During the depths of the last glaciation hundreds of Wooly Mammoths died and froze quickly sometimes with food in their mouths. The beasts became entombed in bogs that froze solid and remain frozen today in the East Siberian permafrost. (Image Wikipedia)
Why were there bogs in East Siberia during the depths of the last glaciation? And why has the permafrost not thawed during 10,000 years of Holocene interglacial?
That is the Mammoth Enigma.
In searching the internet for information to answer this enigma I was surprised to find little concrete data and that web sources on this subject are dominated by creationist views.
My initial interest on this topic was spawned by a TV documentary describing a remarkably well preserved specimen called Yuka with real Mammoth blood. Enter Stephen Spielberg with the script for Pleistocene Park. It does seem plausible that we see a mammoth clone one day.
Age dating (14C) of frozen mammoths reveals two distinct groupings, one centred around 40,000 years old and the other around 11,000 years old. 40,000 years ago the Earth was in the grip of the coldest spell of the last glaciation while 11,000 years ago marks roughly the beginning of the Holocene interglacial. The latter grouping therefore may have been subject to rapid climate change and thawing of ice everywhere, but it remains difficult to explain why the specimens froze and have remained frozen ever since.
The 40,000 year old group rings a bell since this corresponds to The Laschamp event that saw a brief but full reversal of Earth’s magnetic field. It also corresponds to the eruption of a super volcano in the bay of Naples, Italy. But I suspect these may be coincidental.
The ice ages still had seasons. And so I don’t have a great problem imagining summer melting and the formation of melt water ponds that may freeze at night and be covered in snow setting a mammoth trap. The mammoth enigma boils down to (or freezes down to as the case might be) why these creatures remained frozen for 40,000 years, especially the last 12,000 years of Holocene interglacial. Its almost as if the ice age never ended in east Siberia. And why the clustering of ages? Perhaps that mother of Vesuvius is not a coincidence after all. Could volcanic ash spread over ice have aided summer melting and the creation of mammoth traps?
I want to conclude with a look at this fascinating map showing the distribution of permafrost in the northern hemisphere. (Image source, click for large version). I want you to zero in on the line of latitude that is 50˚N. That is the line that clips Lands End, the southwestern extremity of England that is upside down on this projection. And also the line that is 60˚N. That is the line through the Shetland Islands off the N of Scotland. Follow that 10˚ band eastwards, to the left, through Denmark, southern Sweden the Baltic States and into Russia. That band is permafrost free, all the way to East Siberia. But then covered by permafrost all the way to Kamchatka, through the Aleutian Islands into Alaska and Canada.
This is a clear illustration of how thermohaline circulation distorts heat distribution in the northern hemisphere. The UK and NW Europe should be under ice but are not for the time being most likely because of The Gulf Stream that transports heat northwards deep into the N Atlantic and Arctic. The rotation of the Earth and prevailing atmospheric circulation today carries warm moist air over Europe into Russia maintaing ice free conditions. My hunch is that a significant change in both atmospheric and ocean circulation accounts for the shifts from glacial to interglacial conditions in Europe. Linking this in a quantitative way to orbital cycles remains elusive.