Arctic environment during an ancient bout of natural global warming
Scientists are unravelling the environmental changes that took place around the Arctic during an exceptional episode of ancient global warming. Newly published results from a high-resolution study of sediments collected on Spitsbergen represent a significant contribution to this endeavour. The study was led by Dr Ian Harding and Prof John Marshall of the University of Southampton’s School of Ocean and Earth Science (SOES), based at the National Oceanography Centre, Southampton.
Around 56 million years ago there was a period of global warming called the Paleocene–Eocene Thermal Maximum (PETM), during which global sea surface temperatures increased by approximately 5°C.
The warming of the oceans led to profound ecological changes, including the widespread extinction of many types of foraminifera, tiny single-celled organisms with distinctive shells. Plankton that had previously only prospered in tropical and subtropical waters migrated to higher latitudes. Similar changes occurred on the land, with many animals and plants extending their distributions towards the poles.
“Although environmental changes associated with the PETM at low- to mid-latitude settings and high southern latitudes are well documented, we know less about these changes at high northern latitudes,” explained Dr Harding.
Information about the Arctic environment during the PETM has come predominantly from sediment cores drilled from under the pack ice on the Lomonosov Ridge (~ 88°N) by the Integrated Ocean Drilling Program (IODP Site 302-4A). However, these cores do not span the entire PETM and therefore do not provide a complete picture.
“Information from other Arctic sites is needed for a better understanding of PETM environmental conditions, such data can then in turn be used in computer models which will improve our understanding not only of past climatic conditions but also enhance our ability to predict future perturbations,” said Dr Harding.
To help fill this knowledge gap, Dr Harding’s team turned to a site (~78 °N) on Spitsbergen in the high Arctic. Here, 2.5-kilometre-thick sediments span the critical period. During the PETM, the site would have been at around 75 °N, the difference in position being due to the slow movement of tectonic plates over millions of years.
Through analyses of plankton and the chemical and magnetic characteristics of the sediments, they were unambiguously able to identify a 15-metre succession of exposed sediment representing the approximately 170 thousand year PETM event.
At the base of the segment they found the preserved remains of the cyst-forming dinoflagellate Apectodinium augustum, a planktonic species diagnostic of the PETM across the globe. In fact, the species was already present in Spitsbergen before the shift in carbon isotope composition formally marking the onset of the PETM, suggesting that environment change was by then already well underway.
Along with data from other sites, their Arctic evidence suggests not only that sea level began to rise well before the formal onset of the PETM, but also that it peaked about 13,000 years into the period. At the same time, increased surface-water run-off from the land dampened water-column mixing and led to stratification, with an upper freshened layer that overlay denser, more saline seawater beneath.
By carefully comparing their results with those from IODP Site 302-4A to the north, they found evidence for regional differences in the environmental manifestations of the PETM in high northern latitudes. For example, the evidence from the IODP site suggests that the sunlit surface layer of the ocean was often depleted of oxygen, the results from Spitsbergen suggest that oxygen depletion was largely restricted to the bottom waters and sediments. In addition, they found that pollen from flowering plants was scarce, unlike at the IODP site, suggesting that conditions around the Spitsbergen Central Basin may not have been conducive to the growth of flowering plants during the PETM.
“Because this geologically short-lived event is represented by such an expanded section at Spitsbergen by comparison to other deep water sites, this locality has provided us with opportunities for further high-resolution studies of the PETM, which we are currently preparing for publication,” concluded Dr Harding.
The researchers are Ian Harding, Adam Charles , John Marshall, Heiko Pälike, Paul Wilson, Edward Jarvis, Robert Thorne, Emily Morris, Rebecca Moremon, Richard Pearce and Shir Akbari of SOES, and Andrew Roberts of the Australian National University, Canberra.
Preliminary field work was funded by The Millennium Atlas Company Limited, and a second expedition with other members of the palaeo-Arctic Climates and Environments (pACE) group was funded by the Worldwide Universities Network.
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The PETM spans nearly two Ice Ages cycles in length.
What caused this?
A couple of years ago I drove from Calgary to Inuvik, a journey that included 700 km of the dirt road called The Dempster. We travelled through two mountain ranges in the Yukon and down to the southern end of the Mackenzie delta, where the road travelled along ridges to stay out of the muskeg swamps and permafrost muds. We flew to Banks Island where we trundled around in quads seeking muskoxen and cariboo. Unfortunately for warmists, I am a geologist with a multi-decadal interest in glacial and post-glacial events, for what I saw was not wat they wanted to hear about. (Another trip to Churchill where the polar bears, not antelope roams, has a similar, non-saluatory result in discussions with warmists.)
The Mackenzie delta is 150 miles or so long because the land is rising and the shoreline is what they call “regressive”. The shoreline deposits of Banks Island are about 25m higher than they were about 12,000 years ago when the main glacial masses melted. The thermokarst lakes near the shoreline exist because, finally, the warmth of the post-glacial times has melted blocks of ice or frozen ground beneath the surface – not because the air has more CO2 in it. Near Eagle Plains the university geologists are studying a 700,00 year-old perafrost layer uncovered by a landslide. The Arctic is not subject to sudden, significant changes. The land continues to rise.
