. Another theory holds that, during Precambrian times, a belt of ice girdled the equatorial regions of the Earth, which was ice-free at high latitudes.

Earth, Glacial epoch, Ice age, Earth's age

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Mechanism of the biological response to winter cooling in the northeastern Arabian Sea

Article Abstract:

Sinking of the surface layer and convective upward transport of nutrients to the surface layers of the northeastern Arabian Sea, maintain high biological production during winter. The transition from feeding on phytoplankton in the summer monsoon period to the microbial loop during the winter period also helps to sustain the high-biomass mesozooplankton community. Dry continental northeast trade wind causes intense evaporation and surface cooling from Dec to Feb. This cool and dense surface water sinks and the convective upward movement of deeper layers, brings nutrients to the surface.

Observations, Ocean-atmosphere interaction, Biological systems, Arabian Sea

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Cooling the tropics

Article Abstract:

A study of strontium to calcium ratios in corals and noble gas concentrations in ground waters shows a drop of 5 to 6 degrees centigrade in tropical temperatures during peak glacial period. Experiments on snow, from a depth of 160 m, show the 18-oxygen isotope to 16-oxygen isotope ratio to be 8% lower than for Holocene ice. The role of these two factors in lowering tropical temperature is not yet understood.

Natural history, Temperature measurements, Temperature measurement, Glaciology, Tropics

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