Warm Climates
The late Permian, approximately 260 million years ago, may have been a
critical period in the evolution of life on Earth. Late Permian paleogeography featured a
single, hemispheric- scale supercontinent - see fig below - with sea level hundreds of
meters below its present-day position. Paleoclimate conditions are thought to have been
anomalously warm and dry, with little evidence for extensive polar ice cover. Recent
studies suggest that parts of the deeper ocean may have become oxygen depleted, leading in
some way to an environmental crisis at the end of Permian time in which 90% of all species
of life were eradicated in the greatest mass extinction in earth history.
Thus, it is increasingly regarded that studies of ocean circulation are
important not only for understanding ocean and climate change, but for how it has shaped
the course of biological evolution.
John Marshall, in
collaboration with John
Grotzinger, Mick Follows
and Rong Zhang has been working on modeling the warm climate at the
end of the Permian (260 Myr ago) when one large continent
existed centered near the equator (Fig. Permian) and the deep ocean
may have been devoid of oxygen, leading to a mass extinction of 90% of all species on
Earth.
Click here
for a popular article describing their work.
Fig. Permian: Late
Permian 'thermal mode' ocean circulation scenario. Here
convection is triggered by cooling at the pole. The color map
is the sea surface temperature (SST), the overlapped contour
is the stream function showing the pattern of horizontal flow
- look at the 'haline'
mode here.