At Hudson Bay the land continues to rise at about 4 cm/year. If you want to find Inuit camps 4000 years old, you have to go 100km inland. Lake Winnepegosis continues to get bigger because the spillpoint between the Lake and Hudson Bay is still rising.
Sure the Arctic ice is smaller in summer than it was in the 70’s. There were huge malaria outbreaks in the North up to the 40’s. Things change. Without us. Get a grip: it isn’t all us. And the Arctic will not become flooded in our grandchildrens lifetime with even severe changes. Of which there is no long-term indication.
If we went back to the Garden of Eden, the North would be underwater and the Inuit would be periodically starved to death. The great ancestors to the Inuit – themselves interlopers from the west when the Arctic waters opened about 5000 years ago and enabled them to “invade” the country – died out as a result of social collapse of small communities stressed out by a terrible climate.
Huge changes have occurred in the Arctic, and it survives well. And we didn’t cause them. What are the results up there that look any different from what has happened over the last few thousand years, and what are we doing that will make things “worse”? Polar bears moving north? Cariboo herds increasing as plant growth increases? Inuit living in the winter at -30C instead of -35C? In the summer it has always been hot, as my field work in the mid-70s (during Global Cooling) revealed to me.
The Arctic is said to be the “canary in the coal mine” of CAGW. From what I have experienced, the canary is just fine.
I’m intrigued by what I read as increase in fresh water…
The St. Lawrence estuary “suddenly – in geological terms” dumping an entire freshwater inland sea into the north Atlantic currents when a glacier retreated enough to allow water to flow north? ( Or same as an outflow out of the Hudson with the St/ L. blocked by ice)
I have no idea, wild-arsed guess on my part
rbateman says:
February 27, 2011 at 10:42 am
The PETM spans nearly two Ice Ages cycles in length.
What caused this?
———
Greenhouse gases – perhaps related to volcanism, perhaps with a contribution from methane clathrates
“The warming of the oceans led to profound ecological changes, including the widespread extinction of many types of foraminifera, tiny single-celled organisms with distinctive shells.”
I thought they died off because the North Atlantic waters became anoxic when tectonic movement reduce circulation. Have they rewritten history again?
With the PETM as an exception, can someone provide a reference that discusses the apparent quick to cool – slow to warm feature seen in the paleo temp record?
Richard Telford says:
February 27, 2011 at 11:09 am
The boundary layer that marked the end of the dinosaurs is well known, for example, as a layer worldwide.
I could get behind a significant increase in Atmospheric pressure, a la outgassing, as a cause of PETM. In that case, it wouldn’t matter what the ratios of gases were as long as there was significantly more atmosphere.
What other causes have been postulated/supported/searched out?
Situation then and now is not directly comparable. Most of the Icelandic shelf has risen up during the last 50 million years, consequently the Arctic Ocean was more opened to the Atlantic warm currents than it is today.
Thank you for that SWAG.
Not.
Yawn.
Jean Parisot: I think you have that backwards…The ice core record generally shows warming events happening faster than cooling. (Perhaps you are looking at graphs that put the present time on the left side of the scale and have the increasing horizontal axis represent going increasingly further back in time?)
I presume that the reason for this is that ice generally can only build up slowly but it can it can disappear more quickly because the dynamics of this involves not just melting but also breaking up.
“Situation then and now is not directly comparable. Most of the Icelandic shelf has risen up during the last 50 million years, consequently the Arctic Ocean was more opened to the Atlantic warm currents than it is today.”
More the other way around, the seaway to the North Atlantic was just opening up at the time.
“Greenhouse gases – perhaps related to volcanism, perhaps with a contribution from methane clathrates”
To date I think the following mechanisms have been suggested:
Volcanism liberating large quantities of CO2/CH4 by erupting through a deep sedimentary basin between Greenland and Norway (part of opening the Fram strait).
Breakdown of large methane clathrate deposits (perhaps volcano mediated, perhaps due to warming seawater).
Large scale peat fires.
Rapid oxidation of organic deposits in and around an uplifted former epicontinental sea.
Impact of a volatile-rich comet.
Large scale melting of permafrost in Antarctica.
Unfortunately none of these mechanisms seems capable of liberating enough greenhouse gases to explain the warming.
The mention of Apectodinium showing up before the carbon isotope shift is interesting. This is a feature that have been noted in other areas, and it repeats a familiar pattern: the warming comes first, and a bit later CO2 starts increasing.
For once the original paper is easily available:
http://eprints.soton.ac.uk/174901/2/Harding_et_al_2011_EPSL_Sea_level_and_salinity_flucuations_during_the_Paleocene-Eocene_thermal_maximum_in_Arctic_Spitsbergen.pdf
Well worth reading.
