Mississippi megaflood may have ended the Ice Age

Ever since it was discovered that there had been ice ages, scientists have tried to understand what causes the climatic changes. A special problem has been why the ice age ended so abruptly. The ice disappeared much quicker than the energy from the sun can melt it. It is this enigma that the new paper by Ulf Erlingsson, PhD, published in the latest issue of Geografiska Annaler, provides a possible answer to.

The article presents arguments supporting that a jökulhlaup (a sub-glacial megaflood) started at the edge of the ice sheet in SE South Dakota, followed the Missouri and Mississippi rivers, eroded a 1.1 km deep canyon in the continental shelf off Louisiana, followed the sea floor half the way to Cuba, and deposited hundreds of meters of sand in the Gulf of Mexico. The author hypothesizes that as the cold water evidently sank to the sea floor, warm surface water was instead expelled from the Gulf through the Florida Straits, thus warming up the North Atlantic.

The existence of the huge Mississippi Submarine Fan off the Mississippi Canyon has been known since the 1980’s. It consists of 8 stages, all deposited in only 1 million years—the period of the four ice ages—by megafloods in the Mississippi. Two of the stages were formed towards the end of the last ice age, and the temperature rose rapidly twice when it ended. However, it has not been clear what could have caused those megafloods, since they must have been orders of magnitude larger than the normal floods in the river. It has been suggested that the water came from sub-glacial sources and burst forth in a jökulhlaup, an Icelandic term that can be translated to glacial burst, and a phenomenon that at present only exists on the ice cap called “Vatnajökul,” meaning ‘water glacier.’

The unresolved question has been how the water could form and be stored underneath the ice sheet. There is no volcano that melts it, as on Iceland. However, Dr. Erlingsson was recently able to demonstrate that a sub-glacial lake in Antarctica behaves according to the equations for a “captured ice shelf” that he presented in 1994. The same model could explain how so much water could be formed and stored in present Canada. Says co-author of “The Last Great Ice Sheets,” Prof. Terence Hughes: “If the ‘captured ice shelf’ idea catches on, it will transform modeling ice sheets from the current top-down approach that doesn't allow any dramatic changes, to a bottom-up approach that does, and that is supported by the glacial geological record produced by former ice sheets.”

The new paper also throws in doubt an argument in favor of the global warming theory. The argument is that the co-variation of temperature and greenhouse gases in the past indicates that greenhouse gases do cause global warming, just as theoretically predicted. However, Erlingsson points out that the jökulhlaup water cut through an area with oil and gas fields off Louisiana. This released natural gas and oil, some of which probably burned, thus increasing the concentration of methane and carbon dioxide in the atmosphere. It appears that the jökulhlaup drove both the climate change and the increase of greenhouse gases.

During the ice age there were also events of dramatic cooling around the North Atlantic. Others have recently suggested that they were caused by jökulhlaups from a captured ice shelf in Hudson Bay. The large infusion of fresh water would have shut down the sinking of water east of Greenland, and thereby the force that drives warm Gulf Stream water to Europe. These mega-jökulhlaups, driven partly by climate and partly by inner dynamics in the ice sheet, thus have the ability to dramatically change the climate, and most directly in Western Europe.

The alleged jökulhlaup in South Dakota happened close to Pipestone in Minnesota, a holy place for the Lakota tribe. According to their myths a great flood once drowned all the people there. The flood occurred when the water monster Unktehi first dammed the Missouri river and then let the waters burst free. Erlingsson points out the apparent similarity with the location and events of his hypothesis. If the Unktehi myth really recalls the memory of a jökulhlaup 14,600 years ago, it would qualify as the oldest surviving folk memory anywhere on Earth.

Can a flood like this happen now from Greenland or Antarctica? In 2006 Erlingsson predicted that a jökulhlaup might take place at any time from Lake Vostok in East Antarctica, but also that it would be too small to have any impact neither on sea level nor on climate. West Antarctica deserves more study, though, since the ground is far below sea level. There is no indication of any sizable sub-glacial lake on Greenland, but the topography under the ice does not rule out that one could form in the future. A large enough jökulhlaup from Greenland could feasibly trigger an ice age, according to Erlingsson. It thus seems that most—if not all—dramatic climate changes in the past million years, both warming and cooling, could have been caused by mega-jökulhlaups from large melting ice sheets, but more research is needed.

Footnote: This is a re-release since the first release 2008-07-07 had illegible characters due to an encoding mismatch.