The Palaeocene-Eocene Thermal Maximum: anatomy of a tipping pointMike Stephenson, Robert Knox, Melanie

Leng, Chris Vane, Jim Riding

Tipping point

• point at which a slow gradual change becomes irreversible and then proceeds with gathering pace

• point in the evolution of the earth's climate leading to irreversible change

• When a small (unnoticed) thing happens which is enough to precipitate huge things happening….which we can’t repair

Is the climate tipping?

• Some scientists e.g. James Hansen, - tipping point already reached – CO2 at 385 ppm

• Some say - tipping point difficult to predict for non-linear, complex system

• Some say - political slogan - instil fear in policy makers and largesse in science funders

Can we stop the tipping?

• Man made global warming - changing the composition of atmosphere by emission of carbon dioxide and methane.

• Remedial action - reduce greenhouse gas.

• Is this a reasonable assumption?

Research: understand tipping point

• rates of change in biogeochemical cycles

• change in extreme events not seen in the last 10k yrs

• negative feedbacks that bring the system back to normal dynamic equilibrium

Fig. 1, the PETMFig. 1, the PETM and Eocene Optimum

Fig. 1, the PETMFig. 1, the PETM and Eocene Optimum

Palaeocene-Eocene Thermal maximum: natural laboratory

Palaeocene-Eocene Thermal Maximum: why it’s important

• NOW - – injection CO2 into atmosphere. – changes predicted extreme, 5.6° C increase in the

next one hundred years – CO2 atmospheric concentrations higher than at any

time during the Quaternary. • PETM

– similar magnitude CO2 and temperature increase– some of the remnants of the changes are preserved

in the rocks.

• Comparison follows

Comparison: CO2• Drax B - 7% of England's electricity;

lifetime emission 1 Gt• China emissions 3 Gt/yr• Leman Sandstone Formation 3Gt

storage capacity • Bunter Sandstone Formation 15 Gt

• PETM caused by 1500 Gt of methane carbon from decomposing gas-hydrate reservoirs (Sluijs 2006)

• PETM ~ equivalent of 4-8 times the anthropogenic carbon released since start of the industrial era

What is preserved?Clay Layer

Rocks/lithofacies

Forams Dinoflagellates

Various geochemical evidence

What does it suggest?Temperature increase

• TEX86 palaeothermometer

• O isotope excursions in foram calcite and terrestrial carbonates

• Increased Mg/Ca value in forams

• Poleward migrations of tropical marine plankton, terrestrial plants, and mammal migrations

Carbon cycle change

• 2.5 – 6 ‰ carbon isotope excursion

• Believed to represent rapid injection of 13C depleted carbon into the global carbon pool

• Conjunction of warming and excursion: greenhouse gas cause?

What does the CIE

excursion look like?

Steep beginning

Gradual recovery

highlow

Bass River, Sluijs (2006)

warm phytoplanton

temp rise

both precede the CIE

Only biogenic methane (C = -70‰ enough to create a CIE of this sizeFig. 2 High resolution records across the onset of the PETM at Bass River, New

Jersey. BC = bulk carbonate, DINO = dinocysts, VPDB = Vienna Pee Dee Belimnite, mbs = meters below surface. Scales at TEX86 temperatures represent calibrations by Schouten et al. (2002) for the top bar and by (Schouten et al. (2003) for the lower bar.

Fig. 2 High resolution records across the onset of the PETM at Bass River, New Jersey. BC = bulk carbonate, DINO = dinocysts, VPDB = Vienna Pee Dee Belimnite, mbs = meters below surface. Scales at TEX86 temperatures represent calibrations by Schouten et al. (2002) for the top bar and by (Schouten et al. (2003) for the lower bar.

Apectodinium peak and temperature rise (as indicated by TEX86) preceded the CIE

Did heating trigger methane hydrate release leading to the

CIE?

BP Well 22/10a-4Middle of N. Sea

Well 22-10a/4

• North Sea well - probably the most expanded section known – chance to unravel the CIE

• δ13Corg

• Palynology/palynofacies

• Detailed lithofacies

• Organic geochemistry

• Inorganic geochemistry