Guest Blog by : John Strohl
The Paleocene Epoch was the first epoch in the Cenozoic Era,
which is the period including everything from the end of the Cretacious
(extinction of the dinosaurs) to the present. As a point of note, this period
includes the Tertiary and Quaternary. These two
sub-periods of the Cenozoic are distinguished in time by the sequences of
fossils present in rocks from these periods. There is further subdivision of
the Tertiary into the Paleocene, the Eocene, the Oligocene, the Miocene, and
the Pliocene, which were distinguished
by an even finer grading of the fossils present. The first epoch coming at the
end of the Cretaceous Era was the Paleocene Epoch, followed by the Eocene, and
then the Oligocene. These three make up the Paleogene, or the “old” period of
the Cenozoic. (1) The subject of this post is that period
transitioning from the Paleocene to the Eocene during which an event referred
to as the Paleocene-Eocene Thermal Maximum occurred (sometime referred to by
its acronym, PETM – also known in some literature as the LPTM for Late
Paleocene Thermal Maximum).
The
PETM event is significant because it was the last significant instance of serious
global warming before what we are now experiencing. During this period the mean
temperature of Earth’s oceans are estimated to have risen as much as 41 degrees
Fahrenheit over a 20,000 year period. (2) As noted by the researchers in this study,
pinpointing the cause of the PETM requires extremely accurate dating of the
event so that it can be correlated or disassociated from other precisely
calculated events of Earth’s past such as the peak of a Milankovitch Cycle or
other known events. Based on their research, the most exact date span to date
has been generated - between 55.728 and 55.964 million years ago. The
significance of this is that it places the event outside the timing of a
Milankovitch cycle and reinforces the notion that what we know as greenhouse
gases were probably the root cause.
We
all know about CO2 and its effect as a greenhouse gas (GHG). People
frequently overlook, or are simply unaware, of the significance of methane as a
GHG. Methane is estimated to be 20 times more potent as a greenhouse gas than
CO2 and there are huge quantities of it naturally sequestered on the
ocean floor and the continental shelves facing the North Pole in the form of
methane hydrate (note the red dots not on land in the Arctic region - basically ALL of the Arctic).(3)
The map shown above indicates
where known deep sea and continental shelf deposits are located. Red dots indicate
areas where it is considered highly likely that methane hydrate will be found
in large quantities, yellow dots indicate areas that have proven to have large
quantities. Note a number of locations
in the Arctic continental shelf areas, with more having been discovered since
this map was generated. Virtually every red dot on this map has been proven to
have large methane hydrate reserves in the period since 2005, when the data for
this map was published.
Methane
hydrate is basically a pentagonal ice crystal with a methane molecule trapped in
the middle. It is stable as a result of pressure and/or temperature – high
pressure and/or low temperature. It would take a serious change in the processes
that we are familiar with today in terms of ocean cycles, and the hydrologic
cycle in general, to disturb most of those methane hydrate deposits… except for
the methane hydrate on the Arctic continental shelves.(4) The methane trapped there (900+ gigatons)
is not in deep ocean so the only thing that keeps it stable as methane hydrate is temperature.(5) The
cold necessary for hydrate stability was routinely a function of a thick
covering of arctic sea ice, which is now gone.
Original predictions associated with global warming had complete
disappearance of summer Arctic sea ice occurring by mid century. The latest
estimates have it occurring by the summer of 2015.(6,9) The MOST recent reporting indicates a massive melt off has occurred early this year. (7)
The significance
of all this is relatively straight forward. Based on careful work done by
scientists studying the Paleocene-Eocene Thermal Maximum they have been able to
model an effective cause for the PETM event – the abrupt release of methane
into the atmosphere, probably from methane hydrate in the ocean, due to a
sudden shift in ocean warming. (8) Any number of things could cause a sudden shift in ocean warming, but their
notions of the time frame for the PETM event are around ten thousand years, and
the abrupt release could have been over tens of years.
We have a scenario where
we are on the doorstep of several significant factors in oceanic warming in the
Arctic colliding in space and time – loss of sea ice in the summer,
significantly increased absorption of sunlight by the Arctic ocean, general
conditions of global warming and significant increases of methane release
already documented in the Arctic. Is there any reason to think that these
combined conditions won’t change any number of other things related to global
warming and climate change? No. Is there any reason to think that the aggregate
set of conditions won’t create sudden and serious changes in lower depth water
temperatures? No.
Welcome to the Paleocene-Eocene Thermal Maximum - Take 2…
only this time it won’t take thousands of years to peak because we face the probability
of the abrupt release of 900+ gigatons of methane hydrate into the atmosphere
of the Arctic over a matter of months and years, not decades and centuries…
which (if you’ll pardon the pun) has, quite literally, explosive potential for
harm. Imagine something that gets
out of
control in a few years and takes a hundred thousand years to rebalance,
something that is SO sudden that nothing has time to adapt...
Bibliography
- http://www.ucmp.berkeley.edu/cenozoic/cenozoic.php The
Cenozoic Era
- Charles, A. J., Condon, D. J., Harding, I. C.,
Pälike, H., Marshall, J. E. A., Cui, Y. & Kump, L. Constraints on the Numerical
Age of the Paleocene-Eocene Boundary. Geochemistry Geophysics Geosystems 12,
Q0AA17, doi:10.1029/2010GC003426
- Hester, K.C. Brewer, P.G., Clathrate Hydrates In Nature, 2009, Annual Review Of Marine Science
- http://www.huffingtonpost.com/nathan-currier/methane-emissions-urgency-now_b_1069646.html
- https://en.wikipedia.org/wiki/Runaway_climate_change
- http://www.ameg.me/index.php/sea-ice
- http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2013/07/18/snow-and-arctic-ice-extent-plummet-suddenly-as-globe-bakes/
- Gerald R. Dickens, Maria M.
Castillo and James C. G. Walker, A Blast of Gas in the Late Paleocene:
Simulating First Order effects of Massive Dissociation of Oceanic Methane
Hydrate; Geology 1997;25;259-262
- http://www.youtube.com/watch?feature=player_embedded&v=iSsPHytEnJM Arctic
Methane: Why The Sea Ice Matters