Axel Heiberg Island, in the Canadian high arctic, has mummified trees & the remains of a tropical swamp. These have been shown to have grown at this latitude & experienced the months of light & darkness. Also I was under the impression that Spitzbergen started life much further south. Try geodetic forest, Axel Heiberg in Google.
Another candidate for the cause of the PETM is an asteroid or comet impact along the Atlantic seaboard of North America. In particular, there are three or more major impact craters buried in the sediments of the Continental shelf and coastal areas. One of these impact craters is located at the mouth of Chesapeake Bay and is responsible for the deformation of its coastal aquifer.
Evidence of an Impact Trigger for the Paleocene/Eocene Thermal Maximum and Carbon Isotope Excursion. American Geophysical Union, Fall Meeting 2001, abstract #PP32A-0509
http://adsabs.harvard.edu/abs/2001AGUFMPP32A0509K
The Chesapeake crater is too young. It is one in a cluster of several late Eocene impact craters which may possibly be related to the abrupt cooling near the Eocene/Oligocene border.
vukcevic says:
“…Most of the Icelandic shelf has risen up during the last 50 million years, consequently the Arctic Ocean was more opened to the Atlantic warm currents than it is today.” Actually,the Arctic Ocean opened up to warm Atlantic currents only a little over a century ago. This is the cause of present Arctic warming, not some imaginary greenhouse effect. Read “What Warming?”
D. Patterson says:
February 27, 2011 at 2:15 pm
The cataclysmic bolide impact is an argument against a climate model with delicate tipping points.
The refererence is only the abstract. Sure would like to read the whole thing.
Brian H says:
February 27, 2011 at 12:59 pm
“SWAG”
———–
I thought it was an acronym and I came up with several suitable rude words for S, W and A but got stuck on G – so I reached for Wiki and found this:
“Swag may refer to:
Swag (album), a 2002 rock album
Swag (bedroll), an Australian waterproof bedroll
Swag (motif), an architectural element
Swag (novel), a 1976 crime novel
“Swag” (Ugly Betty episode), the eleventh episode of the television series Ugly Betty
Swag, a type of window valance, often in combination with a full curtain underneath
Swag, promotional items given away at trade fairs and events to encourage attendees to visit the vendors’ booths”
I assume you meant the last item in the list.
If only I could find something rude for G …………………….
Wonder what pulled the planet from a greenhouse state to the current icehouse conditions? The azolla fern. A fantastic fairytale of the superplant that we have to thank for ice-covered poles. Enjoy:
http://en.wikipedia.org/wiki/Azolla_event
Brownedoff says:
February 27, 2011 at 3:10 pm
““SWAG”
———–
I thought it was an acronym and I came up with several suitable rude words for S, W and A but got stuck on G – so I reached for Wiki and found this:”
Sophisticated wild ass guess.
[Reply: I believe the acronym stands for “Scientific Wild Ass Guess.” ~dbs, mod.]
rbateman says:
February 27, 2011 at 3:02 pm
The USGS maintains a website regarding the impact/s.
http://geology.er.usgs.gov/eespteam/crater/
There has been a lot of scientific debate going on about the effects the Chesapeake Bay impact/s had upon the global climate and atmospheric-oceanic chemistries versus the Deccan Traps vulcanism. I have often wondered and speculated whether or not they are missing the possibility that the Deccan Traps vulcanism could have been brought about by a series of these major impact events. When the Shoemaker-Levy comet impacted Jupiter, we could see first-hand how the Jovian gravity caused the comet to break into pieces and impact across widely spaced trails across Jupiter. Similar impact events on a far smaller scale may have been detected as trails of impact craters acorss the Midwest of the United States. The Chesapeake crater it appears may have been accompanied by other major imapct craters farther north. There are one or more major impact craters off the coast of India which may have a connection to the vulcanism of the Deccan Traps. I can’t help but wonder if perhaps one or more major impacts at this time were of sufficient energy to disrupt the crust and upper mantle to cause some extreme vulcanism evnts in the Deccan Traps and elsewhere, thereby causing some major changes in climate? The role of such speculated major changes in climate due to impact events versus the PETM is another question.
SWAG= stupid wild a** guess
Richard Telford says:
February 27, 2011 at 11:09 am
rbateman says:
February 27, 2011 at 10:42 am
The PETM spans nearly two Ice Ages cycles in length.
What caused this?
———
Greenhouse gases – perhaps related to volcanism, perhaps with a contribution from methane clathrates
*************
There has never been a time that I have heard about when when CO2 increased BEFORE temperatures rose. Please cite references.
At 50 million years even the 800 year lag reported between warming and CO2 might be undetectable.
I am willing to learn !
SWAG=Scientific Wild Ass Guess.
The impact event could reasonably be expected to send shock waves through the ocean, stirring up the clathrates. But then, any impact should have had similar results, and we have only one PETM.