Australia: The Land Where Time Began

A biography of the Australian continent

Late Palaeocene Thermal Maximum (LPTM)

About 55 Ma, in the Early Eocene, there was a geologically brief period when the temperature of the water at the high latitudes and the deep oceans rose by 5-7^o C. Geologically speaking, this was a sudden rise. It is indicated by an abrupt change in the carbon isotope ratios, the C¹³ dropped by 2.5-3 %, the C¹² rose by the same amount. This indicates there was a massive and sudden input of C¹² enriched carbon into the oceans or atmosphere, over a period of about 10,000 years. It took about 140,000 years for the balance to be restored to previous ratios. It is believed that it required an input at a rate comparable to that of the present rate of addition of carbon from human activity to achieved the amount of change over the short period that has been found. The belief that the amount of CO₂ in the atmosphere remains relatively stable over time has been questioned as a result of the work on C¹³/C¹² ratios that led to the finding of this sudden temperature change. It now seems there is a vast store of carbon, that is enriched in C¹², that may be intermittently added to the atmosphere over very short periods, geologically speaking.

The prime suspect is a large gas-hydrate capacitor (White, 2003), because it is the only known reservoir that is large enough and that is sufficiently enriched in C¹². The trigger for the release 1000 gigatonnes of carbon from this store at the beginning of the LPTM is not known for certain. Whatever the trigger, increased deep ocean temperatures would be involved. A suggestion has been a period of explosive volcanism in the North Atlantic. Whatever the cause, deep ocean water that warmed by only a few degrees would lead to the release of the methane to the water, and then to the atmosphere, where the methane and its oxidation product CO₂, would lead to greenhouse warming on a global scale.

The threshold at which the release of methane occurs is not known, but it appears to have been crossed, at least in limited areas, as methane has been observed bubbling to the surface in a number of places in the Arctic Ocean to the north and east of Siberia. A deposit of methane clathrate that is surprisingly large has been found on the Lord Howe Rise, off the east coast of Australia.

Sources & Further reading

Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003

Aridification of Australia

Glacial Maximum

Runaway Greenhouse

Ice Ages

Climate cycles

ENSO

Global warming to global freezing

Indian Ocean Dipole-IOD

Late Carboniferous Glaciation

Carboniferous Glaciation

Precambrian Ice Age

Early Palaeozoic Icehouse

Pleistocene Ice Age

Aerobacter spp. and cloud formation

Terminal Eocene Event